Scale Soaring UK

Hi All,

I have just purchased a John Slater designed 'short Kit' for an Airspeed Tern sailplane 1/4 scale, does anyone have access to a build log that i could use to help my efforts. I find that having the results of someone else's efforts really helps me with mine.

All the best

Barry Apostolou

Hi Barry,
Pleased you have bought a short kit of the Airspeed Tern, i'm sorry I do not know anything about the short kit other than what excellant quality they are,
I built the original using the method shown in my build thread, before I donated the plan. This was assembled in a jig after first constructing a `box' frame then laying a peripheral keel to slot in the fuselage formers, and then fitting the stringers, this allowed me to almost complete the fuselage in the jig and keeping it all nice and straight ( as long as the box jig is straight ). It then only required the thin ply sheeting to be put on.
Good luck with the build, and the flying which I am sure you will enjoy.
Kind regards
John

Cheers John,

that has been of help re-the jig method of doing the fuz. However I still cannot find your original build thread, would that be on this web site or do you have to send it to me. Sorry for the delay in replying I have been on a flying holiday at Burnham on Sea, flying Crookes peak, Bream Down, Up Hill and other sites, total exhausted now climbing up hills etc..

Thanks for the feedback, all the best

Barry A

Hi Barry,
I'm sorry I didn't do a proper build thread, much to my regret, I have some photos of the assembly which I included in the post build thread. I have included photos I do have,
Kind Regards

John

Thanks for that John, it has been most helpful,

I have now completed most of the Fuselage on the jig as per your pics. I will soon be starting on the tail, rudder, stabilizer and elevators. I have decided to include some carbon 'tows' in these to maintain the strength and the relatively slim structure of the outline. I have also used carbon rod on one of the stabilizer joiners to save weight but have kept the piano wire joiner on the other, to try and get the best of both worlds. (?)

The lower 'longerons' on the fuselage took some bending to get the shape correct, I managed to got this done by soaking them for a couple of days and using rubber bands to hold in place till the glue set. The key to it all was as you said, building the jig to get every thing square and level. I think it would be impossible; to do without this. I am be using 'Oratax' vintage on the turtle decks and wings and perhaps staining and glassing the fuselage sides and bottom. I am conscious though of keeping the weight down.

Many thanks for your help.

All the best

Barry| Apostolou

Hi Barry,
It sounds as though you are making great progress, and as you say bending those stringers is quite a challenge.
Keeping the weight down is of course important particularly at the aft end, please don't make the mistake that I did of not taking some photos of your progress, we would all like to see how its taking shape.
I believe that I used some yacht varnish on the fuselage and vintage solartex for the flying surfaces.
Kind regards
John

Hey John,

I will try and get some help to post some pictures of where I am in the build. Being a bit 'old' I am not very good at doing computer and camera stuff.

That sounds good to me, with the ply sides, I could also use a stain and varnish, it would certainly save a lot of weight compared to glassing. I tend to be a bit heavy handed with glassing and add too much weight. 'Rustoleum' do a gloss clear coat that gives a great finish, and can be sprayed on.

I have added the nose block (with some lead inside), and done the cockpit flooring and installed the rudder, elevator servos, RX, switch and
flight battery. All the 'little bits' in the wing fillets are now done, along with the wing joiner boxes. For the rear wing joiner box I have used a slightly smaller one (3 mm smaller) than the front, again saving a bit of weight (1 oz) behind the COG.

For the joiner boxes 'covers' I did not use the brass backing strip, instead used ply and professional 24 hr Araldite, this then meant I saved the weight of the nuts and bolts as shown on the plan (saved about 3 oz here, all behind the COG ). I have used this method before as per Chris William's plans for Minimoa, Bergeflake and Flamingo. I have never had any problems with the wing joiners on these models.

Did you get a all up weight for your model ? it would be interesting to know. thank you for the advice, it is appreciated

All the best

Barry

Evening Barry,
Good idea about saving weight with the brass backing plate, I tend to think of the rear spar as the main spar with the Tern as it is more in the centre of pressure and the front spar as the incidence peg, this does seem a bit backwards but it has never failed me when doing any manoeuvres, I suppose it really depends on what type of flying you will be doing.
A lot of my models are balsa planked and then glassed on the fuselage, when flying over the Mynd the bracken is very unforgiving but I haven't had any structural failures with the Tern. The landing areas on the Mynd are limited and demanding I suppose and is the reason for fitting air brakes, do you intend fitting any on your model?
Kind regards
John

Hi John,

I will be doing basic flying, a loop, perhaps a roll, chandelle; nothing too strenuous. I have other more suitable models for 'aerobating'. This is just for the sheer pleasure that vintage flying gives in terms of the look and feel of the model.

I have flown at the Mynd last year and I agree it is pretty rough. In the S/E where I am based most slopes are grass covered and in that respect are much kinder to models. So I think if I do use the ply for the fuselage I will simply just stain/varnish it and be done, adding more weight with glassed balsa may not be productive.

I know it may not be true scale but I do intend using air brakes on the Tern. this plus slightly raised ailerons on landing really does seem to help. This was a tip Chris Williams gave re-the Minimoa. If you go to the 'Facebook' page titled "RC slope soarer, sell and chat and general windy chit chat" you will see in the banner photo a picture of my Minimoa 1/3.5 scale taken at White Sheet. I have since also built the 1/4 scale one as well which is easier to carry.

How much did your Tern weigh in the end ? it will be interesting to see how they compare, from your video it looked to fly in very light wind, and climbed away well.

it is interesting what you say about the rear spar being the main one, and the front being the incidence peg I had not thought of it in terms of the center of pressure. I did it to save as much rearward weight as I could but I am pretty certain it will be OK.

Thanks for your feedback

All the best

Barry S

Morning Barry,
I am myself inspired by your attention to detail, particularly as regards weight, when the Tern was built in 1993 and my experience was not what it is now I tended to over engineer my builds and so my model is quite heavy really, and I am not sure but its probably somewhere in the region of 12lbs , will check it and let you know. However it is still a joy to fly, and I am sure you will enjoy the flying as much as your build.
Kind regards
John

Hi John

Thanks very much indeed, I am doing the cockpit now, that is quite a challenge as well. keep you posted.

All the best

Barry

Hi John,

I think I may have actually managed to get some pictures on this of the progress so far. My computer skills are rubbish so I have probably sent your pictures back !!! lets hope it works

Barry

The photo fixer strikes again......



BC

Evening Barry,
That's looking really nice, and the photos tell the story, well done.
I will be over the Long Mynd this weekend for our fun fly, which we are dedicating to John Watkins.
The Mynd can be a challenge but that's the fun of it, sharpens the skills of of finding the lift, or not and then admitting it's time to land before its to late and a long walk.
Happy flying
Kind regards
John

Hi John,

Many thanks to Barry Cole for sorting out my efforts at posting pics., sorry to give you more work to do Barry. I hope you have a good time at Long Mynd this weekend in remembrance of John Watkins; and be careful of that heather, it is never as soft as it looks.

My next task is to complete the centre section of the wing (those bits that are part of the fuz). I will then move onto the tail end and get that sorted. By the time I remove the fuz. from the jig i should just have the sheeting left to do.

I post a picture of my 1/3.5 scale Chris Williams Minimoa, that I built around 10 years ago now.
I have since also built the 1/4 scale one as well, they both fly great. I really like the CW plans and have built the Bergfalke, and Flamingo also. The wing section he uses is great and really favours the pilot, unless you really mess up it just keeps flying.

All the best

Barry A

Hi John,

I will hopefully have attached picture of my progress to date. All the back end is now done (fin, rudder, stab, and elevator), with the top covering and the initial bits of sheeting around the cockpit completed. The wiring loom for rudder and elevator is completed and the connections through to the wing servos done and tested. I have used closed loop for the rudder and a traditional push rod for the elevator. (with built in differential). The next job will be to complete the fuselage sheeting. I am using several sections for this. I will be using two very similar color stains, in this way I hope to give the appearance of different panels as delineated by the variations in stain. These will be brought together by the final coat of clear satin varnish. At the back end the I will use 0.5 mm ply sheeting whilst at the front I am using 0.8 mm ply sheeting for greater strength. ( I have never reversed a model into the ground yet... In terms of the covering I am using my last bit of Antique 'Solartex', mixed with Antique 'Oratex' and using the slight color variation to try for an interesting 'patina of a real aircraft that may have had bits of covering done at different times so they will vary in color and fade. (also covering is expensive, so I am trying to be as economical as possible).

It will take me a bit of time to ply sheet all the fuselage, then it's on to the wings. So far all is going OK, and like most things we build we all know where the bits are that do not bear too much close scrutiny, but overall I am happy with what I have done.

All the best

Barry

Barry,
Thats all looking rather splendid, and brings back very fond memories for me of the original build, you are certainly making a lovely job of it and I can imagine it in flight, you will I am sure enjoy it.
Great photos, keep up the good work.
Kind regards
John

HI, John and anyone who may be following this build,

I have now competed the fuselage ply covering, using the technique shown by John Greenfield. That is 'ironing on the ply sheets'. Much to my surprise after watching John's video on the 'tips' page it worked very well indeed. This saved a lot of 'pining down' and waiting for ages for the PVA. to set. I have used three slightly different color stains. The idea was to try and get a scale effect of different bits having different levels of fade and stain. This may not have been the best option, its OK, but I probably would not do it again and just go for one stain. I plan to use an overall 'stain wash' to get the colors more closely matched before using Poly C to get a finish. This will be after applying the decals. This will 'damp down' the color changes.

Next to do are the wing fairings attached to the fuselage, but before that I once again checked all the wiring to ensure all is still working before restricting access. In terms of the soldered multiplex plugs; what I have done is flooded the 'end bits' with Silicone to make the soldered joints more resistant to every day use, I also used 'supports' in the fairings to ensure that they are under no strain from the weight of the wiring loom. In the hope that anticipation of a problem can make things more resilient.

The main skid and the rear skid, both clad in litho plate, as well as the scale 'Pitot' tube are done and the Fuselage is near completion. I have left open from former one to the nose block to allow any ballast weight needed to be added to get the required COG. So all in all quite a satisfying build so far, with 'JUST' the wings to go.

All the best

Barry

Well done Barry. John's plan certainly makes a nice model

Thanks Vince,

Yup John's plan does give the basis of a great model, with a very interesting back story re-the real ones (only two ever built) and the first broke the UK distance record along the south coast. The 'Air Speed' company was started by Neville Shute Norway, also a famous author. Who in addition designed and built the Airspeed Courier, first UK aircraft to have a retractable undercarriage.

All the best

Barry A

Barry - there is a lot of information in the Docs section

https://scalesoaring.co.uk/airspeed-type-s-1-tern/

Hi Vince,

Thanks for that, I did not know information was there, I just got stuff from the internet. Makes interesting reading.

Barry

Evening Barry,
It would seem that my Tern has a 'twin' a very handsome one, I would like Vince point you in the direction of the docs.there you will find several photos which show in detail quite a lot of detail, and in particular the windshield, which is not framed but a one piece curved windshield. If you are aware of a framed windshield then please share the details, both with Vince and myself.
It is looking very good and wish you well with the wings, John Greenfields video article is first class regarding ply application.
A great build thread, and photos, keep it coming.
Kind regards
John

Hi John,

Thanks a lot. When I get ready for the wings (if it is OK with you) I will post any questions I may have on this thread. Have many other guys built your plan? it is not a model that appears on the slope frequently.

Re-the wind shield, I cannot remember where I got the detail for a framed wind screen. Some where on my internet searches I recall a picture with this, it may well have been on the mark 11 where they put a closed cockpit on the Tern, I am not sure. Also as the aircraft was sold on it may have been other owners that made a modification. My surprise was that given its success there were not more Terns made. Perhaps the war put an end to 'social gliding' ??!!

The wind shield looks 'OK-ish'; but I am not certain. I may leave it or revert to the first option. Often I try something that is relatively easy to alter leave it on the model for a while and work around it to see if it 'rings my bell' if not I will try something else.

I did this with the different stain shades, however I would not do that again, as it did not come out as well as I thought, although acceptable in the final model. Thank you for your comments and advice they are much appreciated.

All the best

Barry A

Hey John,

I probably misunderstood what I read, and maybe that it was the only glider that was modified with a cockpit and then sold off.

I just looked again on 'Wikepedia' and they do say that 2 were made. They also say that a third was made (after the war) from the parts of the other two. if you 'google' Airspeed Tern you will see all the hits that I got when I tried to get more information.

However the trouble with the internet is that information can be recorded with no one checking if it is correct. Not being particularly good on computers, I understand from others that Wikipedia can be more trusted.

Still half the fun is the research.

All the best

Barry

Barry ,

Cliff has very kindly in his last post, included a link to the documents of everything about the Tern, a very compressive history of the Tern and Airspeed which has been meticulously put together by Vince.
When I started the Tern project back in 1993 I was very fortunate to be in touch with a man named Roger Reffell whose father flew it in the 1930's and he kindly allowed me access to all he had when his father flew it, which included a lot of photographic negatives, unfortunately not all were useable but I did mange to get printed quite a few very important ones, particularly of the post war Tern, which I think was salvaged and put together from what was left of the two pre war Terns.
All of the photos have been forwarded on to Vince who has done even more research to compile a truly impressive documental history.
Please view this document, you will find it both informative and interesting.
Kind regards

John

Just to add a tiny bit more meat to the bones - from Norman Ellison's book 'British Gliders and Sailplanes 1922 -1970':

Thanks Guys,

For all that information, it makes interesting reading for an interesting model. Well I have very nearly completed the fuselage including all the bits on the wing fairings. Just a final finishing coat of Poly-C to go.

Does anyone of you have any pictures or advice re-the wing lay out? I have not studied the plan in detail yet; but a quick look showed it needs to be jigged up to a certain height at a particular wing rib, I have assumed this to be same for the entire wing chord and although the wing top is straight, the rising ribs will create a level of dihedral within the wing section it self.

I will try and post pictures at a later date, but have been out flying this week (till the rain came) and have not progressed too much.

All the best and thanks for the feedback,

Barry

Hi Barry,

Re wing construction, I think most modellers have their own method, but if it helps this is my method.

Firstly with all the ribs available I construct the main spar, this can be done nice and straight on a good building board.

The spruce top and bottem pieces are clamped or pinned to the board I then add the vertical webbing to one side but only at every other rib spacing, ie. rib 1 to 2, 3 to 4, 5 to 6 and so on, the wing joiner is not fitted at this stage. when this is done the spar can then be lifted and positioned on the plan again keeping everything vertical straight and true, the wing construction can then begin.
I then slot each rib into the spar at the rib space and rotate it into position against the vertical webbing, 2 ribs into each space can be fitted, ie. ribs 2 & 3, ribs 4 & 5, and so on, rib 1 the root rib is not fitted at this stage but when the wing tip can be elevated and then it can be set at the required angle.
When fitting the ribs you must make sure to align the front and rear of each rib, and pay due attention to creating the washout at the tip rib.
The wing leading and trailing edges then fitted.
The remaining vertical webbing can be added and the wing joiner fitted and boxed in by setting the tip at the required height and using a spirit level to keep the joiner level before the ply `D ' box sheeting is applied.
This is a brief summary of my method and hope it is of help.

Kind regards

John

Thank you very much John.

It will be of great help when I start the wings. I take it from what you say that the wing joiner box in the wing is set to ensure a dead level joining section for the stainless strip to go in, thus making the top of the wing dead straight.

I hope to start the wings sometime next week, I have been out today flying at Butser Hill (Petersfield on the A3) on a very blustery westerly wind, in the region of 15-20 mph, it was great fun. There was a good turnout of around 15 people there flying all sort of models, The Club that run the site is the Meon Valley Soaring Association (MVSA), I have been a member for quite a few years now, they also have westerly and northerly sites as well.

Thank you for taking the time to help it is appreciated,

All the best

Barry A

Hi John,

All well with the progress so far. I enclose some pics of the completed fuselage. I have left the bottom front bit open to locate the ballast weight at the final balancing.


Will keep you updated as I progress with the wings.

All the best

Barry

Hi Barry,
Looking good, at this rate you will be `airborne' quite soon, it looks very much like mine, I enclose a photo from the collection of negatives from Roger Refell.

Kind regards
John

Thanks for your comments John,

I am now preparing all the wing ribs, cutting holes for the wiring loom and lightening holes etc. I have today placed my order for wood for the spars etc from Balsa Cabin, they are able to supply in 48" length, so splices joint will be out towards the tips.

I am struggling a bit with how to proceed with the wing, I would like to build it 'on the board'. I see from the plan that I have to jig up, at wing rib 17 to the tune of 25 mm. My plan is to do two of these jigs one for the front lower spar and the other for the rear lower spar and simply build off these.

I can then incorporate any wash out as I go out to the tip via an additional packing piece. In this way I plan that the top of the wing will be dead level and any dihedral is via the decreasing thickness of the wing towards the tip. What do you think?

I have tried to follow your instructions and build the spar first, but I am not certain I understand exactly how. This is a method I have never used, and I feel uncertain that my understanding is clear. Still; I have lot more thinking to do about this. It will take me a week or so the get all the wing ribs lightened etc. I plan to use servos in the wing and not bell cranks as per the plan.

Getting out of the workshop this weeks as well, I Will be flying tomorrow and on Friday, thanks for the encouragement

All the best

Barry

Hi Barry,
The way you discuss your proposed building process is as I have said really, I prefabricate the main and rear spars, to set up on your jigs so to speak,
but I do not add all the vertical webbing to the spar, only every other rib space webbing so you have a gap in the spar to slide in through the gaps the ribs before adding the remaining vertical webbing to the spars.
By doing it this way I can keep the ribs in one piece, and like you say you can build in the washout on your jigs, I do leave the root rib till the spars are in position to be able to set it at the correct angle.
Kind regards
John

Hi John,

Thank you for the reply, that is great. I agree with you, that we are both talking about the same thing; so I will proceed as discussed.

One further question - How important is the wash-out in your opinion?- given that on landing I will use air-brakes and raised ailerons. This will in effect wash-out the wing for landing.

So I suppose the real question being; is washout vital for general flying?

Having said that; it is no problem to add a few degrees.

John, thank you for your feedback.

All the best

Barry

Hi Barry,
I would say washout is vital, please build in washout as on the plan, the Tern will fly quite `sedately ' so washout is needed in the turns.

Kind regards
John

I will do that John, and will build in wash out as stated on the plan.

Barry

Hi John,

Lots of flying this week and last. So not too much time in the workshop But I am now splicing all the wing spars, leading edges and trailing edges ready for both wings. I have cut the lightening holes in one set of ribs and will start on the the other set soon. The brass wing joiner boxes are cut to size and ready for fitting.

Am I correct in saying the only dihedral on the Tern; is the wing tapering in thickness to the tip from the bottom; the top being level?

So just the wing 'jigging pieces' to make and I will be ready to start getting the wings together. As per your advice I will l remember to add wash out.

All the best

Barry

Hi Barry,
Sorry about delay , we have been on holiday for a couple of weeks, in answer to your question about dihedral I did put a 1" block under the wing tip to give a slight dihedral, in flight this will not be noticed but will aid stability.
Kind regards
John

Thanks John,

Hope you have had a good holiday. Yes I will probably do the same re-the dihedral. Not too much progress to report. But both sets of wing spars have been completed and all the ribs have been prepared ready with the cable holes etc.

I have been doing a lot of flying recently while the weather has been good, so my time in the work shop has been cut down. this will pick up as we move into autumn and winter.

All the best

Barry

Hey John,

Its been a very busy time flying and refurbishing models, a Fair K8, and a Chris Williams 1/4 scale T21. I am doing as much flying as possible before winter sets in.

I am trying to sell my original T21, a 'Mike Trew plan' 1/5 scale (3.5 meter wing span) no luck so far. No problem - I will just keep it and fly it. I guess that not too many people are into vintage sailplanes. If you know of anyone that may be interested please let me know, I am certain we can negotiate a good deal.

Getting back to the Tern, the wings are now well on the way, see attached pictures. Still to do are the rubber bands supports and the rear wing joiner box. The wing wiring, aileron servos and electric air-brakes (250 cm) will complete the installation. For the ailerons I have Hitec wing servos (HS125MG), at 6 volts they give a torque rating of 3.5 kg. From past experience they will be more than enough for the job.

Still to complete is the the bit of sheeting at the bottom of the wing root, this was left open to give access for the band supports, rear joiner and wiring. Finally I will cover with 'Antique Oratex'. The wing D box was 'sheeted' with 1/16" balsa, the ply was great, but the estimated cost was a bit high, and I had loads of balsa in stock. I might see if I can get a paint or stain to mimic the ply after covering.

Please note that using balsa means that the wing is now 1.2 mm too thick, and needs adjusting to ensure a neat join at the root. The wing tip blocks have a 1/64 ply sheet in the middle, to give a datum line for sanding and additional 'robustness'.

I will now move on to cutting the ailerons from the section and facing them off. I intend to use the covering to make a continuous hinge. thus eliminating any air flow through the gap. they will be hinged from the top and articulated from the bottom of the wing.

I have a question re-the ailerons, do you think they need any diagonal bracing to increase their rigidity, or in your experience are they rigid enough ?

Well, that's it for now. I am getting nearer to completing the model and will keep you posted as and when I finally finish the building.

Once again thank you for your help and advice.

All the best

Barry A

Hi all, or any one following this log

I have now started doing the final rear wing joiner box fitting. One side done, as per picture it is a good idea to leave the rear joiner box 'free' till this point then you are able to check the wing incidence v's the tail-plane, around 1.5-2.5 degrees positive AOA for the wing should be about right. This should give a stable sit in the air during flight.

Although you cannot see it from this picture there is also about 2 degrees of dihedral in the wing. This is achieved by lifting the tip 1" during building. Also as per John's plan do remember to build in the 3 degrees of wash out on each wing to ensure good manners in flight. Having checked with John he confirmed that this was important, and should not be ignored.

Spot the 'deliberate error'. I mis-measured the rear fuselage fairing length and have had to add an small infill piece. I hope this will not be too obvious once sanded and stained. It can happen to us all and I take comfort that I am not alone in seeing one measurement on the ruler and noting down another on my plan. Think thrice, measure twice and cut once. Well at least I have not got two right wings !!!!!

All the best

Barry

Lovely build Barry. Really enjoying it.

There's something a bit Jules Verne about the Tern... like a fictitious design in some futuristic comic book of the late 19th century. You could have an aerial adventure, or possibly plunge deep into the ocean inside its hull-like fuselage.

In reality, it was built at a time when there wasn't yet a set notion what a glider should look like, so designers were still trying stuff out. These days sailplane design is more gradual evolution than revolution, a little tweak here or there to squeeze small gains. The only revolution I think I can see (no pun intended) is the nose-mounted electric sustainer, which I think will become the norm. And great for us modellers...

Anyway, thanks again Barry.

Rog

Hi All again,

I know what you mean Roger it is a very unusual model , it is of its time and reflected the fact that gliding had not really got going. In fact the wings could almost be for a power model, not really the high aspect ratios we consider the norm today.

In the 'head on' picture below you can see the slight dihedral on the wings. Technically speaking the real Tern had a completely flat top wing with dihedral only on the bottom of the wing as determined by the rib size. However it is a good idea to add a couple of degrees 'actual dihedral', please note that you will also need to adjust the root rib to ensure a good fit on the fuselage.

Well despite falling over in the modelling room (I have only drunk tea), I have now managed to get both wings on and ensured that they are the same in terms of AOA. The rear wing joiner boxes need to cure and harden over night so that they are totally solid before we can move on to the next phase. this will be the installation of wiring, servos and air-brakes and then on to preparing for covering.

Just for fun I weighed the wings and they came out at 650 gm for the left wing and 648 gm for the right. Still servos, wire, covering and air brakes to add to this yet.

All the best

Barry

Hi Barry,
The answer to your question about aileron bracing is `yes', and my apologies if it is not shown on the plan.
I have included a phot of my Tern in flight to illustrate this.
Sorry about delay in replying I had been away for a few days, very impressed with the model.
Kind regards

John

Thanks John,

Yes I do see what you mean about the bracing. I was planning to do this even though it was not on the plan. As yet I have not cut the ailerons from the wing, but they seem to need a little bit more support.I shall do this as per your model, its has been a very satisfying model to do so far. The wing joiner boxes (front and rear) are now fitted, and glued. I will wait a couple of days for the '24 hour' epoxy to cure and fully harden and move on to aileron servos and air brake installation, and finally covering. I will keep you posted on the progress. Had a good days flying my ASW 24 at Bopeep (NE) today, very light wind and lift but great fun.

Thank you for your advice, it is much appreciated.

All the best

Barry A

Yes indeed it is nice to talk building as well as flying. I went again on Wednesday and 'maiden-ed' my Chris Williams 1/4 scale T21. We got there early and got in 4 flights before the wind picked up to gusts of over 20 mph. Flying was not the issue it was on the ground where the model was trying to ground loop in the gusts. But all in all a very successful first set of flights. Went home tired but happy !

The advice you took from CW re-adverse aileron drag (more up than down) is so vital to these slower vintage style models, it makes those turns a lot safer.

All the best

Barry

Covered wing of the Tern, with 'Faux' scale decals added

Dear Tern watchers,

The wings are now completed and covered with vintage Oratex, only the ailerons to cover and hinge. See the pictures above and below. I have added some 'Faux' scale decals from 'Andy Schafer Graphics', he does some really great stuff and the service is very good. The real aircraft did not have have these on it, but I think they set the model off very well. This will not be for the purists I know, but I like them. There was however lots to do before covering, and in a rough order this is what was done:-

1) Aileron servo and electric air-brakes fitted, with capping strips and sheeting pieces. All plugs and extension wires were secured using good quality string with a bit of 'cyano' on the knot.
2) As per the plan I intend to use cup hooks and rubber bands to secure the wing, these need fitting and reinforcing from the inside. That is why I left the bottom root sheeting till last of all.
3) In order to get the wing bands through the fuselage we need to use a long rod to catch the band and pull it though. At the 'hooking' points I fitted phenolic tubes (cardboard impregnated with epoxy) in the fuselage; through which the rod can be directed, otherwise you might just grab the wiring loom and cause a problem. These tubes also have another benefit as they will serve as compression struts to absorb any forward/back ward motion of the wing on less than perfect landings.
4) The ailerons were stiffened up using diagonal bracing (1/4" x 1/16" hard balsa) as per the picture from John of his Tern, this was needed as they felt a little flimsy. Please note this is not shown of the plan.
5) Before the lower inboard sheeting was completed do please get the wings onto the Fuselage and connect everything to make 100% sure that the electrics work.
6) Having done all the this, there was just the final sanding of the wing. Once completed I used a soft brush to ensure that the surface is dust free before covering.

Well once I cover and hinge the ailerons I can set the ATV up on the Transmitter, I plan to use about 1.5" up verses 0.5 inches down. so a a fair amount of differential. I usually use about -15% exponential to soften the ailerons, although in real terms this is not a lot. Then all that remains will be trying to paint the leading edge to mimic a ply finish, final balancing and maiden flight. I will post some pictures when it is totally completed.
download/file.php?mode=view&id=17354
All the besthttps://scalesoaring.co.uk/phpBB3/download/file.php?mode=view&id=17354
download/file.php?mode=view&id=17353
Barry

Hi Barry, you don't know me but I know John Slater and his very nice Tern. May I suggest that an aileron differential you have of 1.5 in up to 0.5 in down is rather excessive for good control. A ratio of 3 to 2 or 2 to 1 would give you better control plus a "bootful " of rudder to assist on these early vintage types. Anyway great build and I am sure will enjoy flying the Tern. Regards John.

Thanks for the advice John. I will do as you suggest.

Just to clarify....................Do you mean that I should keep the 1.5" inch up, and increase the down to 1.0 " inch ?

I am familiar with the "bootful" of rudder idea as I have several vintage gliders that need just what you say, i.e. a lot of rudder.

Although advice from some one who knows the model is always welcome, as all models do differ, many thanks.

All the best
Barry A

Barry , correct the ratio of 3 up to 2 down is a good starting point but some vintage gliders are more benign with 2 up to 1 down. Regards John.

Hi Tern watchers, (if any)

Please find pics of the finished wings re-covering.

Picture 1.
This shows the covered and hinged ailerons. Using the Oratex top and bottom as a 'living hinge'. Do remember to leave a tiny space (1/32"-1/16") between the aileron and the wing, otherwise when you add the lower bit of covering to seal the hinge the travel for 'down' aileron will be restricted by the tightness of the covering.

Picture 2.
This is the wing root, and shows the final set up with the Multiplex plug, wing retainer cup hooks and wing joiner box ends. I paint this over with poly-c (a polyuranthane varnish that has PVA in it) this gives a wipe clean surface so any muddy finger prints will not stain the wood.

Picture 3.
Shows the aileron servo push rod. I still have to glue the fairing to cover this. I do not think it is essential but, in my view it looks neater, and it 'may' lower drag !!!!??????

Picture 4.

This shows the electric air-brake with its capping piece in place. I have stained this to give a bit of contrast to the wing. The real Tern did not have air-brakes so this is not strictly accurate, however on some sites air-brakes are needed to land safely in a small area..

I will let the wings 'settle' and plan to try and use paint to mimic the ply covered leading edges seen on the real Tern. I am not certain how near in terms of colour I can get. It may be possible to get away with Rustic Brown with Chrome Yellow ? I will post the final paint scheme on completion.

All the best Barry

Hi Barry,
Its all coming together quite splendid now, very pleased for you and I am sure getting it in the air is not far away.

You were talking about control throws and I would like to offer my advice, John Vella has offered some good advice, the control surfaces on the Tern are quite large and any input on these by you will have a significant effect on the attitude of the model, too much on the ailerons for instance will has you are aware I am sure could induce adverse yaw ( drag ), on my model I have about 20mm up and 10mm down and this I find I do not use to the full throw, the model fly's quite gentle and responsive, ( if you have seen the video link Robbie kindly put on my original build thread, page 5 on the forum this is borne out ) and unless a stall turn is done even full rudder is not needed.
I now use a Taranis tranny and have incorporated as much as triple rates on some of the control surfaces when setting a model up to get a nice balance of performance.
Hope you get a good day for your first flight and some nice photos to have a look at.
Kind regards

Hi John,

Thanks you for your reply, I will take your advice and do as suggested.

I will use the 'rates' option to give me 'sedate' rates for general flying and more for basic maneuvers. The 'more up than down' is a set up I am very familiar with due my other scale vintage gliders and fully intend 'locking this in' as part of the ATV set up.

In real terms we are looking at about one 1.25" inches up and 0.5" inches down for the ailerons. For elevator (assuming the COG is as per the plan) we are looking at 1.5 inches up and down. For rudder 2.5"-3.00" inches either way.

Elevator compensation with full air brake 1/16"-1/4" inch up. If needed I will set 'raised ailerons' (up by 1/2") to help with steeper landing approaches on smaller sites.

On ailerons/elevator I intend to use 15-20% exponential to further soften the feel around neutral.

I plan to try to paint the wings next week, then final balancing and flight testing, I hope before Christmas.

I will do my best to get some pictures. I have a good flying buddy who can take over testing etc, while I try to get the pictures. It has been a fun build of an interesting model, thanks to your advice and plans.

If you recall I put my first post on the 8th June 2019, so it has taken me over 6 months to get here on the last leg. But then again I am a slow builder and was trying to get as much other flying in as possible before winter set in. So not too bad

All the best

Barry

Barry, I think 6 months is a fast build . My Charlesworth K8 took over a Year and my MU 13 nearly 2 ! Regards John.

Ah OK then,

Perhaps I am not the slowest builder in the UK. When I talk to other guys they seems to be able to produce such superb models in a short time. I guess it is how much time you are able to devote to a project before 'real life kicks in and drags you away.

Also unless I am sure of the way forward I tend to mull over the next stages, who knows perhaps I over think these things. The important thing is that we all enjoy what we do.

All the best

Barry

Hi, Tern Watchers,

The wings are now painted and drying off. As you will know I did not use ply for the leading edges of the wing. This was mainly due to weight saving and cost and also I had loads of balsa sheets looking for a home. Accordingly I wanted to try and paint the leading edges to mimic ply, this 'Faux' type of painting was a popular decorating skill in recent years, involving 'rag rolling', 'dragging', 'scumble glazing', 'marbling' etc. All being techniques using paint to mimic wood, marble or other surfaces. A good buddy of mine is a sign writer who helped me with this effect. It is applied using a brush to drag across the covered surface to mimic the wood grain, and is just a mixture of Satin Varnish and paint to get the colour you want.

You can buy staining varnishes from B&Q and they do an 'Antique Pine' (Small pot £5.99) which is very like the color of varnished ply. The method is this:-

1) Mask the area for painting using good quality masking tape. This will determine the edge you get. You can use a stick on 'cheat line' in Orafilm to cover the join between the varnish and covering if the join line is too untidy

2) Ensure the surface is free from dust and other stuff found in work shops. I use a large soft brush for this. Also try and get some additional heat in the work shop to help with the flow of the varnish. Otherwise if too cold it gets 'sticky' and does not flow well across the covering. To give an idea of the colored varnish, it looked like clear honey. If you are adding colour make sure you have thoroughly mixed it all up, to prevent color changes during application.

3) Use a 1 inch soft brush to paint on the varnish with positive strokes going from root to tip. Remember each coat used will make the finish darker so you need to be bold and try to get coverage with the initial strokes, do not reload the brush for the same area. Do not paint into the masking paper too vigorously as this may cause the varnish to bleed where you do not want it.

5) When you have painted the whole area take another clean brush, moistened with white spirit and gently stroke it across the entire surface, again from root to tip. this will give the impression of wood grain. Before it gets any drier take off all the masking tape. This removal needs to be 'bold' and pulled away from the painted surface.

6) Having done this the best you can; leave it alone. do not try to 'over work' the varnish. You need to just go away and let it harden for 24-48 hours. Until it is dry and cured you will not improve the final outcome, I know this from bitter experience. Where I have tried to make things better and simply messed them up more.

A day or so later you can inspect the finish to see if you are happy with it, or if you feel it would be better/neater with a 'Cheat line'.

Well that is it for now, my own outcome as you can see on the picture was OK, not perfect by any means.

No doubt loads of people will point this out on the hill. However, as a builder of many vintage sailplanes I do have the perfect answer to this. It is

"When you do yours I am certain it will be perfect, mine was the best I could do at the time." (Tee, Hee )

Just the balancing and the maiden flight now to do now.

All the best

Barry

Lovely covering

Good idea, I am certain then that some one would say........ " Marble ?? That's too heavy"

ATB Barry

Hi Tern Watchers

Belated New years Eve wishes to all. It has been a busy time over the holiday period. With lots to do and the odd health issue. Also I appear to have been the victim of an on line 'trick/scam'. I ordered and paid for a model that was never sent, the guy that did it vanished off the 'Messenger' page' where we 'spoke', and is not responding to phone calls.

So if some one offers a Flair Sunrise gilder on line be very cautious. I suppose I was a bit naive and lost out to the tune of £100.00. Still we live and learn. I am not mentioning the guys name as I understand this is not allowed. It is a shame because he seemed like a nice chap. I am more disappointed than annoyed.

Moving on to more pleasant things, my Fair K8 and Chris Williams 1/4 scale T21 have both been flown and went really well. Now back to the John Slater Tern. The final rigging has been done and the ballast weight added to get to the specified COG. Like most vintage gliders a fair bit of lead was needed to do this, 9.00 ounces to be exact, as you may recall the under sheeting at the front was not finished to allow me to do this. So in this gap went the lead, or least 7.00 ounces of it. Two ounces were left as 'trimming weight'' to be added at the front of the cockpit so that after the test flight and dive test I could go either way with the COG depending on the out come of the test.

If you plan to build this model please make sure you keep the back end as light as possible, the all up weight has come out at 12 lb 6 oz, I don't think that is too bad (?). But with out care during the build it could have easily made 13-14 lbs. The areas to work on here are obviously all the bits at the back (rudder, elevator, fin), however the selection of material remains important, for example 0.4 mm/0.6 mm ply were used at the back and 0.8 mm was used at the front end for sheeting the fuselage. Ply was not used on the wing sheeting, I went for balsa painted to look like ply. The front wing joiner is 10 mm steel and the rear 8 mm. The nuts and bolts holding the wing joiner boxes in the fuselage were replaced with cover pieces of 2 mm ply. This saved precious weight over all. It is never one thing that saves the weight but little bits all the way through the build that do it.

The final sheeting was then added and stained to match the rest of it. I enclose a picture of this. So all that remain now is the test flight, I will keep you posted on the outcome.
All the best Barry

Thus is a very informative build log, thanks John. I see you gave the Tern decal on the side, any chance of sharing it so it can be added to the web page?

Hi Vince,

It is Barry Apostolou here, I am not John Slater, I am simply building his plan of the Tern, and trying to do the build log as best I can.

I will see if I can find the Tern logo and put it on line for you. It was one I lifted from the internet and used decal paper to print it off and get a water slide decal.

All the best

Barry

Hi Vince,

I think I have managed to find those decals and attach the file below. The decal paper can be accessed on line. If you use an inkjet printer you have to spray the decals with a clear lacquer to water proof the inks. A laser jet printer does not need this. Then you can just float off the decals in warm water and apply them. Finally the decals are sprayed over with a clear lacquer to 'lock them in'. With the lacquer/Varnish it is best to use Matt or Satin, as gloss makes the decals too shiny, and they show the edges.

All the best

Barry

Very nice Barry, thanks

Hi All,
On my original I used ` Letter Stencils ' and sprayed a clear varnish over to seal.

John

Well guys, they do say that one good 'Tern' deserves another. Before we go any further I must apologize for the photos, clearly photography is not my strong point. Today (Brexit Friday) I flew the John Slater Tern for the first time. My flying buddy and mentor Jim Addison (wearing the blue Ozee suit) came with me to test and launch the model. We arrived at our local south westerly slope (62 miles away) to find the hill with fog covering most of it. Still, being brave (not) we rigged the model at the edge of the hill out of the wind. Jim kindly did not bring his model along so as to focus on the testing of mine. We trudged out the 100 meters or so to the launch point with high hopes. OK, first things first, the controls were checked once again, and Jim verified that all was going in the correct direction with the appropriate amount of throw. These were the throws that John S. told me to use in previous replies in this build log.

We judged that the visibility was not great so we would need to keep low and relatively near for fear of losing sight of the model in the mist. Lets go for it said Jim, OK lets said I! As a result of an overweight 'LET Minimoa' I tried to throw several years ago my shoulder is not up to launching. The idea was that Jim would launch the Tern and I would fly it out to height. Then I'd give the box to Jim and man the camera (my mobile phone) while he put the model through it paces (and I tried to take pictures). So with a final check of everything and the Volt-spy showing a very healthy battery Jim stepped forward and pushed the model out into the steady wind. I was poised (like an uncoiled spring !?) ready on the box waiting for anything that may need emergency action.

Well, no problem at all, with a dab of 'down' the Tern picked up a little speed and moved smoothly into the lift, no drama, no panic and looking all the world like a well sorted model. I did a few beats, feeling very pleased with how it felt, a little fast, but given the wind strength really good. Like a lot of vintage models it does need a good rudder hand to make the turns balanced and smooth. I un-clipped the TX and passed the box to Jim, who proceeded to test the model re-COG (dive test), control harmony, control rates etc. It looked great even in bad visibility. He looped the Tern and did some elegant chandelles, great stuff. I asked for a few fly pasts to get some pictures. (Did I mention that I am not a good photographer?) Finally it was time to land, this was where I could get a good close up (I did not).

Jim 'finessed' the model round the circuit and brought it in to a well judged landing, making sure he kept the speed up on the 'base to final' leg. What the verdict then ? Well it needed to be a little bit more positive on the air-brake said Jim. Hmm ?. I used the 255 mm electric air brakes for models up to four meters, clearly the Tern needed more. If you plan to build one I would say the 300/350 mm would be better. It was agreed that we could try raising the ailerons a little for landing. Using the 'BYFLY' setting on the TX about a 1/2 inch of raised ailerons were mixed with the air-brake.

Back on the box and Jim launched again; it flew out as before, and this time the mist was clearing so I was able to fly a little further and higher. I handed the TX to Jim who now proceed to test the new air brake set up. After doing a very nicely controlled landing he pronounced the model better, but regretted that my air-brakes were not more effective on their own. Still it is what it is ! I then was able to do three or four further flights including landings secure in the knowledge that we had ironed out the initial kinks in the handling. My first landing was a little fast as I did not want to slow it down too much, but after adding the raised ailerons on my fourth flight I was able to do a landing that I was happy with. Between us we flew another 6 flights, with Jim enjoying a lot of the flying. This was the least I could do as he gave up his flying day to help me with mine. The final verdict was that it is a great model and has given Jim more incentive to build his own. The short kit and plan are already purchased. He now 'just' has to finish a Proctor Kit, Curtis Jenny, built to a standard you would not believe.

The final reckoning being the timer on my TX showing that we had over 1 hour and 27 minutes recorded. (Take off seven minutes for launching etc), giving I hour 20 minutes of air time. Not too bad for a first session. We then celebrated the 'John Slater' Airspeed Tern with a pub lunch, remembering Neville Shute Norway, the owner of 'Airspeed' and designer of a sailplane that John's plan brought so vividly to life. Build one !

All the best

Barry Apostolou

Congratulations! Looks fantastic and well done for having the bottle to fly in that soup.

Thanks Nigel, yup it was a bit murky, but as long as you stayed low and close it was OK, later it cleared up a fair bit.

Shame the weather didn't tern out better.

It looks like a lovely practical model that should be fun to fly. Good job with the build!

Excellent work and the weather helped create some brilliant photos. Hope you have many hours of fun and satisfaction. Thanks for your build thread

Thanks Guys for your kind comments,

Will now take a little rest from building!. In the mean time try and get out for further winter flying.

Barry

Well done Barry, very brave in the conditions you had. Very much enjoyed your build thread, and so pleased it flew as expected, you will soon get the hang of it and as you have found out without brakes landings can be very challenging.
On my first Tern ( without brakes ) I did many landing circuits before it was landed.
Kind regards
John

Thank you John,

For all the help and advice during this build. More especially for producing the plan and helping me when I got stuck. It really was such a bonus having the designer reply to my questions. Yup I fully expect to get much more air time with the Tern. As you say it needs attention to get it to fly and land well, However even after a few flights I was very much at home with it. I have built a 1/4 scale John Slowcombe T46 Slingsby Swallow and the Tern is a little like this in its flight characteristics and shape.

Thank you John, All the best, keep stirring those sticks

Barry A

Barry Apostolou <apostoloubarry@gmail.com>


Hi John,

You will recall that I recently built your plan for the Airspeed Tern. At the same time my buddy also got the same kit of parts and has now built his and flown it. I just wanted to pass on to you some of his comments and thanks for producing this splendid plan. His name is Jim Addison who has been a life long fan of Neville Shute Norway, and consequently the Tern got his interest as a product of the Airspeed company owned by Shute and Tiltman. As an experienced builder of scale vintage sailplanes Jim interpreted the plan based on years of building and flying.

His build involved building the fuselage, not on a jig, but sides first on the board. He also worked hard with weight saving resulting a model that was 16 oz lighter than mine. Any changes he made were purely as a result of preference. Jim redesigned the wing joining mechanism, to have a steel strip for the main joiner and locator dowels for maintaining the wing incidence. All hinging was closed and shrouded to give the best aerodynamic performance.

The finish of the model was achieved by staining the wood and covering with natural Solartex, this was then further stained on top and sealed with Flair Spectrum fuel proofer. Landing is facilitated by air-brakes and raised ailerons. I will try and include some photos taken of the model for your interest. Health permitting, I am certain we will get lots of flying out of the Tern.

In conclusion many thanks from Jim and I for producing such a splendid plan of an evocative part of aviation history.

All the Best
Barry Apostolou, Jim Addison

Great to have some feedback with suggestions for changes. I will wait to see if John sees this post. I very much enjoyed doing the detective work for the documentation on this glider

Cheers Vince,
hopefully it gives you guys a 'kick' to know that your efforts are appreciated, and that your designs are out there and flying.

All the best
Barry

Morning Barry, Jim,

Thanks for your recent post, it's very reassuring to see another `Tern ', and indeed to hear of any improvements, flight has been one of continuous development and I welcome what Jim has done.
I'm sure the forum would be interested of Jim's construction etc.
I do visit the forum on a regular basis but I have not been very active as regards flying, my wife has a serious brain condition and so she has to have my full attention.
Look forward to a few more photos.
Kind regards and happy landings
John

So sorry to hear that re-your wife John, as we get older these things can come along. I hope and pray that she will be well soon.

Jim and I are still getting out and doing some 'stick twiddling'. Each of us has had health challenges this year but are persevering to keep active and current with our models.

I hope you all remain well. All the best
Barry

Hi John and Vince,

Had a chat with Jim and unfortunately he did not record the build log of his Tern as he felt that at the time it may have simply duplicated mine. However if there is another modeller building the Tern then both Jim and I will be happy to answer any questions that may arise. One tip though; for matrimonial harmony Jim has recommended that when staining the model, do not wear a white shirt.

Seriously though, if anyone has any questions Jim would be happy to try and help. As the designer your own input is what may well be needed as a priority.

All the best
Barry/Jim

Well one tern deserves another and I am due to start a build anytime soon the courier arrives with my part kit.

Thanks to Barry for help on a few issues already. MIne will follow Barrys adaptions with airbrakes and Jims alternative wing joiner arrangement,