John Slater Airspeed Tern

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Barry Apostolou
Posts: 35
Joined: 07 Jun 2019, 15:36
Location: Surrey

John Slater Airspeed Tern

Post by Barry Apostolou » 08 Jun 2019, 16:19

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

John Slater
Posts: 52
Joined: 24 Mar 2015, 07:29
Location: Dudley , West Midlands

Re: John Slater Airspeed Tern

Post by John Slater » 18 Jun 2019, 07:54

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

Barry Apostolou
Posts: 35
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou » 25 Jun 2019, 15:20

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

John Slater
Posts: 52
Joined: 24 Mar 2015, 07:29
Location: Dudley , West Midlands

Re: John Slater Airspeed Tern

Post by John Slater » 27 Jun 2019, 08:51

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.
Tern assembly 042.jpg
I have included photos I do have,
Kind Regards

John
Attachments
Tern 041.jpg
Tern 045.jpg
Tern 046.jpg
Tern 047.jpg
Tern 052.jpg
Tern 048.jpg
Tern assembly 049.jpg
Tern 050.jpg

Barry Apostolou
Posts: 35
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou » 06 Jul 2019, 12:07

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

John Slater
Posts: 52
Joined: 24 Mar 2015, 07:29
Location: Dudley , West Midlands

Re: John Slater Airspeed Tern

Post by John Slater » 08 Jul 2019, 20:21

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

Barry Apostolou
Posts: 35
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou » 09 Jul 2019, 22:33

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

John Slater
Posts: 52
Joined: 24 Mar 2015, 07:29
Location: Dudley , West Midlands

Re: John Slater Airspeed Tern

Post by John Slater » 10 Jul 2019, 20:11

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

Barry Apostolou
Posts: 35
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou » 11 Jul 2019, 00:16

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

John Slater
Posts: 52
Joined: 24 Mar 2015, 07:29
Location: Dudley , West Midlands

Re: John Slater Airspeed Tern

Post by John Slater » 12 Jul 2019, 09:24

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

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