John Slater Airspeed Tern

Let us all watch your new project progress.
John Slater
Posts: 51
Joined: 24 Mar 2015, 07:29
Location: Dudley , West Midlands

Re: John Slater Airspeed Tern

Post by John Slater » 15 Aug 2019, 08:16

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

Barry Apostolou
Posts: 29
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou » 15 Aug 2019, 15:04

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

Barry Apostolou
Posts: 29
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou » 24 Aug 2019, 17:25

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
Attachments
IMG_2611.JPG
IMG_2612.JPG
IMG_2613.JPG

John Slater
Posts: 51
Joined: 24 Mar 2015, 07:29
Location: Dudley , West Midlands

Re: John Slater Airspeed Tern

Post by John Slater » 27 Aug 2019, 08:21

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
Image
Attachments
Airspeed Tern - 2017-03-02 at 11-36-35 copy.jpg

Barry Apostolou
Posts: 29
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou » 27 Aug 2019, 20:40

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

John Slater
Posts: 51
Joined: 24 Mar 2015, 07:29
Location: Dudley , West Midlands

Re: John Slater Airspeed Tern

Post by John Slater » 29 Aug 2019, 08:07

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

Barry Apostolou
Posts: 29
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou » 29 Aug 2019, 16:28

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

John Slater
Posts: 51
Joined: 24 Mar 2015, 07:29
Location: Dudley , West Midlands

Re: John Slater Airspeed Tern

Post by John Slater » 29 Aug 2019, 19:09

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

Barry Apostolou
Posts: 29
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou » 29 Aug 2019, 20:09

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

Barry

Barry Apostolou
Posts: 29
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou » 06 Sep 2019, 16:06

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

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