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Re: John Slater Airspeed Tern

Posted: 31 Oct 2019, 20:17
by Adam C
Excellent news. Differential ailerons have tamed the kirbykite no end and made it positively pleasurable to fly.

Time to get the komar flying...

Re: John Slater Airspeed Tern

Posted: 12 Nov 2019, 14:39
by Barry Apostolou
Covered wing of the Tern, with 'Faux' scale decals added

Re: John Slater Airspeed Tern

Posted: 12 Nov 2019, 15:08
by Barry Apostolou
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.
All the best

Re: John Slater Airspeed Tern

Posted: 12 Nov 2019, 17:21
by John Vella
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.

Re: John Slater Airspeed Tern

Posted: 12 Nov 2019, 17:52
by Barry Apostolou
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

Re: John Slater Airspeed Tern

Posted: 12 Nov 2019, 18:29
by John Vella
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.

Re: John Slater Airspeed Tern

Posted: 15 Nov 2019, 11:44
by Barry Apostolou
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

Re: John Slater Airspeed Tern

Posted: 20 Nov 2019, 09:42
by John Slater
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

Re: John Slater Airspeed Tern

Posted: 20 Nov 2019, 14:21
by Barry Apostolou
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


Re: John Slater Airspeed Tern

Posted: 20 Nov 2019, 16:27
by John Vella
Barry, I think 6 months is a fast build . My Charlesworth K8 took over a Year and my MU 13 nearly 2 ! Regards John.