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John Slater Airspeed Tern

Let us all watch your new project progress.
Barry Apostolou
Posts: 47
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post 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
John Vella
Posts: 230
Joined: 20 Mar 2017, 22:09
Location: UK

Re: John Slater Airspeed Tern

Post 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.
Barry Apostolou
Posts: 47
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post 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
Attachments
IMG_2998 finished 1.JPG
IMG_2999 finished 2.JPG
IMG_3001finished 3.JPG
IMG_3002 finshed 4.JPG
john slater
Posts: 43
Joined: 24 Mar 2015, 07:29
Location: Dudley , West Midlands

Re: John Slater Airspeed Tern

Post 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
Barry Apostolou
Posts: 47
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post 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

Barry
John Vella
Posts: 230
Joined: 20 Mar 2017, 22:09
Location: UK

Re: John Slater Airspeed Tern

Post 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.
Barry Apostolou
Posts: 47
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou »

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 :P
Barry Apostolou
Posts: 47
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou »

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
Attachments
IMG_303 Stained wing.JPG
Last edited by Barry Apostolou on 30 Jan 2020, 09:43, edited 7 times in total.
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VinceC
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Re: John Slater Airspeed Tern

Post by VinceC »

Lovely covering
Barry Apostolou
Posts: 47
Joined: 07 Jun 2019, 15:36
Location: Surrey

Re: John Slater Airspeed Tern

Post by Barry Apostolou »

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

ATB Barry
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