Discussion Slingsby T12 Gull Build

[Fred China]

I am scratch building from my own plans drawn up from Martin Simons book "Slingsby Sailplanes" a T12 Gull. at 3.5 scale.
This is a new adventure for me so please be patient as I am a computer dummy and a worse photographer. I am also not a scale purist or great on research but try to follow the drawings and photos as closely as I can. So if I place the laughter shaft or giggling pin in not exactly the right place please don't be critical.
I start with the horizontal tail because once I have it built I feel committed. I cover all my gliders with plywood and follow some of the ways of doing it that have been published, however I do have my own methods.
I use plywood for all the TE's and use a piece of 3/16 by 1/16 spruce or fir as a stiffener glued on with ca. If the TE has biscuits or gussets these are included in the original cutout. The top TE is cut about 1/16" wider so that there is an overlap at the very TE. This gives you a channel to apply the CA. The overlap is then taken off with a small block plane. The block plane is an indispensible tool for covering with plywood. I use contact cement on most of the ply application but not on the TE because when the Solartex is applied with an iron, the heat will melt the contact cement and you get a wavy TE. I have also used 1/32" music wire as a stiffener with good results.
All the the wood for building is cut out on regular woodworking tools such as band saw, table saw, jig saw or by hand and I have two home made disc sanders.
As you can see the fuselage is layed up on one side on a keel. The cross braces when added make a very stiff fuselage which helps prevent distortion and really helps when the plywood is applied.
All the guts (radio, servos, etc.) will be installed before any plywood goes on.

Fred


I missed a bunch of photos (to follow) I hope

[Fred China]

Sorry folks I can't figure how to get back into this thread with pictures.

Fred


Thanks to Dave Smith , I found a way

[dgliderguy]

Very nice, Fred! I'll be following, with a notepad at the ready.

Good choice, btw. I've always liked the clean lines of the Gull.

Don.

P.S. Welcome to RC Groups!

[SZD16]

Welcome! Glad to see you figured out the picture thing....pictures are a real good thing!

[cooper998]

Fred,
So glad you are posting, I watched your work take flight in pictures and videos here and look forward to learning some of your techniques

Tony

[SteveR]

Fred, thrilled you are posting, greatly appreciate all your tips and insights.

Steve

[davidjensen]

Welcome Fred. I can't wait to see more of your building and flying.

[Fred China]

All the working parts and radio equipment are installed in the fuselage. Now it needs to be cleaned up. The former edges have to be checked for allignment and possibly some shimming. I don't have CAD and my drafting is not perfect. Then the balsa former doublers and any fill in between some of the formers has to be done so that when the plywood is applied every edge will have something to glue to.
I am sure most of you have seen and done most of this.

Fred

I put descriptions under each photo but it only came out on the last photo.... can't figure it out... sorry

[Fred China]

All the working parts and radio equipment are installed in the fuselage. Now it needs to be cleaned up. The former edges have to be checked for allignment and possibly some shimming. I don't have CAD and my drafting is not perfect. Then the balsa former doublers and any fill in between some of the formers has to be done so that when the plywood is applied every edge will have something to glue to.
I am sure most of you have seen and done most of this.

Fred

I have put descriptions under each photo but it only came out on the last photo. Can't figure it out, sorry.

[Fred China]

Here are some of the photo descriptions

1 I build a battery box for all my gliders.

2 Not looking forward to covering the nose block with plywood. There is 28 oz. of lead inside.

3 There will be a removable cover at bottom front of fin.

4 Simple tow release

5 Ball joint for elevator is very easy to connect.

6 Guided push rod for elevator.

7 1/32" ply floor board. The opening for the servo tray will also be covered

Fred

[SteveR]

Fred, great photos and description. Questions: on your tow release, is the ring solid and you insert the tow loop from the side opposite the release pin? Also, have you ever sheeted a fuse with narrow balsa planking, sanded it smooth and then applied 1/64 ply over it for a smoother overall appearance?

Regards,

Steve

[Fred China]

Steve

The loop is a hole drilled in a KS 1/2" x 1/16" brass plate then rounded off on the outside diameter. The plate extends upward and is bolted to the pine keel which extends about 3/4" forward of the front former. The extension is plywood backed so the plate and bolts won't pull out of the pine. The tow loop is inserted as you say.
I have never done any strip planking and then covered with plywood. That seems to me to be three times the work. The full size gliders were sheeted with plywood with no backing and they had problems with compound curves just as we do. So I don't worry about it. It's really quite surprising how the panels fair in, regardless. I do use sheeting between some formers and then cover with plywood. On the Gull I will fill in with 3/16" sheet between the two front formers aft of the nose block, but mostly to strengthen the nose area. Also some filling around the wing root and TE.
The large bolt you see will be used for extra ballast if needed.
I use 1/32" ply for the fuselage and 1/64" for all flying surfaces. I find that the 1/64" ply should have support at least every 1 1/2". On the fin for example I will double up on the ribs you see.

Fred

[SteveR]

Thanks Fred. When you do use sheeting between formers. do you glue in the sheeting within the two formers leaving it flush to the former edge (and exposing the edge), with the 1/32 ply running directly over the former edge and sheeting?

Steve

[Fred China]

That's what I do.
When I start sheeting I will take more photos and describe how I apply the panels.
All the formers that don't have the sheeting between them are doubled on the outside edge with 1/8" or 3/16" scrap balsa. Also the keel is usually doubled on each side so there is more area to glue to.
However, I have had no problem contact gluing plywood to a 1/8" outside edge. You have to be careful when you apply the plywood to the balsa facing that you don't press too hard as the opposing panel edge is glued to the plywood former. You can crush the balsa facing slightly and you then have an uneven match between panels.

Fred

When I have the facing and fill in done I will take a few more photos. This is the last thing I do before covering with ply. If you do the facing early you can bruise it as you go about building other things and degrade the fit.

[Fred China]

I am now ready to start covering with plywood. I think that all of the fill in and doubling of the formers is done . There may be a minor amount more to do but I will find that out as I go along.
The plywood will go on from the tail forward. I buy file folders from Staples by the 100 for under $10.00. These are used to size each panel which is traced onto the ply. This is far easier and cheaper than trying to size a panel using plywood only. Before applying the ply panels they will be bent almost to shape with a heat gun. I have found that under bending them is better than over bending. Over bending they tend to pull away in the middle,don't ask me why.
Once I've started I will include more photos.

Fred