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GTC by Levanter

Been on my list for a while now.

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Levanter16/04/2018 15:39:28
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691 forum posts
329 photos

There are a few things that can be mentioned about the tail feathers. I like built up fins, rudders and tailplanes but I also wanted Grumpy to have a solid look. The wings are fully sheeted on the top surface and mainly sheeted on the underside so I did get to fit a few cap strips which I also like doing. Any kind of multi-coloured covering with curves is easier over a sheeted surface because all the overlaps are fully supported.

​The tail feathers were therefore built up and then sheeted. This does give a very strong structure.

Grumpy

First step is to draw the built up structure. Using a series of triangle makes the whole thing very stable. The area shaded red gives good support to the sections that will be glued. In an open structure this would give the covering something to stick to.

​The slot in F8 has been deepened to locate the base of the fin and the post at the rear of the fin extends down through the fuselage. This makes the fin self-jigging when finally assembled.

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Here the rudder has been given the same treatment and I try to get some sort of relationship with the fin. In this case it does not matter too much as it will be covered by sheeting but in an open structure it looks better. A copied section of the plan is now on the board ready to start building as soon as I have covered it with cling-film.

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The tailplane ready as well. The drawing was photocopied twice and one flipped on the centreline to give the other half. The lines showed up well enough to trace them through.


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The centre section is made with a generous allowance to again make sure the glue area has good support. If left an open structure this again provides a margin for covering.

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The centre section being glued in using chocks and wedges to squeeze the joints together.

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The rudder and fin framework is complete and the paper templates that were stuck on with Pritt Stick are release by lightly damping with water. Just enough to wet the paper but not enough to curl the balsa.

p1040649.jpg

Using the rudder as an example (the elevators get the same treatment) one side of the sheeting has been stuck on for strength and the framework is sanded to a taper before applying the opposite sheeting.

Levanter

Levanter18/04/2018 12:38:12
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691 forum posts
329 photos

If my aircraft has a clear canopy then I like the cockpit to be occupied with something. I have not built a true scale plane yet so my "pilots" have not had to stick to any convention. I have carved up and reassembled ping pong balls, re-assigned Smurf fridge magnets and here is Spain, quails eggs are popular so I could easily end up with an eggshell egg-head wiggling the sticks.

​My main beef with bought pilots is that they look so wooden - well plastic really! That straight ahead fixed gaze looks so rigid (plus if there were more goggles down pilots it would make painting a whole lot easier). If ever I get into 3D printing, pilots would be No 1 on the list along with printed fuel tanks.

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​Here is Grumpy's pilot straight from the box of potential aviators. OK some colours have to change and he may end up sporting a goatee but look, straight ahead, rigid and probably paralysed with fear from antics of the person holding the transmitter. Time for something more radical and for those of you with a sensitive disposition I suggest you look away now.

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There were no witnesses but truly it was an odd feeling taking the razor saw to this poor fellow's neck.



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Fortunately he survived surgery and recovery was quite quick with no major complications. After a short period of convalescence he should be fit for duty well before the date set for test flying.

​There is only about 3 degrees of twist but now with his shoulders straight in the cockpit he is definitely looking at something.

​Plastic but no longer wooden.

​Levanter


Tim Ballinger18/04/2018 12:54:40
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382 forum posts
161 photos

Mine is still suffering from whiplash and slumped over his instruments. Needs some micro surgery to get some glue under his bottom again as canopy is still intact around him.

Tim

Levanter18/04/2018 13:04:07
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691 forum posts
329 photos

Tim

​Beware the compensation claim. Perhaps we should have some sort of personal medical / accident insurance before we get a stiff letter from their association. email

​Your post uncomfortably reminds me of an episode relating to superglue, shorts, bottoms and a chair. That is enough information. blush

Levanter

Levanter18/04/2018 21:03:58
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691 forum posts
329 photos

It hasn't only been light hearted stuff. I have been thing hard about the ailerons and flaps combining this with my mission to try something different on every build and stretch myself a bit. In this I have surely been influenced by Danny Fenton whose work I find truly aspirational.

​I now have aircraft at roughly the same stage of build and ready for final details, covering and fitting out. Grumpy has finally caught up with Oodalally (both from the Peter Miller stable) and both share the same basic wing.

​To start with I wanted to try out Danny's shrouded hinged surfaces. To date I have done hinges with the covering as well as conventional hinges and creating the clearance by putting a V on one or both edges. Many years ago I did some shrouded rudder hinges on a model sailing yacht.

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The first stage was to cut a rebate in the trailing edge of the wing. This was done on the upper and lower surfaces for the ailerons and on the upper surface only for the flaps. Here we are looking at the aileron section of the port wing.

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​To do this and again following Danny's method I mas up a special sanding block in balsa. A strip of fairly coarse emery cloth was stuck to the block using Evostick with the width corresponding to the desired width of the recess. In this case it was 10mm. The rail is set at the same angle that occurs between the top sheeting and the trailing edge strip, in this case 94 degrees. This means that when both surfaces are sliding in contact with the wing the rebate will have reached the required depth to receive the 0.6mm ply strip. I chose the emery because it was thicker than the alternative sand paper and also I did not want it to wear out in the middle of the job. That would have made things tricky. On the first go it turned out that the rebate was slightly shallow but this was easily rectified by carefully sanding a bit off the block alongside the emery. This did the business and a few more passes allowed the ply to sit flush with the wing surface.
​Just to remind you that I don't like sanding ply it had previously finish sanded the trailing edge of the wings so they only need "polishing" before covering.

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Here the last tip section is about to be glued in. The dimples are from the clamps used while gluing the bottom strips in place. I took the swivelling feet off the clamps so the ends would bite into the balsa and not slide off the taper. You can see the end of some masking tape that was put on the bottom strip again to stop the clamps sliding.
To get even clamping pressure because 0.6mm ply is very bendy and especially so in its bendy direction. I placed a steel rule over the strip and clamped onto that.

​The finished result was a trailing edge with about 3mm of recess. After dressing the edges with a long Permagrit I estimate the recess will reduce to around 2mm to suite the radius on the leading edge of the ailerons. I know, I did say I hated sanding ply but sometimes you just have to.

Levanter

Peter Miller19/04/2018 08:05:02
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8938 forum posts
1021 photos
10 articles

I like to see people experimenting and adding their own modifications to a structure.

Levanter20/04/2018 07:38:18
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691 forum posts
329 photos

Finishing the ailerons is slightly different as it has to work partly inside the shrouds but the hinge line lies some way outside.

p1060183.jpg

The leading edges are rounded off instead of having a V shape and the hinges (Robart type) have to be deeply recessed so that the centre of the hinge pin sits on the centre of the radius. This is where the overhang of the shroud is critical. Too much and the hinged surface will have very limited movement. Too little and the effect of closing the gap and having a neat hinge line is lost.
This will have to be a little bit trial and error for the first one and the overhangs may have to be reduced bit.



p1060184.jpg

Here is a closer look at the recess. I did have to elongate the hole slightly to get the three hinges to line up exactly.


​To be honest I have some trepidation about final assembly with the covering done and the glue in place. There is not much room for mistakes.



The tailplane and fin had similar treatment but instead of using ply strips, I extended the sheet a couple of mm past the trailing edges to create the shrouds. Before gluing I sanded a 45 degree angle on the inside face taking it to quite a sharp edge. This was then hardened with cyano to give the edges some durability.

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Here you can just see the shroud made by the sheeting on the post of the fin.

​Time now to get to grips with the flaps.

Levanter


Peter Miller20/04/2018 08:32:16
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8938 forum posts
1021 photos
10 articles

I have a special method for marking the holes for hinge points.

I have three 1"nails with the heads cut off and a small washer soldered on near the point.

I drill holes in one surface where the hinges will go and insert the nails. Then I lay the wing and control surface on a flat surface and push them together.

The points of the nails mark the exact spot to drill the other part.

Levanter20/04/2018 08:38:23
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691 forum posts
329 photos

Nice one Peter.
​I will make some up and use them on the tail feathers which haven't been done yet.

​Levanter

Nigel R20/04/2018 08:51:07
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1040 forum posts
251 photos

Very neat. I like the rebating widget - must remember that one. And the wedges for lightly compressing the joints - clever.

I like sheet over framework tail feathers too, they have a habit of resisting warps quite nicely.

I guess you said a few choice words when you discovered the screwdriver stuck into your carefully built fuselage! wink

McG 696920/04/2018 08:55:21
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1987 forum posts
841 photos

Nice work over there, Lev. yes

I remember Danny's 'shrouds' on his Chippie. In fact, his build blog was the first one I followed entirely here at the forum and it convinced me to have a go with Peter's Ballerina.

Regarding your 'pin holes' for the control surfaces, here is what I used on the Bella.

2094_wing_hingenails_900.jpg

It's exactly the same principle as Peter's method and it works perfectly.

Keep up the great job. smiley

Cheers

Chris

 

Edited By McG 6969 on 20/04/2018 09:02:55

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