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FliteTest Legacy

Using Hobbycraft foam board and Easycoat covering

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Dad_flyer15/07/2019 20:34:53
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125 forum posts
148 photos

I have had a lot of use out of the FliteTest Simple Storch, built from the kit. It was the biggest model they did last year when I needed it. However as a representation of a Storch it has enormous and vulnerable tail surfaces. With many an unhappy landings the elevators don't really act as one.

The Legacy has since come out, very loosely based on the Telemaster apparently. It is basically the same size as the Storch, but It has foam doubled up throughout the fuselage and a much more sturdy tail, with a ply elevator joiner.

FliteTest Legacy details.

The weight is also more, which with the lift that the Storch wing has will be no bad thing.

The first decision was not to use the FliteTest foam. Partly because I would have to get it by post, but also because Westfoam board from Hobbycraft seems stiffer. It is heavier, but again, that may not be bad. Buying by the four sheets it is about the same price as FliteTest. Two important issues are that it is not waterproof, and that the paper does not peel off easily to allow curving the board.

So away I went.

Dad_flyer15/07/2019 21:06:00
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125 forum posts
148 photos

Lots of A3 sheets joined together, then cut out to arrange on the board (slightly bigger board than the FliteTest board).

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and after a lot of arm ache, a pile of pieces,

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Having cut all this with a Stanley knife, it is noticeable that the board wears the blades fast. When the blade gets blunt it tears the foam rather than cutting. I think this was 5 new blades in total, but they were a cheap pack of 100. This pile took a couple of evenings.

Dad_flyer15/07/2019 21:34:22
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125 forum posts
148 photos

I found it hard to remove more than 1/4" wide strips of foam from the lower layer of paper. In this build a lot of edges are neatened up by clearing a large area of paper and folding over the cut edge of the foam.

To do large areas I scored into 1/4" sections with a sharp knife

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Then cut through the foam but not the lower paper with a round-ended table knife. I also had to sharpen this knife during the build as it stopped cutting the foam.

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Then peeled away each strip, one at a time

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and removed any remaining foam with the table knife

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All finished and ready to fold over

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That is all much more work than on the FliteTest waterproof board frown.

Dad_flyer15/07/2019 21:35:40
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125 forum posts
148 photos

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Nigel R15/07/2019 23:18:25
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2935 forum posts
470 photos

I've found a breadsaw works quite well for clearing the folded over areas.

One motor or two?

Dad_flyer16/07/2019 07:00:30
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125 forum posts
148 photos

Nigel, I was planning for doing it as a twin with counter rotating props and throttle differential to try to get better ground handling. However that would mean a power harness and I need to buy wire and connectors.

I had one motor already, so single engine for now.

A serrated bread knife sounds a good idea, I shall try it.

Dad_flyer16/07/2019 07:40:40
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125 forum posts
148 photos

Removing the top paper for curving the nose was a puzzle for a while. It is stuck on very hard. I tried cutting it off with a bread knife, but that hacked at the foam.

Then I realised I could use the other weakness of the Hobbycraft board. It is not waterproof, so gentle wetting of the paper to be removed and it peels off a treat!

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Using a lightly damp cloth to get water only where needed.

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The paper never looks wet, but after a few passes with the cloth and waiting a little, the paper peels/rubs off easily.

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Then it can be gently curved. This takes a little more easing than FliteTest board to get a smooth curve, as the foam itself is stiffer.

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There were some angles visible on the outside of the curve, but fine for a chuck-about model.

Dad_flyer16/07/2019 19:10:45
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125 forum posts
148 photos

On most FliteTest models the wings are flat underneath and the top surface is a series of straight sections and creases. A few models use the curving method for a smoother profile. I thought I would try to do that with this model. So instead of using the crease lines, I removed the inner paper from that whole section at the leading edge of the wing.

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Which gives a nice smooth top surface.

Dad_flyer16/07/2019 21:59:33
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125 forum posts
148 photos

The result on the horizontal stabilizer, which in the model is a lifting surface.

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All these FliteTest aerofoils have an undercamber section at the tip, where the bottom surface stops. I have often had the paper split at the leading edge fold at the point where the lower sheet stops. You can see I tried strengthening the leading edge with an extra piece of paper. Success here, but not on the wing.

Dad_flyer19/07/2019 21:39:39
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125 forum posts
148 photos

This model design has extra strength in various places, including the ply elevator joiner, spar strengthener and a ply mount structure for the undercarriage. The design is 2.4mm ply, with laser cut interlocking tabs. I only had 1/8", but it still squeezed in without altering any dimensions to compensate. I put some offcuts to support the corner joins. I used T nuts for M4 nylon bolts, instead of the suggested woodscrews.

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I have a rescued wire undercarriage with a plastic mounting plate to bolt on. I got a pair of used 3 1/4" wheels at the Woodspring show.

The wing is convertible for 3 channel to 5 channel control. As I only had two servos in stock, those went in the fuselage and the wing has no ailerons for now. I increased the dihedral to 1.5 times the plan. It is not huge.

With the model all completed, a cg check reveals the effect of heavier board than the plan. To hit the cg I need 200g of weight in the nose. There is a nice space below the motor for it, but I was out of lead. The cheapest and easiest way to buy "heavy stuff" seems to be bags of M6 steel nuts. 100-off is about 200g for £1 or so.

I did weigh the whole airframe and thought it OK, but now I don't remember the weight.

Flew a short maiden from hand launched to belly landing without undercarriage in quite a breeze. It is nice and stable, and penetrates well which was the hope from a heavier model. Turns well on 3-channel too. The extra weight did not make it too quick for me on the down-wind leg. After all, the design is very very light, so heavier than that is still a low wing loading.

Dad_flyer19/07/2019 21:54:52
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125 forum posts
148 photos

Now something I really should have done before building.

Even with folding paper over to finish off the cut edges of the foam board in many places on this design, it still has some bare edges. The Westfoam board is also not waterproof, and I would like to add some durability and colour. So the question is, does covering film stick and shrink before the foam in foam board melts?

I have a big roll of Easycoat, which is supposed to stick at 100-120C and shrink at 150C. This is the result of the iron set to 120C

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Not a great photo, but there is no sign of melting of the foam, and a nice close covering over the cut edge. I tried turning the iron to 140C, where there is clear shrinking of the film, and not such a neat covering job on a square flat piece, but still no melting of the foam. In the end I even applied the iron straight to the foam without a problem.

Now if I was covering the nice pile of flat pieces that I started with it would be so much easier than getting into all the corners. Or at least covering the tail before fitting the struts indecision.

Dad_flyer20/07/2019 10:21:07
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125 forum posts
148 photos

The hatch is particularly tricky for covering.

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But still, it comes out well in the end.

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Nigel R20/07/2019 13:48:40
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2935 forum posts
470 photos

Good to know the foamboard is resilient to a moderate iron.

Pictures of the finished article please!

Dad_flyer20/07/2019 15:11:32
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125 forum posts
148 photos

Some notes so I don't forget again:

Flying weight 3lb6.5 (1540g) with 3s2200.

Dry 3lb1 (1380g)

Wing 13.5 (380g) - no servos for 3ch wing

U/C 5oz (145g)

Fuse 1lb7 + 5oz nose weight (645+210g)

Power is Airtek Airmax 2830 at 1350kv with GWS 9x5 prop.

Dad_flyer20/07/2019 15:14:33
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125 forum posts
148 photos

Thanks Nigel. Covering is underway, pictures when it is done. For the scheme I have in mind I need to order some red.

Dad_flyer21/07/2019 20:47:53
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125 forum posts
148 photos

U/C has a piece of foam board as a spacer and as a squishy breakable bit for hard landings.

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A couple of card spacers to help the wing with dihedral to sit well.

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Covering is coming along, but white on white so far, so not much to see. The forecast was not too bad so I took it to the patch. It was windier than I had hoped, 10-15 rather than 10 I think. Managed a couple of short and uninformative flights.

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Rather sensitive to elevator. Those experienced who were present suggested adding both some exponential and a little more nose weight.

Edited By Dad_flyer on 21/07/2019 20:49:20

Dad_flyer01/08/2019 21:00:39
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125 forum posts
148 photos

Added a little more nose weight, now really balances at the stated CG.

Flies nicely, but was a pig to get into the air. From the ground it tried to loop left, then climb suddenly steeply into a stall, again loop left. After that hairy start settles down level. Now, some of this is probably me panicking and over controlling but someone also pointed out that the motor thrust line looked a little wrong. The motor pod is foam board with a ply firewall. On a nose over the motor has been pushed back and now has a little upthrust (and left thrust). This will have most effect on high throttle on take-off. 

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This is obviously wrong and I shall repair it, but do you expect that to contribute significantly to the behaviour I saw on take-off? Is there something else I should look for as well?

Another thing is that I swapped the prop from GWS 9x6 to GWS 9x4.7SF (I broke my last 9x6) It seems less willing to penetrate now. Could that be the SF prop?

 

Edited By Dad_flyer on 01/08/2019 21:05:38

Nigel R02/08/2019 20:56:56
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2935 forum posts
470 photos

Yes up thrust could certainly have that effect.

The slow fly prop probably isn't doing you any favours on this one, I would think.

Looks as though a little reinforcement around the firewall wouldn't go amiss either.

Looking good out on the field though!

Dad_flyer02/08/2019 21:11:48
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125 forum posts
148 photos

Thank you Nigel. I reinforced the front part of the motor pod with ply, and added some down and side thrust with washers under the mount.

Take off was better this evening, but the flight was odd, sometimes docile, sometimes very hairy. Got it down in one piece, and a more forthright member took hold of it a wiggled things, rather than just looking. The wing actually can slide about enough to change the CG relative to lift by quite a lot. There is nothing in the design on these models to locate the wing, and with the covering the board is quite slippery so friction does not work well enough.

So, I shall put on some pieces under the wing to locate in the hole in the top of the fuselage and see how we go in the morning.

I think this will be a great model to fly, but I have not been paying enough attention during the build so it is taking time to iron things out.

Edited By Dad_flyer on 02/08/2019 21:12:12

Lima Hotel Foxtrot15/08/2019 21:33:58
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345 forum posts
Posted by Dad_flyer on 16/07/2019 07:40:40:

Removing the top paper for curving the nose was a puzzle for a while. It is stuck on very hard. I tried cutting it off with a bread knife, but that hacked at the foam.

Then I realised I could use the other weakness of the Hobbycraft board. It is not waterproof, so gentle wetting of the paper to be removed and it peels off a treat!

Using a lightly damp cloth to get water only where needed.

The paper never looks wet, but after a few passes with the cloth and waiting a little, the paper peels/rubs off easily.

Then it can be gently curved. This takes a little more easing than FliteTest board to get a smooth curve, as the foam itself is stiffer.

There were some angles visible on the outside of the curve, but fine for a chuck-about model.

I've just done the Explorer with the same Hobby craft foamboard. I found that if you gently steam the paper over a boiling kettle for a few seconds the glue deactivates and the paper area you want to remove comes away very easily in one big piece. I also found that massaging the foam gradually through thumb and forefinger gave a very nice curve with no angles. Maybe because all the paper and glue had gone.

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