Jart L Carbon Lost Foam Version

[Peter Garsden]

Well these bits arrived the other day from the very nice and efficient chaps at Foam Wings. I rang Barry because

1. He made the wings for my Tornado Lost Foam (see my blog) and the were superbly made and finished with reinforced kevlar trailing edges.
2. I have wanted to build a Jart now for about 2 years ever since I saw Andy Ellison and Simon Cocker flying theirs up at the Orme.
3. I have read that they fly so fast that they are very difficult to land without flaps, whereas the commercially available 70 inch wing Jart has flaps. It is also a mouldie as are most of the Jarts, and I have already made 2 lost foam fuselages.
4. I really like the idea of a carbon finish after admiring Julian's Pace Carbon models. I have also read Sensible Nick from Sweden's blog. He built a 2 metre fuselage and took years over it, and I am neither that patient, nor so dedicated to carbon.

[Matt Jones]

Nice.

[Peter Garsden]

Barry from Edinburgh was very helpful. I had tried and failed to get the free downloaded plans blown up to a 70 inch wing and 50 inch fuselage.

Barry told me that he had made a fuselage and wings for Andy Ellison and had it on his computer. He could easily blow up the design to 70 inch.

We then discussed whether he could bag the wings in carbon fibre. He explained that although it was possible the price would be prohibitive. It was easier to lay on carbon fibre under the veneer and reinforce the trailing edge with kevlar.

We then discussed how to attach the wings to the fuselage. The Soaring USA model used the carbon wing joining bar out of an RCRCM Vector.

I decided to use the same wing joining system as the Voltij whcih it vaguely resembles in shape, except updated using 10mm carbon rod and matching tube x 2 so that is what Barry agreed. Should be strong enough.

This build should be fun. Have started by gluing the leading edges to the wings and tailplanes with Aliphatic Resin.

[Martyn K]

Looking forward to this one..

[Mark Kettle 1]

Nice Peter, I un-roll and look at my Jart plan every now and then. Looking forward to your build and I've subscribed. I'll build one -one day- when I've time.

Edited By Mark Kettle 1 on 26/10/2015 16:04:36

[Peter Garsden]

Just some links - Foam Wings in Edinburgh are - **LINK**

I said above that I couldn't get my plans blown up, well I managed to find a very helpful chap who turned round my order the same day and produced the exact size I wanted - blow up to 70 inch - Derick Scott from Model Plans - his website which is principally for swapping and collecting a huge library of plans is **LINK**

I got my carbon tubing and 10mm rod from Easy Composites **LINK** - Barry said they supply Foam Wings and they come highly recommended.

I have noticed some lightweight carbon cloth on the Easy Composites site also which I am going to use for my final layer. It isn't cheap! - **LINK**

Can't work out how to attach the tailplane and do the fin at the moment but will do some head scratching and work it out.

[Andy Green]

I've still to fly mine - its already. Barry also did my wings. Nice job too.

Andy

[Peter Garsden]

Posted by Andy Green on 26/10/2015 16:40:45:

I've still to fly mine - its already. Barry also did my wings. Nice job too.

Ah yes Andy, I was looking at your blog yesterday.

I can't work out how to do my fin as it will be lost foam fuselage ie whether to make it out of balsa or mould it. I think I will go for the latter, by cutting up a piece of foam and sanding it to shape. I say that because I am going for a carbon finish, and if I use balsa underneath it might become too heavy. Not sure what to do. I can see you just cut a hole for the tailplane then glued it in.

Shame it has not flown - I just couldn't do that. They are not for the faint hearted.

I am also thinking of tying the tailplane halves together with a carbon rod for strength - rather than just epoxy. If so how to create a hole in the foam. Andy Meade said use a sharpened copper tube, but if so does one just insert it in the chuck of the drill and switch on?

[Andy Meade]

Not in a drill, no. I just push it through whilst rotating by hand. If you want strength though, just putting a carbon rod in the middle of a bed of foam isn't the best idea. You could use a little out-rigger sort of half-rib sunk into the foam at the rod's end, or box it with balsa to tie it into the skins.

[Chris Barlow]

Yes the carbon spar will be strong but will just crush into the foam.

A square hole in the foam lined with balsa or lite ply epoxied in to the foam and top & bottom skins with the spar epoxied into it will be much stronger.

[Peter Garsden]

Ahhh gotcha chaps - good one - excellent advice - I am going to do this at the end of the wing roots to provide reinforcement ie a half rib of ply for strength. Had not thought of doing the same for the tailplane.

Also going to dremmel out the ends of the wings and put some microballoons and epoxy mix to give strength.

Am also going to do the same to the ends of the ailerons and flaps again for extra strength.

[Peter Garsden]

Well I have sanded back the leading edges of the tailplane using the masking tape method to protect the veneer which I picked up with the JP mass build.

When I think about it the tailplane will be stiffended with balsa spars where the elevator joins so didn't really need a mid carbon spar in 4mm tube but have started so I will finish. Found a brass tube and sharpened it and it works a treat. Tape the carbon tube to line up the cut - found that online - brilliant. Just the other half to do now and then a false balsa sub rib to be inset.

Might still do a hollow fin covered with 1/16" balsa as the plan shows a proper aerofoil and it will be easier than making a lost foam thing

[Peter Garsden]

Here is a picture of the underneath of the wing showing how I am trying to work out how large the flaps are etc.

1. Should the flap go right up to the wing root or stop short - the M70 has them stopping short but all my F3F planes take them to the root, so how to configure it?
2. The M70 uses 1/3 Flap 2/3rds Aileron which is how I was going to do it, but Barry drew a much shorter flap on the wing when planning the position of the tubes, servo wire hole etc.
3. I have measured the depth of the wing for a 2/3rd aileron width and it is about 16mm so should have more than enough for a 10mm thin wing servo. Am thinking of using a KST instead of my usual Hitec MG125 as they are not very reliable in my experience, but do come with a servo mount which makes life easier.
4. Will probably use a Hitec MS85g as usual for the flaps as there is more than enough depth.
5. The wing tubes come out 200mm so I have start beyond them.

Edited By Peter Garsden on 30/10/2015 09:13:36

[Peter Garsden]

I have now cut the elevators off. I used a tip I picked up on here of securing down the metal ruler on the tailplane with double sided tape to stop it slipping. It worked a treat. I will line them with 3/16th leading and trailing edges so have cut off a block of foam

[Peter Garsden]

Once the elevator came off it broke in the middle because there wasn't enough glue surface. I figured I will have to attach the horn to something solid, so I used my hot wire pen to heat up and gouge out some blue foam so I could inlay some scrap trailing edge balsa. Worked I treat. Now it is epoxied in and the elevator much stronger.

[Peter Garsden]

More progress making a template for the side of the fuselage as the profile cut out by Barry is slightly different to the plan, whilst the spars attached to the tailplane and elevator with Aliphatic Resin were drying.

After umming and aahing I have finally decided:-

1. I will make a lost foam fin not a balsa one because

   1. I have decided to use a carbon rod to attach the elevator or maybe a balsa rod and it needs to pass through the fin to the horn behind.

2. I am going to cover the fuselage in Oracover pretend carbon as it is a lot cheaper than real 90gram carbon at £60 per metre - though the Oracover is £30 per 2 metre roll!

3. I am going to use the conventional method of 160 gram fibreglass followed by 2 layers of 80 gram fibreglass finished with a sloppy resin and microballoons mix. It will be a lot easier than carbon and will match the wings a lot better if I used Oracover.

​

[Peter Garsden]

Next I decided to make some 1/8" ply sub ribs for the root of the wing in order to strengthen the leverage of the 10mm carbon tubes and stop them crushing the foam. I used a method I picked up making the Voltij - I made a pencil rubbing of the root of the wing then carbon papered it onto the ply - I drilled out 8mm holes then filed them witih the permagrit file to the right size - perfect.

I hot wire penned some 1/8" recesses in the foam for the ply, and at the ends an epoxy and microballons mixture which I will later sand flush.

[Peter Garsden]

I used GorillaGlue to fill in any gaps in the blue foam and attach the ply to it. I made up a mix of epoxy and microballons and ladled it into the holes which needed filling and left to dry overnight. I did the same at the wing tips - dug out some blue foam and filled it with epoxy and microballoons. Will strengthen it no end.

[Peter Garsden]

I used GorillaGlue to fill in any gaps in the blue foam and attach the ply to it. I made up a mix of epoxy and microballons and ladled it into the holes which needed filling and left to dry overnight. I did the same at the wing tips - dug out some blue foam and filled it with epoxy and microballoons. Will strengthen it no end.

[Peter Garsden]

As I have been busy being Signor O'Hara in the AWMTC production of Sister Act this week - still time to come along either 2.30pm and 7.30pm today - there are tickets online - www.awmtc.co.uk I have not done much Jartiness

I have repaired my D40 which seemed to suddenly dive into the earth last week out of control? Spin and stall?? Not sure Anyone else had a similar problem with a D40?

Have shapened up the fuselage which looks very Jarty and smooth. Also done the fin. Will have to line up both then wrap in parcel tape ready for 1st layer of glass

Edited By Peter Garsden on 14/11/2015 13:08:20

[Mark Kettle 1]

Yes Peter, I like your rendition of ' Signor O'Hara' - especially the Irish accent , it is a excellent production get yourselves over to the theatre.

Practice

[Peter Garsden]

Have now cut off the flaps and ailerons and am preparing them by

1. Hot pen cutting indents in both the moving parts and the wing to take the wipers and to help the silicone hinges.
2. I think it will be easier to make wipers as there is a layer of carbon fibre under the veneer to give it strength.
3. I am wondering therefore if I need to coat the foam with a layer of epoxy and microballoons.
4. I will definitely fill the ends with epoxy and microballoons to give strength.

Edited By Peter Garsden on 21/11/2015 14:20:31

[Peter Garsden]

It has taken some time to cut out the blue foam around the flaps and ailerons. I have shown my hot wire pen, which I just shape into whatever profile I need. Very helpful.

For the aileron and flap I use a rounded end to make a cup shaped indent. I also used it to cut out a slot to take a piece of trailing edge balsa to hold the horns I will use. I am undecided between thin fibreglass circuit board or stainless steel rods onto which to attach some ball joint horns.

For the wing spars I used an angled piece of nichrome wire to scoop out a triangular piece of foam to make a channel for the wiper to slip into.

[Peter Garsden]

So next are the silicone hinges, which are squeezed onto the gap made by the masking tape on the reverse side using a syringe.

In order make the silicone spread over the join, one has to file down with a small round file the edge of the syringe point.

The flap is bottom hinged and the aileron top hinged.

One first of all puts on a base layer which you then spread onto the join using a wet finger then followed with a further bead of silicone to build up the joint.

[Andy Meade]

Still watching Pete, nice build