Hi Phil

Thanks for sharing the videos. If it's any help, I bought blue foam (for use in a boat project) by contacting Knauf directly. They put me in touch with a local dealer who supplied me with the foam. It could be worth getting in touch.

Noel
Philip Lardner wrote, On 20/06/2013 11:35:



Hi Rick,

That's an interesting report on the way the flaperon mixer works and feels at different settings - I'll keep that in mind when I come to fabricate those parts and see if it can be improved to give a more neutral feel at all flap settings. If you have any ideas please sing out and share them! From the few times I've flown in sailplanes with flaps (not all do) I don't recall any change in roll pressure on the stick at different flap settings... but then the flaps were separate control surfaces to the ailerons and not mixed like in the CD.

Amazingly enough I couldn't locate any of the ubiquitous blue foam board (polystyrene?) in any of my local builders' merchants or hardware stores and so I had to go with 100mm thick 4ft x 8ft sheets of polyurethane foam. This stuff (trade name Xtratherm in Ireland) is sold for use in insulating underneath under-floor heated concrete floors. It is very fine grained (it's not really celular) and extremely fragile - you can 'sand' it just by rubbing it with your finger! It's very east to cut with a hand saw or sharp knife and takes a really fine finish when sanded. It is, however, very fragile and needs to be stabilised with a coat of varnish to toughen it up.

My first attempt to skin the beautifully sanded foam plug with plaster (I used a product called Herculite - it's like dental stone used by dentists for moulding your false gnashers) was a disaster. It went on ok (I painted on a layer of thinned out plaster with a paint brush) but when I tried to sand down the surface, the plaster came away from the foam, taking chunks of foam with it! This resulted in a lot of back-filling (with a paste of polyurethane varnish mixed with dry plaster - which sticks nicely) and a lot of sanding! Anyway... trauma over - lesson learned - I'll stabilise the surface of the next foam plug with just a couple of coats of varnish instead (this works well... as I found out too late!)

I am having difficulty finding a supplier of heat-shrink plastic here in Ireland (in suitable widths and sensible lengths - I don't want 500m!!) so I'm going to cover the foam mould in thin builders' plastic and vacuum it down today. I'll let you know if that works.

More exciting videos to come!

All the best,

Phil.

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From: This email address is being protected from spambots. You need JavaScript enabled to view it. [This email address is being protected from spambots. You need JavaScript enabled to view it.] On Behalf Of Rick Mullins
Sent: 19 June 2013 14:55
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Subject: Re: [Carbondragonbuildersandpilots] Phil's Carbon Dragon - progress...




I used a slightly different method to make my plugs. I used the blue insulating foam you can buy at the home improvement stores, then used a hot wire to cut the shape using the plywood ribs as guides. Then I covered everything with sheet rock compound and like you did...sanded, sanded, sanded. Over that I put the heat shrink plastic that is sold to insulate windows. After you tape it down well and shrink it it makes a beautiful smooth shiny surface that is guaranteed to come off the plug.
I haven't been able to fly my Dragon as much as I would have liked. I have been rebuilding our tow plane that was in an accident last fall. The last two times I flew it though were a blast. This glider really does go up in bug farts. I had a six hour flight in March, and a 3.5 hour flight last weekend and had to work my way down. I've finally getting a feel for the controls. The way the mixer is designed gives the stick some quirks. At 0 flaps the roll control is more or less neutral, but takes more force than what is used on the powered aircraft I've flown. I don't have much time in sailplanes so maybe this is normal. As you apply negative flaps (for speed) the stick really wants to stay centered and takes more pressure to roll. It’s significant pressure at -5 degrees. It's just the opposite when going the other way (positive flaps to fly slow). As you move the stick to roll, the stick wants to go farther, increasing the more the stick is moved. It becomes noticeable at the first flap setting. At full flaps it is very pronounced and just feels weird. I've found that I'm only using the 5 and 7.5 settings and that works fine.
Another observation. If you are having to set the glider up every time you want to fly, you’ll discover it’s a pain in the rear. I made tthe fairings around the flapperon control arms pretty tight and I'm constantly damaging them during assembly. On version 2.0 I’ll pay more attention to setup when designing wing assembly.


From: Phil <This email address is being protected from spambots. You need JavaScript enabled to view it.>
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Sent: Wednesday, June 19, 2013 6:22 AM
Subject: [Carbondragonbuildersandpilots] Phil's Carbon Dragon - progress...


Hi Folks,

Just thought you might like to see a short video of part of one of the leading edge mould plugs being fabricated.



I did try another method of making the moulds first (lining 'negative' formers with a sheet of 0.5mm polycarbonate) but I couldn't get the polycarbonate sheet to conform perfectly to the formers no matter how hard I tried! So... I reverted to using the old, tried and tested method of gluing blocks of polyurethane foam between 'positive' rib formers and sanding... sanding... sanding..!

I hope to cover the polyurethane plug I just made with fiberglass this weekend and perhaps even lay-up the carbon fiber in the new mould next week if all goes well.

Enjoy,

Phil.