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Old Oct 30, 2012, 11:00 PM
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Hello Mike, Thanks for the great build--especially the detailed descriptions and pictures. When I've tried to make molds, I've had trouble with the PVA sticking to the mold surfaces when the plug is removed. Did you have to clean off the inner mold surfaces when you removed the plug before waxing them? How did you deal with the PVA residue, if any? Maybe I put it on too thick? Also, why did you use the 2K primer on the mold surfaces for the final fuse outside surface and color, instead of a white gel coat, or even white-tinted resin? Maybe to save weight since you'll paint it to get rid of the join lines? Thanks again, Bob
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Old Oct 31, 2012, 02:45 AM
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Originally Posted by flyingfever View Post
Hello Mike, Thanks for the great build--especially the detailed descriptions and pictures. When I've tried to make molds, I've had trouble with the PVA sticking to the mold surfaces when the plug is removed. Did you have to clean off the inner mold surfaces when you removed the plug before waxing them? How did you deal with the PVA residue, if any? Maybe I put it on too thick? Also, why did you use the 2K primer on the mold surfaces for the final fuse outside surface and color, instead of a white gel coat, or even white-tinted resin? Maybe to save weight since you'll paint it to get rid of the join lines? Thanks again, Bob
Hi Bob,
I found I had a bottle of red PVA but have never used it before, I questioned the guys at my composite shop , and this was the reply, use carnuba based release wax first and polish on and off lots of times, in my case about 6, then after the last polish off, take a soft cloth and totally wet it with the PVA, now wipe it on and if you can imagine trying to then wipe it off again with the same cloth. The idea is to leave only a microscopic layer of PVA.
The mold does not seem to have any visible trace of the PVA , brushing or spraying seems to have problems.
The 2K paint is my prefered material, I have painted some molds with a 2k primer but then the cockpit area looks a strange beige colour, I used white as it also means only a very light finish coat is required to cover the surface.
I have never tried a white epoxy gel coat and would imagine it will also work, although some of my older gliders had it, like a Multiplex DG300 and with some bumps hairline cracks and flakes would appearin the gel coat.
It is important to create some outer surface coating ,to lay the glass cloth against otherwise you end up with pin holes

So far I have had no pinholes or fish eyes in the paint , It is also a good idea to layup the glass within a day or so of the painting, seems to bond a bit better.
About saving weight , a coat of 2k white probably adds about 150grs so on an aircraft that will probably end up about 4.5 to 6kgs not really and issue.
This is why I have never been tempted to try build DLG stuff.


As I have stated on so many occasions , there are so many options to the scratch builder, do what works for you, but keep learning as you go along, and ask others for ideas, and steal the ones you like.

thanks for your interest.
Mike
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Old Oct 31, 2012, 05:11 AM
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[QUOTE=flyingfever;23143717] When I've tried to make molds, I've had trouble with the PVA sticking to the mold surfaces when the plug is removed. Did you have to clean off the inner mold surfaces when you removed the plug before waxing them? Thanks again, Bob[/QUOTE

Sorry to butt in here ... but Bob the PVA is water soluable so when you pull the plug and mold apart you just wash them lightly with water and the PVA dissappears....Ready to start polishing for the next layup.

Nice fuse there Mike .... the extra effort pays off.....cheers Minite
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Old Oct 31, 2012, 03:42 PM
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On my semi-scale ASH25 I sandwiched a layer of Kevlar cloth between some glass and carbon cloth, the idea being that I'd avoid that dreaded fluffing up thing it does whenever you so much as show it a piece of sandpaper. Well it worked well except at the edges of the moulding e.g. the canopy frame where suddenly it was golden fuzz everywhere. What worked quite well was to wick thin CA into it which made it stiff and relatively trimmable.

Probably wouldn't bother using Kevlar again, and I only used it because my sister was about to bin all these big offcuts after making herself a transatlantic rowing boat. Mind you, makes your plane bullet-proof. Literally.

Rog
Rog, a good way to handle those flufffy Kevlar edges is to apply some thin CA, they sand off reasonably well after that. Also there are some super fine sand papers about these days used in place of cutting compound. These will actually sand the fuz. You could just about sand your own whiskers off with this stuff instead of scaving. Car painters would be a source. I think they go to 2000 grit.
I agree, I hate kevlar but I like the end result so still use it in selected applications.
Cutting it was awful untill I learned to run scissor blade along the grind stone to give them some teeth. They cut great after that.
Allan
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Old Oct 31, 2012, 05:17 PM
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Useful tips Allan. Funnily enough my Kevlar was sourced in NZ. My sis says she found a few more bits last year which I'll pick up when I see her in Auckland next Easter. Will take a slope plane too. Gorgeous countryside you have there. Sorry Mike... getting sidetracked here.
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Old Nov 01, 2012, 08:26 AM
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Absolutely stunning work Mike, you almost non-nonchalantly make reality of what I could only dream of for years, but I am determined to learn composites and have many scale designs dying to come to life. See pm in this regard. I really am in utter amazement at your skill and expertise and excited to find someone as passionate as I in my area. I am also a big fan of the Jonker's designs and have a design for a 2m JS1 ...beyond the creative aspect of carving and shaping a plug I just don't know how to turn her into a structurally sound airframe using these extremely high-tech materials.

You folk who turn out slippery and space-age birds in no time at all as and when the fancy takes you are the heart and soul of this hobby and have my sincerest respect!
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Old Nov 01, 2012, 09:58 AM
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*edit* Keen to see how you make up the wings for this smaller bird although I have studied ad nauseum your process on the Nimbus builds.
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Old Nov 01, 2012, 01:19 PM
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If for any reason we don't find each other on my pm request, perhaps you could cut me a set of wings for a Duo Discus design of my own on which I will attempt to bash out a fuz using the techniques you so clearly and precisely described in this and your Nimbus threads.

He'll be showing you how to do the wings on this thread soon!!
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Old Nov 01, 2012, 03:32 PM
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NZ flying

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Originally Posted by Sutton Bank View Post
Useful tips Allan. Funnily enough my Kevlar was sourced in NZ. My sis says she found a few more bits last year which I'll pick up when I see her in Auckland next Easter. Will take a slope plane too. Gorgeous countryside you have there. Sorry Mike... getting sidetracked here.
If you are thinking of getting as far south as Blenheim let me know. I'm sure we can show you some southern hospitality and we have great slope sites 10 minutes away.

Allan

PS Mike won't mind he has NZ connections too!
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Old Nov 05, 2012, 09:40 AM
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JS1 no 2 in the mould.

Hi Guys,
Just a short update, had a weekend of other commitments, but managed to spray up the moulds for JS 1 no 2 and Nimbus4 no 10 and a repair. Sunday I layed up the fuselages and trimmed and hopefully tomorrow evening can join them.
The second JS 1 has a different layup using a satin weave UD glass cloth at 190 gr a bit heavier cloth wise so I left 1 x layer out, will see how it pans out.
Also made up a dowel which will be sprayed , finished and become a plug for a wing joiner 16mm carbon.
regards
Mike
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Old Nov 05, 2012, 09:57 AM
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I am so envious, you make it look like child'splay!! I eagerly await further developments on this project, great work!

I tried a small layup myself this weekend and lets just say the money could have been more wisely spent, not sure I learned anything but how adverse women are to this stuff .
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Old Nov 06, 2012, 03:24 AM
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Originally Posted by wingnutzster View Post
... not sure I learned anything but how adverse women are to this stuff .
Try using a female mould next time.
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Old Nov 06, 2012, 03:26 AM
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Try using a female mould next time.
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Old Nov 06, 2012, 03:34 AM
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Can I ask a stupid question? I understand the value in doing it this way and that the whole process of plug making to mold making to layup to finish and assembly is all a necessary process and well worth the tediousness and effort, but my question is would it not be feasible to create a one-off scale glider just by hand in foam and then glassing it and possibly even removing the foam, I know this is a popular method for creating airframes but never seen a glider done this way and wondered why?

I really do seem to have a talent for shaping by hand and am quite confident I can get a great looking scale bird shaped in foam but when it comes to pluggin and molding and layups etc I stuff it up everytime. So how can I get from a beautiful foam airframe (hotwire cut wings) to a properly finished composite one?
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Old Nov 06, 2012, 03:46 AM
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As I have mentioned I have been collecting research and reference material on sailplanes and sailplane construction and design for a few years now and thought I might share a particularly interesting project in that they have chronicled the entire build from conception to first flights with pictures and descriptions. I imagine this would be of some value to the glider enthusiast and manufacturer?

http://www.hpaircraft.com/hp-24/

follow them on fb too -

http://www.facebook.com/pages/HP-24-...t/200931354951
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