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Old May 21, 2011, 11:17 PM
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Flipso400: hollow molded Slipso400

Last year I've built the Slipso400 from Paul Daniels:

http://www.pldaniels.com/flying/models/slipso400/
http://www.rcgroups.com/forums/showthread.php?t=418625

I loved the plane, but an early crash prevented me to get enough fun from it. So I start building a new one, but in the process of making the fuselage I thought I could put a little more effort into it and use it as a plug to produce a mold. That's what I did. All this stuff was new to me, so I took my time. I did several mistakes along the way, but the mold turned out good.

Here are some pictures of the process of making the plug and the mold.

Next step is to make a hollow molded wing, but I'm not set on the wing shape and airfoil yet. Hopefully, the plug preparation and the mold making process won't go through all the mistakes I made for the fuselage mold

Marco
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Old May 21, 2011, 11:52 PM
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Splitting the molds halves

This step was stressfull. I just went for it. I used a broken GWS 10x6 prop as a wedge. It works pretty good.

as you can see, the plug got destroyed. That's ok... I've learned alot and wont do the same mistake again (i only used on light coat of pva when I did the fist mold half).

The most imporatnt thing is that the mold surface could be rescued. I was able to scratch the paint stuck inside the mold with my fingernail. I used my GWS prop to scrape the mold surface without scratching it. I think that it took me 2h to get it clean.
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Old May 22, 2011, 12:08 AM
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The part

For the fuselage layup I decided to go with a layer if gelcoat followed by 4 layers of 2oz fiberglass cloth. First layer on the bias (± 45 degree), second on 0-90 degree, third on bias and fourth on 0-90.

Mold halves were joined with strips of 2oz FG cut on bias.

I did some battery fitting tests too. looks promissing!
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Old May 22, 2011, 12:29 AM
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#2

I made a second fuselage. This one is black. The surface is as nice as the other one. My goal was to improve my gelcoat. On the first fuselage, the bush stokes are vere visible.

I made the gelcoat a bit thinner for this one, and I used a foam brush. Both modifications helped, but it's not perfect still. For the next one, I will also dye the epoxy for the layup, not only the gel coat. It should take care of the color problem.
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Old May 22, 2011, 12:32 AM
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When I was cleaning my mold after the second fuselage I noticed that a few chips appeared on the edge of the fisrt mold half. My mold is getting repaired right now. I think this is due to the fact that the gelcoat was a bit too thick and air bubles got trapped on the parting line. Next time I'll make the gelcoat thinner and I'll also degass it.
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Old May 22, 2011, 12:35 AM
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My Flipso is almost ready to fly. Yay!

Everything is installed in the fuselage. The wing is also ready to be installed. All I have to do now is to glue on the tail feathers and mount the wing.

The maiden flight should occur pretty soon. I'll make sure I have plenty of pictures and a video of the first flight.

Marco
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Old May 22, 2011, 01:18 AM
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Nice work
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Old May 22, 2011, 04:52 AM
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That sir, is beautiful!
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Old May 22, 2011, 04:55 AM
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Keep it going
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Old May 22, 2011, 09:59 AM
the answer 42 is
Switzerland, AG, Lenzburg
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grat job and thanks for sharing, what layout are you using for those fuselges??

regards

EZ
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Old May 22, 2011, 12:01 PM
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First of all, thanks everyone for the comments.

Edwinzea, look in post #3 for the layup details. It's basically 4 layers of 2oz fiber glass.

I must say that the fuselale is very stiff. It's more rigid that the Rifle. The tail section is very hard. I could easily drop to only 3 layers of glass behind de wing. I could probably do the same in the nose too and add a strip of carbon tow, but the "extra" layer of glass will probably help for those bad launches and landings. Plus, the hollow molded fusleage is already lighter and stronger than the balsa one. I just want to keep the whole thing simple. I first thought about vacuum bagging the fuselages, but i'm not sure that I would get a fuselage that much better for all the extra trouble it requires. I might try to bag one later on, but i'll stick to the easy way for now.

One other mistake I made during the mold making process was to not put enough filler (epoxy mixed with aerosil) between the waxed and pva'ed plug and the edge of the parting board. the gap was completly filled and I ended up with a nice sharp edge, but the filler kinda sank below the parting board surface a many places. This resulted in a very irregular surface at the mold edge and the region is prone to wax and expoxy build up. Maybe this is what caused my mold to chip in some area too (in combination with the bubbles).

I'm sharing these details so if someone want to make a mold they wont do the same mistakes I did. Sometimes you have to experience it to really realise the importance of some statements.

Marco
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Old May 23, 2011, 02:58 AM
the answer 42 is
Switzerland, AG, Lenzburg
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Hello and thanks for the answer :P

I am in process of making my first mold alone, I made some with a friend some years ago, but now I dont remember the whole process.

I remeber that we got a small gap between the parting boar and the plug, how do you filled that gap?? I was thinking in using filler of modelling clay, I would really appreciate your comment

Have you heard about this technique for joining the fuse?? http://www.rcgroups.com/forums/showp...&postcount=204 it is very easy and you achieve great results

regards

EZ
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Old May 23, 2011, 12:37 PM
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EZ, yes, I've watched that video (many times now). You need a "special" mold to use the inflation bladder technique. The mold has to be strong enough to resist the pressure you put in the bladder (between 20 to 60 psi) without deforming or breaking. These mold are "boxed". On top of the layers of fiberglass a mix of sand and epoxy is typicaly layed up. This gives VERY stable and heavy molds. Some use Poraver instead of sand, its lighter. If you want to go this way, you need to plan it BEFORE you start building your mold. You also need a compressor and the plastic film to make the bladder. Its just a different (better?) way to do it. Maybe more pro like!

To fill the gap, you can use different products. I used expoxy thickened with fumed silica. Some will use some kind of clay. Others car putty. I recommand you to take a look at pdawg's thread. He puts lots of details and picture on the how to make mold. I followed his way for most of the steps. Look at the electrolyte thread

http://www.rcgroups.com/forums/showthread.php?t=1260956

Don't hesitate to ask anything if you have questions or problems. People here on RCG are very kind and helpful.

Marco
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Old May 25, 2011, 12:00 AM
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You might be able to get away with it for a bladder even with open ends, I regularly do it with a fuse mold with a long open canopy and a low pressure (<10psi) and it still gives great results.

Next time, try running some carbon tow around the edges of the mold after putting down a first layer of resin/gelcoat. Makes for some really strong edges - my mold is the only one I've ever laid up but it's held up to 13 fuses so far with zero damage despite a few air bubbles I can see.

To get a really good fabric template, lay some strips of masking tape down in the mold, trim flush with the edge then transfer to your template material (thin ply, mylar etc.) and add some (say 5-8mm) for the seam overlap. That way you won't have to cut the seam tape.

Steve
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