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Old Mar 10, 2013, 11:40 PM
Jim in the Desert
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United States, NM, Las Cruces
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Can I make a mold from my fiberglass glider fuselage?

I just bought a glider used on RCG. It has built up wings, and a fiberglass fuse, with the wings mounted mid-fuse. I think I may really like this fuse once I get things airborne, but nobody was able to identify just what I have here. Could I make duplicates of this fuse, which I guess would mean making a mold and either making the fuses myself, or sending the mold to an expert to have some fuses made for me?

Don't really know much about how all these processes work....

Thanks
Jim
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Old Mar 11, 2013, 02:30 PM
B for Bruce
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The 'Wack, BC, Canada
Joined Oct 2002
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Sure you can make a mold from the original.

You'll need to start by building a splitter plate. The fuselage fits down into a cutout in the middle of this splitter plate and you support the shell from below with some bracing and fill the gap between the shell and the plate with modeling clay. Then you fill in the canopy area so it fills out into a shape that will be easy to mold over with the cloth for the mold.

Once this is all preped you'll want to make a wood box that'll be the outside frame for the mold half that'll be bonded to the cloth that is the mold itself.

Now wax up the splitter plate, shell and fairings of the form. Wax it in multiple coats and buff it lightly between coats. You want the entire form well waxed but smooth to form a good releaseable surface.

Now it's time for a coating of gel coat. This produces a fine finish that resists forming air bubbles. When the gel coat is sticky/tacky use some resin and loose fibers or resin thickened with micro balloons to fill in along the sharper corners that the cloth would simply bridge across. With the filler in place drape the first layer of finer weight cloth over the form and butter it up with resin using brushes or special resin rollers. Lay on succesive cloth and matting layers to build the layup out to about 1/8 thick or a little more. Usually you want cloth for the form, matting in cut portions as a thickener then a last layer of cloth to tie it all together. More layers of thinner is better and easier to work with than one layer that is thick.

With the resins still wet lay on the frame around the edge so it bonds to the layup

After it cures to a non tacky but still fairly pliable "green" point it's time to pull it off the mold. A jet of air or even a garden hose can do a lot towards getting in and breaking the bond to get the mold to release.

Now stand back and look amazed at what you created. Don't bask in your own glory for too long though. You need to strip down the shell and splitter plate and reverse everything to do the other side.

As you can see it's a LOT of work. If you're not going to make multiple copies of this fuselage for this and that it's likely more easy to do a carved foam core, mold around it and then melt out the foam with gasoline after the shell is done. Or simply make any needed replacement from wood.
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Old Mar 11, 2013, 09:15 PM
Jim in the Desert
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Wow! Thank you so much for the great answer. Some of it was over my head but I get most of it. You seem to know this stuff. Do you know where i can get more info, maybe pics of the process, etc.?

I'm really happy to hear that this can be done. It sound like a lot of fun, not a lot ot work, to me. I'd love to learn to lay up fiberglass.

Thank you!
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Old Mar 12, 2013, 05:10 AM
An itch?. Scratch build.
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There is a forum here that goes into much of the detail of glassing, molds, and all that's involved -

Composites Fabrication forum

It's a lot of work to create molds, and to get good quality item off them. I would suggest making sure the model you intend to copy is the best, most perfect one for the job you want it to do.

If not absolutely sure, experiment with a few balsa fuselages to get the best fuselage shape, then make molds for that one.

It's not just the external shape, but how easy it is to do all the internal installations, radio gear, (different sizes ?), control runs, battery(s), motor(s), ESC, cooling, access hatches, wing retaining method, tail mounts, etc.

An interesting project if you enjoy designing, but remember it will likely be a one off.
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Old Mar 12, 2013, 08:57 AM
Jim in the Desert
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United States, NM, Las Cruces
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Quote:
Originally Posted by eflightray View Post
There is a forum here that goes into much of the detail of glassing, molds, and all that's involved -

Composites Fabrication forum

It's a lot of work to create molds, and to get good quality item off them. I would suggest making sure the model you intend to copy is the best, most perfect one for the job you want it to do.

If not absolutely sure, experiment with a few balsa fuselages to get the best fuselage shape, then make molds for that one.

It's not just the external shape, but how easy it is to do all the internal installations, radio gear, (different sizes ?), control runs, battery(s), motor(s), ESC, cooling, access hatches, wing retaining method, tail mounts, etc.

An interesting project if you enjoy designing, but remember it will likely be a one off.
Thanks again. Well I can start reading about it and make sure I understand all the steps you describe and then decide if it's a good idea. But this is the sort of think I like.
Jim
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Old Mar 12, 2013, 03:09 PM
B for Bruce
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The 'Wack, BC, Canada
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It IS a lot of work and it's nice if the final product is useable for more than only one model.

For example if you make up a form for a composite fuselage that has a longer than required tail the final product can be cut to fit a variety of designs. So it's more flexible. And instead of designing any one root airfoil if you instead mold in a strong stub to be used for supporting the joiner rods and internal strengthening to handle the leading edge compression forces during "spirited" landings then you can build up such a generic fuselage pretty quicly into anything you wish within reason.

A second mold for a fin can be created that feathers onto the tail of the main fuselage. That would allow you to have different fins or tail mounts to handle a variety of designs for any sort of sailplane.
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Old Mar 12, 2013, 05:44 PM
Jim in the Desert
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Quote:
Originally Posted by BMatthews View Post
It IS a lot of work and it's nice if the final product is useable for more than only one model.

For example if you make up a form for a composite fuselage that has a longer than required tail the final product can be cut to fit a variety of designs. So it's more flexible. And instead of designing any one root airfoil if you instead mold in a strong stub to be used for supporting the joiner rods and internal strengthening to handle the leading edge compression forces during "spirited" landings then you can build up such a generic fuselage pretty quicly into anything you wish within reason.

A second mold for a fin can be created that feathers onto the tail of the main fuselage. That would allow you to have different fins or tail mounts to handle a variety of designs for any sort of sailplane.
You made me think. There are fuses that seem nicer than mine. The Albatross that Soaring USA constantly advertises is much more gorgeous and probably better designed aerodynamically than mine.

But, another motivation is to learn the process. Then I could make many things. I have wanted to learn to lay up (right term?) glass.

It just seemed that mine is a good basic design, and has a major advantage: I already have it
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Old Mar 13, 2013, 12:45 PM
B for Bruce
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Well, it's a hobby. By definition we do it because it gives us joy, fills in time otherwise wasted watching "reality" shows on TV and increases our skill set for some future project.

So go for it!
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Old Mar 13, 2013, 05:52 PM
Jim in the Desert
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Originally Posted by BMatthews View Post
Well, it's a hobby. By definition we do it because it gives us joy, fills in time otherwise wasted watching "reality" shows on TV and increases our skill set for some future project.

So go for it!
Yeah. Want to make fiberglass saddle bags for my Honda too. It's in my future, somewhere...
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Old Mar 14, 2013, 01:27 PM
The Prez....... again
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If you look on You Tube there are some tutorials on mold making. At least you will get the idea of how it's done. DON"T expect to get it right the first time though. I would experiment on something small so a mistake is not such a drain on the wallet and a disappointment so you don't try again. My first molding project was the reed holder for a duck call. The mold was about the size of your thumb! It took me about 5 tries to get it right. Total expense was about $10 for everything.

Good luck on your endeavor. It will be a journey to remember.

Ken
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Old Mar 14, 2013, 08:47 PM
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Try this web-site. Good info. http://www.cstsales.com/tutorials.html

John
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Old Mar 14, 2013, 11:22 PM
Jim in the Desert
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Thanks guys and thanks for the link.

Jim
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