Make Your Own Fiberglass Canopy

[markb]

yes, its a 450 plug. I went for roomy, so I can try some oversize batteries on my stretch 450. It came out pretty good, but it still has some imperfections. This one's more a trial run mold, not something I think I'll use more than a few times to learn the ropes. What I really want, is to make a really lightweight (ie flimsy) f3c style fuselage. Probably with no tail boom, just a full body enclosure. Basically disposable, so I can fly the @#$@ out of it, and not worry.

I've done a little vacuum bagging on airplane parts, kayaks and windsurfer repairs. I expect you'll be really happy with what it does for the cano's. It should completely eliminate the possibility of bubbles and voids in the glass against the mold, no more excess resin, runs, pools or pockets between layers, and a nice dry minimum resin light weight layup. And no blush on the surface, so its ready for bonding another layer, or paint. But you know all that. I was just really amazed the first time I opened the bag to find this perfect part, and hope you're just as psyched! Have fun!

PS. the stretch film looks incredible! Its really hard to get a regular poly bag to fit/fill in a small concave part, that stuff looks perfect for the job.

[Farrell]

helipainter: I was not planning to sell any since they require custom mounts to even fit the desired helicopter (EF Cypher) but if you are still interested let me know.


I did my first vacuum bagged canopy and I like the results. I cut a little more than 20% of the weight (20g vs. 26g) compared to my previous canopy. For something this small I am not sure if it will be worth the extra time and materials cost.

I laid up the mold as usual then applied pieces of release ply. It does not conform to curves like fiberglass so I cut it into rectangles and applied them with a little overlap so they covered all of my glass. The release ply regulates how quickly resin can be soaked up by the breather/bleeder padding -- which goes on next. That was cut into rectangles and applied as needed to cover all of the release ply.

The vacuum tube gets some breather/bleeded attached to it, then the whole mess goes in a vacuum bag. To make my bag I took a rectangle of Stretchlon film, folded it over, then sealed two of the open edges with a poly bag sealer. The mold and vacuum tube go in the bag followed by a strip of sealant tape to seal up the open end of the bag.

One final check to make sure the mold is positioned right in the bag, then I switched on the pump. I tried to guide the film into the mold as best I could.

Here is the mold after being placed in my hot box:




Three hours later the resin is set.



I removed the bag then proceeded to peel off the release ply and breather/bleeder.



After some tugging to get the nose section free I was ready to de-mold.



The release ply leaves a nice texture on the inside of the canopy, making it more translucent and less transparent. This canopy feels a little softer than my previous ones but I will have to check it in a day or two when it firms up. I will go back to two layers of glass if it ends up too soft.

-Farrell

[markb]

OK... this is not as easy as Farrell has made it look!
I got a decent mold off my canopy plug, and have made two canopies from it. Neither one is as good as his, and will need significant touch up before paint. But they will still be usable at least, and I'm learning...

So here's the pitfalls I found...

If you make your plug from a sandwich of foam panels, don't put it in heat to cure coats of filler. I put mine out in the sun (~100 F), and it shrunk non-uniformly... leaving low lines along all the seams.

During all the shaping, and polishing, and plug building... cut a piece of the half inch foam and lay it on your work surface. Its soft enough to prevent dings in your canopy while you work, and if you dribble epoxy filler on it - its a throw away anyway!

If you have trouble with surface smoothness in the plug (I sure did), get some high build primer. Having consistent color really helps to see the low spots... and the high-build will help fill some pretty ugly problems.

An obvious one: Wet sand. Everything. Those screen mesh sheets work great on foam. And wet/dry paper works great on the filler. Its so much better than dry sanding.

When you make the first half of the mold, be sure the seam between the parting board and the plug is really sealed. I didn't, and had runs of epoxy down the back half of the plug (even though I was using a very thick fillet forming epoxy/fairing filler mix). I had to pull the first half mold off the plug to clean up the edges, prior to making the second half. The problem with that is, when you put the plug back in the first half to make the second half, it may not pull up as tightly to the mold as when it was originally created. Now, your second half will form right against the plug, and you'll have a very small step at the edge between them. --- So ideally, (and I read about this technique, haven't tried it) the seam with the parting board will be sealed perfectly and leave a nice clean edge when you remove the parting board. Then you can NOT remove the first half-mold before making the second half. Just clean up the plug around the edge, apply fresh release film, and make the second half mold. This way, the first half is still stuck tight to the plug surface, and you'll get no step whatsoever. If thats not possible, you have to do something to keep the first half in intimate contact with the plug, while you lay up the second half.

Finally, I have to repeat something Farrell already told us, because it was really frustrating! When you lay up glass in the mold, you will leave pinholes if you don't do what Farrell advised earlier. One of my canopies proves his point!

- If you do not apply a gel coat or film of resin before you lay up the fiberglass your finished surface will have TONS and TONS of pinholes. Trying to fill them all is an exercize in futility. I just paint my hold halves with a thin film of resin and let that film cure just past the sticky state before I lay up my cloth.

Farrell, did you have to do a gel coat with the vacuum bag? I did airplane cano's years ago, and don't remember needing that step with the bag.

[Farrell]

I used a layer of resin when I vacuum bagged the canopy. I think it would be even more critical when vacuum bagging since that process removes excess resin quite effectively.

Good luck with the canopies. I still haven't painted any of mine yet

-Farrell

[Socal500]

I have thought about doing this but what are you looking at on initial cost and is it more cost effective than just purchasing one already made and painted ?

[Farrell]

Definitely not cost-effective. It's a lot of work and a fair amount of money up front. It's been long enough that I don't remember what I paid but expect somewhere around $150 to get started. After that it's not too expensive, maybe $3 - 8 per canopy depending on the size. Only time it might be cost-effective is if you're doing something big like a scale fuselage or gasser canopy. Even then, it's questionable. I did it mostly for the fun of it and to learn a little about composites.

You can find really cheap canopies on eBay if you don't need quality. A few years ago I bought about five 450-size canopies on eBay for around $4 each SHIPPED. Quality was non-existent but they were great for airbrush practice.

If you buy some of the dirt cheap canopies off of eBay you should really add an extra later of fiberglass around the inside perimeter to keep the canopy from cracking. The canopies I got would crack if you looked at them wrong.

Some 1/2" fiberglass tape and CA works well:


-Farrell

[Socal500]

I figured initial cost would be a little high and its not something I would want to invest in but I bet it is satisfying to complete your own.

I found some on ebay for $3.99 with $6 shipping. Probably the same ones you to which you are referring. I was about to order 4 but they want to charge shipping for each.

[mattthomas78]

this is what I've been looking for!!!

[erospawn]

I was making and selling model kits for awhile before I get into heli's..I actually got started making canopies just recently. Anyway, interesting to see that you used Fiber Glass as the jacket for your mold. I thought about that, but I had gotten used to using "Ultracal" to make a solid jacket. I made a one piece mold, but it's a pain to pull the completed canopy out of the mold..

We used the process for making the master very similar to what you did. Although the projects I was working on was a like 1/350 scale ( 3ft long) USS Voyager. Basically, you build frame it out and fill the space with a foam you can get from Smooth-On.. then, you shave the foam off using the frame as a guide to shape it.. after which you fill it in with bondo.. Framing allows you to create more complex shapes. But the process is pretty similar.

[GootyS]

Are you using one or two layers of the 5.8oz cloth? Do you get pinholes?

[Farrell]

I used one layer, then added a second layer just around the perimeter for a little extra strength. You can use two layers all around if you want a very sturdy canopy.

You will get pin holes if the mold surface is right up against the fiberglass. If you use some sort of gel coat, you shouldn't have problems. You could simply paint a thin film of resin onto the mold, and let it set up before adding the glass. I've been tempted to brush primer directly onto the mold surface, and let it dry before laying up the glass, but I have not done that yet.

-Farrell

[Airworks]

use epoxy jelly (bondo) as an alternative for a true gelcoat. , mix in some powder pigment to dark color it(makes easy to spot bubbles when making a cano out of it).the epoxy jelly doesnt run, coats "similiar" to gelcoat. not as stong as a true tooling gelcoat , but....for making 100 canopies out of it , will work just fine.

[trillian]

Oops - wrong thread!