Fiberglass Fuselages for Dummies

[model3113]

Apologies if this is the wrong section.

I had a hare-brained idea for doing a fiberglass copy of my HK Walrus, mainly to get something with a bit more interior space, but also for giggles.



I know how FG goes together in like a factory setting, and I've seen people glass foamies for durability, but I haven't really seen a breakdown from a Homebrew pov, is it really just a matter of putting on some mold release, laying down the cloth, rolling out the resin, and then sand/finish when done?

Getting the resin/tools probably isn't too hard, but what weight cloth? How many layers, aside from the obvious reinforcement areas?

 

[willsonman]

You can always do a one-off part by making a foam mold of the part, glass it, then melt the foam out with acetone. In your particular part, I would use at least two layers of at least 2oz cloth and then a top layer of 3/4oz. The lighter cloths are for a nicely finished surface. You can simply do your layup of cloth and sand the part smooth before removing the foam or you can try to reduce sanding work by applying plastic wrap from your kitchen over the part while it cures. Using plastic wrap really depends on how flat the part is as sometimes it's more work than its worth. Some folks have struggles with that so YMMV. You may also want to consider a longer work-time resin. shorter time resins (like 5-15 minute) produce very soft parts. I would suggest at least an hour. I'm impartial to brands but Z-poxy and west systems seem to be popular in our hobby but whatever you can get your hands on will work. Also keep in mind that you want the part to cure out in a fairly warm environment of at least 70 degrees. The reason is that the epoxy can "flash out", meaning that in some climates (humidity) moisture in the air can settle on or even be mixed into the epoxy and the cure will not happen. It will continue to be a sticky mess and you'll have to start all over.

It's really not as hard as you might think and I always encourage folks to try it. It's like any other building medium where it takes practice and maybe even a few mistakes before you get it perfect. Clean up drips with rubbing alcohol from the drug store. Use gloves when in use. DO NOT use polyester resins. They are VERY stinky and melt foam from the fumes.

 

[leaded50]

by nostalgia of the old days.. bottom in magnesium metall cast

 

[Piotrsko]

Depends on whether or not you want to copy an existing or build a one-off when using the foam plug. We used to heavily wax the male pattern and place in open top box then pour plaster of paris up half way. Let set, then repeat with the second half and some sort of non stick mold parting line. If you're doing a quick copy just wax the pattern and glass directly if you don't mind the size increase
Op seems to understand the process.
I have also used verious weights of dacron gotten from fabric stores after washing to remove the starch, not as strong as glass but 1/10 th the price and the failure point is the resin not the fabric

 

[Bricks]

Depends on whether or not you want to copy an existing or build a one-off when using the foam plug. We used to heavily wax the male pattern and place in open top box then pour plaster of paris up half way. Let set, then repeat with the second half and some sort of non stick mold parting line. If you're doing a quick copy just wax the pattern and glass directly if you don't mind the size increase
Op seems to understand the process.
I have also used verious weights of dacron gotten from fabric stores after washing to remove the starch, not as strong as glass but 1/10 th the price and the failure point is the resin not the fabric

Learned something Dacron instead of fiberglass cloth, the weave of fiberglass cloth can be a real pain with the edges unraveling when applying.

 

[jfaleo1]

Depends on whether or not you want to copy an existing or build a one-off when using the foam plug. We used to heavily wax the male pattern and place in open top box then pour plaster of paris up half way. Let set, then repeat with the second half and some sort of non stick mold parting line. If you're doing a quick copy just wax the pattern and glass directly if you don't mind the size increase
Op seems to understand the process.
I have also used verious weights of dacron gotten from fabric stores after washing to remove the starch, not as strong as glass but 1/10 th the price and the failure point is the resin not the fabric

Dacron cloth is one of the things you can cover full scale aircraft with. Though it is different weight it still is very strong so this is a good idea.

 

[wilmracer]

I did a time-lapse a few years back of a FG fuselage build over a plug. Let me know if this makes sense:

 

[model3113]

This is all really good info. Since it looks like the Walrus is being disco it's nice to know that's not much of a challenge to build a more durable version. I was especially concerned that acetone might weaken the resin if I had to use it.

I've done the Saran wrap on CF joints for a bamboo bicycle, what I was thinking was using my mom's vacuum seal machine gathering dust with her kitchen junk. The plastic is just a giant tube that you heatseal after the air gets sucked out.

 

[Piotrsko]

Except for: wrinkles and possibly crushing the pattern, excellent thought process, vaccum bagging the pattern using home equipment. There will be a radius at sharp partitions, however.

 

[Piotrsko]

More thought: warming up the baggies with an actual hair dryer would decrease the radii at corners

 

[leaded50]

also a tip... pro glasfiberwork as eg boatbuilders, make first "layer" as the slick outer colored gelcoat, aka just layer of liquid polyester, then the layers of fabrics (glassfiber/carbon fiber) .
Even when build with epoxy IF coat the form with wet epoxy before put in eg. carbon fiber... chances for pinholes/ airbubbles are less. If put in the carbon fiber first, it needs be soaked through, and already when applying epoxy at "backside" your blocking easier air to disappear.... if you lay it in wet epoxy, use brush/rolls to push in place, that will draw epoxy from outside, not trap as easy air. then you use epoxy at inside.
The whole operation as wet. not any dryed layers.