Barkley
Well-Known Member
- Joined
- Jul 1, 2015
- Messages
- 572
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- 15
I'm a newbie on RF and can't update my profile until I have a minimum post count, so here's a contribution to the forum that will allow me to ... gasp... upload a pic maybe.
The basics:
your mandrel must be hard, and the right diameter for the INTERIOR diameter of your component, and STRAIGHT
the materials matter. A lot. Use the wrong epoxy or mold release and you're basically guaranteed to fail. Speaking from experience on this one.
So... this method works really really well. People at my club were impressed, especially when I told them there was no vac bag involved.
The materials:
Frekote 770 NC mold release. works beautifully. if you aren't going with this, please please please use the dry based agents. I cut 3 perfect tubes off mandrels before I learned my lesson.
mylar film. the thinner the better. If you use Frekote your mylar doesn't really matter.
West System 105/206. Great epoxy. I use nesting cups and fill the bottom one with ice water to give me a longer pot life if it's over 85F where I'm laying up the glass.
I use .4oz cloth from Fiberglast. More wraps with a lighter cloth gives you more control over the overall strength and weight of your finished product.
Airtech econoply for the peel ply. It works very very well.
shrink film. You don't have to be specific with this, as long as you can wrap the whole piece.
heat gun or hair dryer
The process:
spray the mandrel with the Frekote. I put down 3 thin coats.
cut the mylar film to fit the mandrel. 1 wrap with 30%ish overlap.
wrap the mylar film around the mandrel, taped only at the ends. it needs to be tight - no bubbles, no wrinkles. sometimes the middle of the mylar will rise a bit - if it's less than 1/4" that isn't a problem.
spray the mylar film with the Frekote. 1 coat is more than enough.
cut your cloth to fit your mandrel. Assume 5 wraps - you can always add more if it isn't strong enough. Take care of all the loose partial threads now.
cut your peel ply. I assume 1 wrap with about 50% overlap.
put on your gloves, and get everything you need where you need it. paint brush with a spare, bondo spreader, all your materials. put the mandrel on your stand so that when you brush the mixed epoxy on you're pressing the mylar seam down, not pulling the mylar back and off the mandrel.
using a kitchen scale, weigh your glass cloth. You'll want epoxy roughly equal to 110-120% of this weight. Tare the weight of your mixing cup, then put the weight of the cloth in resin in the pot - the hardener makes up your excess. Remember that the moment you add the hardener, it's go time - you're on the clock, and it's just a matter of time before it starts to kick.
when laying up the cloth, only apply the epoxy until the cloth is clear. Anything more just adds weight. The advantage of the thinner cloth is that it will pick up the excess epoxy from the wrap underneath, so don't assume that the new wrap needs a paintbrush sopping with epoxy. But... make sure that every bit of cloth is transparent. White is bad. You don't want any bubbles at all. Ever. Keep the cloth tight against the mandrel or the wrap beneath.
When you're finished, put on the peel ply. Spread it smooth with the bondo spreader. never pull in the direction that would pull your last glass wrap off. go laterally until you know it's down, then wrap the peel ply in the direction of the wrapped glass.
when the peel ply is down, wrap the whole thing in shrink wrap. I wrap it 3 or 4 times, then hit it with the heat gun. The purpose of this is to push the peel ply into the glass, just as the vac bag would.
Then.. open a beer and wait. I didn't get this method right the first time, but I'm more than happy with the results now. I used this method for my 3" 7 foot rocket that hopefully will get me my L2 this weekend. If not... I'll do the same thing with 6 wraps instead of 5.
FTR, I also make glass plate. Get two plates of glass from Home Depot, apply the mold release to it, lay down the peel ply on one pane of glass and do pretty much as above layer by layer. After the last layer, apply your peel ply, bondo spreader it smooth, then glass on top. I put 2 25 pound free weights on top of the whole thing to apply the pressure.
Good luck.
The basics:
your mandrel must be hard, and the right diameter for the INTERIOR diameter of your component, and STRAIGHT
the materials matter. A lot. Use the wrong epoxy or mold release and you're basically guaranteed to fail. Speaking from experience on this one.
So... this method works really really well. People at my club were impressed, especially when I told them there was no vac bag involved.
The materials:
Frekote 770 NC mold release. works beautifully. if you aren't going with this, please please please use the dry based agents. I cut 3 perfect tubes off mandrels before I learned my lesson.
mylar film. the thinner the better. If you use Frekote your mylar doesn't really matter.
West System 105/206. Great epoxy. I use nesting cups and fill the bottom one with ice water to give me a longer pot life if it's over 85F where I'm laying up the glass.
I use .4oz cloth from Fiberglast. More wraps with a lighter cloth gives you more control over the overall strength and weight of your finished product.
Airtech econoply for the peel ply. It works very very well.
shrink film. You don't have to be specific with this, as long as you can wrap the whole piece.
heat gun or hair dryer
The process:
spray the mandrel with the Frekote. I put down 3 thin coats.
cut the mylar film to fit the mandrel. 1 wrap with 30%ish overlap.
wrap the mylar film around the mandrel, taped only at the ends. it needs to be tight - no bubbles, no wrinkles. sometimes the middle of the mylar will rise a bit - if it's less than 1/4" that isn't a problem.
spray the mylar film with the Frekote. 1 coat is more than enough.
cut your cloth to fit your mandrel. Assume 5 wraps - you can always add more if it isn't strong enough. Take care of all the loose partial threads now.
cut your peel ply. I assume 1 wrap with about 50% overlap.
put on your gloves, and get everything you need where you need it. paint brush with a spare, bondo spreader, all your materials. put the mandrel on your stand so that when you brush the mixed epoxy on you're pressing the mylar seam down, not pulling the mylar back and off the mandrel.
using a kitchen scale, weigh your glass cloth. You'll want epoxy roughly equal to 110-120% of this weight. Tare the weight of your mixing cup, then put the weight of the cloth in resin in the pot - the hardener makes up your excess. Remember that the moment you add the hardener, it's go time - you're on the clock, and it's just a matter of time before it starts to kick.
when laying up the cloth, only apply the epoxy until the cloth is clear. Anything more just adds weight. The advantage of the thinner cloth is that it will pick up the excess epoxy from the wrap underneath, so don't assume that the new wrap needs a paintbrush sopping with epoxy. But... make sure that every bit of cloth is transparent. White is bad. You don't want any bubbles at all. Ever. Keep the cloth tight against the mandrel or the wrap beneath.
When you're finished, put on the peel ply. Spread it smooth with the bondo spreader. never pull in the direction that would pull your last glass wrap off. go laterally until you know it's down, then wrap the peel ply in the direction of the wrapped glass.
when the peel ply is down, wrap the whole thing in shrink wrap. I wrap it 3 or 4 times, then hit it with the heat gun. The purpose of this is to push the peel ply into the glass, just as the vac bag would.
Then.. open a beer and wait. I didn't get this method right the first time, but I'm more than happy with the results now. I used this method for my 3" 7 foot rocket that hopefully will get me my L2 this weekend. If not... I'll do the same thing with 6 wraps instead of 5.
FTR, I also make glass plate. Get two plates of glass from Home Depot, apply the mold release to it, lay down the peel ply on one pane of glass and do pretty much as above layer by layer. After the last layer, apply your peel ply, bondo spreader it smooth, then glass on top. I put 2 25 pound free weights on top of the whole thing to apply the pressure.
Good luck.
