Pulling up cured fiberglass?

[aviator_edb]

I need to redo one side of one of the forward LG bulkhead. I maanged to layup the BID with a serious curve in teh orientation fo the fibers plus there are a couple of quarter sizes bubbles.

 

I was planning to completely redo this part but I've been reading about people reheating a layup after its cured and peeling it up? Is this really possible or would it be easier to just redo the piece (which means buying more foam) or is pulling up the glass a viable option?

[Derek449]

I have done it with my heat gun. Just remember the foam will melt with to much heat.

[schmeddz]

Bad Idea. Start over from scratch. Chalk it up as a valuable learning experience. Better than going OH S***!!! in a few years on a collapsed landing gear and finding out the part failed because you were trying to save a bad part and a few bucks! Remember, experience comes at a price.

If you wait more than a day the heatgun will not work for you as the resin sets up.

 

Besides, that is one of the tiniest parts you will ever layup. If you're thinking of trying to save it, you are thinking way too cheaply! I used more fiberglass and foam and resin to make the bookend that was a practice layup in the Long-Ez plans! I have spent hundreds (if not thousands) on pieces I never felt good about using and never did. (I was doing other stuff, I even built a fiberglass canoe mold I never even used.) Cost of doing business, and education.

[aviator_edb]

Yah, I'm doing it over. I had a piece of sandwhich that was trimmed off the layup in question and I tried to pull the glass up. Yah, time for a do-over. I ordered a new sheet of foam last night. Bummer. Serves me right for doinga layup in a crappy mood.

[Phil Kriley]

Yah, I'm doing it over. I had a piece of sandwhich that was trimmed off the layup in question and I tried to pull the glass up. Yah, time for a do-over. I ordered a new sheet of foam last night. Bummer. Serves me right for doinga layup in a crappy mood.

BTDT!

 

Also best not to push yourself when you are tired or when you have other things to do following a layup - like anything that has a set time. Several times I've started a layup thinking I had enough time before having to go somewhere, only to find myself up to my elbows in epoxy and still needing to shower and shave to make a dinner reservation...

 

Good thing nice restaurants turn the lights low...

[brainfart]

If you redo it anyway then why don't you try removing the glass, or practise doing repairs on that part. Don't throw it away.

[steve]

never discard old layups, there are so many things you will do with them

its fun to cut up chunks for your friends to try to brake them:p

sanding blocks.

[Phil Kriley]

never discard old layups, there are so many things you will do with them

its fun to cut up chunks for your friends to try to brake them:p

sanding blocks.

I save samples of some of the layups that get cut off so I can look at them. One interesting piece of scrap is the portion of the fuselage you cut off when making the cutout for the canard. In one piece you have portions of the longeron, some blue foam, some yellow foam, several layers of fiberglass - good for "show and tell"! Probably useful as part of your project's documentation too.

[gullikson]

You can always try and peel the whole layup off the core. Just re-prep the core and/or patch core as necessary. Make sure everything is dull and do over. This is done on composite military aircraft on occasion (on parts that are about the same size as your bulkhead) and should work okay. You can grab the corner of the layup with vise grips. If you ruin the part then just start over. If the core is salvageable, you are good to go.

[Big Steve]

I took the cut out for the nose wheel to work. Nobody has been able to break it yet. STeve:D

[schmeddz]

I did a two foot long canard practice layup in the Alexander Aeroplane composite workshop back in the 90's. You could smack the spar cap layup with a hammer and not break it! Can't do that with an RV spar!

[Phil Kriley]

I did a two foot long canard practice layup in the Alexander Aeroplane composite workshop back in the 90's. You could smack the spar cap layup with a hammer and not break it! Can't do that with an RV spar!

True, but if I'd ponied up the money for an RV kit I'd have been flying a year ago instead of looking forward to another 4 years of building.

[schmeddz]

I bought my current long-ez flying (with engine) for a third less than the price of an RV-8 fast build kit. (What do engine and instruments cost again?) It needed work sure, but I was flying in 6 months. It's a better option if you can't afford an expensive outlay of 10k at a time.

 

No I can't use grass strips. I got over it! 170 mph on 20K. ZAP!

[Marc Zeitlin]

... You could smack the spar cap layup with a hammer and not break it!

You could smack the spar cap layup with a hammer and cause millions of invisible microcracks, delams, and flaws in the layup that will kill you later and you wouldn't know it.

 

Do not smack composite layups with hard things and expect to have a useful structure afterwards.

 

Can't do that with an RV spar!

Actually, impact resistance is far better with metal. You put a dent in something, but you can't delaminate it, and usually you can see if you cracked something.

[schmeddz]

I said it was an example of a spar, not the real thing! I would hope that was clear. Like flying into thunderstorms, Don't do it! Nor did I recommend doing it to the spar you are building! It was a strength sample. Burt Rutan and Mike Melville did that jumping up and down thing on the same type of example vs an aluminum spar in the building video's they did back in the seventies. DON"T HIT YOUR REAL SPAR WITH A HAMMER! It's called destructive testing y'know?