Reworking a B model cowling

[C5Engineer 1170]

Bit the bullet today and commited to my cowl makeover. After 2 mos and 14 hrs it's time to permanently replace my ghetto fab cardboard patch. Spent the afternoon scraping 25 years worth of crap off the inside of the cowl. I picked this cowl up used years ago and knew it needed attention but today was a big eye opener. Looking forward to reworking it. The pics show the big hole where the B model side radiator used to be. The scoop attached separately with cam locks. Drilled them all out today. First order of business is glassing in the big hole and making it look decent. My first time doing fiberglass work so wish me luck. 

 

Edited 17 Jan 2016 by C5Engineer

[Bandit 286]

Joey I have a cowling you can have if we figure out how to get it to you. It has never been fit to anything.

[sioux201 84]

Why not cover the hole with .016 or 20?

[EDMO 1078]

Joey,  Whatever (tin/aluminum?) you use as a support for the fiberglass cloth, be sure and put so much wax on it that it don't stick (it will) when you get ready to remove it.   We used 3 unbuffed coats of Johnsons Paste Floor Wax at Chrysler to keep the FG from sticking to car parts -Maybe there is something better now?  I know that there is a release film that you can use, but I have never used it.

EDMO

Edited 17 Jan 2016 by EDMO

[1avidflyer 1983]

You can also put packing tape over anything you don't want the fiberglass to stick to.  fiberglass won't stick to plastic once it dries/hardens up.   Jim Chuk

[EDMO 1078]

You can also put packing tape over anything you don't want the fiberglass to stick to.  fiberglass won't stick to plastic once it dries/hardens up.   Jim Chuk

We used so many layers and epoxy for our fixtures that sometimes they created enough heat to warp metal - I figured that the heat might melt or shrink the plastic tape and let the FG contact the support metal.

EDMO

[Luked 71]

+1 on the packing tape. I've used it many times. It's perfect for quick one off jobs like this.

[marksires 484]

You can also put packing tape over anything you don't want the fiberglass to stick to.  fiberglass won't stick to plastic once it dries/hardens up.   Jim Chuk

We used so many layers and epoxy for our fixtures that sometimes they created enough heat to warp metal - I figured that the heat might melt or shrink the plastic tape and let the FG contact the support metal.

EDMO

That's too much for a single layup then.

[Guest]

Wow my friend, you have started down a time consuming path. it sure was on my Fat Avid! 

[EDMO 1078]

You can also put packing tape over anything you don't want the fiberglass to stick to.  fiberglass won't stick to plastic once it dries/hardens up.   Jim Chuk

We used so many layers and epoxy for our fixtures that sometimes they created enough heat to warp metal - I figured that the heat might melt or shrink the plastic tape and let the FG contact the support metal.

EDMO

That's too much for a single layup then.

Mark,  Ours didn't have to fly - and the "engineers", (who thought they knew more than us dumbasses who did the layup), decided on how thick.   Sometimes they wanted 12 to 20 layers of cloth in one pour, and we did not use vacuum bagging - just poured and brushed epoxy on each layer!  Sometimes it was about an inch thick.

I learned a lot more in Av School.   

I think I was having a flashback when I wrote the above!   EDMO

Edited 18 Jan 2016 by EDMO

[marksires 484]

You can also put packing tape over anything you don't want the fiberglass to stick to.  fiberglass won't stick to plastic once it dries/hardens up.   Jim Chuk

We used so many layers and epoxy for our fixtures that sometimes they created enough heat to warp metal - I figured that the heat might melt or shrink the plastic tape and let the FG contact the support metal.

EDMO

That's too much for a single layup then.

Mark,  Ours didn't have to fly - and the "engineers", (who thought they knew more than us dumbasses who did the layup), decided on how thick.   Sometimes they wanted 12 to 20 layers of cloth in one pour, and we did not use vacuum bagging - just poured and brushed epoxy on each layer!  Sometimes it was about an inch thick.

I learned a lot more in Av School.   

I think I was having a flashback when I wrote the above!   EDMO

Lucky it didn't just spontaneously combust.  No reason you couldn't do that as several smaller layups, sanding between each cure.

[EDMO 1078]

You can also put packing tape over anything you don't want the fiberglass to stick to.  fiberglass won't stick to plastic once it dries/hardens up.   Jim Chuk

We used so many layers and epoxy for our fixtures that sometimes they created enough heat to warp metal - I figured that the heat might melt or shrink the plastic tape and let the FG contact the support metal.

EDMO

That's too much for a single layup then.

Mark,  Ours didn't have to fly - and the "engineers", (who thought they knew more than us dumbasses who did the layup), decided on how thick.   Sometimes they wanted 12 to 20 layers of cloth in one pour, and we did not use vacuum bagging - just poured and brushed epoxy on each layer!  Sometimes it was about an inch thick.

I learned a lot more in Av School.   

I think I was having a flashback when I wrote the above!   EDMO

Lucky it didn't just spontaneously combust.  No reason you couldn't do that as several smaller layups, sanding between each cure.

We sometimes had them turn brown from heat.   Supervision - Time - Manpower - Deadlines!

EDMO

[Fly-n-Low 181]

Use to work for a guy that built race boats. Also managed a fiberglass production shop. I like using wax as a release agent. Don't have much epoxy or vacuum bagging experience. That was after my time. Mostly polyester and vinylester.

Haven't had any parts get hot. We mostly used multiple thin layups on the boats because it was lighter and more consistent . Gelcoat, that is another matter. It would get hot and go to smoking. Stunk like all get out!!!

 

[EDMO 1078]

We argued for years about not having proper ventilation system for grinding fiberglass, and improper masks - Got nowhere with company representatives.  Finally figured out that the epoxy could cause cancer - maybe that's why several of us got cancer later after retiring, or maybe from breathing welding smoke, or both?  Difference between working with this stuff constantly for years, and just doing a cowl repair, is huge!

EDMO

 

[Luked 71]

I like to use a couple coats of wax and then some PVA if you are using a mold with some compound curves. If it's a fairly simple shape though without a lot of compound curves the packing tape works great. I've done repairs like Joey's cowl patch with just some stiff card stock and packing tape. Just feather the edges around the area to patch a little.

I've found that the biggest thing for getting good results with fiberglass is good planning and preparation before you ever start mixing the resin. Everything has to be planned out and in it's place ready to go before you start. The right tools help a lot too. I like these rollers (especially the little one) to remove air bubbles.

http://www.fibreglast.com/product/Barrel_Rollers_1151/Supplies_Tools_Rollers_Squeegees

If you don't have the rollers, some cheap paint brushes from Home Depot can work too. Just buy a bunch since you just through them away. The flexible squeegees in the auto body section are good too.

One other trick I found helpful when I was starting out was to use a thin piece of clear plastic to wet out each later of cloth. cut the plastic a few inches bigger than the cloth piece all around. Lay the cloth on top of the plastic, but reversed from the way it will go onto the layup area. Wet out the cloth on the plastic, and squeegee any excess resin off the side. Then flip the whole thing onto the layup area. You can use a clean squeegee to work the cloth into the previous layer. Then just peel the plastic off.

After the last layer, a layer of peel ply helps with the finish too. Wet the peel ply just enough that it is completely wetted, but just barely. Fiberglass is a lot of fun once you get comfortable with it.

[EDMO 1078]

We used the cheap nylon brushes used for cleaning up machine chips - short, strong bristles used to pat the epoxy down into the weave of the cloth as each layer is applied - just put a coat of epoxy on your taped/waxed support piece, lay the dry cloth on it, more epoxy spread on the cloth, and patted into the weave with the nylon brush - then repeat layer of cloth, pat with brush, epoxy if needed, then next layer.  Yes, peal ply for last layer if going to paint or bond to something else.

EDMO

[Luked 71]

Oh yeah Ed, good point I forgot to mention. If you use the cheap paint brushes from HD, cut the bristles about half their length so they are stiffer like you mention.

The method you described works just fine. Not saying my method works better. The reason I like the plastic is that it is the poor mans way to get a very accurate resin to cloth ratio to keep weight down. It especially seems to help beginners. You can even put the cloth between two pieces of plastic and it works almost like vacuum infusing. Just dump a pile of resin in the middle, and you can dry squeegee the whole piece of cloth in seconds. Either way works fine though. Just depends on your preference.

[EDMO 1078]

I forget what the proper name is for the chip brushes - I think sometimes they are called Acid Brushes.   I used to buy them by the box at Harbor Freight - Almost white nylon bristles, and very coarse - not something I would ever use for painting, and sometimes we did cut them shorter. 

Luke,  you method sounds fine, and probably turns out lighter than what we did - The weight of ours was no concern.

EDMO

Edited 19 Jan 2016 by EDMO

[Luked 71]

Oh, acid brushes. I know what you mean now.

[Fly-n-Low 181]

I use camel hair brushes. The cheap ones. They are the only ones that would stand up to the acetone bath they got after the job was done to reuse them (metal can with a lid so the acetone wouldn't leave). Rollers work great for rolling the air out of mat and squeegees work well with cloth. We use to use nap rollers on larger jobs. It was a two in one, add resin and roll air out. You got through, knock the nap off in the garbage can and put the roller in a can of acetone.

[Fly-n-Low 181]

We argued for years about not having proper ventilation system for grinding fiberglass, and improper masks - Got nowhere with company representatives.  Finally figured out that the epoxy could cause cancer - maybe that's why several of us got cancer later after retiring, or maybe from breathing welding smoke, or both?  Difference between working with this stuff constantly for years, and just doing a cowl repair, is huge!

EDMO

 

I am with you there. If bad I use a paper suit taping up the arms and legs, and stuffing a small towel around the neck opening, a head sock, and a respirator.

Most of the time I put multiple fans in several locations that blow the dust away and out of the shop.

[C5Engineer 1170]

Getting ready to start playing with the foam and see what I can come up with.

[EDMO 1078]

Joey,

Unless you have some clearance issues, or want to do something fancy, why not just rivet or screw / tape a sheet of tin, aluminum, thin plywood or stiff cardboard inside the cowl and lay your fabric over that?  All that foam, wood, and bondo looks like a big mess is going to be made!

EDMO

Edited 25 Jan 2016 by EDMO

[Luked 71]

Ed, I think there might be a little bit of a compound curve in that part of the cowl. If so, I think I would try the foam. It it's flat though, some cardboard with packing tape would probably work good.

[Av8r3400 1179]

Is your plan to make the foam mold on the outside or inside?