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Old 09-04-2016, 08:01 AM
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Two dumb questions

OK, here are two more questions in my series of dumb questions. One is on a metal question. If I join two pieces of, let's say, 18 gauge metal sheets, perpendicular to each other, with an exposed corner, what is the best way to get a slight radius on that outside corner? Do I just grind it on a slight angle and then mud it? Second. If I want a flat fiberglass panel that is two inches thick, how is that done? That is, would I make a mold for two halves so the outer skins are smooth and paintable and then bond them together and if so, what type of bonding material would I use?

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Old 09-04-2016, 11:12 AM
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On the metal question I would bend a piece in my metal brake for the corner and then weld that on the flat to make my corner. If it is to be curved then some work with the shrinker stretcher to make the curve to suit.

On the glass question make what we call flat and then bond the flats to a foam core or other suitable core material to make the thick piece that you want. Use a structural bonding adhesive or a contact cement for the bonding. Need to check that the bonding adhesive is compatible to your materials.

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Old 09-04-2016, 11:29 AM
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If using a brake at the edge of the panel or bumping the edge isn't feasible... for a slight radius that can be rounded a little when grinding I'd say just widen the welding gap a little so that your radius will be within the weld rather than extending onto the metal sheets.

I think Sam told you right on the thick part, use a suitable core. Possibly a board, maybe stacked cardboard depending on part strength requirements. When making sailboat keels we made the sides in molds and dumped steel plate punch out scraps in one side, filled with resin, and cap with the other half, bonding with more glass. But that was for max weight. There may be a foam out there you can just lay glass directly on, and I'm fairly certain you could just use wood but that's heavy. That would negate the need for bonding anything though.
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Old 09-04-2016, 02:21 PM
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Quote:
Originally Posted by idrivejunk View Post
If using a brake at the edge of the panel or bumping the edge isn't feasible... for a slight radius that can be rounded a little when grinding I'd say just widen the welding gap a little so that your radius will be within the weld rather than extending onto the metal sheets.

I think Sam told you right on the thick part, use a suitable core. Possibly a board, maybe stacked cardboard depending on part strength requirements. When making sailboat keels we made the sides in molds and dumped steel plate punch out scraps in one side, filled with resin, and cap with the other half, bonding with more glass. But that was for max weight. There may be a foam out there you can just lay glass directly on, and I'm fairly certain you could just use wood but that's heavy. That would negate the need for bonding anything though.
Thanks for the reply. So, on the fiberglass panels, these will be flat panels, smooth on one side. If I were to use a form core, say two inches thick, when I lay up my glass, on the foam, does the foam core stay in between the panels for good? How will I achieve a smooth finish on the outside if the foam core stays in between the panels?
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Old 09-04-2016, 02:24 PM
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Quote:
Originally Posted by OneMoreTime View Post
On the metal question I would bend a piece in my metal brake for the corner and then weld that on the flat to make my corner. If it is to be curved then some work with the shrinker stretcher to make the curve to suit.

On the glass question make what we call flat and then bond the flats to a foam core or other suitable core material to make the thick piece that you want. Use a structural bonding adhesive or a contact cement for the bonding. Need to check that the bonding adhesive is compatible to your materials.

Sam
Thanks for the advice.I need all the help I can get.
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Old 09-04-2016, 03:24 PM
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Originally Posted by V8Square View Post
Thanks for the reply. So, on the fiberglass panels, these will be flat panels, smooth on one side. If I were to use a form core, say two inches thick, when I lay up my glass, on the foam, does the foam core stay in between the panels for good? How will I achieve a smooth finish on the outside if the foam core stays in between the panels?

Oh... now I'm just guessing here but depending on how big said part is...

You could lay up one side then quickly after rolling bubbles out, flip it over onto a flat non-porous surface (or put down tape or paper or plastic wrap, mold release, whatever) then repeat on the other side and sandwich with plastic wrapped plywood and maybe a little weight. So both sides end up kinda smooth after you peel off what you can once cured. You could then sand / block off the rough stuff and finish with a layer of body filler and / or polyester primer.

I don't know just how technically correct this is, it would depend on the part. And yes the core would stay, just like wood in boats.
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Old 09-04-2016, 04:40 PM
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Originally Posted by idrivejunk View Post
Oh... now I'm just guessing here but depending on how big said part is...

You could lay up one side then quickly after rolling bubbles out, flip it over onto a flat non-porous surface (or put down tape or paper or plastic wrap, mold release, whatever) then repeat on the other side and sandwich with plastic wrapped plywood and maybe a little weight. So both sides end up kinda smooth after you peel off wh at you can once cured. You could then sand / block off the rough stuff and finish with a layer of body filler and / or polyester primer.

I don't know just how technically correct this is, it would depend on the part. And yes the core would stay, just like wood in boats.
So, if I were to take a two inch piece of foam, cover it with fiberglass, I could squeege (?) out the resin to get as smooth as possible, let dry, block sand and then apply body filler and finish . Correct?
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Old 09-04-2016, 04:50 PM
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Quote:
Originally Posted by V8Square View Post
So, if I were to take a two inch piece of foam, cover it with fiberglass, I could squeege (?) out the resin to get as smooth as possible, let dry, block sand and then apply body filler and finish . Correct?
If you do it that way you will have to apply some filler to make it smooth. wrapping it in plastic allows a smoother coat because it fills the weave of the cloth. Using a squeegee will make the weave patter stand up from the resin.
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Old 09-04-2016, 05:04 PM
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Quote:
Originally Posted by V8Square View Post
So, if I were to take a two inch piece of foam, cover it with fiberglass, I could squeege (?) out the resin to get as smooth as possible, let dry, block sand and then apply body filler and finish . Correct?
Well, you'd want to use a roller not a squeegee. They look like this-



Unless you're doing a very small part, then I like a paint brush. I'm not fit to give a fiberglass lesson but OldTech has the right idea. Masking tape works pretty decent for that if you butt the strips closely. Sands off easy enough.

But yeah, just treat it like you would a broken gelcoat area on a repaired factory-made part. You're just using filler instead of gelcoat.

I was talking about making a sandwich while its wet, to help mash the glass flat on the big sides before it cures. Heck, you could stand a part on one end and glass the top then knock that back and flip it over to do the other half. If it isn't structural.
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Old 09-27-2016, 12:55 PM
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Quote:
Originally Posted by idrivejunk View Post
Well, you'd want to use a roller not a squeegee. They look like this-



Unless you're doing a very small part, then I like a paint brush. I'm not fit to give a fiberglass lesson but OldTech has the right idea. Masking tape works pretty decent for that if you butt the strips closely. Sands off easy enough.

But yeah, just treat it like you would a broken gelcoat area on a repaired factory-made part. You're just using filler instead of gelcoat.

I was talking about making a sandwich while its wet, to help mash the glass flat on the big sides before it cures. Heck, you could stand a part on one end and glass the top then knock that back and flip it over to do the other half. If it isn't structural.
What's the best way to clean these rollers? Acetone? P.S. Check your mail for a private message I just sent you.
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Old 09-27-2016, 07:43 PM
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Yessir, acetone is the ticket. Don't splash any on your pants

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