General fiberglass materials questions.

i386

Captain
Joined
Aug 24, 2004
Messages
3,548
First off, I have never worked with fiberglass, epoxy or polyester resins except for all the grinding/cutting I've done lately. I need a lot of advice on materials and methods. I tend to over engineer things that I don't have any prior experience with.

Please take a minute to click the Boat Restoration link in my sig and look at the pictures. You should have a pretty good idea what I'm dealing with.


For starters, I don't know which resin was used to build the boat. I intend to do my repairs with whichever resin was used to build it. I've read all the debates about both systems and what I take from it is that epoxy is better but polyester is cheaper and good enough for most applications (and probably mine). If I was building a boat from scratch I'd use epoxy for sure.


These are the things I need to do. Any help on specific materials would be extremely helpful.

1. Repair some small holes in the hull. There's a place on the keel up front that was repaired externally by a previous owner. I'd like to repair this from the inside so I can grind/sand the repair off the outside and refinish. Resin? Fabric(s) weight?

2. Install a new floor. The plywood that came out measured 3/8" thick. 2 sheets of plywood should do the floor and the piece that goes in the transom. I know the plywood in the floor needs to be cut to size, and sealed on both sides. Then I need to glue it down with "peanut butter". How do I make peanut butter? Cloth needs to go over the plywood too. Cloth weight? Resin?

3. Repair the transom. I think I need to do a layer of cloth across the back to replace what I ground off. Then I can cut the wood. I saved the rotten piece for a pattern. I need to glue up 3 layers of plywood. Resin? Peanut butter? I need to glass in that piece of wood too. Resin? Weight of cloth?

4. Rejoin splashwell to the rest of the "top half" I had to cut apart. I figured I'd do some grinding at the joint to make a "V" in the top side to put peanut butter in (fillet?) and use some cloth on the back side where you can't see it. Cloth weight? Resin? Good idea?

5. When it's time to join the top half with the hull, the stern section (splash well) needs to be peanut buttered in. I say this because as the boat was originally constructed there was a layer of peanut butter between the outer skin and the splashwell. This is why I had to cut off the splashwell and pop it loose using a car jack.

6. Finish. I'd like to gelcoat the whole thing white. Roll & Tip? Add some nonskid stuff to the "deck". Good idea? Gallons required?



The days of 90 degrees outside are gone. This is also something to be considered.



Sorry such a long post, just trying to provide as much detail as possible.
 

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: General fiberglass materials questions.

First, you are going to need quite a bit of resin to do your project properly. I'd say start with 2 five gallons buckets (polyester or vinylester). I'd then buy a combination of 1708 and 1.5 oz mat cut 38" wide. The 1708 is the structural stuff and the mat is a finish layer to more or less hinder print-thru of the 1708 pattern.

On the deck I would use no less than 2-3 layers of 1708 followed up by some mat. I'll be the first to say I am not a runabout guy and havent' worked with them before...but typically the a transom core on a fiberglass fishing boat is two sheets of 3/4" marine grade AB plywood. You don't necessarily need marine grade for the deck, exterior grade AC fir will work fine and the cost is much less.

You can make your own putty with resin and cabosil. Mix the cabosil in the resin until the desired thickness is reached. Adding milled fibers makes for the strongest putties and when gluing things together or making fillets around deck joints and transoms, you gotta add some milled fibers.

In general when repairing any damaged fiberglass you need to grind back the area to 12:1 bevel, which usually equates to 4" inches or so. I would then go back in with increasingly wider layers of 1708 until the area is built back up to proper thickness.

With the transom, I'd put at least 3 full layers of 1708 and them some additional 1708 tabbing at the angles between hullsides/bilge and transom .

Also, remember make all corners rounded. No 90 deg. like corners at all. Just take a look at any boat..that's were the cracks start. Go over all edges that need to be glassed over with a round-over bit on the router.

This is about it in a nutshell.

If you need a good place for materials.

www.mertons.com

Joe is the owner and is always of great help.

PS. He sells this product called Hull & Deck Putty. It's great. I stopped making my own structural putties. THis stuff is strong, just at MEKP

http://www.mertons.com/Epoxy/polyester_Resins/putty.html
 

i386

Captain
Joined
Aug 24, 2004
Messages
3,548
Re: General fiberglass materials questions.

Wow. I never thought it would require 10 gallons of resin and so many layers of cloth. That will probably triple (or more) the amount that was originally in the boat. As for the transom in this boat, the only wood was that small piece in the middle (see pics). If I add too many of layers back there I'll never get the top-half back in. The strength (in this boat) comes from the splashwell (I think it's called).

Lots of good information in that post though. Please keep 'em coming. :)
 

andy6374

Lieutenant Commander
Joined
Aug 4, 2005
Messages
1,617
Re: General fiberglass materials questions.

Like I said I have limited to zero experience in Runabouts. But for sure when making any repair, make it the strongest part of the boat (of course with out making a hardspot).
 

BillP

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Aug 10, 2002
Messages
3,290
Re: General fiberglass materials questions.

Google and you can find the formula for how much resin it takes before buying. Basically, the math will be how many total oz of glass are used and the same weight in resin is dupuclated for the estimate.

Fabrics are sold as oz per sq yd or oz per sq ft. Be sure to use the same conversion when mixing different types.
 

i386

Captain
Joined
Aug 24, 2004
Messages
3,548
Re: General fiberglass materials questions.

OK with a little more digging I've learned that:

1708 means 17oz bi-axial woven at 45 degrees.

Mat needs to be applied over 1708 to relieve the bumpy texture.

Cabosil & milled fibers added to resin for fillets and peanut butter or use pre-made putty.

Make nice round fillets before laying cloth so that there are no sharp 90* angles.

12:1 bevel for joining my cut pieces.

I can use my regular paint roller frames. I just need special rollers to go on them.

Good stuff. What about Gelcoat? I've heard horror stories about paint being bad because it'll only last 3 years and gelcoat bubbling up because it wasn't compatible with the resin.
 

neat

Seaman
Joined
Jun 28, 2006
Messages
52
Re: General fiberglass materials questions.

You will have no problems with gelcoat as long as you are using Polyester Resin.
I also heard horror stories how difficult is to spray gelocat.
Beleive me, it is easy as 1-2-3. I did mine in one hour and it is perfect, no drippings or nothing like that. It is cheaper than paint ($48 galon) and last 10 times longer.
 

i386

Captain
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Aug 24, 2004
Messages
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Re: General fiberglass materials questions.

neat, I looked at your pics. I noticed you put down some strips of mat before laying the plywood. Did you use straight resin or add some kind of filler when you glued it down? Does the mat help the plywood stick to your stringers? What's your plan to go on top of the plywood? Cool boat by the way! I wouldn't mind restoring one of those someday.
 

Holymann

Cadet
Joined
Sep 24, 2006
Messages
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Re: General fiberglass materials questions.

i386,

You asked the same questions I was writing out to ask.
Since our boats are so similiar, I can't wait to share pics, info, and compare notes.

I will not have a center console, but I will do some sort of inexpensive remote steering.

Holymann
 

seven up

Petty Officer 1st Class
Joined
Jun 4, 2006
Messages
275
Re: General fiberglass materials questions.

Hi,

Layering the plywood for your transom (cold molded) is going to produce an incredibly strong panel.

And when your panels are cut-to-fit for your new floor...consider going around all of the endgrain with the thickened resin you are using.

This space or chamber under your floor is going to be hot/cold/damp etc. A restoration completed and shown here on another thread shows a teak shower grate type of floor hatch next to the captains seat with trim...what a brilliant idea to get some ventilation under that terrific new floor(sole). Warm+Damp+Little Ventilation means Dry Rot.

Ther was something else I was gonna put but I forgot what else you are doing.


Enjoy
 

i386

Captain
Joined
Aug 24, 2004
Messages
3,548
Re: General fiberglass materials questions.

I forgot to mention I intend to fill all voids under the sole with foam. I'll need to use some of the center void to run cables to the stern. JasonJ ran into the same problem and I saw how he tackled it in his pics.
 

seven up

Petty Officer 1st Class
Joined
Jun 4, 2006
Messages
275
Re: General fiberglass materials questions.

hey again,

That shower grate I was raving about belongs to Denny787 on their Carvelle restoration...shown on the two pictures for "Monday May 08". Ummm, sole grate !

Yea, that's alot of foam and lots of flotation.

From the research I've done on repairing fiberglass hull holes; an accepted way to go about it from the inside is to go with a small cloth patch then a larger and then a larger cloth patch. The idea is for the finshed work to have a "bite" on the good glass at several locations. Stepping back...the idea looks very good as one layer is supported by the next, each with bite onto new surface. That is one way I've read about. Sounds logical.

Enjoy
 

neat

Seaman
Joined
Jun 28, 2006
Messages
52
Re: General fiberglass materials questions.

i386 said:
neat, I looked at your pics. I noticed you put down some strips of mat before laying the plywood. Did you use straight resin or add some kind of filler when you glued it down? Does the mat help the plywood stick to your stringers? What's your plan to go on top of the plywood? Cool boat by the way! I wouldn't mind restoring one of those someday.

Just the resin, no fillers.
Nothing will go on top of the plywood except cloth. Sides will be plywood too + some glass over. I love the look of the wood.
 
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