Fiberglass cloth and roving questions

trendsetter240

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I'm in the process of replacing transom, stringers and deck in my 17 foot runabout. Here are the supplies that I have already.


9 yards of 6oz cloth 50" wide.
3 yards of 24oz woven roving, 50" wide.
1 gallon of West Systems Epoxy 105
1 quart of West Systems Hardener 205


My plan is to use a thickened epoxy to bond the stringers to the hull followed by filleting an edge along the joint to the hull. Then to use a 8" strip of cloth over the joint between the hull and stringer. (4" of cloth extending up stringer and 4" onto the hull).

Then I plan to place a strip of the 24oz roving, 12" wide over the first layer of cloth. Then to finish it off another layer of cloth wrapping over the entire stringer and extending 12 inches out on the hull from the joint.

Does this sound like enough strength and waterproofing for the stringers? can I do this job using the cloth and roving that I already have?

Advice would be much appreciated, I've never done this before.

Thank you.:)
 

Cadwelder

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Re: Fiberglass cloth and roving questions

Not an epoxy guy but strength wise sounds fine, but 1 gallon ain't gonna do it.
 

trendsetter240

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Re: Fiberglass cloth and roving questions

Not an epoxy guy but strength wise sounds fine, but 1 gallon ain't gonna do it.

Hey, thanks for the reply. Do you think the 1 gallon of resin will be enough for 3 stringers? They are 1.5"x 8" high. I planned on buying more resin for the transom and floor last.

Do I need to do the transom first? Now that I think about it that would probably be easier but I don't know.
 

ondarvr

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Re: Fiberglass cloth and roving questions

Add up the total weight of glass you plan to put on each stringer and it will about equal the weight of epoxy you will need. You will actually use more epoxy than that due to some waste and inexperience though.
 

trendsetter240

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Re: Fiberglass cloth and roving questions

Add up the total weight of glass you plan to put on each stringer and it will about equal the weight of epoxy you will need. You will actually use more epoxy than that due to some waste and inexperience though.

Hey ondarvr, I was hoping you might reply. I've read many of your posts and you really know your stuff.

What do you think about the cloth/roving/cloth idea I outlined in my first post? Is that what you might do if you were in the same situation with the same supplies? Would it be sufficient to just use the cloth or to just use the roving?

As you can see I'm totally inexperienced but I'm trying to learn.

Thanks
 

Woodonglass

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Re: Fiberglass cloth and roving questions

Welcome to iBoats!!!!

Usually the Stringers tie into the Transom so you should always install the Transom First. You are going to need a MINIMUM of 5 gallons of resin. You do NOT have to use epoxy. It is OK but MUCH more expensive to use. Easier on the lungs and nose but not the wallet. If you stay with the epoxy you could use the 6oz cloth to cover your stringers and the deck. The roven woven would be good for the transom. I'd guess you'd use 2-3 gals on your stringers.
 

trendsetter240

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Re: Fiberglass cloth and roving questions

Welcome to iBoats!!!!

Usually the Stringers tie into the Transom so you should always install the Transom First. You are going to need a MINIMUM of 5 gallons of resin. You do NOT have to use epoxy. It is OK but MUCH more expensive to use. Easier on the lungs and nose but not the wallet. If you stay with the epoxy you could use the 6oz cloth to cover your stringers and the deck. The roven woven would be good for the transom. I'd guess you'd use 2-3 gals on your stringers.

Hey woodonglass, thanks for the reply!

The main reason i chose epoxy is I can't have strong chemical fumes where I am working on the boat. I have the budget available for this project so even though cost will be high I'm will to do it.

I guess I will try to do the transom first with the 1 gallon I have. With the hardener mixed in it's a little more than a gallon all together.

I guess my concern is strength on the stringers. I read somewhere that cloth doesn't have much strength to it. But using epoxy with several layers of 6oz cloth do you think that will be sufficient?

Thanks everyone.
 

ondarvr

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Re: Fiberglass cloth and roving questions

It's not that cloth isn't strong, it's that you need many layers of it to equal the same strength of heavier weight fabrics and that cloth is very pricy per pound. 17 oz Biax will cost less for the same strength, 18 oz roving will cost even less. For the most part the strength is determined by the total weigth of the glass used in the laminate (leaving out the mat), so two layers of 6 oz cloth won't be as strong as 1 layer of 17 oz biax. This is just a general statment because each type of glass (woven or stitched) will have different properties.
 

88BLiner

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Re: Fiberglass cloth and roving questions

Hi trendsetter, I don't want to give you miss information on your use of 6oz but will try to help by telling you what I used on my transom. For my transom I used 3 layers of 1708 biax cloth. One layer of 1708 is about the same as three layers of 6oz. I am also using epoxy and it took me about 2 gallons but there was some waisted epoxy. My stringers will also get three layers of the same. I could have probably got away with two layers of 1708 but I wanted to be safe. I hope this helps a little. If you have any questions about 1708 biax then I will gladly help as much as I can. The main persn I would listen to in my opinion would be ondarvr. I certanly hope he will one day take a look at my project.:)
 

trendsetter240

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Re: Fiberglass cloth and roving questions

Hi guys, believe it or not none of my local fiberglass suppliers carried the 1708. Initially that is what I was trying to find. Even tried for the 1700 Biax (which I understand is the same as 1708 but without the mat).

In the end I only went with the cloth and woven roving because I got it dirt cheap in bulk. I mean, I could potentially buy more glass but I'd like to use the stuff I've got if I can.

Using the roving for my transom and the cloth for my stringers and deck is where I'm leaning at the moment. Maybe I will have to go 4 layers with the cloth on the stringers. I should have enough for for that. I have 112 sqft of the 6oz cloth.
 

Woodonglass

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Re: Fiberglass cloth and roving questions

Using Epoxy You do NOT need the 1708 Biax. It has 8 oz of mat sewn onto the back and is NOT needed with epoxy. In fact it is a waste in that it adds no strength and just soaks up more epoxy thus cost more. the 1700 biax ondarvr suggested IS what I would also recommend for your transom. 88 IS correct in that you will probably use about 2 Gallons for your transom. You will also need some cabosil or some sort of thickening agent for filleting and for attaching the transom to the outer skin. I think 3 layers is over kill. Two should be sufficient for the transom. I agree with Ondarvr that the 6 oz cloth is not much good for your application. Possibly for the underside of your deck.
 

trendsetter240

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Re: Fiberglass cloth and roving questions

Using Epoxy You do NOT need the 1708 Biax. It has 8 oz of mat sewn onto the back and is NOT needed with epoxy. In fact it is a waste in that it adds no strength and just soaks up more epoxy thus cost more. the 1700 biax ondarvr suggested IS what I would also recommend for your transom. 88 IS correct in that you will probably use about 2 Gallons for your transom. You will also need some cabosil or some sort of thickening agent for filleting and for attaching the transom to the outer skin. I think 3 layers is over kill. Two should be sufficient for the transom. I agree with Ondarvr that the 6 oz cloth is not much good for your application. Possibly for the underside of your deck.

Let's say that I use the 24oz woven roving (which I already have) for my transom. Would a single layer be enough? The outer skin is going to stay intact. I will only be replacing the inner skin.

Maybe I am confusing myself. Is it safe to say that for my transom I could use a combination of roving and cloth totalling 30oz? And for the stringers 3 layers of the 6oz cloth totalling 18oz?
 

Woodonglass

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Re: Fiberglass cloth and roving questions

I suppose that would work, but You will REALLY soak up a LOT of Resin IMHO. Especially on the stringers. Hopefully Ondarvr will revisit or you could PM him. I typically use Poly on Glass boats and Epoxy on wood boats. Don't use roven woven much. He would be much better qualified to comment.
 

trendsetter240

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Re: Fiberglass cloth and roving questions

I suppose that would work, but You will REALLY soak up a LOT of Resin IMHO. Especially on the stringers. Hopefully Ondarvr will revisit or you could PM him. I typically use Poly on Glass boats and Epoxy on wood boats. Don't use roven woven much. He would be much better qualified to comment.

Ok, thank you. I really do appreciate your input. Soaking up lots of resin means soaking up lots of $$$ so I will be keeping that in mind.

I would love to be able to use the fiberglass I have but I will go shopping again if it means saving money on resin and a better rebuild on the boat.
 

ondarvr

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Re: Fiberglass cloth and roving questions

Maybe I am confusing myself. Is it safe to say that for my transom I could use a combination of roving and cloth totalling 30oz? And for the stringers 3 layers of the 6oz cloth totalling 18oz?


This would probably be fine, just use the glass you have on hand and if you think it looks thin or weak add another layer.
 

trendsetter240

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Re: Fiberglass cloth and roving questions

This would probably be fine, just use the glass you have on hand and if you think it looks thin or weak add another layer.

Thanks ondarvar, I still have some grinding to do before glassing the transom this weekend. I'll post back some pics and questions if I run into any issues.

Thank you again everyone for your advice.
 

trendsetter240

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Re: Fiberglass cloth and roving questions

Just wanted to post an update now that I have glassed in the new transom.

The previous construction was a repair/replacement done by the previous owner.

Old repair that failed:
All previous repairs were done with poly and CSM for the transom
From the outside in it went:
1. Outer skin
2. Layer of poly/CSM
3. 3/4 plywood
4. Layer of poly/CSM
5. 3/4 plywood
6. Inner skin of poly CSM.

The failure was under the splash well thin glass allowed water to enter the transom and soak the wood. The glass didn't fail just looked too thin and patchy and allowed moisture in causing the wood to fail.

My repair from the outside in:
All my repairs were done with Epoxy.
1. Outer skin (patched all holes with 2 layers of 6oz cloth on outside, filled holes with thickened epoxy, two layers of 6oz cloth on the inside.
2. 1 layer of 6oz cloth wetted out and applied to the outer skin.
3. 3/4 plywood coated in epoxy. (Clamped in place and allowed to cure for 1 hour)
4. 1 layer of 6oz cloth.
5. 3/4 plywood coated in epoxy wetted out and applied to 1st transom section. (Clamped in place and allowed to cure for 1 hour)
6. 1 layer of 6oz cloth.
7. Filled spaces around transom with thickend epoxy.
8. Built up seams where transom joins hull with 2 layers of 6oz cloth. (cut into strips 10" wide like tape)
9. 1 layer of 24oz roving covering entire inner skin of transom.

It's all cured now and is solid as a rock. I'm quite certain this will be more than enough strenth for the transom. Next step is to lay the stringers. I will be using the same 6oz cloth to tab in the stringers to the transom with a single layer of 24oz roving over the stress points in the joint.

Thanks again for your help guys. If you have any comments or suggestions about my repair please post back,

Cheers.
 

rickryder

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Re: Fiberglass cloth and roving questions

Sounds like your making good progress! Get some pics up! We love them pics :D
 

lvl

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Mar 22, 2009
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Re: Fiberglass cloth and roving questions

I am by no means any type of expert but will point out one thing I haved learned reading here. When putting down new stringers never put the wood directly on the hull. It will cause hard spots on the hull. I think you should put down a layer of peanutbutter type epoxy mix to glue the stringers to the hull. Some people use PL premium construction adhesive. Just my 2 cents like I said not even close to an expert like many others here.
 
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