[cal1320]

The hull on my johnsen skiff is waaaaay thin. What weight and type of cloth would be recomended for this?
Is there a formula for amount of epoxy per sq yd of cloth?

 

[Brett]

The weight of fiberglass per square yard is about
equal to the volume of epoxy needed to wet it out.

http://www.rotdoctor.com/products/landl.html

I like 6 oz tooling cloth for all my work.

 

[firecat1981]

is it designed to be that way? or did you grind it down to far?
I built my boat using 6oz cloth, on the hull bottom I had atleast 2 layers everywhere and 3-5 between the cloth and tape on the seams. I've had no issues yet, and it was very easy to apply and wet out. As far as epoxy to cloth ratio I didn't measure it out, I mixed it in small batches and did segments at a time, this also allowed my to take more time so I didn't have to rush when doing large parts.

 

[Frank_Sebastian]

Typical formula for laminate is 1:1.2 where 1=weight of glass cloth and 1.2= weight of epoxy to wet out the glass and ready it for installation. Amateurs may do a little more, say 1:1.3. This will not include enough to fill the weave, just to make a strong laminate.

For what you describe 5 oz "S" glass would be stronger and lighter.

Best regards,
Frank_S

 

[DuckNut]

I built my boat using 6oz cloth...

You used this to cover wood. I think his is solid glass and has no wood. Made from a mold.

 

[firecat1981]

You used this to cover wood. I think his is solid glass and has no wood. Made from a mold.

I fail to see any difference, cloth is used all the time for repairs on all types of boats. Plus the covering of wood only applies to the first layer, after that you are laminating to another layer of glass just like they do in a mold.

 

[cal1320]

Thanks guys. The hull has decent strength from the middle boxes back. It's just in front of the boxes it's flimsey becasue there is no support there. The strakes were originally the support  for that area but they were rotted out and it allowed the hull to crack. The PO tried to fix the strakes by using caulk and bondo. I removed them and will rebuild them with new wood and glass tape after I put a layer of glass on the bottom.