resin/mat,cloth ratios

is there any way of predicting how much polyester resin is needed to wet out different weights of mat and cloth? If I knew the optimal amount, it would give me a target to aim for as I laminate the boat I'm working on. We try to keep a slow cure time and acheive a wet laminate on the whole surface and roll it down very well. Still, we have no idea if we are close to optimal. Another part of the question is how much of the resin by weight is comprised of volitiles. I'm sure that the boat doesn't weigh as much as the combined glass and resin weighed before lamination. It would help to predict bare hull weight for a rowing boat that will be used to compete in open water races. At this point, I'm only comfortable with low tech lay-ups with no vacume bagging, resin infusion or exotic fabrics. Extreme light weight is not a prime consideration, strength, durability and low cost construction are more important at this time.

 

This is from "Fiberglass Boatbuilding For Amateurs" by Ken Hankinson, available at Glen-L.

https://www.boatdesigns.com/prodinfo.asp?number=12-435

http://www.glen-l.com/

You have to click on the thumbnail photo and then again on the resultant image to make it big enough to read.

 

Sam Sam, beautiful! just what I needed. The first 1/2 of the hull is done and now I need to weigh it to see how I did with the resin ratio. Many thanks Jeff

 

lay up weights

our current prediction for bare hull weight is 80 pounds. based on the charts, it is only about 4 pounds above optimum weight. We're doing a hand lay up with the resin lightly catalyzed and rolling the devil out of it as we go. The goal has been to get all three layers in before the first layer kicks off. So far So good! Now all we have to do is be VERY careful about adding too much weight in as seats decks and gunnels

 

What kind of rollers are you talking about? If you're talking bubble buster rollers and are using cloth, you might do better with a plastic squeegee.

 

Just ran accross this and remembered your post:

Chopped strand mat:
The general rule for chopped stand mat is 1.5 to two times the weight in resin to the weight of mat. So one pound of chopped mat would take two pounds of resin. One square yard of 1.5 ounce chopped strand mat weight 13.5 ounces so it would take 1 pound 11 ounces by weight of resin to wet it out. Or mat is 50 inches wide. One linear yard of 1.5 ounce weighs 18 ounces so it would soak up 2 pounds 4 ounce of resin by weight.

Here is a helpful table for cloth:

1.5 ounce cloth….1 gallon wets out 40 square yards

2.5 ounce cloth….1 gallon wets out 25 square yards

4 ounce cloth……1 gallon wets out 15 square yards

6 ounce cloth……1 gallon wets out 10 square yards

10 ounce cloth…..1 gallon wets out 6.5 square yards

18 ounce woven roving …1 gallon wets out 4.5 square yards

24 ounce woven roving …1 gallon wets out 3.5 square yards.

Please remember several things:

- these are estimates not hard and fast rules.

- if you are laminating over wood, the raw wood will soak up some resin, which is good, but you will use more resin on the first layer.

- thin resin goes farther than thick resin.

 

rollers

we use 4" paint rollers to apply and roll the resin in. the Aluminum rollers tend to move things around a lot and pull the mat out of the hard knuckles in the chines and keel.

 

bonding

we have laminated our new boat in several sections. each edge is tapered so that it can overlap the piece it mates with. they will be ground out from the inside. 2 layers of mat and 1 layer of 10 oz. cloth will unify the joint. My specific question is if epoxy is a good idea to initially bond the two mating surfaces before we add the mat and cloth.

 

The aluminum(?) rollers remove bubbles. If they pull stuff out of a corner, just repeatedly roll towards the corner , not away from it, and stuff will pack in the corner somewhat. They have to be kept clean so they roll easily or they will pull the glass no matter what you do. You can take the screw out of the end and clean the axle and drill out the roller part as resin builds up even if you clean it a lot. The grooves have to be kept clean or they won't work right, if resin builds up in them you can start them on fire with a propane torch and the resin will burn off, then use a wirebrush. Roller bubble busters or squeegee's will improve your layup a bunch compared to paint rollers or brushes. Practice.

 

we used the bubble buster aluminum rollers on the flat panels we laminated to use to fill in the mid section of the boat. Results were obviously superior, Will try to perfect roller work on next hull. I like the 20' boat so much that I'm thinking of building a 16' version as a single for my self and to possibly sell if anyone who sees it seems interested