Fiber glass hull, cloth and resin help

[Riotvan88]

Hi guys 

 

Building a scratch Zwarte Zee and now approaching the time to fiberglass the Hull. Previously built a smit rotterdam and used west systems Gflex epoxy only but this time I want to use cloth aswell. 

 

What is the best weight of cloth to use and what epoxy resin to use? The Gflex used previously was thick and probably not suitable for wetting out cloth. 

 

Just looking for suggestions and tips as to what everyone else uses. 

 

Cheers 

[JerryTodd]

I use 4oz cloth I get from DuckWorks, they sell 30" and 60" by the yard

 

Edited December 24, 2023 by JerryTodd

[Roger Pellett]

Experience from failed fiberglassing attempts over 50 years of full scale boatbuilding projects (I’m a slow learner):

 

1.  West System’s regular (I believe it’s their 105) Epoxy is expensive but very reliable if properly measured and mixed.  The ratio is 5 parts Epoxy to one part hardener so you need to figure out a reliable measuring procedure ahead of time.  Their calibrated mixing pumps make this easy.

 

2.  Do not try to glue the cloth onto the model’s hull!!  This will result in ugly wrinkles and air bubbles.  The correct procedure is to drape the cloth over the dry hull and to then apply the resin, working it into the weave with a small plastic squeegee.

 

3.  The resin cloth combination does not adhere well to sharp corners.  

 

4.  West System has a HUGE free collection of Information Sheets covering correct application of their materials.  Although aimed at builders of full sized boats, they are worth studying.

 

5.  Wear gloves.  The cloth is still glass regardless of how fine.

 

Roger

[64Pacific]

I am about to start putting glass cloth on my hull, at the moment work continues by reinforcing the rib to plank joints with a resin / filler mixture. I am using West Systems products as well, when I called their local distributor he had a lot to say and a lot of tips. My model is styrene and my concern was warping or other reaction issues, which there were none, see below.  My process will be to apply body filler on top of the plastic, then lay cloth on top and in some cases add more filler.  Another concerned was delamination and warping.

 

To test this a couple of quick models were built using the same method as the plastic tug hull; one had body filler applied and sanded, followed by cloth; the next had cloth applied and then body filler; both test pieces had  resin with filler applied on the inside to reinforce the rib to plank connection. Once everything dried it was left outside for a few nights at -40 and then brought back into the house, the idea here was to test extreme temperature differences and the resultant material expansion and contraction rates.  I was purposely rough with these to test the inter-layer adhesion, additional rough handling tests (trying to twist the test pieces) yielded no failures. While they could be snapped significant force was applied to them with out failure, the pieces did flex a bit and it was a surprise that no cracks appeared in the filler. No sanding was done at all with the exception of smoothing the body filler, after sanding the filler was wiped down with Acetone which was allowed to evaporate before the glass was laid.

 

My advice is to get some product, find some things with interesting curves and hard edges and try a few tests. Get familiar with the process on something that you have no problem throwing into the trash, nail down your technique before you touch your nice model work.

 

The attached images are my test pieces, quick and messy. The piece at left (light green) has body filler applied over glass cloth, while the one at right is cloth applied over the filler - on this one the cloth actually fell off as I was moving this around, I tossed it back on, added more resin and carried on. One piece (left) has a small strip of cloth inside between the ribs as well, this did add a small bit of rigidity to the structure. While not the nicest work this did let me dip my toes into the fibreglass world and disprove a few concerns that arose.

Edited March 10 by 64Pacific