Vinylester vs Epoxy on new plywood?

I don't believe it will make much difference. My gut wrenching experience was from quarter of a litre in an ice-cream bucket, I bet you spill more than that in a layup process.

Have a talk to Derek Kelsall. He specialises in Multihulls using Poly resin on Hi Density Foam, and says its a good solution using old tech materials. Engineered right, with a quality Poly resin, it may be all you need.
Catamarans - Kelsall Catamarans - Summary of Articles http://kelsall.com/TechnicalArticles/SummaryOfArticles.htm

 

There are some advantages to a hand-laid resin-rich laminate. If you have to do a repair, environmental conditions are not as critical. Also, the tools needed are minimal: a grinder and some brushes.

 

I'm not sure if you were referring to Derek in that comment there Gonzo, as Derek used to be a hand layup type of guy, but he does the bagging on a flat bench these days. One of his most recent converts was Rob Denney of HarryProa fame INTELLIGENT INFUSION – Harryproa http://harryproa.com/?p=1845. They improved on the technique for their particular application after getting Derek to do a demo for them years ago.

 

I wasn't referring to anyone in particular; just an observation for people that cruise in remote areas.

 

Ok, fair enough. I have trouble thinking why hand laid glass would be easier to repair than bagged layups. The "richness" of the underlying resin/glass ration wouldn't have any implications that I can think of.

 

If the laminate is engineered for hand-laid, the repairs can also be hand-laid. I think that is and advantage in remote areas where a repair needs to be done out in the weather.

 

As others have mentioned the savings in resin cost is not as much as you would think, I typically use VE on resin infusion projects and epoxy when wood is involved. In the US there are quite inexpensive epoxies available. I recently bought epoxy that is available for about $36 per mixed gallon in a 5 gallon kit size. A friend of mine did some tests with VE on cedar and the failure was the cedar, not the bond line. I still don't see a reason to use it though but he wont stray from west epoxy so there is a significant price difference for him. I do agree with dynel over plywood as a sheathing but there is no reason to use mat anywhere near VE if you vacuum bag or infuse, in fact Derek Kellsal dosn't even use it with polyester and he's been doing this longer than any of us. Mat was necessary back in the days of heavy woven rovings where there was not much contact area with roving on roving and polyester but not with the low profile fabrics weve been using for the last 35 years or so.

 

Yeah, but even IF the laminate was bagged, why on earth couldn't you do a good repair job in any conditions ??

 

Because sometimes all you have is a grinder and a brush.

 

Oh dear. You are not doing this on purpose are you ?

I will try to be super simple here. Why wouldn't a grinder and a brush work just as well on a bagged hull, as a hand laid hull ?

I dont think it matters how the hull was originally built - you can hand repair any polyester hull.

 

It would be impossible to make a proper repair on a vacuum bagged laminate with a brush. Hand laid laminates are resin rich and much thicker for the same amount of fiberglass. That means they will be stiffer, and create a hard spot at the edge of the repair. It is possible to make a patch, but not a good repair.

 

Thats what I thought you were thinking, but I dont believe it myself.

For a start, it would depend on the thickness of the skin, the location of the repair, the strength of the hull scantlings, etc.

Also, hand laminates are NOT all that much thicker in all cases. The couple of glass boats I have owned under say 26 ft, the hand laid laminates were around say 4-6mm. Even if they had been bagged, you would still have to have that same thickness to get the required stiffness. The only advantage of bagged production would be an overall stronger hull with more re-inforcing amongst the resin.

I bet most glass repairers would just do a hand layup on any damage less than a few metres in area.

Have you got any actual examples to show the pros and cons ?