glass/epoxy over wood

here we go again.. i'd like some of your opinions on lamenating fiberglass and epoxy over a double planked hull. she's a 40 foot cutter-rig sailboat. 1st layer of planks run at a 45 degree angle to the oak frames which are 10 inches on center. the outside planking runs with the waterline, horizontal. all is resorcinol glued, plank to plank and all edges. i want to cover her with 6 oz. cloth and epoxy for about a 3/8" total thichness, for added strength, water tightness etc. i have re-fastened all planks already, plugged and faired.
whats the general concensus? she's not a race boat, 35 yrs old, but being re-fit for cruising...
thanks,
jomo
jomoman55@yahoo.com

 

I had a 35' prawing boat that had been covered in glass to extend it's working life. In this instance, all the covering did was condem it to death. The moisture in the wood had nowhere to go, and it was literally just held together with the fiberglass. After cutting out the fish hold, cutting some areas of the existing fiberglass off the hull, I realized it was time to scrap her, and I was able to salvage the valuable items , engine , electronics etc which I pieced out for what I had paid for her. The general concenus at the dock was that it was the covering that had killed her. Just my own personal experience here, but I thought it was worth mentioning. There are a lot of experts here, (of which I am not, nor claim to be), which I'm sure will point you in the right direction.

Cheers!

Kevin

 

Jomo,
So you are basically saying the hull is double layer srtip planks? No wide planks? If it is strip planked say 1or 2" wide planks, it shouldn't be a problem, wider planks are much less dimensionally stable. The hull would need to be thoroughly air dried and epoxy coated on the inside as well as out. 3/8" thickness seems to be way overkill as well as adding considerable weight to the hull.

 

Jomo

If you wanr\t to do it for added strength, thenleave it. The present construction looks pretty strong already to me construction. The more that account is taken for the fact that wood, when wetted or wet looses about half of it's strength.

Resorcinol gluein is good. Very good indeed. It means that the seams are thin and such a bond will hold for tens of years.

So a casco cover of glass/epoxy will not make the boat stronger but may avoid leakage and what counts more it will prevent wood getting soaked.

You have to do it till the top of the wind/waterline, or if you want it per sé you can do the whole boat.

You have to make sure that the boat is sufficiently dry (less than 8% which will be difficult to get, but go for the max.)

Remove all paint and rough it up with 60 or 80; make sure that all pain has gone, underwatership idem.

Primer i by way of an impregnation-epoxy; this is a thin epoxy that will be applied to get a maximum attachment between the glass and hull.
Sand the 1st layer with 80 after it has dried out then continue to apply the glasscloth.

Note: You have to fair the hull afterwards. A heavy glass-fabric requires more fairing compond than a lighter one, Remind that for fairing you will need to apply between 2 and 3mm fairing compound - no Bondo (= polyester) use an epoxy fairing compound that fits in the range of epoxies you use.

A good epoxy I believe is RAKA. You will find it somewhere in the threads it seems to be good stuff and less expensive than WEST systems, although WEST is very good quality resin.

Look very carefully at the instructions the resin manufacturer might issue.

And, of course, use protective gloves and safetyglasses. (spectacle)

Best working temperature is around 23 deg C,

To avoid cohesion, wet out the surface very good before you lay and attach the cloth - look out for white spots. Any white spot is not wetted out enough and does not contain sufficient resin.

Very generally ths is how it works If you are using more tha one layer, work as much as possible wet in wet.

 

Kevin

You had the misfortune to get hold of a boat that had been cascoverd with polyester.
Twentyfive years ago, one did not know that a polyester-wood bond had a limited lifetime.
Polyester is not water- and vapour tight so it comes loose after a certain timelapse, and let the wood rot below the sheeting as it takes lesser time to get the moisture in than out.