Stitch & glue outrigger to glass inside or not?

Well, I thought that was clear enough:

when the designer has calculated them with a layer (or severals) of glass fabric then it should be done of course. That was said three times now.
If not, it is just adding weight.

The seams are almost always covered with a glass tape in stitch and glue technique. Yours is most probably no exemption.

No offense taken btw.

Regards
Richard

 

There is no need to glass the inside of a 1/4" ply ama. 1/4" ply has been used to build the hulls of 50' commercial catamarans and they only had light glass on the outside. Just coat the interior with epoxy resin.
Gary

 

I would agree with Chris. No need to glass the inside except along the keel line.

No need to glass the outside either, except along the keel line, if the boat is normally stored at home and only day sailed.

If you plan to leave the boat in the water then sheathing the outer surfaces is a good idea. It makes it a more waterproof surface and it helps stabilise the wood, so paint sticks better and lasts longer.

BTW 6mm ply is quite thick for a 16ft outrigger. Had you been building a very round bilge outrigger in say 3mm ply then glassing the inside would be sensible

Good luck

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

I think it would be a bad idea to glass the iside of the 1/4" hulls because they are already overbuilt. If you had built them in 3 mm ply, an option on the amas on my 24' tri, then light glass might be part of a package that reduces the chance of rot or damage over the years. My amas are at least 20 years old. Stored out of doors, and they were not glassed inside, yet they have held up well.

One thing I did do was glass the underside of the decks at Jim Brown's suggestion. Condensation can rise into that area and cause early rot. Unfortunately the decks go down with blind stappling/screwing, and even one erant hole in the glass can invalidate all the good work it might do.

 

Thanks everyone for the information. Thom D, I used 1/4" (6mm)thick Marine Ply because I guess I assumed that since I was using 1/4" thk strips to strip the main hull, and since I wasn't stripping the outriggers that 1/4" thick ply would be ok. I also believe that in Gary's book, he mentioned something about building ama's out os 3 or 6mm ply, but the ama's in his book were a lot smaller then the one I had built.

I calculated that these outriggers that I am building will weigh approz 60-70lb a piece, this includes glass on the outside. The dimensions are 16ft in length, 16" x 16" x 15" triangular shaped hull, tapered at the front. I do not think 60-70 lb will be too heavy for the main hull and beams I will be using.

 

You made the right choice with the 1/4inch ply anything less and you can hole it pretty easy.

 

In general you should do whatever the designer says to do. If you don't have his or her input and have to make the decision yourself, there are some points to bear in mind. These are my thoughts:

Glassing both sides will increase weight and strength naturally. With the triangular section, the strength gain is primarily from the outer glass skin. Inside glassing has its main effect on the stiffness of the chine seams which is largely irrelevant with a triangular cross section which is inherently stiff. Inside glassing will increase impact resistance too, but impacts will tend to be on the gunnels and keel; an impact on the heavily flared sides will tend to be deflected.

If water does penetrate into the interior it will remain in the wood if the inside is also sealed, having no opportunity to dry out. With marine ply, I would prefer to leave the inside unfinished and have a watertight hatch for inspection and drying out; a leak can be detected with a sniff as the smell of wet wood is noticeable.

 

Bote Cote epoxy has a timber preservative additive that also thine the epoxy to facilitate good penetration of the timber, unfortunately I don't think its available in America but you may find similar.
Cheers,
RR.
http://boatcraft.com.au/bc_products.html#TPA

 

thins, thins the epoxy

 

Do´nt ever thin epoxy, except with active diluents, or by temp. control! NO diluent makes the resin penetrate the wood better, thats a myth. Thinner could do that trick, but destroys the resins properties, leave it.

Regards
Richard

 

Apex, did you read the link or are you shooting from the lip?

 

The claim that the epoxy resin penetrates deeper with their product added is just wrong.
Epoxy does not penetrate deep into wooden surfaces, not even in endgrain Balsa! And there is no need to force it to penetrate deeper, hence my comment.

ahh, yes I gave it a short look, was´nt worth more.

Regards
Richard

 

Folks might want to thoroughly read this on-line document from Progressive Epoxies http://www.epoxyproducts.com/penetrating4u.html regarding penetrating epoxies, how they work, what works best, myths and the whole tamale.

 

Quite true Mr Ostlind!

Especially when one of the vessels built with that crap fail, and injuries or life losses are on your list of sins!


Solvents and thinners are a strict NONO in Epoxy resins......period!
Active diluents are another animal, but as mentioned do´nt do much to penetrate the wood deeper. (which is´nt necessary anyway)

the link provided leads to amateurs opinoins rather than experts advice.

Regards
Richard

 

Interesting, Richard, when you originally said this... "NO diluent makes the resin penetrate the wood better, thats a myth."

Amateurs opinions...? Did you read the credentialing material regarding the author?


Paul Oman, M.S. MBA

Member: American Association of Petroleum Geologists (AAPG)

Accredited: Certified Petroleum Geologist #3688

Member: National Association of Corrosion Engineers (NACE)

Member: Society for Protective Coatings (SSPC)


Now, I don't know about you, Richard, but I get that this guy is qualified and well-versed with his products. I'm kinda tending to the person who works with this stuff everyday, has the education to make it well-founded and openly discusses the facts and fantasies about thinning epoxies.