Thread: To Seal of not to Seal

i'm sure one of the more knowledgeable members will be along soon but i'm sure if the timber is dry then is will be ok but if it does have any moisture it will be trapped and cause rot over time.

by the way nice job on the exterior of the hull

Yap agree with HKP!

it is a really big job to remove lots of paint from the inside, epoxy seal and fillet. Sometimes a shortcut will help get the boat used again.

Epoxy will help take care of the boat if it gets treated badly. But if you did the filleting only it would help a fair bit and providing you prevent water from sitting inside the boat when it is not used it will be OK.

Full epoxy would be better still ... but it is a lot of work on the interior.

MIK

Thanks guys,
wow! channel islands, the internet is amazing heh!
I suppose what I meant to say was if I partially epoxy the inside sections of the boat to strengthen it and it gets wet, which it will... trust me. Will the water/moisture wick into these areas and then remain trapped and remain wet?

I'm kind of already getting the feel that I should strip all the paint out, epoxy and be done with it.

Thanks
Martin

Well Martin, you've just learned a lesson about slapping fibreglass over wooden boats and a lesson about the scouts as well - that's not knocking the scouts but sometimes they go to extremes to do things the hard way. But that's cool. The boat you have will become a practical and useful craft ... which is why the scouts bought it in the first place. Good pick up I reckon.

Have fun rebuilding her. I won't offer any sage advice because you're digging in areas in which I'm only fooling myself I know something.

Richard

The worst type of water sits inside a boat when it is on the trailer or stored. The water while sailing is only a tiny time in comparison.

An epoxy sealed boat will resist poor storage a lot better than one that is not fully epoxy sealed ... but using the boat is such a tiny time - fixing the leaks with epoxy and painting it conventionally will give you a life similar to a painted and non epoxied boat.

Michael

being a bit new I'm not quite sure what the go is, so I'll just say I appreciate your thoughts so thanks to Michael, Richard, & HKP, I've got some clarity to go forward with for the time being.

If you're convinced the boat is strong enough as built, then adding an epoxy fillet to the seams will be redundant. Fill them with a polyurethane sealant. If on the other hand, you think the hull is flexing and opening up these seams a wee bit, then you need to strengthen them and an epoxy fillet can do this job nicely.

Epoxy is great for waterproofing and bonding, but it resists sunlight/ultraviolet poorly, so if you do clean it down to bare wood in those leaky areas and then seal with epoxy, do paint over it. Just expecting a layer of epoxy to have a long life on wood is not a good idea. Gougeons, the makers of West epoxy recommend in their boat building book that one needs 3 coats to really seal wood on a boat. My experience is that it pays to epoxy a layer of glass cloth or glass tape over the problem area, the glass stops hairline cracks from forming in the epoxy as the wood beneath shifts or swells in use. Painting epoxy always requires that the surface be cleaned of any amine blush, by washing well with soapy water and rinsing thoroughly, then it helps to sand the surface to provide a key for the paint, which would much prefer to have some wood to soak into and grab hold of.

A fillet with a radius three times the ply thickness is adequate. Won't need glass unless the plywood is deteriorated in the area you intend to fillet.

MIK

I will not argue with you about the adequacy of a good fillet on sound wood, I just say that on the kayak and the dinghies I have built I always felt that a taping of light cloth over the interior seams was always worthwhile insurance. "Yer pays yer money and yer makes yer choice"

Yep, but there has been real research in real university departments using real testing machines that show that the fillets actually work without glass. Uni of Queensland did testing to work out required fillet and timber sizes to join plywood.

As boats get bigger, I would agree with you as the size of the fillet gets so big it becomes uneconomic making a fillet and glass a better choice. After 9mm I am usually using either timber or a smaller fillet with glass to save on the epoxy cost.

Insurance where it is not needed is making a choice to pay extra money.

Like all the seakayak designs coming out of the US at the moment with 6oz (200gsm) glass inside and out of 4mm ply. I am sure both of us would be scratching our heads over that one! For most uses anyhow. It is insurance gone mad.

Best wishes
MIK

I've seen research along the same lines Michael and it backs up my own testing as well. Traditional fabrics in particular aren't really necessary on small fillets and correspondingly light loads, the wood fails first. On the other hand I reach for biax when the fillets get around 1/2" or loading will test the structure.

What's wrong with a kayak that has 6 ounce inside and out? Maybe 8 would be better . . .

I'm not a paddler or rower. I've a torn rotator in my shoulder that makes either uncomfortable quickly. If I can clamp a trolling motor to it, I'm good. I do have a few kayak designs, one is a not so stable, but a very good performing puppy. It has a 1/4" bottom with 1/8" sides and deck. Very maneuverable (by reports, because you wouldn't catch me in it) and quite stiff, which apparently some folks like more then others. It's 4 ounce outside, with 4 ounce inside the lower cockpit area for abrasion, fillets only everywhere else. Would this be typical of you're light weight stuff?

Howdy PAR,

I have moved my goalposts in the last year.

Most average use plywood kayaks don't need any glass covering at all. We had scores of the things built in my early days when iwth duck flat and they never seemed to suffer much or any damage.

Formerly once moving away from basic recreational stuff my thinking would have been in line with yours.

But after hearing that the 18 ft cabin Jarcat is mostly 4mm ply with 2oz glass on the outside only and knowing how many of them have been built ... I would probably go that way for anything more than a boat that is being used recreationally or less that true sea expeditioning.

However the practical side for a boatbuilder or materials supplier is that it is simply one more roll of cloth to pay for to sit in inventory. it is OK if it gets used regularly!

Every ounce that can be kept out of a kayak makes it more usable and more pleasurable. And something to impress people with who think that "wooden boats are hearvy"

MIK