LEAK TEST

[P Doug (WA)]

I am at the point of needing to test my hull for leaks before putting the deck on.  This is a little minicup.  Right now it is not easy for me to get it to any amount of water to put it in.  I was thinking why not put water in the hull to see if any leaks out.  Any reason why this wouldn't be a good test for leaks as long as I made sure it was really dry before adding the strafoam and glueing/screwing the deck on?

[Bikermouse]

My only thought would be that any flex or allowance for movement designed into the joints is designed to resist pressure from the outside in.  By putting water on the inside, you may weaken the structure.

Compare it to tryin to kick in a door from the frame side as oppesed to the outside.  One way, the dor opens.  The other way, the doorframe is splintered.

Of course, I'm not a naval architect, so I may have no idea of what I'm talking about.

[lewisboats]

You can do it if you are prudent. DO NOT fill the thing to the brim. It is not designed to contain a thousand + lbs of water. Put only the weight of water that the boat will ultimately displace into it. Say the max displacement is 400 lbs...only put 50 gals (preferably less) of water into the boat and tilt the boat around to see if it leaks. Is the boat sealed completely on the inside?...if not you may be introducing water into endgrain of any exposed wood...not a good thing. Make sure your interior is sealed properly before filling. Personally I would look for a way to use a pool or something to test it in...someone you know perhaps?

Steve

[Andrew_Butchart]

There's a number of parts of the MiniCup that don't lend themselves to being filled with water.  If it were me (and a few years ago it was), I just turned the hose on the boat while upside down.  Mind you that was when I was cleaning the sanding dust off it anyway.

[P Doug (WA)]

Thanks for your input and I will yeild to the advice to not put water in it.  I will either get to water (not very heavy, wife could help) or wait for global warming to get the water to me! I wonder which would happen faster --wife help?--global warming?

[tjtansey]

Good luck P.  Luckily I have a handy river in my backyard.  Of course I'd have to cut down abot 50 trees to get the boat there   So I can drive around the block I guess.

[JeffM]

This is beside the point, since you're not going to fill it with water, but--

The water pressure inside the hull might not be a problem, but the fact that that water-filled hull has to bear down on the ground would be.  Filled with water, the boat would weigh many times its normal load, and all that weight--normally distributed over the entire submerged surface--would instead be concentrated at the point where the hull is resting on your lawn or whatever.  I'd lay odds the hull would fail there.

[Barry Pyeatt]

Just out of curiosity, is the outside of the hull glassed?  Or is it still bare plywood?  If it is glassed, then what is your concern about being leakproof?  If it isn't, then it will be once glassed and painted.

I too would be concerned about putting any more moisture than is occuring naturally inside an unfinished plywood hull.  Takes a long time to get all the little tiny seams dried out and plywood really doesn't like direct exposure to water.  Veneer is a thin layer with lots of exposed end grain.  It will swell unevenly and I think you are going to create more issues than you need to.

[P Doug (WA)]

Will, I never intended to fill the boat with water.  That would amount to an excessive amount of weight.  I would only put in a few  inches in each compartment to get above the waterline.

The outside has 3 coats of epoxy on it, the inside is cocked and painted.  I didn't put glass on this boat because I'm cheap and I look at this as a throw away boat.  I want to try learning some boat building, some sailing it to see if I like it and if I am smart enough to learn to sail.  If I like it, the real boat will be a CS17 or maybe Princess 22??!

As I said I will take it to water, I'm working on my wife. 

[PAR]

A high pressure stream of water directed at the obvious locations, like seams and joints, will usually tell all. Use bathroom tissue in crevices, like the stem and along joints and seams on the inside of the boat. This will show the slightest amount of moisture that may have seeped in. Of course, you don't want to splash any from the garden hose into the boat to spoil the bathroom tissue paper test.

[Ken_Potts]

  I built a "throwaway" wood & fabric kayak because I was bored one February.  I used substandard materials and I expected to get two years service from it.  I was pleasantly surprised that there were no leaks the first time I took it out.  I subjected the boat to quite rough treatment and eventually I ran it over some rocks on a river (a lot of rocks).  It started to leak.  After some more beating it started to leak more.  Eventually it leaked a lot.  The reason I finally stopped using the boat was because one of the side decks collapsed after six years - Not because it was leaky   If I had protected the wood from water better the deck would have been solid for many more years but from its very conception the boat was meant to be a short-term diversion to see if I had a good hull shape.  The next kayak will incorporate what I learned from the first one while paddling it for hundreds of hours.   Leaking was never really an issue because even when I had beaten the boat up quite a bit I could still go out for a couple of hours without having to empty it.

  I'd say if it's a throwaway boat do your best to make sure you've got things watertight and then go enjoy it.  any leak that is really bad will be visible.  If you are building a non-throwaway boat the chances are you will have been careful enough that it won't leak.

  I guess what I'm trying to say is there have been lots of leaky but functional boats.  Finish her up and go have fun.  If you do end up having a leak or two you can take a look at where and why it leaks and it will be a good bit of knowledge for a future build.  It takes a pretty big hole to make a leak that will render the boat unenjoyable.

  And if it leaks and you decide it's not a throwaway you can dry it out over a winter and sheath the bottom with glass in the springtime.