Replacing rotted wood on a 17 foot fiberglass tri-hull.

[rs2k]

There is about a 4x4 section of rotted plywood flooring in the back of my 17 foot fiberglass Duo tri-hull. I cut it out and found the two beams spaced about 1 foot apart that go down the length of the boat are also a bit rotted right where the floor was the worse. The rest of the boat is fine. What can I do to fix it?

I was thinking about bolting a few feet of treated 6x2 wood beams to the outsides of both rotted beams and using aluminum plates to sandwich the rotted part on the inside. I then plan on replacing the plywood and fiberglassing the surface of the floor. Will this be OK?

 

[oops!]

Re: Replacing rotted wood on a 17 foot fiberglass tri-hull.

nope.....it wont.....

the idea is good but the materials are wrong....

1. use plywood to sister the stringers after the rot is cut out.

2.treated wood needs to be dryed (lots) before it will take resin...

3. treated wood does not like to be beside alum at all !

treated ply wood is great if you are doing a total rebuild.......you are doing a patch.

just use ext grade ply....and sister the stringers....then glass the deck down.....expectd life of jod 10 years

to do a total porper repair........see the compleated projects forum expected life of proper job.....25 years plus

cheers
oops

 

[rs2k]

Re: Replacing rotted wood on a 17 foot fiberglass tri-hull.

What type of wood do I replace the rot with? I'll get rid of all the rot later today to see what I have.


Take a look at the attached picture. Will something like that work? I am thinking of fiberglassing the plywood before bolting it to the stringer. Should I fiberglass or waterproof the decking in anyway?

What happens if the stringer is rotted all the way through? I don't think it is but it might be.


Thanks!

 

[oops!]

Re: Replacing rotted wood on a 17 foot fiberglass tri-hull.

use exterior grade plywood for that type of repair.....and yes....that diagramme is good.....you dont need that meny bolts....just some glass.

ther is a good possibility that the stringer is rotted all the way from top to hull in certain parts of the boat......cut out all the rot....do not leave any behind....it is a fungus and will keep going.

understand.....what you are doing is a patch......

if the stringer is rotted thru....cut it out, and add a new peice in that section. glass it in and sister it like the picture......

 

[oops!]

Re: Replacing rotted wood on a 17 foot fiberglass tri-hull.

but of course you realize.....another 15 hours labor....taking the whole stringer out and making new ones.....it will be done right.....permanant. weigh less, and give you peace of mind when its on the water.

 

[rs2k]

Re: Replacing rotted wood on a 17 foot fiberglass tri-hull.

What does it take to replace the entire stringer? Will I have to bend or shape the wood? Everything past the rear of the rear facing seats look good. I'm afraid to cut into any of fiberglass up front. I don't know how to remove the middle and front sections of the boat without cutting into the formed fiberglass.


Here are some questions I have if I decide to do the patch:

Should I attempted to make a simple diagonal scarf joint or should I just cut the stringer end to end?
Do I want to fiberglass any of the wood before bolting it together?
Do I want the fiberglass over the bolts?
What weight fiberglass should I use? Should I use mat or cloth?
Should I fiberglass the replaced stringer section before I put the sister boards on it?
Should I fiberglass the sister boards before adding them?
How much longer should the sister boards be than the repair?
Can the replacement stringer be treated? (I have two treated 2"x6"x8's ready to use.)
Will I just need two bolts at each end? (I like the idea of using bolts, but maybe they aren't necessary)


Thanks!

 

[oops!]

Re: Replacing rotted wood on a 17 foot fiberglass tri-hull.

all good questions.......

time to read....read....read.....

check out hull extension in progress.....it has everything you asked.

also read the compleated restoration forum...in specific...a project called skanky beast !

also erik green's unintentional stringer job !...

after that.....you will know all you need....but in a sec ill try to answer som of the questions

 

[oops!]

Re: Replacing rotted wood on a 17 foot fiberglass tri-hull.

if you want to do the patch....just cut the plywood 15 inches longer than the repair section of the orig stringer.....id just glue and screw...and glass the whole shabang togeather !

if you are using standard polyester resin....(unwaxed) i would glass over the screws....allways use a layer of matt next to the plywood and then a layer of cloth.....there is a product called biax....it has both mat and cloth togeather

read this one twice...it answers most of your questions

 

[rs2k]

Re: Replacing rotted wood on a 17 foot fiberglass tri-hull.

Thanks again for the information. I have done quite a bit of looking around. I'm a bit squeamish when it comes to taking off the cap. What kind of problems can I run into if I decide to do that? I'm afraid of not putting back on correctly or breaking it.

I took a skillsaw and cut out about 5 feet of plywood. I then removed about 4 feet of stringer on each side. There were small places of rot all along the top of the stringer where there were screw holes through the deck. Another problem is that the safety foam has water in it. I am tempted to do a complete restoration of the deck, but that's not really the reason I got this boat.

It looks like it will only take me about a day to finish this project if all I do is replace the cut out stringers, sister and fiberglass them, and replace the decking and put a sheet of fiberglass over it.

My plans for this boat are to use it for a while in the lakes of Kansas and then take it to San Diego, CA for the winter to fish in the ocean. If things go well for me I hope to have a nicer boat by next year. I would really like a Deep Vee hull with an I/O with a Chevy or Ford small block.