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CompKing
11-30-2002, 11:51 AM
Removed carpet to replace and found my outer starboard stringer was cracked.:eek: Decided to check the whole boat with a pick and was all solid except the port outer stringer:( The stringers are 13' in 2 peices that butt just in front of the seat box ( yellow arrow) the crack is 3" behind the butt at the front of the seat box.The rotted one is rotted in the white area middle of the stringer , worst at the top.I need some advice on best way and materials to use.I plan to replace the back 8' of the rotted one but want to know if I can just replace the broken part say 4' of the port one?I am also rebuilding the whole seat box.
What kind and grade plywood?
Best way to remove old stuff?
I have 3-1 epoxy with med hardner and a good supply of 7.5oz cloth 5.6oz carbon fiber and 8" 10oz cloth/ mat.What else do I need?
Thanks for any opinions and ideas.:)

Alan Power
11-30-2002, 01:28 PM
Hi comp king,

Bummer about the stringer but these things seem to happen to all of us, well this is how I would go about it. It's just my opinion and I would welcome anyone else's thoughts.

First of all the crack in your stringer, this is no major task, grind out the crack back to the wood, taper the edge of the repair out 5 times the thickness of the laminate, build up with 10oz cloth and lay two layers over the whole repair and surrounding area. If you are weight conscious you can taper out 10 times laminate thickness and not lay extra layers over.

For the stringer section removal, cut though the GRP 6" beyond the affected area at a 30 degree angle and about 1/2" above the hull along the length of the repair leaving the old radius, this will make things easier when you glass back. Remove the old laminate with a chisel. Now cut the stringer timber at the same angle as before 3" away from where you cut the GRP skin. Remove the rotted section and clean out the bottom between the two skins you left along the bottom. Make a replacement piece of timber to fit snug in place of the old. Brush some epoxy onto the 4 joint faces and along the bottom of the new piece where it will join to the hull, allow this to cure. Mix up some more epoxy this time mix in some colloidal silica until you get a consistency like honey or a bit thicker! Apply this to the joints and again along the bottom, fit the piece and put some weights on it. Scrape off any ooze and allow to cure.
Taper the glass again 10 times the thickness of the original laminate.
When cutting the glass cut the first one so it will just run onto the tapered area of the old GRP and out about 1" onto the hull, over the 1/2" of original skin left at the bottom. Cut the next pieces larger and larger again so they build up and up along the tapered GRP and out over each other onto the hull at about a 1" stagger. As for weights of materials, try and go back with what was there before, just build up the same thickness using the materials as close as possible to the originals.

The grade of plywood we use over here (Ireland) is BS-1088 Marine grade, the BS is for British standard so I don't know if you will have the same system?

For removing Glass from timber, cut around the perimeter of the area to be removed with a grinder and remove the glass with a chisel.

Well thats it, if you have any questions on this post them. I know I'm not the best at explaining things so I hope you can understand this, good luck and have fun! :D :D

Regards; Alan...

CompKing
12-09-2002, 09:37 PM
Been busy so I havn't done anything but get supplies,marine plywood fresh gal of epoxy with med hardner,tabing,7.5oz cloth,brushes,spreaders and roller.Got a cutoff wheel in the grinder,sawsall, rotozip and good wood chisels.Want to get stuff ripped out this weekend and lay new stuff over X-mas(got 10 days off:) )Thank for the ideas Alan I think thing will go good.Anyone else have any advice or ideas I'm listening.Motors are easy for me this stuff is kind of new so any help is welcome.
Thanks Dave

Alan Power
12-10-2002, 03:12 PM
Hey, I hope the work goes well for you over Christmas, I have 10 days off too and not too soon either!!! I am the reverse of you I think; GRP is one thing, but perf. mods to outboards are all new to me. Any suggestions would be great, the engine in question is a 2 cyl., OMC 55Hp on the back of a 13' V-hull. Any rigging suggestions would be much appreciated too.
Regards Alan...
:)

Techno
12-10-2002, 09:36 PM
If it's plywood then marine ply will work. If it's solid wood then something like sitka spruce. You should try to use the same kind of wood as whats there for expansion contraction stuff being the same. Any furniture type hardwood is OK for marine use except maple. But soft wood, Needle leaves, is usually used. Stay away from pine, It's kind of sappy.

The wood thing is called "scarfing" and I think it's 12:1. 1/2" thick wood you go back 6" on the taper.
the grinding wheel will cut the wood if slowly. It will give a starting point for the angle. It might be faster than the right way.
The rotted parts of the wood should come right out so just cut enough to be close. The wood won't be bonded to the glass anymore.

For the seat box just about any plywood will last a while but marine plywood is stronger than the rest. It can be thinner to supply the same strength. ( or the regular needs to be thicker to do the same) If you want to save wieght foam core will cut the pounds by about half but is pricy too.


No one mentioned it but make sure the boat is supported before removing the sections. You don't want to reinforce a rocker.

sho305
12-11-2002, 01:38 AM
I got a box of latex gloves and loved them. Had to mix lots of small batches with the fast epoxy as it was hot then. No mess on the hands. Used a plastic measuring tub for resin to mix but used pumps. Stupid, but just squeeze the tub when it gets thick and the dry stuff falls out. Used some dollar store paint brushes, and found that plain laquer thinner seemed to clean them better than the acetone did. Try to use a mold, or plastic wrap any place you can as that is easier to hold it in place that way. Make sure you sand/grind/and clean well any area you put epoxy on so it never peels off later. Try to do it all fairly soon when started, as it is supposed to get a better bond when it is over fresh stuff than it will on the old material. Can't remember, after a couple days or something it fully hardens and you have to grind it good to put more on. I tried to lay a section all at once as fast as it hardened. I wanted to sand/grind it flat between coats/layers on mine anyway. Force of habit I guess. Make sure you are all ready to go before you mix too.

Alan Power
12-11-2002, 02:06 PM
Forgot to mention to support the boat well before you cut out any structure, I should know I've been there!!!

CompKing
12-17-2002, 08:09 PM
Spent last sat. tearing out and things went real good.I used both the roto zip with a carbide bit till I broke it.It made less dust and has a light in the end so was easy to see what I was diong.Then I used the angle grinder with the cutoff wheel but only had 2 wheels and wore them both out but got done what I wanted to.I took out all the rotten wood and some that was still nice and the good stuff sure comes out a lot harder!!Got 13 days off over X-mas so should be able to finish cleaning things up and lay new stuff in.Just orderd a new Dell for the lake place so if I need any help I get on line now:cool:

CompKing
03-15-2003, 08:51 PM
Well it's turned into a bigger project than I thought it was but am getting close to done.Figured as much time as I was putting into it I might as well replace everything.
I am going to carpet again but was wondering since I used epoxy and can't use gel coat what kind of paint should I use in the back where I'm not putting carpet?It's not a very big area so a brush or roll on would be nice.

CompKing
03-15-2003, 08:52 PM
A nother

sho305
03-16-2003, 07:38 PM
Can't use gelcoat? I thought you could. I used Rustoleum commercial HD spray can:D It was great for the bayliner:cool: Only thing that sees it is the gas can anyway. I'm not recommending it, but it worked great.

Looks like a great job you did there too!! Very nice.

bulldogdaddy
03-16-2003, 07:55 PM
great job indeed! are those holes for some speakers?

CompKing
03-16-2003, 09:17 PM
sho305,
I was told gel won't work over epoxy and I'm no expert at all on this stuff.I thought I heard someone say KILZ works good:confused: I even thought about leaving it natural but think some kind of paint would look better.

bulldogdaddy,
I am putting a tunes in this time but those aren't for the speakers.I have access covers for them thought they would be good dry storage areas.They would sound good though as long as it never rained:D

sho305
03-17-2003, 12:20 PM
http://www.westsystem.com/frames/tier1/usingepoxy.htm

I don't know, I hear that gelcoat thing one way and the other. I wanted to use it (epoxy) for the extra adheision mostly for a transom repair, and to waterproof it better. I had it stick to unsanded gelcoat so hard it tore chunks out when I tried to knock it off! I also wanted to paint the thing with one paint, and not pita gelcoat. I used the VC performance Epoxy and did the well, transom, and about 4' of the bottom. It was great.

As you can see, my inside hardly shows so the spray can was ideal(I think is was supposed to have a curtain anyway). It seems to be sticking well and this is no show boat. I went over it with a red scratch pad is all, after washing it well. Scrubbing it with soap seems to be important, though I had hardly any blush anyway. That commercial Rustoleum appears to be good stuff for spray paint, and worked well on an old LU I had too. I might consider a urethane car paint, but would have to investigate more. It does need something to protect from UV. I also installed some 1/8" nylon or acrylic(?) strips on the floor for the gas cans to wear on.