Rebuilding the Engine Bed Stringers
Materials Tips:
http://www.uscomposites.com/ - I have used West System a great deal and really like it, but its expensive. For this job I used material from Us composites and had great success with it. It has a little longer pot life than West which was nice, and its almost 1/3 the cost. You need mixing pails with printed ratios on them to use it.
http://www.devoecoatings.com/home.jsp - To paint the bilge I used a product called Rust Bar 235. It worked well, adhesion seems good but time will tell.
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One thing I really want to emphasize to anyone repowering is to reinforce the engine bed stringers. I had planned on doing this all along based upon the recommendations of others but until I really got poking around did I realize how important this was.
I should have taken more and better photos to show what I'm talking about but in preparing the stringers I took a grinding wheel to them in order to square up some really bad lumps on them. Well each of these lumps turned out to be giant air pockets. All in all the Mainship's a good boat, and I'm sure the guy who put these original stringers in would say, "hey they lasted 30 years" but I was surprised at how poor the glass work was there.
If your going to put a new motor in, you defintely want to take the time to address this area.
With all of that said I took some oak and really shaped them to fit the outside of the stringers. You can see one below.
Here it is in place, this is just a dry run. I unbolted them to get the epoxy in between them.
I counter sunk the nuts on the outboard side. You can see the bolt heads on the inside, I talk about those more down below but their going to be trouble when I start with the cloth. I wish I had done that part differently. These bolts play a role in sucking everything together, but they were way overkill, and now their in the way.
Once I had those ready I cut some wood to fill in the dip on the top. I have nevered figured out what those dips were for. I'm sure some day, someone is going to tell me and I'm going to feel really stupid, but as of now I just have no clue. At first I thought about leaving them there but then realized that would make the glass work that much harder.
Here is everything just placed in their, ready for the eopxy.
When I got ready to epoxy it, I took a grinding wheel and sanded as much of the entire area down as I could. This was a NASTY job, and the best tip here I can give is if you have to do any major prep sanding do it all at once; just get it over with. I covered as much as I could with plastic sheeting.
Below is the port side epoxied together. I made some fundamental mistakes here that I will share. Originally I had drilled holes, two at each end, and two in the middle for 1/2 inch stainless steel bolts going through old and new. The plan was to mix the epoxy, with filler and get it about like peanut butter, then after wetting everything out, lay it on thick on the outside of the old, and the inside of the new and then bolt it all together. However, just prior to that I began thinking about trying to glass over these big bolt heads. On the outside I did counter sink holes for the nuts, so no problem there. But with this plan I would have six good sized bolt heads to have to try and cut the cloth around.
So, in the end I did use the bolts but not all of them. Once I had the epoxy all ready to go and laid on I put bolts through the holes where I felt I needed them. (I figured this out previously through a few dry runs. The old stringers were out of whack here and there so these bolts really helped suck that new board right to the old)
Heres the port one epoxied together.
If you look closely you can see bolt heads, on the inside in the middle.
Right now I'm not sure what I'm going to do, I may even try and remove the bolts I did use. If they won't come easy I'll leave them and just work around them best I can. Tips; If I was to do this again, I would have only done three bolts each side, in the middle top to bottom, and would have used 1/4 inch. Remember the whole thing will be bolted together again from the installation of the angle irons for the motor mounts. The real purpose these bolts served was to suck the new and old together for the curing process.
Well, I decided to remove the bolts. They came out pretty easy considering there was epoxy on them. You can see below I filled in the bolt holes and where the nuts were counter sunk.
After I got the stringers reasonably smooth with fairing, I started laying up the glass. I cut cloth the length of them and my friend Tom Drew gave me a great tip for wetting the cloth out. What you do is use a paint brush and wet out the smooth side of the cloth, and roll it up as you go. This keeps it neat and tidy and also lets the resin seep into the matt, or "fuzzy" side.
Here's a few more pictures of the cloth, rolled up. Once its all rolled up you can put it somewhere until you need it.
Heres a roll all ready to go, its the length of the stringer.
I made up one entire side.
Here they are, all done. I probably could go another coat but I'm going to quit here.
Well the new tanks are in, the new floor is coming together and the stringers have been reinforced. Next up: painting the bilge.
Well, here it is after I applied the Rust Bar 235.
