Stringer/ Floor Replacement Lessons Learned

Not sure the wax on dixie cups won't dissolve into the resin.

I cut off the tops of beer cans (doesn't take much), for mixing cups.

dgray007 wrote: it doesn't. i went through about 5 sleeve of them... 8 or 10 oz worked well for me.

Daniel,
How do you know the coating doesn't affect the resin?

8122pbrainard wrote: Chris, Make sure you rinse that beer out before mixing up the resin. You sure wouldn't want any disbonding!

I always thought beer was a great bonding agent

That sentence is more of a word of warning than anything for the people who are new to fiberglass. Small projects or repairs are pretty safe all in all. When you get into reglassing an entire floor in a 20ft boat in let's say a 2 or even 3 car garage it doesn't take long for the fumes to become overwhelming. With proper ventilation and heating fiberglass is very safe.

Most people opt for the epoxy resin over the polyester resin. I personally used a high quality polyester resin purchased in bulk from a friend who owned a fiberglass tonneau cover company for 15 years. Most of my knowledge on fiberglass came from this gentleman. My point was to make people do their research before purchasing something. Marina's charge an arm and a leg for the same products you can buy elsware for a 1/4 the cost. For most repairs high quality polyester resin is more than sufficient. Stringers are a major project. Anything to make it easier should be considered.

ill street composites was a good source for fiberglass related products.

Smc is rare to say the least but it is still out there. Just something to consider depending on the age of your boat and the repair being performed. I hate doing things twice...

Closed cell vs open cell expandable foams. You can still purchase open cell expandable foam Don't use this stuff.. In the 80's open cell foams were commonly used in recreational boats. They were great at keeping boats afloat in emergencies but they are also great at absorbing and holding water. This is partially the reason your stringers are rotting out. Closed cell foam forms a "skin" around each air bubble that is less likely to hold water. When I removed the foam from my 89 i could wring out the chunks like a sponge. There was probably an extra 1000 lbs in overall added weight to the boat. when completed with repairs I actually gained 9 mph.

All good questions... Hope that clears up a little bit of it.

Daniel,
Thanks for filling in the blanks as well as posting the pictures.
Earlier it was mentioned that epoxy resins seem to be the recommended choice. Couple benefits are they bond better, are higher strength and they don't smell as bad polyesters. Also, an important benefit is epoxy isn't hygroscopic like polyesters are. Wet foam isn't the only thing that contributes to getting moisture into the wood. Polyester being hygroscopic certainly isn't a factor when you are making tonneau covers.

6gal for an entire stringer job? Sounds like 1/3 to 1/2 as much resin as is typically needed for a stringer/floor job. Just mat, no cloth? Curious about the glass schedule you used, sounds lighter than most here use? Fillets on corners is a great recommendation, not sure bondo would make my list of recommendations though. Certainly better than no fillet I suppose.

If you haven't used epoxy before, you may be amazed at the difference in fumes and ease of working. I've used both and found poly (and vinyl) more sensitive/temperamental to environmental conditions, less than perfect mixing, etc.

Good tips though, certainly more than one way to tackle this beast...

im on the other end of the scale with 25g of vinyl ester resin in the floor, stringers and
other repairs and modifications. im waaay overkill with glass and resin.   no data on how much to use when converting to coosa board though.   well it will never break ..........

correct, bondo is not a structural component rather a means to fill air gaps that could form and allow the cloth/resin combo to be as strong as it should be. nor is bondo a glue....

Big difference between 6gal and 15gal! Probably somewhere between using all cloth. 25 does seem on the high side... But if you're using a heavy weight material (mat, biax, woven roving, etc) it will suck up a lot more resin than a lightweight cloth will.

Stringer and floor replacement 86 SN 4 years ago with help from this site and everything is still together with out any problems.
I used a straight edge laid across gunnel for measuring down to old stringer height.
and drew a sketch of stringer on the straight edge helped tremendously. If going back with plywood a adjustment will have to be made for finish height of stringers.
Two mistakes I made
Engine mounts- Give your self some room so you can get under the cradle when it goes back on to hold the bolt. I did not cut this area deep enough in stringer and it is a pain to get bolts back in.
Dog box- Front two corners where it closes- sounds real dumb, Be careful that you have left enough floor in this area for box.

Also the chase for wiring harness think that part through. I would have pulled all wires through before I put floor in.

***Have boxes shipped to work so your wife does not start to wonder how much your spending**

One last thing be committed,
Vinegar works nice to clean up epoxy.

When doing a stringer job should the boat be removed from the Trailer or is it ok to leave it on the Trailer?

Depends on how far you are going with the stringer replacement, the best way is to hang the boat from the factory hooks. That's assuming your factory hooks are stable enough to do this. I didn't have the space to completely suspend the boat so i hung the front with a cherry picker. Definitely not ideal but it got the job done. The hull will conform to the trailer and stay that way after you reglass everything. Fiberglass is amazingly flexible...

TRBenj wrote: I don't agree. Whether or not doing a stringer job on the trailer, or whether the lifting points are sufficient will vary from boat to boat and how far the boat is stripped down. The more structure and hull thickness is removed, the more external support needs to be added. The bottom line is that the hull needs to be supported sufficiently in its original shape when doing structural work. Trailer bunks plus additional support points from below (corners) is what I've done in the past.

I agree. I'll see if I can find the treads were members have built additional stands while the hull sits on the trailer.

dgray007 wrote: . That's assuming your factory hooks are stable enough to do this....

If the stringers are bad enough to undertake a replacement, then the chances are high that blocking for the lifting rings are also bad.

One members hull supports

Very informative post, I have one question..
It is noted that the boat should not be sitting on a trailer when the stringers are removed..
I am looking to replace only the secondary stringers.
Does envy one know if those can be replaced as the boat sits on the trailer..
The primary stringers are ok, but the secondary ones must be replaced.