The Plan:
Ran into a small delay this week - I needed to refortify my stock of filler (West Systems 406 and 407) before starting on the joint repair. Ordered but when the box arrived I clearly received someone else's order!
Error resolved but still waiting on filler. I filled the time this week by doing some cabinetry - pics will be up soon on that.
So while I'm waiting, here's the plan for the keel/hull joint. First let me say that I am not a fan of slathering gobs of filler to build up low spots/areas. I come from the old school (auto body) thinking that there should never be more than 1/8th inch of filler - if you need that much then go back and straighten the sheet metal a little better! I will make allowances when working with fiberglass and epoxies but I still want to limit the buildup of filler. My personal limit is about 1/4". Any more than that and I would rather use glass layers for fill. A big problem with thick layers of filler is shrinkage - as I saw with the area on the aft end of the keel - any filler will shrink as it cures and if too heavy you'll get cracks as it shrinks. Another issue is heat buildup during drying - I saw evidence of that too. So, what's the plan?
First thing is to make some assumptions. Based on the condition of the joint and surrounding filler it looks to me like the cracking and rusting was not caused by the keel moving, rather by the filler failing. Sure, there's going to be a little movement but in the grand scheme of things not enough to have caused an issue by itself. Most of the actual seal (5200) was and is intact and plyable, as I found when trying to dig it out! What I did find was a too-generous application of the wrong type (my opinion here!
) of filler which as it aged started cracking and letting water seep in and attack the keel.That started the rust, which degraded the surrounding sealer and filler.Then unnamed yard apes tried to fix it. Lather, rinse, repeat! Another assumption is the design of the keel attach points - can't get much more solid than what's there. The only wild card is the repair (?) on the aft section of the keel - I still can't conceive of what happened, but whatever it was, the keel is stronger now than before, so I can work with that.
So with this in mind, I will be doing the repair in four stages. First is to re-fill and fair the aft end of the keel up to the rear flange:
The area outlined in red was all filler before, completely covering the actual joint. I will first fill the joint (now clean and properly prepped and rust fixed!) with G-Flex, then build up alternating layers of 1708 and chopped strand mat to fill until close, then final fairing for good looks.
second is to properly fair in the flanges. The problem here with all four of the flanges is they are not flush - the flange sits a little proud of the hull:
Same treatment here, first fill the joint with G-Flex, then 1708 on the hull only for buildup. When it's flush I plan to overlay two layers of 1708 over the hull and flange to cover the joint. My thinking here is a thin layer of glass will have some flex to allow a slight amount of movement of the keel, but if the keel sees a hard jolt, say from a grounding, the thin glass will crack and can be seen during an inspection.
Next is the sump area:
No real issues here, fill the joint with G-Flex, two layers of glass and fair to smooth. This area forward of the sump:
I'll have to treat a little differently since the joint is so close to the hull. Here I'll fill and fillet with G-Flex, then glass over.
Fourth is to address the nose:
As the arrows point to, the keel and hull fairing don't line up too well, so I'll first build up the hull with glass, then address the joint with G-Flex, then a final two layers of 1708 and fairing compound.
In the end, most of this is cosmetic - I could just slap some 5200 all around and call it good, but that's not my style
!
And for those wondering how the hull prep from sandblasting is going:
getting there. I'm about 2/3rds to 3/4ths done working over the hull, sanding and filling a little at a time, giving my shoulders a break between sanding sessions.
Next up, more carpentry!
Cheers,
Mark