Re: [Amel Yacht Owners] Bow locker and hawse pipe deterioration
Craig,toggle quoted messageShow quoted text
Thanks for the interesting discussion. 3/8” of solid glass will easily span 16” with adequate stiffness and in fact is probably overkill. On the other hand I would look at this from the standpoint of spanning the entire distance between the two sides of the boat rather than relying on the fore aft center panel and the deck to effectively support the floor. I still think that this might require a method to stiffen the floor panel some. It would be interesting to know the details of the engineering for sure but the design of the lockers and the positions of the panels suggests to me that these panels add quite a bit of strength and rigidity to the hull an deck in bow area. The center partition panel for instance I believe would see some of the windlass and forestay loads while the locker floor would stiffen the hull quite a bit. In other words, if I find the need to rebuild my forward lockers I will be sure to completely restore the original strength and stiffness and probably a bit more just to be sure that the boat has not been weakened at all.
I am surprised that the plywood forming the floor of your lockers was not glassed over even on the top side of the panel? Is there any chance that the floor had been replaced before you bought the boat? The floor on my Maramu is glassed on both sides though the glass on the bottom stops at the edge of the plywood leaving a gap at the hull since it would have been almost impossible to cover that joint from the bottom. I have seen other Maramus where the bottom of the floor panel as viewed from inside the chain locker was not glassed so it is curious as to why the construction is different. If you only have 20 square feet in the locker floor panels then the weight is certainly not going to be an issue but I think that it will be a little heavier than you thought. I am getting about 60 lbs. for the floor panel in solid glass based on your 20 square foot estimate: 20 square feet x .375 = 7.5”/12 = .625 x 96 = 60 lbs. You will also be removing the old plywood so the actual increase in weight would be less than that. For sure with the all fibreglass panels you will never have to worry about the floor rotting again.
You are correct, a 3/8” 4' x 8’ sheet of fir plywood would weigh in the neighbourhood of 36 pounds and so would a 12” x 12” x 12” block of Fir since other than the glue both of these are essentially the same thing. (grin) The 12” x 12” x 12” solid block of fibreglass would be around 96 lbs. so about 3X the density.
I do wonder if the steel pipe originally installed by Amel as the chain pipe might be needed from a structural standpoint as a compression member between the floor of the lockers and the deck in certain circumstances. An anchor launched in deep water running out fairly quickly and a ball/loop of chain jamming in the chain locker under the locker floor for instance cut put quite a bit of upward force on the locker floor. A strong compression member could carry that stress to the deck which should be quite a bit stronger than just the 3/8” fibreglass floor… Henri might have had that concern in mind when the steel pipe was specified but I am only guessing. So while I might upgrade some materials when making repairs such as using stainless pipe instead of the original steel, I personally would be a little uncomfortable reducing the strength as compared to the original design.
Best of luck with your project.
SV Suneo, Maramu #220