A Photo & Discussion Forum for Wharram Design Enthusiasts
I'm at the stage of lining up the hulls and would like opinions on whether a rubber cushion under the beams where they sit on the gunwhales are necessary, nice to have or a nuisance. I have this recycled rubber product that is used as a flooring in horse stalls and crossfit gyms.
Also, what type of plastic would you recommend to reduce friction on the fore and aft parts of the beam that contact the beam box sides. Teflon? uhmw, or starboard?
Hi Mike! Sounds like you are really getting there!
On Peace we have the beams on hardwood pads and it is ok so far (50,000 miles). Nev put nylon rubbing pads on the beams where they almost touch the sides of the troughs and he put stainless sheet on the trough where the beam almost touches. He made dimples in the stainless and screwed and sikaflexed them in place using machine screws that were not sticking out at all. No problems we know of so far. He also used the nylong and stainless rubbing together where the rudder sits on a little platform and swings back and forth at the bottom there. I am not so good with the word pictures. Hope you can figure out what I am saying. Nev is sleeping. Call if you need to talk about it.
Life looks good for you! Makes me happy just thinking of it all..... X
Thanks, Ann. That was something i wasn't completely sure about either, about the beams touching the sides or not. But your description of "almost touching" is perfect. Glad Arthur left you well. Was thinking of you both.
We are using 1/16" thick reinforced neoprene as a pad for the beam blocks.
Definitely not wetsuit material! That is neoprene foam and would disintegrate in short order. You want solid neoprene. I have doubts about recyclyed rubber flooring as that may also come apart under the huge loads it will be subject to. The best bet is conveyor belting which has fabric reinforcing weave built in and is nearly indestructable. I got mine from "Rubber Cal", you can google that. 9mm thick is good. Sika 292 will bond it very effectively if you solvent wash the rubber, then lightly flame it with a propane torch before applying the adhesive. The idea of flaming is not to melt the rubber, just a light pass opens electron valences on the surface that gives the 292 the means to attach chemically. Back that up with countersunk screws and you will not have any trouble. Without the rubber, your beams will chafe and you will have rot potential.
As for the side bearings, UHMW (in UV black) is your best bet. I would suggest fitting those as closely as possible. It might surprise many, but this material also glues very well with Sika 292 using the flame method. A test sample in my shop, of uhmw sika'd to epoxy/glassed ply, would not pry off without destroying the ply. That convinced me to go ahead that way, and it is holding up very well.
Don't compromise on the beam load points and attachment method...the forces acting on these are enormous, and offshore, constant. Small amounts of movement under such pressure can mean big chafe!
All the best,
good work Alf.
Thanks for all the advice. I really appreciate all the different opinions. i'll be sourcing those materials but in the meantime, i'll be lining up those hulls. That could take 1 day or 3 weeks, Hard to tell before i start.
I have also used conveyor belt rubber under the beams on my Narai and found it wears very well
Thanks for the interesting information on bonding technique
thanks, all. i bought 1/8 inch neoprene rubber and it looks perfect for the job.