I think I might have fabricated a replica shroud anchor plate similar to the design used by Hobie that has been discontinued. A few years ago, I scored a pair of SX wings for my 1984 redline boat and I’m currently in the process of refurbishing the boat and preparing to mount them. I’ve purchased or fabricated all the hardware for the wings, except the reinforcement bracket.
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EDIT: here is the completed bracket, this thread will outline my design and fabrication of these brackets to facilitate the addition of sx wings to my Hobie 18
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I’m also in the process of completing the Hobie interior hull patch to take strain off the crossbar, but with my extra-susceptible early redline boat, that didn’t seem like enough for me.
I’ve considered a few possible designs to replicate the shroud anchor plate. One idea I had was to cover the hull in wax paper where the bracket goes, and lay carbon fiber with epoxy over the wax paper, effectively using the hull as a mold. Then, once the carbon fiber cured, remove it from the boat, and clean it up, and reinstall it as a carbon fiber version of the shroud anchor plate.
That seems like a lot of prep and work for a design I couldn’t adequately test or know for sure would not fail when I needed it the most -though I figured something is better than nothing. But before I attempted that, I wanted to see if I could fabricate one out of 316 ss, of the same gauge and design as used by Hobie. Hobie has done the engineering analysis and settled on that design, so it most likely is the easiest, most cost effective, and fully adequate.
I think I’ve managed to replicate it, and I’m going to outline my process here for anyone (crazy enough) to attempt to replicate it themselves. Obviously, my version isn’t exactly the same, nor do I expect it to be of similar strength characteristics, but if it provides 75% of the strength the Hobie version did, I would be happy. With the hull reinforcement patch, this is added protection.
I first purchased a cheap 304 ss circular stamp scrap off Amazon, in a diameter of 8” and 1/16” thickness for $14 (
https://www.amazon.com/dp/B08L45139V?re ... b_ap_share -- 1/16" Thick Stainless Steel Disc, 8.00" Diameter). This first version will be a feasibility analysis to determine if it’s even possible for an average person to make one at home, so I went with the cheaper 304 in a common gauge simply to save money. My calipers indicate that the Hobie version is 5/64” thickness, so 1/64” thickness less probably isn’t going to affect my home manufacturing process too much. I saw no use special-purchasing 5/64” 316 ss just to bang it up and fail.
First thing I did was measure the one on my boat as well as I could. My measurements are not perfect, but hopefully good enough. I sketched the measurements out on the blank circle. I drew a straight line through the midpoint (one 8” circle makes 2 brackets). I then drew a second line 90* from the first, and two more lines offset 1.5” on either side (the lip part of the bracket is about 3” wide). I also roughly sketched in the two diagonal lines, to make a pattern on the blank.
I then used my angle grinder to cut the circle in half, and them cut out the blank plate. I also grinded two shallow lines in the location where the plate has to bend (discribed by the dotted lines). Having a large bench vise makes this project doable. you can pick one up in menards for $50 or less on sale.
I then placed a bend at both points using a vice and a hammer. I put tape over where I struck the metal to help keep the finish as decent as possible. I used a piece of sacrifical wood where possible.
I messed around with how it fit in the crossbar groove, and bent it more as necessary. As you can see below, the 4" radius isnt exactly correct, so I shaved it down a bit, test fitting as I went.
I then chucked it up back in the vice, and placed some hammer strikes to put in the curve necessary for the plate to sit flush with the fiberglass.
This photo below is before the bend.
This photo is after the bend. The difference is subtle, but it now sits against the fiberglass as well as I think I can get it.
I have yet to drill the hull holes and mount the bracket, but when I do I'll be sure to follow up. I have some 316 ss shipping in now, I hope to at least make 4 for the front. When I get around to putting an inspection port in the rear, I'll do 4 more for that. Hopefully this post will help someone or inspire someone to do a better job than I did! If anyone has any comments or suggestions, I'm all ears. I hope that with the fiberglass patch and the brackets, I'll be set to go.
Maybe I'll post up a full breakdown on my hobie 18 restoration project if anyone would be interested. I'm taking an old boat and completely sanding, buffing and polishing it, and installing the fiberglass patch, amongst other things.