Hi, I don't know the best fix, but as an FYI, the screws go into a threaded stainless steel plate in the hull, not a wooden backing block.Chances are also good that the wood backing is strong enough to support new fasteners.
I'd be more worried about the rivet deforming in the hull as opposed to the thing shearing off or pulling in two. And I would prefer to not have quarter inch holes in my hull. Plus rivets are hollow and in the water a lot. If you try rivets, let us know how it works - it could be a good solution.A 3/16 pop-rivet has a tensile strength of 320 lbs and shear strength of 260 lbs. If
that's not enough a 1/4 rivet gives 1240 lbs tensile and 1000 lbs shear.
Thank you for all the suggestions. My Sunfish is relatively new: a 2013 model. I took the remaining stainless steel bolts to West Marine today and found that the bolts are actually metric o.7 threads (3/4" long). I did buy some bolt extractors from Home Depot and I'm considering drilling out the old bolts with a bolt extractor. With luck I should be able then to simply install new stainless bolts.Foulweather Jack what year is your sunfish?
'Wonder when that started? I'd guess that'd be for authenticating a stolen/recovery Sunfish claim.Interesting (?): there's a second boat ID (under the gudgeon) on newer boats.
I think you meant, "Titanium Nitride". (Or, TiN).A cobalt drill bit (M35 or M42) at slow speed w/ lube is the machinist's preferred way to drill stainless steel. Note: there are quantities of cheap, fake, "cobalt" drill bits on the market. A drill bit with "cobalt nitrate" coating is not the same as an M35 or M42 cobalt bit.
You got that right!!!It's really finicky to try to drill out small broken bolts or screws, even if the part holding the screw can be clamped on a drill press table. Stainless steel can be an especially tough material to drill.
The hard way, would be to take a Sawz-All to the transom, and repair it from the inside-out."...Personally, the easy way is to just put
in a inspection port, knock the plate out and buy or make a new one. Use bolt and locknuts,
pop-rivets, a metal tap or whatever you preference is. It's all good.
So the bits I bought to drill out the old corroded bolts were supposed to be cobalt bits; purchased from my local Home Depot. An online search re cobalt drill bits results mainly in confusion. Can anyone recommend a reputable brand of cobalt drill bits?
So I dropped by my local West Marine on the way home and bought a 4" inspection port, mainly because the color on that one seems closest to my white gel coat on the deck. I'm hoping that will be big enough to do the repair, but if some of you have experience with this and are convinced it's too small please let me know and I'll get a bigger one.