Steve Sanford
Well-known member
All~
I just installed a s/s U-bolt to serve as the bow eye on my latest project. Over the years I have installed many on various vessels. They have varied in small details - and some have kept me wondrin'... Hence, I am seeking your thoughts.
Here is the process I just completed over the last couple of days:
1) I reinforced the 'glass hull inside of the "nose" so that it was now about 3/8" thick. I used a couple of layers of 1708 biaxial with mat set in epoxy.
2) I made a backer from 1/2-inch AC plywood - which I coated with epoxy. I have long used these plywood backers for any hardware/features that might need to support the weight of the boat, e.g., cleats, eye-bolts.
3) As I am trying to keep the finished weight of this vessel to an absolute minimum, I am tracking the weights of everything I add or subtract. The U-bolt is 5/16" in diameter; is 316 stainless; and is rated for 3500 pounds. It and the backer weigh a bit over 6 ounces. Although this will be a very light vessel, it may need a bow eye for towing, dragging and anchoring at various times. It will likely NOT be winched onto a trailer as I plan to transport it on my roof rack.
4) As I do with any s/s hardware that will show, I sanded the U-bolt with 400-grit, washed it with acetone, then sprayed it with Rustoleum Self-Etching Primer.
5) I bored the holes in the hull and the plywood backer at 3/8-inch - to leave some room for the 3M 5200 bedding (adhesive caulk).
6) After perusing several YouTubes - which varied the placement of the s/s backing plate that comes with the U-bolt (and some come with 2 backers), I decided to locate the backer inside the hull and use the 2 flat washers between the outer nuts and the hull - with plenty of 5200 coating the entire length of the U-bolt threads. I see no advantage to putting the backing plate on the outside of the hull. My seat-of-the-pants engineering tells this old brain that the fundamental need is to prevent the U-bolt from pulling through the hull.
Other opinions?
7) I put LOTS of 5200 'twixt the hull and the plywood backer because the hull was not perfectly flat and I wanted any potential void to be filled with cured 5200 when all was said and done. There was LOTS of squeeze out to prove I had filled to void - and I was not concerned about "working clean" - as I would on the deck or the outside of the hull. I faired it onto - and into - the surrounding 'glass. All will be painted once I have completed framing the interior of the vessel.
8) I cleaned around the hardware with a paint thinner-soaked rag - so that I could put a wrench on the nuts - inside and out - if I ever needed to in the distant future.
Just let me know if you have some other insights into this common task.
All the best,
SJS
I just installed a s/s U-bolt to serve as the bow eye on my latest project. Over the years I have installed many on various vessels. They have varied in small details - and some have kept me wondrin'... Hence, I am seeking your thoughts.
Here is the process I just completed over the last couple of days:
1) I reinforced the 'glass hull inside of the "nose" so that it was now about 3/8" thick. I used a couple of layers of 1708 biaxial with mat set in epoxy.
2) I made a backer from 1/2-inch AC plywood - which I coated with epoxy. I have long used these plywood backers for any hardware/features that might need to support the weight of the boat, e.g., cleats, eye-bolts.
3) As I am trying to keep the finished weight of this vessel to an absolute minimum, I am tracking the weights of everything I add or subtract. The U-bolt is 5/16" in diameter; is 316 stainless; and is rated for 3500 pounds. It and the backer weigh a bit over 6 ounces. Although this will be a very light vessel, it may need a bow eye for towing, dragging and anchoring at various times. It will likely NOT be winched onto a trailer as I plan to transport it on my roof rack.
4) As I do with any s/s hardware that will show, I sanded the U-bolt with 400-grit, washed it with acetone, then sprayed it with Rustoleum Self-Etching Primer.
5) I bored the holes in the hull and the plywood backer at 3/8-inch - to leave some room for the 3M 5200 bedding (adhesive caulk).
6) After perusing several YouTubes - which varied the placement of the s/s backing plate that comes with the U-bolt (and some come with 2 backers), I decided to locate the backer inside the hull and use the 2 flat washers between the outer nuts and the hull - with plenty of 5200 coating the entire length of the U-bolt threads. I see no advantage to putting the backing plate on the outside of the hull. My seat-of-the-pants engineering tells this old brain that the fundamental need is to prevent the U-bolt from pulling through the hull.
Other opinions?
7) I put LOTS of 5200 'twixt the hull and the plywood backer because the hull was not perfectly flat and I wanted any potential void to be filled with cured 5200 when all was said and done. There was LOTS of squeeze out to prove I had filled to void - and I was not concerned about "working clean" - as I would on the deck or the outside of the hull. I faired it onto - and into - the surrounding 'glass. All will be painted once I have completed framing the interior of the vessel.
8) I cleaned around the hardware with a paint thinner-soaked rag - so that I could put a wrench on the nuts - inside and out - if I ever needed to in the distant future.
Just let me know if you have some other insights into this common task.
All the best,
SJS
