Murdered 170 Centerboard

R

rcairflyer

.
May 21, 2021
12
Hunter Hunter 170 Bricktown, NJ
The lifting point on the centerboard gave way - seems to have torn out. It was patched up, but not restored. See the JB weld in the attached picture. The previous owner added a great big eye bolt to lift the centerboard...
The stainless straps from the factory allow for a block and probably better distribution of forces.
I could drill a hole and mount the same straps further back, but I am afraid of them tearing out again. Would you do so after reinforcing the centerboard? I want to go back to something resembling the original strap system.
I have considered other ways of attaching a sturdy lifting point -
  1. sandwiching the centerboard with 2 to 3mm stainless plates (could also go with glass and epoxy) and drilling a mounting hole behind the original hole (behind the JB-weld).
  2. adding a 2 to 3mm stainless strap that wraps around the narrow dimension, from the pictured eyebolt, to the opposite side and drilling a mounting hole behind the JB-weld.
  3. attaching one half of a stainless steel strap hinge to the centerboard for use as an anchor point.
What would you do?
 

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stickinthemud57

stickinthemud57

.
Apr 11, 2020
792
MacGregor 26s Scott's Landing, Grapevine TX
At first, I was thinking that a strap that wraps around the sides would be how I would approach it. Upon reflection, going over the narrow dimension could be a more practical solution. Use as long a strap as you can to spread the load out, and bury your screws as deep as you can. The main concern would be the screws pulling out, but if the holes are properly sized, this should not be a problem.

Wrapping a strap around the sides might be a more robust approach. This gives you the opportunity to use a large enough strap to spread the load out over a larger area further from the edge. Also, you could pass bolts through from strap to strap as long as there is enough clearance at the trunk. If the bolt head and nuts jam in the trunk, you could pass the bolt through, cut off the ends, and pound the bolt ends with a hammer to spread them out far enough to prevent slipping. If the strap sticks out and jams at or damages the trunk, you could grind the end of the centerboard to allow the strap to rest at or below the level of the side of the centerboard.

Hope this helps!
 
R

rcairflyer

.
May 21, 2021
12
Hunter Hunter 170 Bricktown, NJ
stickinthemud57 said:
At first, I was thinking that a strap that wraps around the sides would be how I would approach it. Upon reflection, going over the narrow dimension could be a more practical solution. Use as long a strap as you can to spread the load out, and bury your screws as deep as you can. The main concern would be the screws pulling out, but if the holes are properly sized, this should not be a problem.

Wrapping a strap around the sides might be a more robust approach. This gives you the opportunity to use a large enough strap to spread the load out over a larger area further from the edge. Also, you could pass bolts through from strap to strap as long as there is enough clearance at the trunk. If the bolt head and nuts jam in the trunk, you could pass the bolt through, cut off the ends, and pound the bolt ends with a hammer to spread them out far enough to prevent slipping. If the strap sticks out and jams at or damages the trunk, you could grind the end of the centerboard to allow the strap to rest at or below the level of the side of the centerboard.

Hope this helps!
Click to expand
Thanks for pondering this question. I'd like a good length (6" to 10") of substantial stainless steel (something over 1/16" and maybe 1/8"). I'm thinking about half of a strap hinge or a chain plate, or 1/8" bar stock. How do they strike you?
 
stickinthemud57

stickinthemud57

.
Apr 11, 2020
792
MacGregor 26s Scott's Landing, Grapevine TX
1/8th or 1/16th should do. The forces are not that formidable. 8" either way (16'' total) would give you 4 screws each way for 8 total. If sunk 2" in I can't imagine how they would tear out unless the centerboard is just plain falling to pieces. 10" total would probably be fine, but I would not do less. Care would have to be taken that the screws grabbed well, but did not cause the board to split. Going in from the sides would prevent this, but comes with its own aforementioned challenges. Either way, bed everything properly so that moisture does not cause problems.

I would put a U-bolt through the strap where the block and tackle would attach. All SS hardware, of course.
 
R

rcairflyer

.
May 21, 2021
12
Hunter Hunter 170 Bricktown, NJ
stickinthemud57 said:
1/8th or 1/16th should do. The forces are not that formidable. 8" either way (16'' total) would give you 4 screws each way for 8 total. If sunk 2" in I can't imagine how they would tear out unless the centerboard is just plain falling to pieces. 10" total would probably be fine, but I would not do less. Care would have to be taken that the screws grabbed well, but did not cause the board to split. Going in from the sides would prevent this, but comes with its own aforementioned challenges. Either way, bed everything properly so that moisture does not cause problems.

I would put a U-bolt through the strap where the block and tackle would attach. All SS hardware, of course.
Click to expand
stickinthemud57 said:
1/8th or 1/16th should do. The forces are not that formidable. 8" either way (16'' total) would give you 4 screws each way for 8 total. If sunk 2" in I can't imagine how they would tear out unless the centerboard is just plain falling to pieces. 10" total would probably be fine, but I would not do less. Care would have to be taken that the screws grabbed well, but did not cause the board to split. Going in from the sides would prevent this, but comes with its own aforementioned challenges. Either way, bed everything properly so that moisture does not cause problems.

I would put a U-bolt through the strap where the block and tackle would attach. All SS hardware, of course.
Click to expand
I found some material - stainless bar stock. I'm thinking about 1 foot (or more) of 304 along the edge of the centerboard attached by 10 screws. Could even double the length and fold it over. McMaster-Carr
 
stickinthemud57

stickinthemud57

.
Apr 11, 2020
792
MacGregor 26s Scott's Landing, Grapevine TX
I think you are on the right track. Let us know how it goes. Be sure to grind down the corners to protect feet and ankles!
 
stickinthemud57

stickinthemud57

.
Apr 11, 2020
792
MacGregor 26s Scott's Landing, Grapevine TX
Mine was solid fiberglass, I'm pretty sure. Weighed around 80 lbs. I think it would have tended to float otherwise. Also, I don't recall anyone ever reporting rot of the core. Text Crazy Dave Condon for an definitive answer. He helped design the 170.
 
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