Backing Plate

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D

Don

Ok so I picked up a 2 by 10 inch piece of oak its about a 3/4 of an inch thick I think. My plan is to cut this into a backing plate for my sampson post which I will moor from and my forestay. Should I double it up? I'm assuing that covering it in resin would be a good idea to keep it from rotting. Any other ideas or thoughts... am I on the right track... I feel like I have just enough information to really screw this up :) Don
 
Joseph Shirley

Joseph Shirley

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Jun 13, 2005
559
Irwin Barefoot 37 CC Sloop Port Orchard WA
Don, I originally thought we were talking about a larger area

but I would think that 4X5 X3/4 would make a decent backing block. I wouldn't cover it with resin however, because it could rot out of sight then. The rot you had, or have, may have been caused by water coming through your bolt holes. You want to see it rotting before it disintegrates. Joe S
 
RichH

RichH

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Feb 14, 2005
4,773
Tayana 37 cutter; I20/M20 SCOWS Worton Creek, MD
Explain a little bit of how this 'backing plate' will

work on a Samson post. Do you mean to apply a 'collar' on the underside of the deck to help spread the load (at 90 degrees to long axis of the post)? and if so is the deck cored?, etc. etc. etc. If its white oak it will be OK without encapsulation; if red oak which rots easily then by all means encapsulate it especially on the end grain ... but still keep an eye on it.
 
D

Don

2 feet by 10 inches :)

Hmm any suggestions on protecting it from the damp if I don't hit it with some resin? The reason I'm replacing the sampson post plate is the size the orginal is only 4 inches by 4 inches and it has caused some stress cracking my guess is during high winds been through two canes on the mooring. Plus I think its orginal from the 70's its not really showwing any signs of wear though just want something bigger. The plywood one on the forestay is a bit rotted and the washers have compressed way into it so I thought I might as well do both with one piece and make it stronger. I figure I can increase the backing plate size to fit the front of the boat maybe 10 inches by 7 1/2 at the base and 4 inches towards the very front of the bow. Replacing the two 4 by 4 backing plates. Am I on the right track here? Don
 
D

Don

Yes it is cored....

Its a 77 O'Day 22 it is cored but the coring around the forestay seems good no problems that I can feel. I haven't gotten the sampson post off yet as the bolts are really rusted. My guess is the backing plate for the post was to small in bad weather since she was designed as a trailer sailor. Thus the stress cracks in the gel coat. Hoping the stress cracks are only in the gel coat and the gel coat repair stuff I have will seal it up alright so I won't have any water getting into the core. Don
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Soaking the oak in copper naphthenate will go a long

way to preserving it. FWIW i have four pieces of red oak nailed to some plywood and have propped it up where the rain water from the roof will fall on it and splash dirt up on it. After three years there is still no sign of rot. Edited for spelling
 
Maine Sail

Maine Sail

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Feb 6, 1998
11,703
Canadian Sailcraft 36T Casco Bay, ME
Don..

Those stress crack could be a couple of things.. #1 The drilled holes were not counter sunk or feathered. Feathering the edges of gelcoat prevents crazing and crazing is the beginning of a spyder crack. Just like a windshield if the edge of the fastener hole was rough, and a crack started, it will and can grow.. #2 You have moisture in your core and thermal expansion of the liquid and decomposition of the core have taken it's toll in combination with the loads.. P.S. a 4X4 backing plate on a 22 footer is HUGE!! In contrast I have seen bow cleats on 36 footers (no names) with 1.25" X 1/16" of an inch thick fender washers holding a 14,000 Lb. boat. That's 5 square inches of fender washer holding 14,000 lbs.! You have 16 square inches holding 2600 lbs.. Do the math!! Hurricane or not you should not need to go bigger...
 
Joseph Shirley

Joseph Shirley

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Jun 13, 2005
559
Irwin Barefoot 37 CC Sloop Port Orchard WA
Rich, I don't think he is talking about a Sampson Post in the

traditional sense, where a 4X4 goes through the deck all the way down to the lower stem area. Rather I believe he is talking strictly about a 3"X3" square hollow bronze casting with a pin through it and flange around the base that is bolted through the deck. I think of this as a small bollard. Any size backing larger than the flange would suffice but if you want to make one that's 10" at the base and 4" across the top, that's OK also. Have fun. Joe S
 
Maine Sail

Maine Sail

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Feb 6, 1998
11,703
Canadian Sailcraft 36T Casco Bay, ME
And if...

Yeah, and if he had a 24 foot tall garage, and a chain hoist, he could store his 22 footer vertically, hanging from the ceiling attached to the bit, and he'd have a lot more garage space..;D
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
When I was rebuilding Bietzpadlin I found two

mooring bits in cast bronze, one with a six inch base and the other with a five inch base. I set one at the bow and the smaller one at the stern. It would tear out a big section of deck to pull either of them out.
 
B

bffatcat

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Jun 8, 2004
853
Pearson 26W Marblehead
Backing Plates

I usually use 1/2 inch Marine plywood Ive found that over the years it dosent rot. And thats without, soaking it, or epoxying it,
 
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