What type of bolts to secure bunks

J

Johnny Be Cool

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Jul 22, 2010
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Hi All!

I have a 23' Cruiser, 4000 lbs. It's a keel supported trailer with 4 single poles on each corner to support balance. I'm getting rid of the poles and will be using 2x6 bunks mounted to Bunk Bolster brackets.

Before carpeting the bunks. Do I install the bunks to the braces from underneath the bunks, first going thru the brace then into the bunk or drill a sink hole from the top of the bunks and install the bolt all the way thru the 2x6.

If going from the bottom then I'd have to use lag bolts, something that has a screw type of thread on it.

I'd rather go from the top personally. My concern is if something might pierce the hull.
 
ezmobee

ezmobee

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23,767
Re: What type of bolts to secure bunks

I used carriage bolts from the top. I banged the s__t out of them to get them about flush. Then I carpeted the bunks and installed them.
 
R

RicMic

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Re: What type of bolts to secure bunks

If the bunks are pressure treated wood then you will have to go with hot dipped galvanized minimum, the other choice is stainless steel. I think you will find it easier to make and cover the bunks then just lag bolt them from the bottom, you will have to predrill. If you use carriage bolts from the top, you can counter bore(make a bigger diameter hole) just deep enough to set the heads below the surface.
 
J

Johnny Be Cool

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Re: What type of bolts to secure bunks

I was thinking along the same way. Thanks for answering and reassuring my thoughts!
 
U

Utahboatnut

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Re: What type of bolts to secure bunks

I just did mine and went the carriage bolt thru the top route. I measured real well the layout that was existing and had the bunk boards all pre built, put the boat in the lake removed old ones dropped new ones on installed nuts and washers and was done. I used like a 1" speed bore to countersink the heads a bit then drilled the shank hole, that way I didnt have to hammer the crap out of them. I also filled in the countersink hole with some const adhesive before I carpeted, just to insure everything was nice and flat.
 
ajgraz

ajgraz

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Re: What type of bolts to secure bunks

Every time I've ever lag-bolted PT lumber the lag bolts eventually loosened up and fell out. The lumber just doesn't hold a thread, whether because it is soft, from repeated dunking, whatever.

When I re-do my current bunks, I'm going to use stainless through-bolt, either carriage bolt from the top or long T-nut in the top / bolt from the bottom.

(I'll probably go t-nut because then they can be re-tightened from the bottom at any time)
 
G

grassman

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Jul 17, 2008
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Re: What type of bolts to secure bunks

I just rebuilt my bunks yesterday. I used pressure treated lumber, drilled/counterbored for stainless steel carriage bolts then covered with carpet. It worked out well. The old bumnks were starting to rot and would not hold a lag.
 
J

Johnny Be Cool

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Re: What type of bolts to secure bunks

Thanks to all of your advise. It was great to hear from you all :) !!!!!

I'm going galvanized carriage bolt, 1" counter sink hole, 1/2" deep with lock nuts.

THE END! :D
 
B

bob1340

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Re: What type of bolts to secure bunks

I have read on here elsewhere that pressure treated lumber can rot the carpet and/or stain the hull. Not sure on this. I just built some from regular redwood 2x4's as that was what I had. It's a light aluminum boat. I drilled the holes and hammered elevator bolts in they resin coated the whole works before putting on the carpet. Lots of places don't have elevator bolts so carrage bolts will do.
 
R

RicMic

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Re: What type of bolts to secure bunks

Most bunks are made from PT lumber, the thing is, they PT it right from the tree, so its full of water, if you use lag bolts when its still wet, it will dry and shrink and loosen the bolts, you will find the carriage bolts also loosen, but it usually dosn't get noticed. If you use regular carpet the chemicals will attack it as well, you have to use the 100% synthetic, like astroturf. I use screws and lags on pt lumber all the time, I just like to let it dry out or make sure I allow for the shrinkage.
 
ajgraz

ajgraz

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Re: What type of bolts to secure bunks

RicMic said:
Most bunks are made from PT lumber, the thing is, they PT it right from the tree, so its full of water, if you use lag bolts when its still wet, it will dry and shrink and loosen the bolts, you will find the carriage bolts also loosen, but it usually dosn't get noticed. If you use regular carpet the chemicals will attack it as well, you have to use the 100% synthetic, like astroturf. I use screws and lags on pt lumber all the time, I just like to let it dry out or make sure I allow for the shrinkage.
Click to expand...

Well yeah, but it's my belief that repeated dunking makes the bunk go through swell / shrink cycles that eventually makes the lag bolt release. Maybe some 3M 5200 helps with that, I dunno.

Also have seen carriage bolts eventually twist loose in bunks because the wood softens. Maybe countersinking and filling with a sealer helps prevent that?

Anyway, that's why I'm thinking counter-sunk stainless T-nuts. With their teeth, the T-nuts won't twist loose, and you'd be able to tighten the bolts from the underside/backside alone, even with the boat sitting on the trailer. Just have to be sure to get just the right length of bolt to hit the T-nut threads but not protrude above the bunk. ;)

Then again, considering budgetary constraints, most (including me) would probably just use countersunk galvanized carriage bolts.
 
X

xeddog

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Oct 23, 2009
Messages
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Re: What type of bolts to secure bunks

My trailer is 20+ years old and it is losing the lag bolts. The wood in the bunks is getting old and the lag screws themselves are rusting and just falling out. I hope no one driving behind me has run over one.

When I re-do the bunks I am going with counter sunk SS carriage bolts from the top. I will also use self locking nuts on the bottom side. That should keep them there until I want them to come off. ;)

Wayne
 
A

asm_

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Messages
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Re: What type of bolts to secure bunks

I just recently replaced both bunk with red wood. While taking off the old 13 years bunk installed by Tracker, noticed the wood is not treated, and they use lag screw to secure the board. With that setup, it appears to work fine for 13 years.

Oh, the only reason I replaced the bunks was I wanted to moved 2" further back and the carpet on one bunk was torn. In any case, I did use SS lag bolt for replacement.

B
 
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