Attaching bunks to trailer, what fastener?

[Gavin17]

A carriage bolt in a counter bored hole covered in carpet should never come in contact with the hull.  My 2004 trailer bunks are attached with lags and I'm going to re do them with lags due to ease of installation.  I agree that nuts and bolts would be more secure but by the time the lags wear out or come loose the carpet will probably need to be replaced anyway.  With the lag screws I can pre carpet the bunks at home.  Launch the boat and then install the new bunks quickly using a dirll and an impact driver.  

There is an option C I read about on another forum.  Someone suggested using flat head machine screws and nyloc nuts.  They cut the bunks to length and then clamped them to the trailer and drilled the mounting holes. Then they countersunk the holes and covered the bunks with carpet.  Use a knife or pick to punch holes in the carpet.  Then they installed the bunks on the trailer with the flat head screws going thru the carpet. This means that the head of the screw will be exposed so you can keep it from spinning with a screwdriver.  The holes in the bunks should be countersunk enough that the screw heads don't come in contact with the hull.  

[MadMan]

5 hours ago, Gavin17 said:

 With the lag screws I can pre carpet the bunks at home.  Launch the boat and then install the new bunks quickly using a dirll

This is how I did mine.

[Andrew63]

15 hours ago, ahopkinsTXi said:

How do you use a nut on lag bolts?

Sorry, I checked in Galv cup head bolts during the re carpeting process, then used nylocs to stop them working loose.

I found with the lag bolts they would continually work loose with the trailer flexing as I tow a bit. Some even dropped out.

when I tried to tighten the lag bolts, some had stripped no doubt from the flexing which is why I went to cup head bolts.

 

[ahopkins22LSV]

1 hour ago, Andrew63 said:

Sorry, I checked in Galv cup head bolts during the re carpeting process, then used nylocs to stop them working loose.

I found with the lag bolts they would continually work loose with the trailer flexing as I tow a bit. Some even dropped out.

when I tried to tighten the lag bolts, some had stripped no doubt from the flexing which is why I went to cup head bolts.

 

That's what I figured you meant. Just wanted to double check to make sure you knew something I didn't!

[Gavin17]

It sounds like I need to inspect my trailer and see how many of my lags are loose. I haven't replaced the bunks yet but plan to soon. 

[shadetreefab]

Use a clamp to keep downward pressure on the bolt head, c clamp, Irwin, pipe or bar clamp, then use cordless impact to tighten the nuts. 

[Asmodeus2112]

Brass nuts go best on stainless bolts. 

[whiplash]

I used stainless steel torque washers on the carriage bolt head when I replaced the bunks on a previous trailer. They dig into the wood and don't come loose one time if a lock washer is used on the nut side. I got them from a fastener supply store as the big box stores didn't carry SS.

https://www.wclco.com/lock-washers/torque-washers-for-carriage-bolts/

[Technicallyabu]

Lots of options. Lag bolts with lock washers, flat head allen bolts or regular hex bolts with nylocks, carriage bolts with lock washer and regular nut. All through-bolt options countersunk. Carriage with nylocks is a pain in the a** more often than not. Getting them in and out.

[Arick]

So I had a buddy stop over with a cordless impact and air impact.  He works in construction..  We drilled in a test piece of wood and pounded the bolt in and hit it with both impacts, the bolt still spun.  It did not sync into the wood at all.  He was stunned.. So back to alternate options..  I had to do some interior house work all day Friday(install all new base moulding) and got back to it the trailer today.  

I decide to drill holes in fresh wood so that I have to pound the bolt in.  I countersunk it with a spade bit. Pounded the bolt down and left a little gap to stick some silicone in there.  Put some on the bolt and pounded it in the wood.  Going to let this sit while I got attend some mothers day activities.  When I get back.  Its going to get some carpet and the dam thing is going on the trailer.  I don't care if it takes vice grips or whatever.  I'm done messing with it.

On a side note I talked to a guy at the local hardware store and he claims that stainless steel bolts come with a wax on them to help keep the threads from heating up from tightening a nut on. This prevents the mangling of stainless steel threads.

[whiplash]

2 minutes ago, Arick said:

So I had a buddy stop over with a cordless impact and air impact.  He works in construction..  We drilled in a test piece of wood and pounded the bolt in and hit it with both impacts, the bolt still spun.  It did not sync into the wood at all.  He was stunned.. So back to alternate options..  I had to do some interior house work all day Friday(install all new base moulding) and got back to it the trailer today.  

I decide to drill holes in fresh wood so that I have to pound the bolt in.  I countersunk it with a spade bit. Pounded the bolt down and left a little gap to stick some silicone in there.  Put some on the bolt and pounded it in the wood.  Going to let this sit while I got attend some mothers day activities.  When I get back.  Its going to get some carpet and the dam thing is going on the trailer.  I don't care if it takes vice grips or whatever.  I'm done messing with it.

On a side note I talked to a guy at the local hardware store and he claims that stainless steel bolts come with a wax on them to help keep the threads from heating up from tightening a nut on. This prevents the mangling of stainless steel threads.

Torque washers on the carriage bolt head. They will grip into the wood and keep the carriage bolt from spinning.