Through-Bolting Boom Block Straps - Hardware?

Bungo Pete

Member
Hello Everyone:
I am going to replace my boom blocks and through-bolt the straps. My question is what to use for fasteners; specifically nuts. I am aware of the vise-grip trick, as well as using LANOCOTE. However, do I use just two plain nuts with some loc-tite, one nut with a lockwasher (split or star?) or or a plain nut and a nyloc on top. Also, is it advisable to through-bolt the vang key holder while I have the thing apart?
 
I would think a nyloc nut would be fine.

I recently built another boom and purposely didn't bolt the eye straps on. Wanted to see how long it took before they got loose. Used stainless rivets with a washer on the inside with duralac. Vang key has always been riveted on here. Been about 100hours so far in medium to heavy winds, everything still holding.
 
Chainsaw:
Thanks for the reply.

RE: Rivets - How did you get the washer into the inside of the middle of the boom? Also, what is Duralac?

I like nyloc nuts myself and use them on the power boat. However, the screw must be long enough to hold while I tighten it up, and nylocs are not meant to screw down very far after the threads engage the nylon ring. I have seen rigs where a regular nut is used first and tightened. Then, the "stud" is cut to length and the nyloc nut is screwed down on top. I just wanted to know if there are other methods.

As for the vang key, it now has aluminum rivets due to an emergency repair I did last summer. I could replace them w/ ss rivets or as I said before, through-bolt them.

Thanks again.
 
I normally use just a regular nut - if I have some threadlocker around, I'll use some of that, otherwise after cutting the bolt off just above the nut, I peen it over a little to prevent the nut from backing out.. Never had one back off and never used a star or lock washer.. Nothing wrong with a nyloc nut, (since you'll end up grinding or cutting all of them to remove), I just never seem to have any around that fit the bolts I'm using.

You will need to change out the alum rivets in the vang fitting, unless the holes in the boom are still tight with no corrosion, you'd be better off thru bolting it back on.
 
Only the end boom block straps have stainless washers. The mid boom strap never came loose regardless. Clearly not much load there, or not as much as the boom end - since it takes the big pumps from gybes.

Duralac is a yellowish anti corrosive lacquer that comes in a tube for joining dissimilar metals. It's supposedly the best stuff to use and costs accordingly. Fairly readily available in marine stores.

The last boom I had that was bolted with a nyloc nut at the boom end was just that - a washer and a nyloc nut. The bolt was almost as long as the diameter of the tube. It never came loose, no standard nut required.

If you're looking for real piece of mind on your vang key fixings you could use monel rivets which seem to be even harder than standard stainless steel, even though the monel is apparently only a covering over the stainless. I used 304 stainless and have had no problems. 304 is stronger than 316, but not as anti corrosive in some marine environments. Since I live two minutes from the sea on both coasts, you could say whereever I go I'm always at sea. No corrosion problems yet using 304 (which surprised me). When I made it I went round and backfilled the holes in the rivets with silicone to stop water and salt collecting in there. That may have made some difference.
 
My boom needs to be bolted or new rivets what length or size rivets do you use???
Also , this might be a silly question, I have a spare top section and was wondering is it the same diameter as a boom, could I make a boom from it??

regards
JasonB
 
Rivets are 4.8mm diameter (3/16") 7.9mm grip (5/16")

boom is same section as topsection. It seems to make a stiff boom, perhaps because it will have been work hardened by being flexed by the vang and wind as well as general aging. You could then make the jump of logic that a stiffer boom means more power from the vang is sent to the sail rather than have it lost in a flexible boom. (But i'd not like to start more lasering myths. There are enough already.)
 
Hi BP-
I just did that work on my booms- through bolting with basic hardware from a hardware store. i bought the best and used plain old washers. bold screw head on topside.
use 2.5 length. but don't remember dimensions- matched the rivet hole diam. and the fitting is tight.

also, when drilling do the measurement and also hold drill tight and press down. reg. drill bit worked well.

the result on my booms are successful. rivets were working loose and through bolting assures cooperation with full load on rig.

JRF
a girl laser sailor/ Delaware, and reg. visitor back to TX
 
use 2.5 length screw and be sure to get the heads that lay flush on boom. buy from hardware stores; just the same and better price.
JRF
 

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