Plastic Classic Forum

My Sea Sprite 23 has no boom vang at all. I intend to install a boom vang, a Schaefer 4:1 tackle which I bought cheap at Defender.com. However, to use it, I need to install a boom bail and another bail for the mast to attach the vang. I have been researching about how to install them and I am a bit confused at the moment... I thought that it was just a matter of drilling a hole then attaching the bail with a thru bolt but with further researching it seems I need to install some kind of backing plates OR a "compression tube." Could somebody tell me the right way to install a bail on the boom and the mast?

Well, it seems this thread went unanswered but since I have another related question I thought I would tag it on here.

My spars had a couple of bails installed just as you said. In each installation a hole was drilled through the spar and then a bolt was installed through the hole and bail. Based on my spar I would say this is the wrong thing to do. My spar was this way when I bought the boat and the bolts through the spar have been working side to side elongating the hole. Now the bolt rattles in the elongated hole and the spar looks like hell. The aluminum just isn't strong enough to handle the side loads from the bolt and bail.

Adding a tube inside the spar that the bolt goes through would keep the bolt from crushing the spar as the bolt was tightened although I don't think that contributed much to my problem. The main issue is the soft aluminum elongating from the hardened steel bolt.

What I like is what Tim has on his boom and my question is where can I pick up one of these.



Any thoughts?

BTW, my mainsheet traveler was not connected to the boom with a bail but with a simple bolt through the end fitting. With the nut inside the fitting there was no way to notice that the nut was backing off other than the bolt was loose but then it had to be loose to swivel correctly soooo..... One gusty day that bolt released the traveler block with a bang that made me leap halfway down the length of the boat and the boom took off like a rocket. Luckily it went the other way from me.

-Britton

Adding a sleeve how to:

Find a suitable sleeve just large enough to fit over your through-bolt. Drill one side of your spar just large enough to slip the sleeve into the spar and against the inside of the other side, where the bolt hole is. Insert bolt, tighten. Make sure that your bolt head or washer/nut assembly is larger than the larger side opening, in order to cover the sleeve and part of the spar. This is what keeps the sleeve from slipping out.

Hope this made sense!

-Tony

Sorry, no. That ISN'T the correct way to install a compression tube. The point of a compression tube is to carry the compression strain of the bolt, with no load on the extrusion.

The correct way is to find a tube that your bolt will JUST slip through. Drill a hole the size of the OD of that tube through BOTH sides of the extrusion. Cut the compression tube so it EXACTLY long enough to match the width of the extrusion. It should sit on a washer under the bolt head and should be precisely long enough to have a washer under the nut sit flush on the extrusion. You may have to file it down even so it's flush. Done correctly when you tighten the nut, it will compress the tube ever so slightly and still have a tiny amount of movement. This allows you to torque down the nut with no compression on the extrusion what so ever.

Thank you Charlie,
I wrote that in a hurry what you wrote is what I meant, though I was wrong about it going entirely through the mast. You learn something new everyday!

Tony

I'm also considering adding a bail to my boom. However, I'm thinking of lashing the block to the boom a'la Harken http://www.harken.com/blocks/carbofeat.php
anyone have experience with such a lashing?
Obviously, you need to have a loose-footed or slug-footed sail to do this.
Oh, this isn't a fancy race boat it's a 22' catboat but the lashing appeals to me 'cause I can do it and undo it if I'm not crazy about it.

My vang is lashed to my boom.

Three wraps of small stuff, loose, but fixed in place because they pass through the base of my outhaul cleat.

It ain't racy, but it works. My boom has enough of that "swiss cheese" feel already.

Not a thing wrong with a lashing. Lashings have been used on masts, booms, and other places on boats for centuries. They certainly should still work now.

bcooke wrote:What I like is what Tim has on his boom and my question is where can I pick up one of these.



Any thoughts?

Sure. Contact Metalmast Marine, the source of the one on my new boom. They'll make you anything you want for any spar...for a price, of course. Fine work, excellent welding.

www.metalmast.com

BE FOREWARNED: new hardware discussions with a spar maker are likely to lead to a difficult financial decision, vis-a-vis whether or not it makes sense to add expensive custom hardware to a 40 year-old, weak extrusion, or whether you should just bite the bullet and replace the entire section. This is the situation in which I found myself last year, which ultimately led to the replacement of the entire boom (when all I really wanted, originally, was a new gooseneck fitting).

That said, I love my new boom and don't regret the decision. But it was not inexpensive, either.

Also remember that the newer/stronger you make one piece of hardware on a spar, the more strain may be placed on the next elderly piece down the line, possibly leading to an earlier-than-expected death. One thing can very much lead to another here. I recommend you look long and hard at what you want and expect out of your boom, based on your realistic sailing and cruising plans for the boat, and use this information as a basis for any decisions.

We had Metalmast Marine built four masts, four booms and all hardware for us for two 35 foot trimarans (mine and a buddies) back in 1980. They did a great job for us then. Good to know they are still around and still doing good work.

Charlie,
This DIY approach is good to know, as I was afraid it meant getting a sparmaker to weld a tube in place.
Assuming an aluminum spar and stainless bail, I guess one would use an aluminum tube and stainless bolt & washers?

either one, although an aluminum tube is often easier to find, particularly where I live. I would rather use a stainless tube over a stainless bolt myself, but as I said that isn't always a snap to find. In fact when I built the masts for the last boat I did I had a buddy up in Canada send me some stainless tubes.

If you wind up using an aluminum tube, just coat the bolt with some TefGel before you insert it and you should have no problems with it.

BE FOREWARNED...

Oh yes, I did go to the website but fear of what may happen drove me away. I have already caught myself thinking, "why not just get a new spar and be done with it..."

At the moment I am juggling several ideas for upgrading the rigging. The weak link seems to be my boom. I keep trying to find ways to keep it simple and just upgrade what I need but as you say, one thing leads to another. If I follow your (Tim's) choice of boom vang then all the more reason to just get a new spar. I think I am correct in saying the original can't take the strain. Of course with a new boom would look nice with a new mainmast to attach to...

I can see those "tubes" acting to protect the spar from compression loads from the bolts but do they do an adequate job of protecting against shear loads elongating the holes in the spar too?

-Britton

By spreading the load over the length of the tube, the pressure/friction/chafe that causes the hole elongation is dramatically reduced. For all practical purposes, the hole elongation is eliminated.

Just for yuks....
lets say that the boom's width is 3" and that the wall thickness is 1/8" or so. Without the tube, the 3" bolt is actually only chafing against 1/4"* of bearing surface. With the tube in place, that chafe is spread over the full 3", or 12X as much bearing surface.

*actually 1/4" times the bolt diameter times pi divided by 12(assumed), for my fellow nerds following along at home. ;P

Maybe a new forum category, "Boat Nerding", should be started for those that enjoy thinking about these technical details. I was making winch covers from sunbrella last night and momentarily forgot how to calculate the circumference of a circle knowing the diameter. 2-pi-D? No, wait 2-pi-R! So pi-D! Yes!
Tragic. Obviously that A in diff eqs is doing me good.

Floatingmoneypit wrote:No, wait 2-pi-R! So pi-D!

You may have figured this out, but 2-pi-R is not the same as pi-D, unless R=1! You'll get quite a different result otherwise.

That said, I always have to look up various shapes' area formulae, and can never remember the circle stuff without double checking somewhere. The only book I kept from High School was the geometry one, and I have referred to it on rare occasion. (Usually, I Google it first, though!)

I know this is a really old thread, but I was searching the site to see if I could find a solution for this dilemna and thought I would dredge it up. Looks like the vang got ripped out of the boom. Originally #10 sheet metal screws were used. I was going to drill and tap the boom to 1/4 inch, but the holes in the spar are elongated and don't fit 1/4. Should I go to 5/16? Seems like that would be too big for the bracket. Ideally I would be able to through bolt it, but there is no way to access the inside of the boom. I found this at McMaster-Carr http://www.mcmaster.com/#threaded-inserts/=coianq under rivet nuts. Would one of those be strong enough to hold the vang bracket? Any advice would be really helpful. Oh, and I can't lash it due to the boltrope groove.

Thanks!

Doug

Hmm, couldn't help but notice Tim's post above. Last I knew 2 π r always = π d as 2 r = d . Not that this has anything to do with the latest question.

bigd14 wrote: Ideally I would be able to through bolt it, but there is no way to access the inside of the boom.

My vang and sheet bails are both through bolted with one bolt all the way through the boom. These must be kept snug or the holes will elongate. But by using a nyloc nut and occasional inspection this is not difficult to do. Actually, the holes will still elongate if the bale swivels, but that should not happen for a vang as the angle never really changes. Anyway, you might find the one long bolt method works for your application.