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Old 30-03-2012, 21:34   #1
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Raising the Boom

I am considering raising the boom about 200mm to give us more room to create a hard top over the cockpit. (center cockpit).
Is it OK to use SS self tapers into an Aluminum mast to do the job? It's what is in use currently but thought I would check first to see if thats OK or if there is a better way to do it.

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Old 30-03-2012, 22:59   #2
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Re: Raising the Boom.

I'd never use self tapping screws to fasten anything that I wanted to stay attached. They are just too prone to stripping out whether stressed or not. Drill and use course thread tap for something as important as the goose neck.
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Old 30-03-2012, 23:49   #3
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Re: Raising the Boom.

Can you just simply raise the aft end? Shortening the leech of the sail is trivial.
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Old 31-03-2012, 00:12   #4
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Re: Raising the Boom.

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Originally Posted by roverhi View Post
I'd never use self tapping screws to fasten anything that I wanted to stay attached. They are just too prone to stripping out whether stressed or not. Drill and use course thread tap for something as important as the goose neck.
Ok, I can tap a thread sounds like a better way.

Daddle
Part of the reason for raising the whole boom is to help the vang clear the dodger. I will be getting a sailmaker to adjust the main.

Thanks for the tips.

Any problems using the SS screws, or is that the norm?

Jeff.
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Old 31-03-2012, 00:37   #5
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Re: Raising the Boom.

Threaded Rivets are the proper way to go for such a light metal. then you wont be dealing with any nasty issues down the road.
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Old 31-03-2012, 00:45   #6
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Re: Raising the Boom.

G'Day Jeff,

Looking at the picture it appears that the boom has already been raised once. Are you proposing yet another raise? That is gonna leave an awful lot of holes in a highly stressed part of the mast no matter what sort of screws you use to attach the gooseneck. Might want to ask a trusted rigger if it is a reasonable thing to do... or get the old holes welded up.

As to the s/s screws: you should use an isolating compound on the threads. One called Duralac is the standard potion here in Oz, and works well. No boat should be without a tube of this stuff. If you use nothing the screws will cause corrosion in the aluminium which both weakens the join and eventually will make it impossible to remove the screws. It is currently trendy to use something called TefGel instead, but it is very dear and does no better than many less expensive compounds. IN fact, being teflon based it is sorta slippery, and may lead to screws backing out in use.

Cheers,

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Old 31-03-2012, 04:04   #7
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Re: Raising the Boom.

Also be aware that raising the boom will bring it closer to the backstays. It might be possible an accidental gybe could see the boom striking the backstays hard.

You might need to shorten the boom as well if you raise it.
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Old 31-03-2012, 04:51   #8
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Re: Raising the Boom.

Jeff, that looks like a right dogs breakfast. The existing attachment seems to have a mix of rivet, cross head and slotted screws holding it on to the mast.

Can I suggest that you consider altering the stainless steel widget with "xxspar" written on it instead by extending this upwards. Just had a local welder do this for us with a spinnaker pole mast fitting so an old pole could fit a modern mast.

The mast end cap doesn't look to clever either. Sorry mate, looks like a bit of work to do to make this good again.

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Old 31-03-2012, 05:42   #9
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Re: Raising the Boom.

X2 to Jims post re isolating compound, also, be sure to use cutting fluid on the tap to ensure you get nice clean, sharp threads. Not much thickness to work with. Bruce.
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Old 31-03-2012, 12:37   #10
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Re: Raising the Boom.

Lanolin and LocTite also work well to cut down the galvanic corrosion between the aluminum S fasteners. Even without an insulating agent, stainless fasteners in aluminum masts are usually good for the life of the mast. Without the insulating agent, the screws may be near impossible to remover after a short time, however.

I wouldn't worry about additional holes in the mast. Those small holes won't weaken the extrusion, just make it lighter. After 49+ years, numerous hardware additions and deletions, the mast on my boat looks like swiss cheese in places but shows no sign of any problems. If you see any sign of cracks eminating from any of the pukas, then it's cause for concern. Even then, drilling stop holes at the end of the crack may be all that's required. Used to see that a lot on the planes I flew in the Navy.
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Old 31-03-2012, 12:42   #11
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Re: Raising the Boom.

Are you planning on extended cruising? If so, the gooseneck is not something to trifle with. That is a very common trouble area. Looks like you are in Sydney. Consider having a respected spar builder do the work.
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Old 31-03-2012, 18:44   #12
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Re: Raising the Boom.

Thanks everyone, this is really good advice.

Nemo, Threaded rivets? I assume they are available at Whitworths. Are they a full screw thread?
I will get myself some Duralac, thanks.

44". I am almost certain I have plenty of clearance from the backstay. Hadn't given it a second thought until you mentioned it, will check it today. Thanks.

Roverhi. Thanks for putting my wife’s mind at rest

Pete.
I hadn’t thought of extending the widget but will look into it. I think you would need to place a second bracket on top of the setup to give it additional support.
You are correct. It does look like a dogs breakfast. The boom is coming off today and will either be completely refurbed or replaced.

Roverhi.
Again. Thanks for putting my wife’s mind at rest.
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Old 31-03-2012, 19:07   #13
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Re: Raising the Boom.

Quote:
Originally Posted by roverhi View Post
Lanolin and LocTite also work well to cut down the galvanicrrosion between the aluminum S fasteners. Even without an insulating agent, stainless fasteners in aluminum masts usually good for the life of the mast. Without the insulating agent, the screws may be near impossible to remover after a short time, however.

I wouldn't worry about additional holes in the mast. Those small holes won't weaken the extrusion, just make it lighter. After 49+ years, numerous hardware additions and deletions, the mast on my boat looks like swiss cheese in places but shows no sign of any problems. If you see any sign of cracks eminating from any of the pukas, then it's cause for concern. Even then, drilling stop holes at the end of the crack may be all that's required. Used to see that a lot on the planes I flew in the Navy.

I have wondered about this, it looks as though my boom was moved two times, so the mast is OK with a few extra holes in it?
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Old 01-04-2012, 00:23   #14
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Re: Raising the Boom

Why do you need to lift both ends? Can you not simply recut the sail to lift the back end, giving more clearance over the cockpit, but leave the mast end in place?

Need an answer on this, cos this is what HWMO is planning to do once we hit a country with a decent sailmaker!
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Old 01-04-2012, 00:34   #15
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Re: Raising the Boom

Pete7,, had a good idea i think,,that is if i understood him right.
Make an extension to the Boom Gooseneck so the boom is mounting actually higher up the mast sort of like a Pintle connection,,then run a re-enforcing clamp at the upper part of the goose neck at the mast.
This will be plenty strong i assure you.
If ya want i'll make a few drawings and post them for you,,(chicken scratch style)
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