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Old 11-04-2016, 04:46   #1
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Shortening a boom

I am considering shortening the boom on our tartan 34c. It is an early hull number, with the 13.5 foot boom. Over the production run of these boats the boom shortened first to 12 feet, then 10.5.

I have 2 mains, one old but still usable with an 11' foot, and a new one with a 10' foot. The boat sails very well with the short main, so I don't foresee going back to a sail with a longer foot.
Other than having to redo the outhaul and move the reeling blocks, is there a good reason not to do this?
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Old 11-04-2016, 08:26   #2
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Re: Shortening a boom

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Originally Posted by tsell View Post
I am considering shortening the boom on our tartan 34c. It is an early hull number, with the 13.5 foot boom. Over the production run of these boats the boom shortened first to 12 feet, then 10.5.

I have 2 mains, one old but still usable with an 11' foot, and a new one with a 10' foot. The boat sails very well with the short main, so I don't foresee going back to a sail with a longer foot.
Other than having to redo the outhaul and move the reeling blocks, is there a good reason not to do this?
If you do shorten the boom, cut it at the inboard end. that way you don't have to re arrange the outhaul and all the reefing blocks. just remove the inboard gooseneck fitting, shorten and then reattach the gooseneck fitting.
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Old 11-04-2016, 08:33   #3
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Re: Shortening a boom

Thank you! I am going to shorten a mizzen boom, and for some reason I did not come up wit the idea of cutting it at the inboard end. You just saved me a lot of work!
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Old 11-04-2016, 18:25   #4
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Re: Shortening a boom

Yes, Thank you for that idea. it will be much simpler than moving all the hardware at the end of the boom. There shouldn't be much in the way, as the reefing hooks are part of the fitting that attaches to the gooseneck.
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Old 11-04-2016, 18:34   #5
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Re: Shortening a boom

it may depend on where the mainsheet attachment, and other things are regarding shortening the forward or aft end of the boom.
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Old 11-04-2016, 19:15   #6
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Re: Shortening a boom

With a main which is longer in the foot, do you have excessive weather helm in moderate air; say up to 12kts+/-? Of the magnitude such that dropping the traveler, & using the other main depowering tools, can't dial out?

Also, what kind of shape are your mains in? New'ish, with great draft shape, & crisp, stiff cloth, with lots of life left in it? Or old, soft, baggy, D-Cup type sails.

Plus, what's their batten configuration, & what does the sail look like at the inboard ends of the batten pockets?

And too, have you ever had a sailmaker, or dialed in racer, gauge their sail shape, & condition?
Ditto on asking the above folks about retrofitting full battens?

For, as crazy as it may sound, a bigger, more aerodynamically shaped main, will reduce weather helm, & increase your rig's horsepower. As will a well shaped standard main, on a properly tuned mast (with a good trimmer).

Basically, what I'm getting at, is that there are a lot of things to consider, & options that you have, in order to reduce weather helm, without loosing sail area in your main.

But... if you do decide to chop your boom. First measure, or rather, template the boom where you intend to slice. And compare said template to the front end of the boom. So that you can be fairly sure that your gooseneck fitting will slide into the chopped tube without a hitch. As some booms have tapers, or change shape along their lengths.
So it'd suck to cut the boom, & then find out such information. Doh!

PS: There are some other crucial "tricks" when performing such a mod, but I'm overdue for dinner.
Also, on weather helm. To check how much you Really have. If she's a boat with a tiller, put marks on the deck in say, 3 degree increments. Ditto on the wheel, if she's wheel steered. In addition, of course, to watching your inclinometer.
As it gives you a no BS check of how much helm you're using.
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Old 12-04-2016, 05:45   #7
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Re: Shortening a boom

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Originally Posted by UNCIVILIZED View Post
With a main which is longer in the foot, do you have excessive weather helm in moderate air; say up to 12kts+/-? Of the magnitude such that dropping the traveler, & using the other main depowering tools, can't dial out?

Also, what kind of shape are your mains in? New'ish, with great draft shape, & crisp, stiff cloth, with lots of life left in it? Or old, soft, baggy, D-Cup type sails.

Plus, what's their batten configuration, & what does the sail look like at the inboard ends of the batten pockets?

And too, have you ever had a sailmaker, or dialed in racer, gauge their sail shape, & condition?
Ditto on asking the above folks about retrofitting full battens?

For, as crazy as it may sound, a bigger, more aerodynamically shaped main, will reduce weather helm, & increase your rig's horsepower. As will a well shaped standard main, on a properly tuned mast (with a good trimmer).

Basically, what I'm getting at, is that there are a lot of things to consider, & options that you have, in order to reduce weather helm, without loosing sail area in your main.

But... if you do decide to chop your boom. First measure, or rather, template the boom where you intend to slice. And compare said template to the front end of the boom. So that you can be fairly sure that your gooseneck fitting will slide into the chopped tube without a hitch. As some booms have tapers, or change shape along their lengths.
So it'd suck to cut the boom, & then find out such information. Doh!

PS: There are some other crucial "tricks" when performing such a mod, but I'm overdue for dinner.
Also, on weather helm. To check how much you Really have. If she's a boat with a tiller, put marks on the deck in say, 3 degree increments. Ditto on the wheel, if she's wheel steered. In addition, of course, to watching your inclinometer.
As it gives you a no BS check of how much helm you're using.



Thanks for the in depth reply. Many good points to think about. The cross section of the boom seems to be consistent along the length, but I will definitely check.

The main that came with the boat has a 12' foot, so there is already 18" of unused length on the boom. That sail is pretty baggy, but I did take it to a sailmaker who thought it was still serviceable. The other main I picked up from another T34, someone started a refit but abandoned the project. One of the first things he did was buy new sails. I bought both the main and Genny, basically unused. The main is loose footed, with 2 full and 2 partial battens and a 10' foot. I don't plan on buying a new main for at least several years, and looking at 3 feet of unused boom over the cockpit made me start thinking about this.

I noticed an immediate difference when I put the new shorter footed sail on, the boat heels less ( although the T34 is a pretty tender boat), points higher and is generally more responsive. Most of that is related to the difference in condition of the sails. I don't really think the weather helm is excessive, I can balance the boat with a combination of sails and centerboard in most conditions. So really it comes down to deciding whether carrying the extra boom length is worth it vs the additional headroom.
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Old 12-04-2016, 06:12   #8
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Re: Shortening a boom

Doesn't your boat have end boom sheeting? If so cutting three feet from the boom will require moving the traveler as well, about three feet forward (ideally far enough that the sheet drop is verticle).

I am not sure what the gain is in doing this, but I am not familure with the boat either.
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Old 12-04-2016, 06:42   #9
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Re: Shortening a boom

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Doesn't your boat have end boom sheeting? If so cutting three feet from the boom will require moving the traveler as well, about three feet forward (ideally far enough that the sheet drop is verticle).

I am not sure what the gain is in doing this, but I am not familure with the boat either.

No, it was converted to mid boom sheeting with a cabin top traveller before I bought it.

The only gain is headroom in the cockpit. I am not certain I will shorten it, just trying to weigh the options.
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Old 12-04-2016, 09:47   #10
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Re: Shortening a boom

In that case I probably would cut the length from the back. It's probably easier to take off the end cap than to move the traveler... But it's really a judgment call. There isn't really a wrong way, just easier ways.
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Old 12-04-2016, 10:17   #11
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Re: Shortening a boom

To OP:

How long would you estimate this whole "cutting down the boom" business will require? Half a day perhaps? More? Less?? Why not just visit your local boat junkyard, assuming there is one within a reasonable drive from you, and just pick out a shorter boom with same foot track for about $100-200 max. This way you will still have your original boom intact just in case or/and you can sell it once your new boom proves worth keeping.

PS I see from your info that you're in VT. There is a decent size boat junk yard near Squam Lake are in NH (cant recall exact name but it should google easily), mostly power boats but they may have a few sailboats and hardware as well.
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Old 12-04-2016, 11:31   #12
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Re: Shortening a boom

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Originally Posted by Island Time O25 View Post
To OP:

How long would you estimate this whole "cutting down the boom" business will require? Half a day perhaps? More? Less?? Why not just visit your local boat junkyard, assuming there is one within a reasonable drive from you, and just pick out a shorter boom with same foot track for about $100-200 max. This way you will still have your original boom intact just in case or/and you can sell it once your new boom proves worth keeping.

PS I see from your info that you're in VT. There is a decent size boat junk yard near Squam Lake are in NH (cant recall exact name but it should google easily), mostly power boats but they may have a few sailboats and hardware as well.
It takes about 3 hrs. 1hr to de-rig the existing boom, 20 mins to measure and cut, 1hr 40 to put it back on.

We just did it with a Selden boom, cutting 1m off the end. The outhaul and reefing lines all ran through an ally fitting, so we just popped that off, cut the boom, then re-drilled and replaced the ally fitting.

Piece of cake.

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Old 12-04-2016, 11:35   #13
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Re: Shortening a boom

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It takes about 3 hrs. 1hr to de-rig the existing boom, 20 mins to measure and cut, 1hr 40 to put it back on.

We just did it with a Selden boom, cutting 1m off the end. The outhaul and reefing lines all ran through an ally fitting, so we just popped that off, cut the boom, then re-drilled and replaced the ally fitting.

Piece of cake.

n
Then buying a used one in my scenario would not be cost effective. ))
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Old 12-04-2016, 11:54   #14
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Re: Shortening a boom

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Then buying a used one in my scenario would not be cost effective. ))
I have considered buying a shorter boom as well. Good info about the place near Squam Lake. I have also been to Mass Marine parts in Quincy, Mass, they usually have a pretty decent selection.

I think the hardest part of the whole process would be taking off the end cap. With a boat as old as mine, there are sure to be some fittings that refuse to come off.
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Old 12-04-2016, 13:10   #15
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Re: Shortening a boom

It's pretty common to convert broken masts into booms if you are looking for a new one. Pretty much the entire Olson 30 fleet is using broken Melgus 24 masts as booms these days. It's probably the cheapest way to switch to a carbon boom.
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