Running mainsheet inside boom

[dreamer]

I'm working with a design where the client has specified the use of a boom gallows.

Rather than run the mainsheet along the bottom and potentially hanging up on the gallows, would it be a bad idea to run the mainsheet inside the boom?

I've tried to find examples of this and haven't found any.

Thanks.

[gggGuest]

I've done it on a dinghy, and the challenge was organising a suitable exit block which will give a fair lead at all the possible angles without ending up with an excessively large hole in the boom at what is, definitively a high load area. Since then I've always used a external sheet and a sailcloth sleeve attached to the boom with velcro to stop it catching. How that translates to your scale is another game entirely.

[gonzo]

The easy solution is to cut an extra groove on the bottom of the gallows' notch for the boom. That would accommodate the sheet without costing anything extra.

[CutOnce]

Originally Posted by gggGuest

I've done it on a dinghy, and the challenge was organising a suitable exit block which will give a fair lead at all the possible angles without ending up with an excessively large hole in the boom at what is, definitively a high load area. Since then I've always used a external sheet and a sailcloth sleeve attached to the boom with velcro to stop it catching. How that translates to your scale is another game entirely.

I've done it on a dinghy as well. Mine turned at a block under the gooseneck and ran back along the bottom of the boom to another block/camcleat combo that led down, therefore the angles issue did not come into play, as the entry and exit were always in alignment.

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CutOnce

[dreamer]

A notch in the gallows is fine when the boom is stowed. But my concern is the sheet catching on the gallows during a tack as the mainsheet will be slackened.

CutOnce, that is the arrangement I am thinking. Possibly a conduit along the bottom of the boom to ensure the line doesn't slide around inside the boom. I want to ensure there would be no chafing inside the boom.

[gonzo]

You can also use the common system of bringing the sheet to the gooseneck and then back to the cockpit along with halyards and other control lines.

[michael pierzga]

If your re a designer you better have a good reason for taking the main sheet from the back of the boat, to the middle of the boat, then back to the cockpit. The system is mechanically inefficient. The same with a boom gallows....justify it with a sketch.

[gonzo]

Is this one of the designs in your website? I really liked the Amazon design.

[maarty]

Can you post a sketch of what the design issue is?

[dreamer]

Gonzo,

That Amazon 50 boat is something pretty special. The guy who designed it is a Westlawn grad and a Real Estate developer by profession. He built the boat back in the spring and she's a beauty. One of these days I hope to get a ride on it.


The boat I'm referring to here is a Ketch. The Main is double-ended and needs to be controlled from the cockpit. There would be no way to run a mainsheet from the traveler to the cockpit.

The designer of this vessel (not me) has several decades of successful design experience, and 'having a good reason' isn't something I'm going to question. So before too many people start asking 'why are you doing it this way', just know that it is what it is. The client wants a ketch. The client wants a gallows. Etc, etc. This particular issue is a minor one. The designer doesn't see an external sheet as a problem and in fact mentioned that the way I've got it, there would be a huge bending moment on the leech attachment point. Maybe due to the notch?

In the end it will get built the way he wants to build it. I'm more or less exploring this out of my own curiosity.

This image doesn't show the mainsheet rigged and shows liesure furl boom (which the client is undecided on at the moment)

[gonzo]

Why is the sheet going to the forward winches. Is it possible to contain it around the traveller?

[dreamer]

The sheets actually go back to the aft cockpit OR the winches you see in this center cockpit.

Clients have their reasons and ideas. As I mentioned, it is what it is. Questioning the client's decisions is not up to me.

We could run the sheet right off the traveler and take a 90 degree turn aft, but that would eliminate the CC winches. Again, not my decision.

Back to the original question, I'm not clear as to why there'd be a problem with my proposed solution of running the sheet in the boom. Designer says there will be huge bending moments at the leach with this arrangement. I'm thinking it's because of the 'notch'. But we could easily reinforce that with gussets.

[ggray]

This is common to all (I suppose) Voyage catamarans.

Sorry I don't have a photo, but there are two small sheaves (maybe 1 1/2 to 2 inch diameter) one at either end of a slot perhaps 8 inches long on bottom of boom. Obviously, mainsheet is on top of foward sheave, and below aft sheave. Turning sheave at gooseneck alongside those for reefing lines.

Spars are by Sparcraft in Cape Town, SA.

[gonzo]

I see two winches at each side of the companionway. Does it mean that there are two fairlead blocks next to them? A solution would be to have a half pipe welded under the boom where is sits on the gallows.

[RHough]

Originally Posted by dreamer

The sheets actually go back to the aft cockpit OR the winches you see in this center cockpit.

Clients have their reasons and ideas. As I mentioned, it is what it is. Questioning the client's decisions is not up to me.

We could run the sheet right off the traveler and take a 90 degree turn aft, but that would eliminate the CC winches. Again, not my decision.

Back to the original question, I'm not clear as to why there'd be a problem with my proposed solution of running the sheet in the boom. Designer says there will be huge bending moments at the leach with this arrangement. I'm thinking it's because of the 'notch'. But we could easily reinforce that with gussets.

How does client intend to use gallows with furling boom? Boom/mast angle is critical for furling to work, how does client think boom will drop into gallows with rigid strut holding boom at proper angle for furling?

Why only centre line boom position on gallows? Should be able to lash boom to leeward gallows position when storm tri-sail is in use.

Either a normal boom/gallows/lazy jack system or a furling boom with in mast furling a last choice IMO.

Client and designer need to talk to a rigger?

R