Mast/Boom question

[voxxmd]

Recently got a Grampian 28 and am learning the boat. One thing I'm trying to figure out is the design intent of the boom connection to the mast.

The extruded aluminum mast has the track, or channel, for the mainsail, of course. About 4 feet above the deck, the channel is cut away so you can attach or remove the mainsail. Unscrew the "holding pin", insert the plastic slugs into the track, replace the pin so the slugs don't fall back out...voila. No question there.

The track continues to the bottom of the mast. The boom's gooseneck sits in this track as well. It sits between two metal slugs, which are attached to the mast with through-bolts. There's about 7 inches of travel possible between the upper and lower slugs, or "stops". The gooseneck slug rests on the lower stop. In other words, I can grab the boom and readily lift it up 7 inches. (Normally wouldn't happen, as we have the boom vang fairly tight.)

Is there some design intent of having this 7" of vertical travel for the gooseneck? Or is the upper stop simply there to prevent some force from having the boom accidentally come off the mast? (like grabbing the boom in a rough sea!!)

I'm planning to raise up the boom by this 7" to give me (a) more headroom in the cockpit, as I'm 6'1", and (b) more headroom to install a bimini. Haven't decided yet if I want to have the bimini up during sailing, or just collapse it back to the backstay when sailing.

So my plan was to raise the lower stop such that the TOP of the gooseneck slug would butt up against the upper stop. This would eliminate any vertical travel. Any issues with this?

[Dos Gatos]

designed to allow setting of tension with a downhaul. raise the sail with halyard until boom rises to top slug or mark. tension luff with a downhaul. usually a ring welded to the sliding bit to run a line through to cleat on the mast lower down. other than that it's your boat, do as you please. don't need permission.

[jeremiason]

I suspect your missing a locking pin of some sort or as Dos Gatos mentioned a down haul.

Grampian has an owners group with a Yahoo page... If you can't find the answer here... You might want to try the other Grampian owners.

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[Cheechako]

As long as you have room at the top to raise it and still get the sail up, go for it. and nail that boom down in one place!

[Paul Elliott]

The boom track is there to allow adjustment of the boom position. There should be a downhaul line from the boom to the base of the mast that keeps downward tension on the boom (and so on the mainsail luff). You can adjust mainsail shape by adjusting tension on the boom downhaul.

Or, you can fix the boom position in the track by inserting stoppers. These slide into the track and have locking screws to clamp them in position. You will want to set the boom height so you can get the desired mainsail luff tension when the main is at full-hoist. Your main may have a "Cunningham" adjustment, which uses a grommet, or the first reef grommet at the luff, to carry a line that runs down to the boom. You tension the cunningham line to control mainsail shape.

I realize that I haven't given you all the necessary information for sailshape adjustment, but this should get you started.

[voxxmd]

Thanks for the insight. From what I had read (I'm still pretty new to sailing), I thought that the terms Cunningham and Downhaul were used interchangeably. I understand the benefit of being able to adjust the luff tension (for sail shaping), although I'm not quite certain why there is any advantage to pulling downward versus using the halyard to pull upward.

If one is going to adjust tension by pulling downward, I'm thinking that pulling the boom downward is a more elegant solution. Pulling the sail downward works fine, but the sail's luff would be crinkled up a bit below the Cunningham grommet. Pulling on the boom would keep the luff tight and smooth all the down.

I read somewhere that there is some limit imposed on sailboat racers for the range of luff tension, where they would actually make marks on the mast to indicate the range of luff length. Is this boom track system intended to simulate this this? Also, I'm curious, how common is this boom track arrangement? I'm no expert, but most other boats I've seen seem to have the boom location fixed, not travelling.