Horizontal booms

[royt]

Why are booms always level?


The boom on my 43' aluminium cruiser (she is about 10yrs old, I bought her last year, and am planning to start cruising next year) is high enough not to threaten the heads people standing in the cockpit, which is great. But the problem is that the base of the mast is forward of the coach roof top. This means that the deck level at that point is quite low. I have also had a batcar system fitted, but this with the low deck has resulted in the headboard being over 2metres (6-7') above the deck, managing anything that high is a problem.

I would like to move the gooseneck down by at least a meter (3'), but leave the clew height were it is. This will result in a boom that is no longer level. But I can only see advantages (lower on the mast will reduce loads on the mast caused by the gooseneck, working on the sail at any other position along the boom is also easier, lower COE on the sail, bigger sail area, longer luff). Are there any major negatives that I am not thinking of? (Horizontal airflow?)

Why do I never see booms that are not level except on open 60s?

Regards
Roy

[chris_gee]

Maybe if you draw it out it will be clear to you.
1 you are not changing the luff length.
2 nor the sail area.
3 the air flow in the base will be less ie there is sail at the mast but none aft. At the top relatively there is none at the mast but some aft.
I don't see how batt cars move the headboard.
If you can't reach the top of the sail eg to shackle it on ( if it isn't permanent, and can't lower the whole boom temporarily then I can't see why the headboard occupies a metre. Presumably eyeheight would be over 1.7 m, so if you have a problem cut down the head board and reshape the sail.

[sailingdog]

Actually, if you're not getting the sail recut, you are going to cause a problem. By lowering the boom, you effectively shorten it, unless you have a non-loose-footed main, in which case, you'd have to recut the sail to do this anyway. This means the sail will be fuller under most conditions, and that can cause you some serious problems when the winds are very strong, since it will be difficult to depower the main. Also, unless you use a pennant at the tack, the sail won't be able to be hoisted fully. It'll be a meter short of full hoist. If the sail isn't re-cut, and you're not using a tack pennant, then the sail will be lower by a meter for its entire length—since the sail is what supports the aft end of the boom.

Also, reefing the sail will be a problem. If the sail reefs using tack hooks, on the boom, you're going to have a problem because if you do use the tack hooks the new, reefed clew is going to be higher than the reefed tack, and the leech of the sail will bag.

Personally, IMHO, you're asking for trouble. Why not just install a few mast steps, and use them when you have to work on the boom or headboard of the lowered mainsail. It is probably far less trouble and definitely going to cause far fewer problems.

[Hawkeye25]

One other little item - the vang. If you have a vang rigged, lowering the gooseneck 50% may result in actually tripling the loading on the vang, possibly resulting in an explosive failure, maybe even having the lower mast fitting coming at the cockpit approaching the sound barrier, though it would probably only fail if the boom was well overboard. Put a folding step and a handhold on the mast and simply step up to fuss with the headboard. It's not perfect, but it helps.

[royt]

Thanks for the responses.

Something I didnt mention was that I need a new main as well, so it would be cut to suit the new boom angle. Including putting in the reefing points to suit the boom angle.

To explain how the batcars raise the headboard.

The boom is perhaps 5' off the deck, the combined length of the batcar sliders and headboard when the main is lowered is perhaps another 3', resulting in the headboard being at least 8' off the deck. I agree that you could get at this with a few mast steps, but it certainly doesnt feel like a safe option for a cruising couple who may/will be caught out in poor weather.