mastbox angle

[richard]

I plan to use a bermuda rig on a weekender, since I have a complete mast with sails and all available with the correct surface.

The mast in the plans is not at a 90 degree angle, but it is leaning a bit to the back of the boat. With a bermuda rig I think the mast should be at 90 degrees or the boom will touch the deck.

Should I change the position of the mastbox (and the bulkhead) to get it at 90 degrees or should I leave it and put the mast at an angle on the tabernacle?

Richard

[T. Nelson Surbrook]

IMHO you should forget the marconi and go with a gaff rig. You can make a lot of changes with the boat and get away with it. I personally don't think it's a good idea to change the sail plan as much as you suggest. Then on the other hand, she wore a glove!

[Barry Pyeatt]

Richard,

You might address that to Paul J. As our resident Sailmaker, he is probably the most familiar with Bermuda rigs and how they would adapt to a Weekender hull. I know that there have been a couple of others in the past. He frequents both this and the B&B forum. He is quite willing to address questions like this and give some insight.

Good luck.

[Stuart Benbow]

Doing your homework is going to be a big part of this change. I swapped from the gaff sloop rig to a schooner rig, and I spent almost a whole winter reading, studdying, doing math and making model mock-ups to make sure I don't mess it up.

I've learned a lot, and it's prompted me to start studying yacht design through the MacNaughton Group as a result as I found I really enjoyed all the sketching, thinking, actual useful math, tinkering and adjusting until I got it right. Of course, I still haven't finished building my boat yet, so there's not telling if I really did the math right or I'm just content with being blissfully ignorant.

Either way, the one thing I've noticed with reviewing various sail plans is that the bermuda rig seems to have a different Center of Effort than gaff rigs when offered by designers as optional changes. You'll be quite busy working out how to do this change properly long before you touch the wood. Of course, since I've changed more than the rig, I've also learned that having to design my own panels at every step of the build really slows down progress too. Ah well, all in the name of getting the boat I really want. :wink:

[Mark Hughes]

Ok, Stuart. I've been searching all over for the information you've had to get for this. I can find all sorts of info on mast and spar length and diameter, but nothing on placement. Can you pass on some of your sources you used to do the calculations?

[Stuart Benbow]

Ok' date=' Stuart. I've been searching all over for the information you've had to get for this. I can find all sorts of info on mast and spar length and diameter, but nothing on placement. Can you pass on some of your sources you used to do the calculations?[/quote']

Here's where your problem and mine differ. since both masts on my boat are flying gaffs, I made an assumtion (that may yet prove to bite me in the a%#) that proved out in the 1/12th scale model mock up I made.

I basically kept the stock mast location and angle the same, and started working out calculations for the center of effort of various rig placements against the stock center of effort. I figured, if I get it very close to the original, it should work out fine.

To do this, I took the lines drawing that is available on the web, made several sketches of what I wanted the boat to look like from a side view with the full sail plan, and worked out the effects.

Once I saw how things were playing out, I was able to narrow down what I needed, and through that I was able to determine where I wanted the mast for best effect. I definitely wanted the original mast location to be kept in case this idea failed, so that I could return to the sloop rig if all else went wrong. Ideally, I would have liked to move the foremast forward slightly so that the foresail could have been more useful, but it should work out well enough with the compromise.

There's probably a better way to do this, but as I haven't gotten anywhere near the yacht design lessons involving rig design, this hack job approach was the best I could do.

Here's a link to an article on figuring out sail area, center of sail, and center of effort. I haven't read this particular article, but I assume that it uses the standard methods for calculating this.:

http://homepages.apci.net/~michalak/1jun02.htm/

Hope this helps,

[Sailor3356]

Stuart Benbow, I would like to see pictures of your boat. I have sailed (crewed) on a boat with two gaft rigged masts (65 foot Yawl) but it was allot larger then a Weekender. Please share what you have found out.

[Stuart Benbow]

Hi again,

I've been doing a fair job at keeping my website updated with my progress on boat construction, so there's a reasonable amount of progress photos already there. http://stuart.benbow.com is the url.

I have a modification section, but the main modifications are only now starting to really take shape so there isn't much to see. I haven't started the spars or rigging yet (apart from the bowsprit, which I finished on Saturday, so other than mast stumps, you won't see much.

As far as schooners go ... as I understand it, making a schooner this small is a fools erand, as the sails are too small to really be of use, and the rigging becomes too cluttered ... but what can I say, everybody lvoes a fool. I think the suggested minimum boat length is 40' but I could be wrong. It's been about a year since I did most of my digging for facts, figures, and formulas.

To give you an idea of the dimensions I went with, my masts are 6' apart, with the foremast in the same spot as a typical weekender mast, including mast angle. I have extended my bowsprit by 12" to offset the shift of my center of effort to aft caused by the main. I used the formula for gaff sail dimensions found in the Gaff Rigg Handbook for the main, and used the old eyeball technique on the foresail, as it will be skinnier, and taller than the recommended gaff sail.

To make things more crowded, I'm rigging her as a cutter, so there likely be no way to single-hand her when she's done.

I have gone with a slightly higher mast, even though the sails themselves will have a lower height. I did this for two reasons ... first, I think it will give me better leverage for raising the gaff and adjusting the peak (pure speculation). Secondly, I wanted the option of topsails open to me ... which may or may not be the sane thing to do considering the fact that I've already increased the sail area by 40 square feet.

I would post more sail dimensions, but they're all at home ... still in boxes from my move mostly, and these are the only ones that I can remember right now.

If you're looking for a specific picture or series of pictures that isn't already on my website, I'll be happy to take them for you and post them. Also, you're only about three hours away. If you ever find yourself in the neighborhood, feel free to swing on by and take a look. I'm usually home and working on the boat most evenings and weekends.