Raising boom height - Any thoughts?

karonoko · Post by **karonoko** » Mar 31st, '11, 13:13

I am looking at a CD27 on which the owner has raised the boom height 10" on the mast to accommodate a bimini. Does anyone have a reaction - positive or negative - on how this will affect the sailing performance (or safety)? Below is the expalnation i got from the owner - a good guy - when i posed this question:

after consulting with Mack Sails we took about 10" off the foot of the sail (bottom) and it actually makes the boat sail better. If anything, it puts you just a smidgen down on how much sail you can carry before you have to reef. I can carry full mainsail now at a little higher velocity of wind range than before, which is a good thing. I sailed in 20 knots of wind the other day with full 135% genoa and full main, and that was on the edge of when I should be starting to reef the main. before, I would have been overpowered in that wind range. The mainsail is fully battened and it sets very nice. This boat sails very well with just her main on all points of sail including close hauled.

Sea Hunt · Post by **Sea Hunt** » Mar 31st, '11, 14:19

Some time ago I looked at a CD 25D that also had a raised boom (also to accommodate a bimini). It is my recollection the owner said the "shortening" was done by Mack Sails also. The owner said he was very happy with the performance, etc.

There was a discussion of raised booms on this board at:

http://www.capedory.org/board/viewtopic ... aised+boom

M. R. Bober · Post by **M. R. Bober** » Mar 31st, '11, 14:24

karonoko wrote:I am looking at a CD27 on which the owner has raised the boom height 10" on the mast to accommodate a bimini. Does anyone have a reaction - positive or negative - on how this will affect the sailing performance (or safety)? Below is the expalnation i got from the owner - a good guy - when i posed this question:

after consulting with Mack Sails we took about 10" off the foot of the sail (bottom) and it actually makes the boat sail better. If anything, it puts you just a smidgen down on how much sail you can carry before you have to reef. I can carry full mainsail now at a little higher velocity of wind range than before, which is a good thing. I sailed in 20 knots of wind the other day with full 135% genoa and full main, and that was on the edge of when I should be starting to reef the main. before, I would have been overpowered in that wind range. The mainsail is fully battened and it sets very nice. This boat sails very well with just her main on all points of sail including close hauled.

How is the helm, any lee tendency? Is she more tender, as you have raised the center of effort?

Mitchell Bober
Sunny Lancaster, (where there are many Lee tendencies) VA

CD-Sailor · Post by **CD-Sailor** » Mar 31st, '11, 14:44

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Russell · Post by **Russell** » Mar 31st, '11, 17:47

Cape Dorys have a tendancy for weather helm, I know my CD36 does and I have heard plenty of other owners say the same of their other models. The mains are basicly a bit too big as it is on CD36s at least. I know my boat balances far better with a single reef in. Though people who sail with a large genoa rather then the yankee/staysail may not experience this as much.

While its easy to say Carl Alberg knew what he was doing, thus modifying it would certainly mess things up, I do not think this is entirely true. For example, when he drew these boats mainsail technology was very different, sailmakers are making far more efficient mains then they were in the 70s.

So, a raised boom isnt nessisarilly going to ruin the boat, it may actually improve it. But thats a huge maybe. I would be suprised if whomever did do the raising was a naval archetect themselves, so expecting them to have done it knowing full well how it did effect the performance is unlikely.

Personally, if I wanted to permanently reduce mainsail area to improve balance, I would opt to shorten the boom, rather then raise it. Raising the center of effort higher on what is already a tender boat I do not think is a good idea. Even as you add a reef or two, the force will always be 10" higher then it should be. And in my opinion 10" is huge on a boat that size. Now if one opted to shorten the boom to reduce mainsail area you wouldnt have this problem. Though of course it would do little to aide in easy installation of a bimini.

I would be cautious of buying a boat modified this way, unless you have a chance to sail it on every possible point in every possible wind condition, you will never know how well it performs with the modification. And such things takes years of sailing a boat, not something you can do in a prepurchase sea trial.

But of course, its always an option to move the boom back to its origonal position, it really would be no big deal. You would need to buy a new main if you want the full sail area, but I imagine given my opinions about CDs oversized mains, the smaller main wont be an issue, you will just now have 10" at top rather then bottom (ie always sailing with a reef, but in the proper location). Obviously the bimini wont be able to be used underway though (but should still be fine at anchor, raise topping lift to get boom out of the way and setup bimini).

So really, cost of a new main is the only downside of this boat, so it shouldnt be a total deal breaker. Mainsails are not cheap, but you may find the next boat you look at for the same price has a main thats close to replacing anyway, or the third boat is in worse condition, etc.. just factor in the mainsail cost as part of what you are willing to pay for the boat.

CD-Sailor · Post by **CD-Sailor** » Mar 31st, '11, 18:04

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Russell · Post by **Russell** » Mar 31st, '11, 18:21

Sea_Runt wrote:
Russell wrote: ... While its easy to say Carl Alberg knew what he was doing, thus modifying it would certainly mess things up, I do not think this is entirely true ...
Yes, I agree, and that's why I never suggested "it would certainly mess things up." Instead I suggested "thinking long and hard" first.

I was not refering to your post when I said that, no need to be defensive. I meant in general, for anyone, its easy to say "Carl Alberg knew what he was doing...".

Sea_Runt wrote:
Russell wrote: ... Personally, if I wanted to permanently reduce mainsail area to improve balance, I would opt to shorten the boom, rather then raise it ...
The original post never said anything about wanting to reduce mainsail area. It said modifications were done so the bimini would fit, which is a completely unrelated issue. It's also a distant third place reason to limit mainsail size. I don't even play a nautical architect on TV, but I'd be much inclined to go with Alberg's original idea on this one.

[/quote]

I realize the bimini was the reason, I mention it in my post. But I figure if someone is coming hear to ask what effect raising the boom might have, its best to explain fully what effect it might have and why. Thus my post was more about mainsails then biminis.

Just trying to be helpful.

CD-Sailor · Post by **CD-Sailor** » Mar 31st, '11, 18:46

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johnny of STORK · Post by **johnny of STORK** » Mar 31st, '11, 19:22

Everybody's talking about the sail plan, but not the effect of the Bimini. I'm not a fan of these things, and I'd bet it would *increase* the weather helm, with its own CE so far back, as well as being a potential handful in a real blow. If you were to heel over to a nice 20 or so degrees, it'd be kind of like a giant anemometer scoop......

Johnny

The Patriot · Post by **The Patriot** » Apr 1st, '11, 07:30

Russell wrote: ... if I wanted to permanently reduce mainsail area to improve balance, I would opt to shorten the boom, rather then raise it. Raising the center of effort higher on what is already a tender boat I do not think is a good idea. Even as you add a reef or two, the force will always be 10" higher then it should be. And in my opinion 10" is huge on a boat that size. Now if one opted to shorten the boom to reduce mainsail area you wouldnt have this problem. ...

Howdy, Russell. Let me say, of course that I'm not a naval architect nor by nature do I enjoy picking nits, but your post raised some questions for me. First, shortening the boom as you suggest in your post will move the overall static CE forward (as well as the mainsail CE, of course). For the CD27 and probably other boats in the line, this is probably a bad idea. By moving the overall static CE forward, the inherent weather helm designed into the boat is reduced, and this of course means that the boat will have less tendency to round up naturally. This tendency is an intentional safety factor designed into all fore-and-aft rigs and is there for very definite reasons. In an extreme case, the boat might not only have a reduced weather helm but may even have a lee helm which is very bad (and very dangerous).

Next, it may be worth stating clearly that weather helm is not "evil" and changes in helm due to rig modifications may actually be counter-productive. These designs have a certain "feel" for the helmsman because of the intentional weather helm. I don't know if you steer your boat with a tiller, but on my CD28 I can essentially keep her going well with a blindfold on, solely by using the "feel" of the tiller (I do not recommend this activity for extended periods of time in confined waters). This is what the proper amount of weather helm is all about. Note that I am not talking about conditions where the helm becomes unmanageable due to heavy air. In such cases, these boats, when reefed down to match conditions, do very well and still keep the desired "feel." But of course you must already know this from experience with your own vessel.

Finally, raising the boom 10 inches does not raise the overall CE 10 inches. I have not calculated exactly how high the static CE would be raised on the CD27 if the boom were raised, say 10 inches, but it is less than 10 inches because the static CE is the combination of the mainsail CE and the jib CE, which itself remains unchanged. In other words the actual changes must be carefully calculated. BTW I have specifically emphasized the static CE, because the dynamic CE is always changing due to speed and conditions, and is itself very difficult if not impossible to actually calculate.

Interesting discussion, although my views are perhaps worth only the price I'm paid for them. In the end analysis, I'd be much inclined agree with earlier sentiments in this thread and let old Carl Alberg do all the messy work. Then I can just sit back and learn to enjoy the results.

karonoko · Post by **karonoko** » Apr 1st, '11, 09:00

I thought this topic might gereneate some good feedback! Thanks. I learned some stuff, and it confirmed my instincts and am inclined to either return the boom height, etc. or not pursue this boat. At any rate - thanks, and i am in the market so please keep an eye out for a CD 27 for me!

Dean Abramson · Post by **Dean Abramson** » Apr 1st, '11, 09:19

This is not (to say the least!) my area of expertise. But in addition to what Armond said about the CE's "actual raising," it is also the case that when the boom got raised, the sail area of the main got reduced. My guess is that the performance/handling difference would be negligible, and easily dealt with by just learning the boat and finding her groove.

My opinions are also worth what you paid for them, but somehow still less valuable than Armond's.

Dean

WaywardWind · Post by **WaywardWind** » Apr 1st, '11, 10:05

I'm not sure why anyone would want to have a dodger on a CD27. Mine came with a dodger and I took it down immediately and have never put it back up.

A dodger makes a windvane out of an otherwise good boat. The boat sails more poorly because of the dodger. A dodger makes it hard to go forward on the deck (to drop or retrieve the anchor, or to adjust the main halyard tension, or to reef).

A dodger usually means a LOT of high friction deck gear to get the lines back to the cockpit, and even then is only good 90% of the time.

A dodger means the boat is motored more often.

Reducing the main sail area by cutting off the bottom ten inches of the sail reduces the well-known "Alberg Effect" which is his boats' tendency to round up seriously when long on canvas in gusty winds. In addition, cutting the bottom ten inches off the mainsail makes the boat even slower in light winds. (EDIT: Raising the unchanged boom up by ten inches cuts ten inches off the TOP of the sail, which still means less mainsail area, but also means the CE of the mainsail is RAISED as well.)

The CD27 is awfully small to be used as a seashore weekend home, but a boom raised ten inches means less chance of knocking one's head on the boom, a bit of a concern for those over 5'6".

Dean Abramson · Post by **Dean Abramson** » Apr 1st, '11, 10:26

You might want to start a new thread on the plusses and minuses of dodgers. It would probably get a lot of traffic.

After sailing without one for twenty years (on three boats) we finally got one. I would NEVER go back. Best thing we ever did. Ours is pretty low profile. (I like seeing over the dodger.) Going forward is no big deal, and as for halyards, I like mine at the mast, so I go up there a lot.

If you regularly sailed to weather in Maine, or wanted to hang out in the cockpit at night, you would appreciate a dodger! I do not sense that the dodger slows us down. Plus, now the cat will hang out with us a lot more in the cockpit!

True, aesthetically, they can look a bit odd on smaller boats, but I have seen a 25D with one that looked pretty sharp.

But each to his/her own.

Dan

CD-Sailor · Post by **CD-Sailor** » Apr 1st, '11, 10:45

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