Changing Old School Sail Plan

[thomm225]

Originally Posted by psk125

It sounds like the plan is to reduce weather helm by reducing sail area. We had friends with a Bristol 27. They were always the last boat to arrive on any cruise because it was so slow. Is there so much wind on the Chesapeake that you can afford to reduce sail area and not have the boat be even slower than it already is? To actually spend money to make this change to new short-footed sails before exploring other options is absolutely baffling. As others have pointed out, weather helm can be caused by blown-out sails - which your comments make it sound like you have. Rake adjustments can also fix weather helm problems. Shortening the foot of the sail in this situation is like cutting off the bottom of the centerboard when you hit an oyster bed instead of raising the board with the pennant.

I was going to increase the luff and shorten the foot just a foot or so like the boats pictured above.

I don't believe the sail is blown out yet even though it is about ten years old this coming Spring. It's an 8 oz main and holds it's shape well. Weather helm didn't change much when I replaced the 40 year old original main with my new one in 2012.

Since then and 2 new autopilots, I rarely feel the weather helm because Mr. Autopilot is usually doing the steering

As far as speed, it's not a fast boat but can hold it's own. Recently I got out and made the turn toward Hampton on race day ahead of three racing boats. We sailed the coastline toward Hampton for about 8 miles and they only gained a bit on me. I did notice my SOG at one point was 6.5 knots so I had the tide (hull speed in 5.97) and winds were around 9-12 knots and building. Maybe I had more tide than they did as they were in tighter to the coastline where many times there's more wind

It was 0930 and still early.

Good idea on the rake but not on this boat. The PO actually has the mast raked forward a bit already with no adjustment left. Looks a bit strange at times. That's another concern but if I keep the boat I'll be replacing the rigging and have the mast at least centered as far as rake. It would be nice to rake it back a bit to maybe get better pointing but that would definitely increase the weather helm

I can still get a decent shape out of the main. I getting some protection from the land here though so good wind small waves.

https://www.youtube.com/watch?v=iViRCw8KB2Y

[thomm225]

Originally Posted by psk125

We had friends with a Bristol 27. They were always the last boat to arrive on any cruise because it was so slow.

Except for a few instances when sailing on the bay, I'm usually not close to other boats so speed is not that big of a deal. It's usually who has the tide and which boat started out first to cross.

The crossing is only 20 miles so boats don't have that much time to overtake one another. My sail to Mobjack Bay/Severn River is probably 35 miles but usually after crossing the shipping channel 5 miles out there are few boats around. You will see a sail here and there but usually 3-8 miles away

I watched the guy in the video though make some gains but I crossed the shipping channel ahead of a tug towing a barge which I don't really like doing. The tug Captain though radioed the boat behind to check intentions. The Thimble Shoal Light is just ahead and can be seen in the video

After that he headed right toward Norfolk/Hampton and I went left toward Little Creek/Virginia Beach and ran the coastline. He was about a 40'-45' boat I believe but he was still a ways back when I got a decent look and the tug was to his port side in the channel

The other boat to port is a catamaran ..... motoring of course.

https://www.youtube.com/watch?v=l7hBFO7DHX0

[Spot]

Thomm, is your current main to the Bristol 27 sail plan or something a little different? Will the back stay be an issue with adding more cloth up top? Image from sailboatdata.com:

[thomm225]

Originally Posted by Spot

Thomm, is your current main to the Bristol 27 sail plan or something a little different? Will the back stay be an issue with adding more cloth up top? Image from sailboatdata.com:

The sail maker did some measurements due to the dodger then for some reason just went with the sail plan from Sailboatdata.

If I put the boom at the stop the luff is 2' too short. The old main measured about the same but would stretch and go all the way up but would still be loose in the luff. The Bristol 27 has a floating gooseneck to I set the boom a bit high to clear the dodger using some line which you can see in the attached photo and the videos above.

Photo of B27 with Catalina sail has boom at the stop which I can do also just have to lower dodger and remove the line. Notice that sail is a bit short on the foot also.

The new sail was 8 ounce and didn't stretch at all.

https://sailboatdata.com/sailboat/bristol-27

I think the backstay would be Okay. Bacon Sails had a mainsail on their B27 site a while back that was like 26.5' in the Luff (P) which is a foot more than the sailplan and it was maybe 10'8" on the foot (E) which is about 1.33' shorter

I should have bought it as it was new for $750.

[thomm225]

Sailboat data has the P measurement at 25.5 (Luff) and the E measurement at 12.2' (foot) which is B27 sm

Bacon sails has the P at 28' and the E at 12.3' for the Bristol 27IB and OB.

My boat was originally IB with the Bukh Diesel

[Pauls]

Thomm,

You did not understand my point about sail balance. Of course a main can bring a boat's head up. The same way a jib can be used to make her head off. The point is that a a boat can be designed with a balanced rig regardless of the length of the boom. If you want an extreme example look at the gaff cutter Curlew, only a couple feet longer than your boat and with a very long boom. She was well balanced.

You're used to performance sailing. You'll like your boat with more sail area. Adding or lengthening a bowsprit has been used to fix weatherhelm for centuries.

[thomm225]

Originally Posted by Pauls

Thomm,

You did not understand my point about sail balance. Of course a main can bring a boat's head up. The same way a jib can be used to make her head off. The point is that a a boat can be designed with a balanced rig regardless of the length of the boom. If you want an extreme example look at the gaff cutter Curlew, only a couple feet longer than your boat and with a very long boom. She was well balanced.

You're used to performance sailing. You'll like your boat with more sail area. Adding or lengthening a bowsprit has been used to fix weatherhelm for centuries.

Thanks for the info.

I'm thinking of just shortening the foot a bit from maybe 12'2' to 10'8" to 11'2" and maybe have the luff go from 25.5' which my sail maker got off the sailboatdata site to 26.5' (Bristol 27 IB at Bacon Sails and Sailrite have the luff at 28')

Not a big change especially since I have been sailing the boat for ten years with a luff 2.5' too short with now big difference in performance.

I say no big difference for cruising. If I were racing one design all Bristol 27's, I'd have the 28' luff and 12.3' foot and no dodger or a very short small dodger.

The boom is very low in the original configuration.

[psk125]

The height of your boom may be the culprit for your weather helm. By raising the boom you have moved the CE of the sail up. That means that it makes the boat heel more than it would otherwise, with less sail area available down low to push the boat forward. To exaggerate, imagine lifting the boom up ten feet. There would be a lot of leverage from the wind to make the boat heel. The boat's heel is causing the immersed shape to change, resulting in weather helm. It should be easy to test this by striking the dodger, lowering the boom to its original location, and hoisting your existing sail. There could be less weather helm because you're heeling less.

The review article you quote also talks about using a bigger (150%) genoa to balance the boat. How big is your jib?

[thomm225]

Originally Posted by psk125

The height of your boom may be the culprit for your weather helm. By raising the boom you have moved the CE of the sail up. That means that it makes the boat heel more than it would otherwise, with less sail area available down low to push the boat forward. To exaggerate, imagine lifting the boom up ten feet. There would be a lot of leverage from the wind to make the boat heel. The boat's heel is causing the immersed shape to change, resulting in weather helm. It should be easy to test this by striking the dodger, lowering the boom to its original location, and hoisting your existing sail. There could be less weather helm because you're heeling less.

The review article you quote also talks about using a bigger (150%) genoa to balance the boat. How big is your jib?

I'm actually not that much worried about the weather helm.

The boom is maybe 7" higher than the stop. The mainsail is 2.5' too short so I'm on the good side as far as weather helm is concerned due to raising the boom.

The slight weather helm is manageable and the autopilot is doing the steering 99% of the time anyway

Also, I'd hate to have that boom at shoulder level because an accidental gybe wouldn't be pretty on an old man or anyone for that matter if you are tired and forget to duck.

My jib is like 120% but I will be looking for one a tad larger.

I simply do not believe the foot needs to be 12" 2" long. That's 1960's technology.

Regardless since I have posted this I have found sails between $450-$700 that will work. Sailmakers are wanting $1600 plus for a new jib and $2000 for a new main so I will use what I have for the next few years and think it over.

I also have an almost new 90% storm jib that came with the boat and could be used in strong winds with my one reef in.

[thomm225]

I have the boom and mainsail quite high on this light wind day maybe 5 years ago and still the main is a foot below the top of the mast.

You can also see the boom stopper screw about a foot below where the boom is in the video.

https://www.youtube.com/watch?v=NN-Rv4UObWI

[waterman46]

Originally Posted by thomm225

Thanks Ann but usually in light air the wind is better higher up so having lots of sail at the boom level doesn't help.

As a racer we know on light air days to sail by the top tell tales.

I'm trying to go for a more efficient sail with maybe cutting a foot off the "foot" and adding a foot to the luff.

And at the same time reducing weather helm.

You will be fine as long as you keep the changes small. But consider the effects just the same. Other than adding convenience items, it is unusual for the layman to improve on the sailing performance of a well designed sailboat.

All sailboat designs include calculations of center of effort of the sails vs the hull shape and ballast. If you go with shorter foot and taller sail, but the same total sail area, you will heel more in any given wind speed. So the same heel angle will be achieved in a lower wind speed. In terms of boat speed, this may offset the efficiency improvement of the higher aspect main.

To overcome this the designer can increase righting moment by adding more ballast or increasing draft, but then the stress on the hull and rigging will increase at the same heeling angles as will the wetted area (bad).

[egodsey]

Your Bristol 27 was designed prior to the finalization of 1967 version of the CCA Measurement Rule ... but am sure Carl Alberg (et al) designed with the CCA rule in mind. I mention this because the CCA rule would limit the length of the top batten in the mainsail to something less than 2.22'. (Per the '67 CCA rule the top batten could not exceed 0.1 x B + 1 ft. ... or there would be a penalty applied to the P measurement ... where B was the length of the foot of the main and P was the length of the hoist of the mainsail. In today's parlance that's the E and P measurements.)

And all of this is to say ... if you want to shorten the boom you could achieve the same sail area as the original sail plan by going to a full batten for the top batten in main ... thus increasing the roach of the main. This would move the CE forward ... which would reduce weather helm. But is shortening the boom really a good idea?

As several of the other replies have already mentioned ... it is more likely that your weather helm is the result of sail condition and /or sail trim ... than it is of boom length.

I submit you might be better served by keeping the boom as per the original Alberg sail plan ... significantly increasing the roach with a full batten top batten ... and having at least two (perhaps three) reef points in the main. This will deliver better overall performance ... but with the requirement that you reef often and early.

At least that's how it has worked for me on my Hunter 25.5. The top batten is so long that in light area I have to help it past the backstay when tacking. But I was able downsize from a 150 genoa (that came with the boat when I bought it 10 year ago) to a furling 130 (from Bacons) with no loss in overall performance. Indeed, the overall result has been better balance on the helm ... and better boat speed ... with reduced sail area and the attendant easier sail handling.

[thomm225]

Originally Posted by waterman46

You will be fine as long as you keep the changes small. But consider the effects just the same. Other than adding convenience items, it is unusual for the layman to improve on the sailing performance of a well designed sailboat.

All sailboat designs include calculations of center of effort of the sails vs the hull shape and ballast. If you go with shorter foot and taller sail, but the same total sail area, you will heel more in any given wind speed. So the same heel angle will be achieved in a lower wind speed. In terms of boat speed, this may offset the efficiency improvement of the higher aspect main.

To overcome this the designer can increase righting moment by adding more ballast or increasing draft, but then the stress on the hull and rigging will increase at the same heeling angles as will the wetted area (bad).

I'm actually not trying to improve the sailing performance. I'm no nautical engineer but that super long foot sometime simply appears out of whack with the rest of the sail plan.

Also as I've posted above many other boats including the Bristol 27 have replacement mainsails with a shorter foot. I'm not sure why I have just noticed it a lot and it's simply not that hard to look up a the proper measurements ......most any sail maker knows this also

[thomm225]

Originally Posted by egodsey

Your Bristol 27 was designed prior to the finalization of 1967 version of the CCA Measurement Rule ... but am sure Carl Alberg (et al) designed with the CCA rule in mind. I mention this because the CCA rule would limit the length of the top batten in the mainsail to something less than 2.22'. (Per the '67 CCA rule the top batten could not exceed 0.1 x B + 1 ft. ... or there would be a penalty applied to the P measurement ... where B was the length of the foot of the main and P was the length of the hoist of the mainsail. In today's parlance that's the E and P measurements.)

And all of this is to say ... if you want to shorten the boom you could achieve the same sail area as the original sail plan by going to a full batten for the top batten in main ... thus increasing the roach of the main. This would move the CE forward ... which would reduce weather helm. But is shortening the boom really a good idea?

As several of the other replies have already mentioned ... it is more likely that your weather helm is the result of sail condition and /or sail trim ... than it is of boom length.

I submit you might be better served by keeping the boom as per the original Alberg sail plan ... significantly increasing the roach with a full batten top batten ... and having at least two (perhaps three) reef points in the main. This will deliver better overall performance ... but with the requirement that you reef often and early.

At least that's how it has worked for me on my Hunter 25.5. The top batten is so long that in light area I have to help it past the backstay when tacking. But I was able downsize from a 150 genoa (that came with the boat when I bought it 10 year ago) to a furling 130 (from Bacons) with no loss in overall performance. Indeed, the overall result has been better balance on the helm ... and better boat speed ... with reduced sail area and the attendant easier sail handling.

Glad it worked out for you.

I won't be shortening the boom though or adding roach, but may just buy a sail with a bit shorter foot.

After noticing boats with mains like this, I also saw for sale under Bristol 27 a mainsail with a 10.8' foot and 26.5' Luff. B27 sail plan calls for 12.2' foot and 28' Luff. Mine is 12.2' and 25.'5 luff as per sailboatdata.com.

Bacon Sails said it would work fine on my boat . It was a new sail that I guess someone never picked up.

Btw I had about the same weather helm when the mainsail was new as I do now. Haven't really noticed it lately though because I rarely steer more than a couple minutes during a 40 - 70 mile sailing trip.

I am hoping though that when I have new rigging installed and rake the mast back to straight up it doesn't increase the weather helm. By mistake, accident, or choice, the PO has the mast tilted forward a bit with no adjustment left

You see these shorter foot mainsails quite often on the Contessa 26 which may have been designed so that the main's foot does not go all the way to near the end of the boom

[malbert73]

Originally Posted by Pauls

Don't know where you got the idea that "long old school booms make weatherhelm" but that just isn't true. Your boat has weather helm because the actual center of pressure of your sail plan is aft of the actual center of effort of your underbody.



Old, stretched out sails that have become cupped can move the center of pressure aft significantly. If you haven't, it would be worth checking with other owners to verify if they all have this problem, in an attempt to ascertain whether it's a design problem or just shot sails.



If you conclude it's a design problem I'd suggest you consider adding a bowsprit. You will move the center of pressure forward and add sail area at the same time. More sail area beats the hell out of less.

Exactly. This.