Motion Comfort Ratio

[bobconnie]

I was taught to make the boat comfortable for me! and it's my job to sail it that way ! I don't like sailing stright downhill or uphill !! To me cruiseing has nothing to do with speed !! Altho Ive done 200 mile days at times ! I bear off 10 -15 deg to make things comfortable for my crew and I ! Why beat your self and your crew up to make 20- 30 more NM a day?? Ive never raced so I guess Im missing something! But Im never covered with bruises and my crews happy !! and for yall cooks ! it's much easier to put a good meal on the table when your able to sail with vane or auto steering! Just my 2 cents

[Suijin]

Originally Posted by colemj

If I were to get a mono, I would look for as much waterline length as possible, a fin keel and moderate underbody, good beam but not carried all the way back and squared off, and on the lighter side of displacement rather than heavier.

I guess I am describing a low "comfort" boat, but I think speed, maneuverability and space contribute more to comfort than Brewer thinks.

Mark

Based on your first paragraph, you'd probably get a Valiant.

Long WL for her day, fin keel, moderate displacement and beam, and an almost elliptical underbody. She's a pleasure in a seaway, even a following sea. That said she's fast for what she is and what she was designed for, but gives up a few points to more contemporary designs on the speed front. It's all a matter of priorities and where and how you sail. I'm happy to give up .5 to maybe even 1 knot for the sake of a more forgiving motion.

I think the achilles heel, in terms of motion comfort, of most of today's designs is the lack of any real deadrise in the forefoot. Plumb bows that lead fairly rapidly to the sweet perfect circle which allows for minimum wetted surface. That, and the wide sterns that often lead to bad behavior down wind in a swell. It's just simple physics; the rounder and briefer the forefoot of your hull, the more uncomfortable it's going to be when it's sawing up and down. You trade that for speed, period.

[Pblais]

In the ten years I've been following CF no index ever mattered enough to either buy or not buy a boat. Nobody would ever not buy or not buy a boat based on a motion index. It is good way to never buy any boat. There are enough indexes to rule all boats as to be excluded.

[colemj]

Actually, I always intended on getting a Valient 40 or Pacific Seacraft 40 before I saw the light. Really, those are nice boats and I agree with you on that.

After cruising on a catamaran, however, I now think if I were to visit the typical cruising grounds on a mono, it would be of the Beneteau-type of design (don't jump on that name - just focus on what I mean by "type"). I have come to appreciate speed, space and maneuverability. A V40 would probably just fit in here, and maybe even save my butt in some conditions.

But for beating to weather, I really miss our old boat's comfort.

Mark

[Suijin]

Originally Posted by colemj

That's a gorgeous boat. Grew up drooling over them.

(Oops, sorry for the gigantic picture...dunno how to make it smaller)

[sailorboy1]

I miss the point sometimes when reading about a comfortable motion on a old design boat that is designed to be sailed at 20+ degrees heel.

[Jolly Roger]

It’s the first time I’ve ever seen my Down East 45 on any list. They’re so old I though they had gone off the edge of the world. Just as a matter of interest, I sail downwind one handed, the other clutching a pint . Get yourself a square sail lads !!

[robert sailor]

I'm a mono hull guy but I do like Cats. I sailed with Blair on a homebuilt Cat named Capricorn Cat in the Marshall Islands a dozen years ago and that was a real eye opener. It had deep dagger boards and would go uphill with most cruising boats and really flew off the wind. We went diving a lot on his boat and its terrific for that as we loaded up half the anchorage and headed across the lagoon at 12-15 knots with a little rooster tail. We were all mono hull guys sailing the hell out of this cat and loving it. It did have a strange motion that you couldn't predict and it was a very quick motion compared to a mono hull. I didn't like it but thats just me but boy I liked the way that thing cooked when it was on a reach. It was a 45 foot boat but was smaller than these huge cruisers you see today. And yes it was very comfortable at anchor.

[thomm225]

Originally Posted by Jolly Roger

It’s the first time I’ve ever seen my Down East 45 on any list. They’re so old I though they had gone off the edge of the world. Just as a matter of interest, I sail downwind one handed, the other clutching a pint . Get yourself a square sail lads !!

You might want to get an autopilot for downwind use so you can have two hands available to hold your pint. You wouldn't want to spill any...........

[rw58ph]

I don’t think Motion Comfort Ratio is all that important especially for a sail boat that is under sail? Motion comfort. roll period, is more when at anchored and/or motoring like the sail boat in the above picture. I would think for a off shore sail or power the stability angle, capsize formula and D/L ratio would be more important. If there are no other figures to compare, I have run the rations on boat/trawler that I thought where long range, blue water capable with a high stability. So you might want to pick a couple of sail boats and compare your boats ratios to get an idea.

Auto pilots are great, nice out in open water I put the boat on auto pilot and don’t touch the helm for hours, which allows me some freedom of moving around the boat. the auto pilot has a 25 ft wire remote so I can pilot the boat sitting on the front deck rather than in the pilot house. However, having a heated and/or AC pilot house is nice to have.

I see the sail boat in the above picture has a small sail, I assume is used like a weather vane to reduce swing, and might increase the comfort. Power boats call a small sail like that a steadying sail. Yes, many power boats have sails. We have one that is used at anchor to reduce the swing and keep the bow into the wind/waves.

[robert sailor]

They are called riding sails

[rw58ph]

Originally Posted by robert sailor

They are called riding sails

Well actaully on a trawler/boat they are a little bit bigger and they can be used to steady/stabilize the boat also thus know as steading sails. However, I have found the steady sail does very little in stabilizing the boat, so we only used it when anchored this a RIDING SAIL.

One sister 58 trawler was converted to a motor sailor to increase the range and stability at a cost of 20+ grand. They were planning on crossing the Pacific, the last I heard they were in Panama, but they got into a tiff, thought it best not to be isolaterd for 20+ days as one might not make it, and they separated. As far as I know the boat is still in Panama, and a local bought it. I looked into adding sails but figured 20+ grand it was not worth it as 20 grand will buy a lot of diesel, 5000 gallons or 10,000 miles

[Northwindbob]

Thank you so much for this information. I recently looked at a Passport 47 (upgrading from an Endeavour 38) and I noticed that the Passport rocked and rolled at the dock when stepping on and off. The Endeavour doesn't move at her dock. Of course, there could be a lot of factors at play for the Passport's rocking: salt water, shoal draft, high mast, loading, etc..., but it was enough to pass on the Passport for now. I am learning more and more about the Motion Comfort Ratio and this number will affect my decision for an upgrade. I like a stable ride. Thanks again.

[Adelie]

Use the Motion Comfort Ratio with a large piece of rock salt.

Ted Brewer himself indicated there really isn't any science behind it, just his opinions and half in jest at that.

Of course the use of the Displacement to Length ratio is even worse. It was developed for the design of power vessels but has been adopted by the sailing community to compare whether one boat is stronger/weaker or faster/slower than another when in reality the ratio is not good for comparing either except in the most gross terms.

[Cheechako]

Originally Posted by Northwindbob

Thank you so much for this information. I recently looked at a Passport 47 (upgrading from an Endeavour 38) and I noticed that the Passport rocked and rolled at the dock when stepping on and off. The Endeavour doesn't move at her dock. Of course, there could be a lot of factors at play for the Passport's rocking: salt water, shoal draft, high mast, loading, etc..., but it was enough to pass on the Passport for now. I am learning more and more about the Motion Comfort Ratio and this number will affect my decision for an upgrade. I like a stable ride. Thanks again.

Pretty old thread. I used to own a Passport 47. Rocky and rolly it was NOT.
Also, I would take formula numbers with a grain of salt for sure, as others have said.