Cruiser Displacement and Sail Area

[Hiracer]

Originally Posted by S&S

That's probably where the idea that heavy= pig comes from. Production boat designers think that most people want beam, not depth. (rightly or wrongly)

Many heavy designs suffer from three problems: 1) lack of cord depth in the keel so poor windward ability, 2) low B/D which makes for great seakindliness but inability to stand up to sailpower, thus necesitating: 3) lower SA/D. All three together surely makes a pig.

Now to really make her bad, add narrow beam so she's a bitch downwind, and make her ends fine so she hobby horses in wind chop. Wonderful boat--not.

[Hiracer]

I truly believe it's harder to make a good heavy boat, than a good light boat. A heavy design has more limitiations.

Not that it can't be done. It can. But frequently isn't.

If a person doesn't understand design somewhat, I think it best to hire an expert like Bob P, or stick to mid-weight boats.

[Joli]

Tell that to Ted Hood?

Originally Posted by Hiracer

I truly believe it's harder to make a good heavy boat, than a good light boat. A heavy design has more limitiations.

Not that it can't be done. It can. But frequently isn't.

If a person doesn't understand design somewhat, I think it best to hire an expert like Bob P, or stick to mid-weight boats.

[Hiracer]

Originally Posted by Joli

Tell that to Ted Hood?

Yep, I like Ted Hood boats. He promoted centerboarders more than a left coast guy like me does, but otherwise I likie.

[S&S]

Originally Posted by Hiracer

Many heavy designs suffer from three problems: 1) lack of cord depth in the keel so poor windward ability, 2) low B/D which makes for great seakindliness but inability to stand up to sailpower, thus necesitating: 3) lower SA/D. All three together surely makes a pig.

Now to really make her bad, add narrow beam so she's a bitch downwind, and make her ends fine so she hobby horses in wind chop. Wonderful boat--not.

Agree with you on 1 2 and 3 but I don't see how fine ends promote hobby horsing (bluff ends would be worse). A (fairly) narrow beam with a good deal of depth goes fine downwind.

[Hiracer]

I had an IOR inspired boat with fine ends (the old diamond shape hull). She was a fantastic sailor, but in certain short steep seas she would hobbyhorse. A fatter stern would have help dampen that.

I think it's all sea state dependant. Just about any boat can misbehave if the sea state is pefectly 'wrong' for that boat.

* * *

Yes, depth cures lots of problems, but creates another one.

[S&S]

Originally Posted by Hiracer

I had an IOR inspired boat with fine ends (the old diamond shape hull). She was a fantastic sailor, but in certain short steep seas she would hobbyhorse. A fatter stern would have help dampen that.

I think it's all sea state dependant. Just about any boat can misbehave if the sea state is pefectly 'wrong' for that boat.

* * *

Yes, depth cures lots of problems, but creates another one.

Aah, now I understand- ours is a CCA boat (she's skinny all over but draws 8'). No hobbyhorsing but she's a wet ride to windward.

[Hiracer]

It's a crime what IOR did in the evolution of boats from the CCA rule.

Cruising boats should be completely blind to racing rules, but unfortunately that's not always the case. Witness the racer/cruiser designation.

Eight feet draft: I'm jealous.

Pretty boat, btw. In the picture in the slings, draft doesn't look like a full 8 feet but I'll take your word for it. I would have guessed 7 feet.

What's your B/D ratio?

Sweet boat.

[RainDog]

As several others have mentioned, do not put too much stock in the DLR. It can be misleading.

As an example compare the Pacific Seacraft 40 to the Valiant 40. They have nearly identical rigs (the PS has a longer boom), displacement, LOD, beam, draft, and PHRF. They also have similar underbodies. I do not know the wetted surface area, but for the sake of argument, let us assume they are in the same ballpark.

However the Valiant 40 is almost 3 feet longer on the water line. This gives the PS a DLR of 335 while the Valiant is 255. This makes the PS a "Heavy Displacement" cruiser and the Valiant is firmly in the "Moderate Displacement" range. But what does this really mean? Since they have nearly identical rigs and displacements, they will sail similarly in most conditions. In theory, the extra three feet on the water line means the Valiant can sail 7.8 knots vs. 7.5 on the PS. However in cruising conditions, I think few cruisers would often sail these boats at hull speed. If they did that would be 187 mile days for the Valiant vs. 180 mile days for the PS -- still not much of a difference. In light conditions, since they have the same displacement, similar rigs, and similar underbodies, I think they would also have very comparable performance. The PHRF numbers seem to verify this.

I am not saying the DLR is useless, just that it should be treated with care because it can be deceiving.

[S&S]

Originally Posted by Hiracer

It's a crime what IOR did in the evolution of boats from the CCA rule.

Cruising boats should be completely blind to racing rules, but unfortunately that's not always the case. Witness the racer/cruiser designation.

I'm in complete agreement.

Eight feet draft: I'm jealous.

We do have to use the dink- a lot. there're always compromises.

[Hiracer]

Originally Posted by RainDog

I am not saying the DLR is useless, just that it should be treated with care because it can be deceiving.

Agree completely. It's one of the least 'dimensionless' numbers.
Also, I think the bigger the boat the easier to go lighter.

[sailorboy1]

Not disagreeing with the above, but I don't believe I posted this as DLR question. It was really about displacement and sail area. Yes I gave a DLR for the 2 boats which changed with the displacement as one would expect.

Some of those old heavy Hood boats only had a power ratio of 14.5. Not going to go anywhere fast, but going to comfortable while doing it so guess that is agood thing.

[S&S]

Originally Posted by Hiracer

Pretty boat, btw. In the picture in the slings, draft doesn't look like a full 8 feet but I'll take your word for it. I would have guessed 7 feet.

8' from the LWL, probably 7' 10" /7' 11" in real life. Lines drawings say 7'11" but it's 8 if I put a lot of stuff on.

What's your B/D ratio?

Not quite sure of the exact weight so calculated to be somewhere between 48 and 52%. Derecktor didn't follow the plans exactly and some mods were done early on. About 18K lbs lead and 34K disp.

Sweet boat.

Thank you!

[dcstrng]

Originally Posted by Hiracer

Many heavy designs suffer from three problems: 1) lack of cord depth in the keel so poor windward ability, 2) low B/D which makes for great seakindliness but inability to stand up to sailpower, thus necesitating: 3) lower SA/D. All three together surely makes a pig.

This probably sums up conventional wisdom nicely… on the other hand, the heavier of the two proposed boats is actually somewhat lighter than our pocket-sized B24 (D/L 385 or so, SA/Disp around 14.2 depending…). Very comfortable for its size, amazingly able to ghost along, but doesn’t point particularly well compared to a fin-keeler even though its 50%+ ballast ratio allows it to carry sail in a fair breeze… We break out our drifter earlier than many, just to get the extra oomph and I’ve seen boat speed jump nearly a whole knot, going from jenny to drifter with 6-7 knots of wind… nonetheless, she will kick up her heels and we’ve seen 6.4-6.6 knots on the GPS more than once (which ain’t bad for a 19 ft waterline in a boat with standing headroom – assuming no one is over 6’). So, it depends on the complete package, very difficult to just look at the D/L to get much sense of the boat – although it may indicate to which group the vessel is marketed…