How slow can you stay on plane?

B

BillE

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C Dory Year
2004
C Dory Model
25 Cruiser
Vessel Name
TBD
We usually ran our C-25 around 15 to 18 mph and liked it there. Dropping down into the lower teens it became difficult for me to tell when off plane other than watching the growing size of the wake. Curious how slow other models can stay on plane?
 
Our 23 Venture, with full fuel and water and fully equipped for a 2 week travel on the water for the two of us has an honest true plane of about 13 Knots or 15 mph. During these travels, 90% of the time we are going at about 15.6 Knots or 18 mph which for us is the sweet spot to make good time in travel and to get the best fuel economy.
 
My flat bottom classic 22 falls off around 10 knots but I feel it’s labouring near there so in chop I keep it about 12 knots.
 
This topic is good to know to avoid it; called 'plowing' by some.

This is where your engine is probably working the hardest (maybe except WOT).

This is where your fuel economy really sucks (maybe except WOT).

This is where you commonly see inexperienced uninformed Captains (or worse
uncomplimentary adjectives) driving their vessel producing the boat's maximum
wake in "No Wake" zones, or elsewhere, contributing to some or all of: shoreside
erosion, damage to nearby docked vessels, damage inside of or injury to
occupants of nearby vessels underway, further division of the "sailors vs stink pot"
boaters stigma, the invention of new curse words directed at all boaters, etc.

Another example of how "one rotten apple spoils the rest of the barrel".*

Aye.

* Old European Proverb.
 
Is "plowing" staying on plane? My question was to slowest *effective* speed, without plowing.
 
BillE":cs2tf6wb said:
Is "plowing" staying on plane? My question was to slowest *effective* speed, without plowing.
Click to expand...

Plowing is not really on plane. It is when the boat has enough speed to start climbing the bow wave, but not enough speed to get on top of it. Worst point is when the bow pitch angle is greatest.

Probably depends a lot on how your particular boat is loaded (i.e. gross weight, CG) as what the slowest effective speed is. Trim tabs may help in adjusting the boat bow angle which could affect the size of the wake, but extended trim tabs are going to make their own contribution to the wake.
 
ssobol":5l64j3fb said:
BillE":5l64j3fb said:
Is "plowing" staying on plane? My question was to slowest *effective* speed, without plowing.
Click to expand...

Plowing is not really on plane. It is when the boat has enough speed to start climbing the bow wave, but not enough speed to get on top of it. Worst point is when the bow pitch angle is greatest.

Probably depends a lot on how your particular boat is loaded (i.e. gross weight, CG) as what the slowest effective speed is. Trim tabs may help in adjusting the boat bow angle which could affect the size of the wake, but extended trim tabs are going to make their own contribution to the wake.
Click to expand...

You can also tell you are plowing by your wake. If you are moving and have a kind of rolling wave in your wake that is pretty much the full width of the stern (the part actually in the water, except the engine thrust line) that stays right behind the boat (on the C-Dory it is about 1-2 feet from the stern), you are plowing.

When you a planing this wave is not present.
 
If the helmsman is attempting to find the slowest speed his vessel will plane,
he will plow it. It's inevitable.

It is a continuum starting from dead slow to planing and back to dead slow.
When planing your boat properly, you plow it twice thankfully going thru this
undesirable phase quickly minimizing unwanted effects for others.

Trying to find this exact spot/speed of your boat between plowing and planing for
useful nautical knowledge is codswallop.

Aye.
 
I agree with Foggy's "codswallop" comment. Just get it well up there.

But for interest sake, on my CD25 fairly heavily loaded, I find that if I get well on a plane, and then back off ever so slowly, once I get to 14 MPH it is clear to me that I have started to plow.
 
Based on what I have seen and read, the most economical speed for most O/B powered planing hulls is around 4000 RPM (if your motor is propped correctly). Doesn't matter what the speed is much, just set the power and cruise at whatever speed this gives you.
 
I find the two optimum speeds for my 22' is at 2200 RPM for hull speed around 6 knots, and at about 4200 RPM for 13 -14 knots. I have played around with speeds to find the optimum speeds for low fuel consumption. Generally my boat is heavily loaded as I am often on longer trips of about two weeks or so. I very rarely travel at WOT.

Last year I modified my boat to open up the storage space in the v-berth area. I have now added weight to the bow of the boat and I think that it makes the boat more balanced and the result is a more comfortable ride and this is especially so on plane.
 
Foggy, you know damn well that some boat designs have to plane at least in the mid 20s, some low 20s, some high teens. Can any go lower? That was the question. Yet for asking a question--on a boating forum--- about how other people's boats perform at what speeds, I am a "rotten apple" engaging in "codswallop", and mindlessly wrecking marinas with my wake? Ridiculous. Your answers are rude and condescending. You no doubt have lots of experience and knowledge but you can keep it to yourself as your comments are both unhelpful and unwelcome. The post itself was idle curiosity on a day when I'm at home, I'm bored, and I like thinking about boats, and reading other (friendly) boater's comments, which I thought was the purpose of this place. Please ignore my posts and resume admiring your own self importance.
 
Gosh BillE, that's not what Foggy's comments sounded like to me. But I have to admit that's the first time I've been introduced to codswallop. Even the dictionary couldn't set me straight. Foggy's sure right about the twits who plow, making a huge wake trying to squeeze another knot or two out of a 7 knot zone--or wherever. I see that all the time. But I don't think he was implying at all that you're that kind of skipper.
 
Gosh BillE, that's not what Foggy's comments sounded like to me.
Click to expand...
:oops: Foggy's comments didn't sound that way to me either.

P.S. One needs to understand that Foggy seems to enjoy being oblique (which, if the truth be known, I rather like :wink: :lol: ).
 
We have the CC23 and we can run on plane at about 3000rpm at 12-13 mph When we run at 4000 rpm we get about 20-21 mph This is with a semi loaded boat fuel water and camping supplies I usually run about 4200 at 23 or so that seems to be the sweet spot WOT is 5600 and 33-34 mph This is with a clean bottom and lighter boat
Engine is a 115 mercury CT. 15 by17 p
 
Cayman I Found it !!!

Definition of codswallop
British, informal
: words or ideas that are foolish or untrue : NONSENSE
The notion that Scott was waylaid by bad luck is "a lot of codswallop," said Roland Huntford, a British historian.
— Kenneth Chang
"Some say he died. Codswallop, in my opinion…"
— J. K. Rowling
… I muttered, "Yes, that's right," knowing all the while that it was a load of codswallop.
— Steven Pinker
:lol:
 
jennykatz, thanks for the answer. That's a real nice speed to stay on plane. I imagine that Venture hull is good for that with it's extra fullness to the stern.
 
Well...I guess you can go pretty slow and still be on step. People must be pretty bored today....lol...
 
Jennykatz , interesting I get the same results with a 90hp Merc CT using 15x17 prop. on a 22 cruiser heavy loaded. My fuel consumption is quite linear from 14 to 22 knots.

Jim.
 
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