Why do deep V hulls lean into the wind?

[Synergy]

I have asked this question of a lot of people and nobody has been able to explain, why do deep V hulls lean into the wind? While you are thinking about this, what is the best way to counteract this problem. I have a Signature 650F with a 225 Suzuki at the moment but I have seen the same problem on many boats, all deep V monohulls.
Any of you gurus out there have the answer.
Synergy

[blaze]

trim tabs will fix it
cheers
blaze

[Noelm]

mostly it is due to the fact that the steering needs to be turned to keep a straight line and in fact when you do this you are leaning as if you are doing a turn (which in theory you are as you have the wheel turned)

[ahoj]

Buy a Cat.... ;D

[Noelm]

or you could buy a cat!

[Noelm]

seriously though, it is not much fun leaning like that, and having the boat sort of slamming/smacking down on the water half on its side. But I guess trim tabs would help considerably, never tried a boat with and then without (the same boat that is)

[Synergy]

Thanks Noelm, that is the first time anyone has gone close to explaining this problem. Trim tabs would definately fix this, I was wondering if a foil or a Permatrim might help as well.
Synergy

[Noelm]

glad I was able to explain it correctly, it is always hard to put into text what you are trying to say (sort of) but it is a problem that is a pain, you have to correct for the force of the wind and end up on a lean!!

[PinHead]

electric trim tabs...they work a treat

[Dignity]

foil wont help, dont know about permatrims - what are they

sam

[lucyloo]

put the fat bl;okes on other side but serious good ?

[Grand_Marlin]

Permatrims are similar to a foil...

You could always fit twin motors..... :D

[familyman]

Any type of foil will not help and if the boat goes ok without crosswind then adding a foil may make your problem worse.On a boat of your size trim tabs are the only solution as to shift weight to retrim boat you would need to move 2-300kg of stuff and or crew.A strong crosswind on my boat and I need to stand on the other side to fix the trim :o
As to why they do it I'm not sure but I've never noticed having to correct my coarse due to the wind ,well at planing speed anyway.
cheers jon

[Braddles]

I used to have an old swiftcraft seagull - an amazing boat that took us places we probably shouldn't have gone at times - but anyway...

It had been retrofitted with new cockpit, massive canopy (some of the problem) and a (then) new evinrude V4 90HP. This wasnt an overly deep V bow, in fact it was very flared out just above the bow waterline, good for stability and really roomy cockpit - but bit harsh in a big swell..

ANyway... we had the same problem, the boat would lean right over like a sailing boat and scare the crap out of everyone on board...

It didnt take much wind, and sometimes it would and sometimes it wouldnt.

We spoke to a man from a North side marine dealer in Brisbane (who sold us the engine) and he said to put a horizontal foil / fin on the outboard leg.. He even fitted it, and came out with us to test it... It made it a little better - but still tipsy.

Tabs were an option, and I am sure they would have fixed it - but I was going O.seas and didnt want to outlay the rather big $ for electric tabs. (Lucky I didnt - the boat's transom and floor was rotten on my return - thats another story tho)

In the end, I found always heading INTO the wind the best if possible, while underway removing the side canopy section (acted as a sail) and trimmed the leg in a bit more, balanced the boat weight against the tilt if I had a long run along the wind face... and this improved things considerably in my instance.

Good luck,

Brad

[MulletMan]

I reckon it is because the sides of the hull have a much larger area than the windows and superstructure and therefore the force of the wind is acting against the lower section of your boat and exerting pressure on a much bigger area. This would tend to "push" the lowest part "inwards" and of course the top part of the boat (with you in it) will heel into the wind.

The front and rear decks being "open" offer little or no resistance to the wind. Most (not all) boat sides also slope inwards and this has the effect of also forcing the wind downwards towards the waterline and causing this unusual situation.

If you are already side on to the upstream current then this will also be tending to push the keel "downstream" #:-/ :-/ :-/

The actual angle of lean can be simply calculated as follows:

(Boat length in metres x wind speed) + (compass heading - freeboard + beam width) + (current speed by the square root of the transom width) and divided by one twenty fourth of the wind direction (360 degrees whatever).
i.e. (6x20) + (225-0.75 + 2.0) + (20x2.6571) all divided 360/15 (24) and that gives us the answer of:

Lean angle of 16.656 degrees

Basic sort of stuff really! ;) ;)

[Noelm]

to shift weight around to correct lean does take a lot of shift, just try to see how much difference it makes doing a turn (on smooth water of course) with all people on one side ,then same speed and all on the other side, it is just laws of physics and gravity etc, very hard to counter act, not too sure of Pink Panthers mathmatical equation though but, hey sounds pretty good

[Geoff_Atkinson]

I have a mate in Western Australia who had a 28' fibreglass boat with twin Volvo Penta V6 petrol engines which suffered badly from leaning into the wind.

He had it out of the water for maintenance and the engineer at the boat shop explained the leaning as an aerodynamic phenomenon and as my memory goes;

- When any boat is travelling, the slipstream causes a pocket of low pressure in the cockpit area.

- Because of this low pressure, any cross breeze (or wind) flows into and over the cockpit, causing lift on the opposite side (similar to how an airplane wing works) and the boat leans into the wind

I dont know if it was a load of crap or not, but I do know that the boat would only lean into any breeze, not when there was no breeze or we were pushing into a breeze, so it made sense to me.

Cheers

Geoff

[Synergy]

Thanks for all the answers guys. It seems I need to fit trim tabs. The only other option is take a laptop out and compute the square root of the total wetted surface of the after trim area and then cut it out with a chainsaw, may detract from the value though :) :)

[Mad_Barry]

If the lean gets annoying, just turn around and head in the opposite direction for a while. ;)

[ahoj]

With deep V you will experience always this problem of leaning there just is not enough support ---- to keep it level not like flat bottom or tri-hull or cat therefore trims are to support your leaning side. you have to earn how to use them once you turn away from the wind have to keep operating them at all times not so much on a calm day... 6.5 meter is a long boat will need strong trims... ALTHOUGH Heins-Signature is a very slim and low profile boat.

AHOJ
As noted, the 650 F scored one of
the first of the true Signature
"variable deadrise" hulls ("VDH")
and with the wisdom of hindsight,
perhaps a little too much attention
was paid to getting the hull design
(6.5 m LOA x 2.5 m) right, and not
enough to how it was going to be
powered, trailered or fuelled.
It has catamaran-like levels of
stability at rest and underway; it is
remarkably soft riding, and very dry,
even in heavily chopped up bay and
estuary waters. Then, you just put the
hammers down, lift this big rig up on
top of the water - and go !
Just about the only downside of this
whole combination was the fact that
it’s a fairly heavy boat, with a bare
hull weight in excess of 1,000 kgs plus
toys. This means it must have fairly
big horsepower to realise its potential.
. . . thus began a Catch 22 situation
that has kept this superb sportfishing
boat on the back burner for several
years.
Because it needed pretty big
horsepower to work properly, the 650
F has to carry a fairly substantial fuel
load - or, alternatively, be fitted with a
4-stroke sterndrive . . . or, perhaps
twin engines, so the skipper could use
just one (smaller) engine for all the
trolling this sportsfisherman was
designed to do.
Well, that’s how, in theory, it should
have been.
But in a cruel irony, such is the
complexity of the 6.3 m long,
fibreglass inner liner and its crucial
role as an integral part of the 650 F's
"chassis", to change the 650 F
transom over to allow a sterndrive to
be installed, means the factory has to
virtually retool the whole boat. You
guessed it - the deck moulding, the
inner liner and the hull mouldings all
have to be extensively modified to
allow a sterndrive to be installed.
A similar problem affected the
many requests for twin engines from
dealers in the more remote areas of
Australia. But once again, the inner
liner interfered, and again,
developing a twin outboard transom
involved a massive retooling project
for a relatively small number of boats.
Thus the Catch 22 situation
emerged. Here was an extremely
sophisticated sportfishing boat

[PinHead]

mate...trim tabs are simple to use..nothing to them..I love em.

[saurian]

Synergy , tabs should pull you up nice and straight . Bennett pretty
good ones, check out boats at the yards or ramps for most common.

ahoj, high sided cats still lean into the wind especially if they have hard tops . 2 motors on each corner are mighty big trim tabs.
I think your new hull should have 2 donks.

[Roughasguts]

Hi guy's well yeah it is kinda Aerodynamic phenomena.
But then it kinda isn't.

Okay it acts like an aircraft in the fact that you need to turn the rudder to put the nose in to the wind to lay off the drift.

Makes sence if you didn't lay off the drift she wouldn't lean.

Okay so you have laid off the drift by turning in to the wind but she ain't going to turn cause you will correct that if she does.

The turning force in relationship is called yaw acting straight down in the normal axis. So the primary effect of rudder is called yaw.

But of course there is a secondary effect just like aircraft and that effect is called roll and that would act through the longnitudinal axis.

Therefore turn slightly right then secondary effect will make it roll slightly right. eg lean in to the wind.

Obviously an aircraft turns differently cause you barely use the rudder unless landing in a x wind and you can counter act the roll by using opposite aileron to keep the wings level.

And yep the boat don't have ailerons to stop the roll so tabs would be the only thing to do the trick.

Sounds a bit techy and boring I know but that be the answer, if any one be interested.

And yeah theres one more axis be the lateral one. But best to leave that one alone unless you have problems with your foil, digging in and wanting to throw you outa the boat.

[mcgilld]

That's the showstopper Roughasguts.
Very interesting!

[fishingjew]

bugger the tabs ill just put wings and tail on me boat ;) ;D ;D ;D ;D

[Volcano]

I have a signature 542F, and had almost the exact problem as you.
I fitted 18" Bennett trim tabs and have not looked back. You can adjust them as you go to suit the conditions. They are definitely worth the money.
They are quite easy to fit as well - took me and a mate about 3 hours and half a carton to get them installed :D

[INDULGENCE]

I have a plate aluminium 6.7m very deep vee.When original it was fitted with a Volvo stern drive and leaned into the wind until I changed the rotation of the drive.Very easy to do on the Volvo.This corrected it
I thought it was my 130kg but you guys are trying to convince me otherwise,anyway I got smart and fitted duo prop with the repower and still dont have problem
I would change the rotation prior to fitting trim tabs as I think they are just another thing for your line to foul at the back of the boat where most fish.

Wally

[spudie]

being in the boat building game myself.(alloy)every one of our boats that we build custom for people.handles as well as any on the market.BUT every boat that we hand over. even though the new owner is more than happy with its ride.the same old thought goes through my mind........(put some trim tabs on her mate!) most of the new owners offer me& the boys a fishin trip out in there new pride & joy. (never nocked one back yet!)& buy the time we get back in.i have dropped a few suttle hints containing the words (trim tabs) to cut a long story short. There is not a boat (mono) out there that wont handle a hell of a lot better with a set of tabs.

[ahoj]

Saurian... 2 donks on my cat would be SUPER but they don't make then small enough for my 30Km speed limit...but i do not suffer from lean on my boat... where my lean is a trim tab will not fix it lol ;D :D ;D :D
My second cat is almost finished just doing the comfort seating arrangements took her for a test run yesterday ----Its just unreal ----will send pic later
Ahoj

[saurian]

ahoj , put the 2 donks on the new cat and a set of those wing foils these guys are talking about , then the speed limit will not apply once airborne.
look forward to seeing the new beast.