# Planing Trimarans

Discussion in 'Multihulls' started by Doug Lord, Sep 30, 2006.

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### ActionPotentialJunior Member

Skimming across the top of the water, supported by the heeling force, just like the farrier centre hull.

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### RHoughRetro Dude

LOL ... yep ... we get right back to definitions being the stumbling block.

When the hulls are at rest and the boat is not moving they are supported by displacement.

When one or more hulls are flying clear of the water the flying hull is supported by the heeling force.

In between those states, the windward hull(s) are partially supported by heeling force, and partially supported by either displacement or hydrodynamic force. If it could be proved that the windward hull(s) create hydrodynamic force greater than the displacement required, could they be considered to be planing?

In other words, if a hull produces hydrodynamic lift equal to it's weight (or effective weight) is it planing?

As you say, it is all in the definition of what planing is.

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### ActionPotentialJunior Member

Yes it is.
If it could be proved that the windward hull(s) create hydrodynamic force greater than the displacement required, could they be considered to be planing?
I wouldn't consider that planing, just as the previous example of the boat partially lifted by a crane or by a fan or by a hot air balloon.
For me it has to be lifted only by hydrodynamic force. The effective weight doesn't qualify it has to be the actual weight. That's my definition and that's what happens with a monohull cos there is nothing else to lift it (ecclusing the crane/fan/hot air balloon.
As soon as something reduces the effective weight it becomes easier for the hull to 'skim' such that anything will skim given enough reduction of effective weight and will do this without producing the bow wave which I see as a necessary prerequisite for planing. As you say, definitions. I am an all or nothing person.

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### PI DesignSenior Member

AP, the way you are defining planing, a trimaran can never plane, because the windward hull will always have some support from the heeling moment. Dan Savitsky, who has surely carried out more research into planing craft than any other man, defines planing as:

To the researcher dealing with the hydrodynamics of
planing craft, the inception of planing is associated with complete
separation of flow from the chines and transom and full development of
the stagnation line at the forward edge of the wetted bottom area.

extracted from discussion on planing performance of concave hull sections - http://boatdesign.net/forums/showthread.php?t=14289

and I agree with this. If you look at this way (with no reference to Froude number, heeling moments, buoyancy, number of hulls etc), then there is no reason why a trimaran couldn't plane. Whether Ian Farrier's designs do or not, I have no idea, but if he claims they are designed to, then they probably do. Suggesting that a professional designer has failed to meet one of his fundamental design objectives is a very brave statement.

5. ### Chris OstlindPrevious Member

Nice exchange

Brave, maybe, but without constant examination of claims such as these, the industry would soon lose sight of its obligations to substantiate the claims with proofs. That would result in a freefall of total vaporous marketing hype and then where would the industry be in the eyes of the public? Picture a long series of used car lots with greasy-haired salesmen with pocket mouth fresheners.

The Farrier (et. al.) claims are totally committed to the use of the leeward ama as a support system in order to facilitate the planing function. There have been many colorful scenarios rendered to counter that point. The champions of the premise have ignored most of them in order to further the cause. One can only wonder, therefore, what other mechanism is also opportunistically useful to the proponents to continue that furtherance? For example... Is it OK to fire-up a 30 hp outboard on the transom of an F-Boat while under sail, in order to "give it a boost" to planing status?

We now see many canting keel yachts on the racing scene that make use of a full time, running engine to facilitate the advantages of the swung ballast, as well as providing hydraulic power for the running stays, rudder assit, main sheet winches, etc. Why not an outboard, running discretely, in order to complete the picture that a leeward ama depressed, trimaran can plane? What's to keep the claim from being hampered? Are we not already moving ourselves to the location in which our sense of professional respect for Ian Farrier is such that the discussion is being turned in a favorable direction for his position? If Ian tossed-out the motor assist notion on the table, would any of us balk at that claim? How much erosion is too much before the planing claim of any boat becomes moot?

Personally, I find the whole, planing claim with the ama in the water, to be slippery slope marketing hype. (the science not withstanding that it "could be possible") Lots of stuff could be possible, but none of us would observe it to be so without some rather rigorous proofs presented.

For instance, I could claim that I have built a rocket that is capable of interstellar travel. I could support that claim by demonstrating that I have the scientific data that shows the propulsion system, the properly configured vehicle and the necessary life support system to reach escape velocity. Yep, we are on our way to interstellar travel, alright.

Oh, did I forget to tell you that I will need the assistance of a conveniently pre-placed living quarters package outside the atmosphere in order to truly accomplish my goals. Do keep in mind that my original claim was not for a detailed substantiation of the reality bound complexities of going to the stars, it was only a claim that I had designed something that was "capable". The fact that I need a substantial boost from an outside source to get there is of no consequence to my original claim of capability.

"Yeah right, Chris", say the onlookers. "Let us know when you really do get that interstellar thing together, won't you? Send us a tape of it leaving the atmosphere complete, intact and within the accepted norms of the definition as the rocketeer community knows it... then we can talk and take a look at the numbers that support the claims and the nice pictures."

We've been haggling over this subject for almost a month now and the only video proof offered-up by the Farrier community has not shown a planing trimaran. Since Ian has taken the time from his busy schedule to chime-in on this, one would think he could at least call on the numbers of folks out there who own his products to cough-up a suitable tape demonstrating an F-Boat up on plane without using the amas for support.

He has not done that. In fact, he has made it clear through direct comments, that his argument is apparently more of a substantiation of widening the center hull for accommodation. You can make your own conclusions as to the performance effectiveness of a wider, wetter multihull. The planing claims have apparently, conveniently fit themselves into a stretched version of the traditionally accepted norms of planing as a sidebar benefit that help counter the argument of a fatter hull in favor of a bigger salon.

From Ian's post:
The F-Boats have been around for quite awhile now and have enjoyed considerable respect, as well as economic success, in a rather diffcult marketplace. They have been essentially unchanged in form, save for the odd redo of the lines here and there, for a subtle "freshening" of the product. Ian's original vision has proven itself with extraordinarily long legs in the marketplace and I very much admire that kind of inspiration for the enhanced benefit of the boating public.

Now, a widening of the center hull, in order to make the tri more like a monohull in the eyes of the buying public is a decent endeavor from a strategic commercial position. But, to extend the design choice process of "improving the competitive creature comforts" by making additional, outside the norms, claims for planing is one stroke of the pen too far, in my estimation.

Perhaps there is another, outside the marketing bubble, energy at work here with these planing claims?

6. ### Doug LordGuest

planing tri / Ian Farrier

You know , I don't think accusing a man of the talent and obvious success of Ian Farrier of "hype" is accurate at all-just read his comments on the F22. I think that kind of comment is inappropriate, insulting to him, to his owners and to the facts.
------------------------------------------
I really don't think the problem is with the definition(s) of planing; I think it is more of a case of not understanding how to apply "the definition(s) of planing" to the main hull of a heeled trimaran.The argument is made that if the
the main hull is supported by the ama to any extent(like the 30% in my example) then the main hull is incapable of planing.I've tried to make it clear in a number ofways but apparently haven't been succesful. The best way --besides the numbers below --that I can approach it is that the main hull is still supporting 66% of the load and that there is NOTHING in any definition of planing that prohibits part of the load of a trimaran from being supported by the ama.Mixing the definition(s) of planing with the characteristics of a trimaran must be done carefully. When considering planing on F boats you can only look at the main hull not the ama's which are displacement hulls. To determine if the main hull can plane you have to determine the ACTUAL LOAD the main hull would have to lift when planing.
To reiterate, (again):

==========================================
If Bethwaites ratio "SCP divided by boat weight" is proof of planing AND you subtract the displacement of the ama from total boat weight(1800-600 =1200) to arrive at the actual loading of the main hull then this is true:
SCP=5049 (RM) divided by 12.75(CE-CLR distance)=
396. The ratio "SCP(396) divided by total weight( load on the planing hull=1200)" = 396/1200= 33%.
According to Bethwaite anything above 30% is capable of upwind planing. Not only that but both rules of thumb-"SCP divided by total weight" and "500 sq.ft. per ton to plane" indicate the main hull will NOT plane UNLESS THE AMA ABSORBS SOME OF THE LOAD.
It is simply absurd to use any other figure for the load on the planing main hull than the actual load; if the total weight of the boat was used it would not plane according to either rule of thumb(in addition to being completely inaccurate). You must deduct the displacement of the partially immersed ama to arrive at the actual load on the planing hull....
++++++++++++++++++++++++++++++++++++++++++++++++
Once you understand that the numbers all fit from the old axiom "500 sq.ft. per ton" to the
Bethwaite formula ,to the SA/D. And the numbers for the F22 match the actual experience on the water of other F boats and Mr. Farriers comment that in order for the boat to plane part of the load must be taken by the ama.
++++++++++++++++++++++++++++++++++++++++++++++++

7. ### Chris OstlindPrevious Member

Doug's Quote:

Why not Farrier, Doug? You seem to have a small bit of talent and everyone here knows that you will readily jump to the hype card if necessary.

Do you think that Ian is so non-human that he wouldn't try to play his most opportunistic cards if the situation arose? Maybe you think he’s a God of some sort and we should all just shut-up when he makes these kinds claims. I think he’s a normal guy who is trying to keep the whole set of balls in the air and someone should be saying “Ahhh, come on, Ian. What’s up with that?”

Why did Ian spend so much time tooting the horn of expanded roominess in the hull while dumping on other designers and their work with trimarans and so little time actually addressing the issues surrounding the business of planing?
It amounts to a non-denial denial and nothing could be more vague than that position.

Ian admits as much that other boats have superceded the performance claims of his designs, but takes great pleasure in attempting to define them into market competitive oblivion with this kind of statement...
What exactly is an impractical boat? Most of the boating world would say that a boat with small accomodations, a complicated folding apparatus and pricing structures that do not deliver cabin room for the hard-earned buck are impractical. You can decide for yourself.

Ian Farrier is a boat designer of high regard. I don't think there's a question at all about that. But this isn't about his regard, owners or any of the massively conflicting facts that are out there swirling around. It's about the fundamental question of making claims with stretched applications for purposes of extending a marketing position on a style of boat that has, perhaps, lost some of its luster over the years.

Take a look at the history of the previously named, Datsun 240Z, as an example of design and function in a changing market atmosphere. Since the F-Boats evolved about the same time as the Z cars and they sort of attempted to fill a similar, performance/GT gap in the marketplace, they have distinct relevance.

Now look at the Nissan 300Z roadster and tell me that you could put those two in the same family without knowing, beforehand, that the same company made them.

The same is not true for the F-Boats. Right down through the years, the boats look and behave virtually the same with very minor differences. Now, with boat sales everywhere declining, Ian has decided to transition his sports GT boat by giving it a fuller hullform for more room inside. I know you read the previous post and that you choose to ignore the obvious, but this is a serious change in mission.

It would be like Nissan taking the Z roadster and morphing it into a station wagon so that ageing dudes could justify the boat to the little woman and the scrutiny of the pocketbook.

Along the way, arguments apparently sprang-up that allow the flatter, fuller, roomier, less trimaran style hull form to be declared a planing vessel. In this declaration, the previous performance claims get to be refreshed with new vigor and the boat has now attained the status of speed due to the proximity of other sportboats that do, in fact, plane readily.

If it isn't clear to you, it should be now. Ian is moving the design into a middle age, "I can still get a woody", status. It's not uncommon for the owners of a mature product to make one last run before fading out, so I get the process.

Personally, I don't see the need to make these kinds of claims. The design is aging gracefully, there are still boats being built and plans being sold and the F-Boats can still show a turn of speed in the best hands. It's true, other boats have closed the gap, and even passed the F-Boats for performance claims, so what's the hand that Ian has left to play?

Why planing hulls, of course, along with criticizing other designs for being skinny and uncomfortable. Ask any cruising monohuller if he thinks an F-Boat is suitable for cruising and he'll say the same thing... "they're skinny, cramped and uncomfortable”.

Maybe Ian has run out of ideas, maybe he's just plain old tired of screwing around with the whole boat thing in general and wants out... I don't know the answers to those issues.

What I do know is that it is not planing when you have to stick a crutch in the water to get it up.

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### WillallisonSenior Member

If I take my powerboat, on the plane with a single 50hp outboard, and add anotehr 50hp outboard, is it still on the plane?

Yep - it's just going faster

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### Jimbo1490Senior Member

This is kind of an 'all-or-nothing' position and as such can easily be shot down. For instance if a boat, say a small runabout that planes when properly loaded, gets overloaded so that it can no longer plane, is it or is it not planing when the excess weight is removed? If you build a boat too heavy so that it fails to plane because of its excess weight despite having the correct hull architecture, then build a second boat identical to it saving half the weight, and that boat planes, is it really planing?

If one hull of a sailing trimaran gets partially unloaded under way and (apparently) planes, is that real planing? Then where do you stop? Soon that skimming cat hull is planing too Shades of gray, IMO

I think an objective way to look at this is to calculate the theoretical dynamic displacement of the supposed planing hull and then see if that hull form and displacement can or cannot plane at the selected hull speed. Would that not satisfy?

Of course the wrinkle is that the hull actually displaces more than that theoretical amount. But could a hull be built as light as the theoretical weight? And if yes, does that fact then make the planing valid? More shades of gray

Jimbo

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### WillallisonSenior Member

AP - On further consideration, I agree that the fact that tabs act hydrodynamcally means that they're not really a good example to use. It was an example of an assisted body being on the plane. But, still, as I said - not a very good one.

That got me thinking about our RIB. Here we have a centre, planing hull, with two inflatable tubes either side, that are not unlike a displacement hull shape.
If you remove the two tubes, the boat will still plane. I've seen this done - it's just not very stabe and is very wet!
Put the tubes back on. The speed is still essentially the same, and clearly the boat is on the plane.
So here we have a centre planing hull with two stabilising tubes, which are basically of displacement form. They remain in contact with the water, so are providing lift to the boat as a whole, both in the form of displacement and hydrodynamic lift.
Not unlike a 'planing' trimaran really......

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### RHoughRetro Dude

Planing Tri <> Triplane

Yes, there is such a thing as a triplane ...

As the debate circles around yet again ...

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### ActionPotentialJunior Member

I think Ian says it all when he says:
"However, being able to plane (or skim across the top of the water - whichever you prefer) changes all this."
He is quite happy to define planing as skimming across the top of the water and his centre hulls can and do certainly do that.
And, regarding:
"That got me thinking about our RIB. Here we have a centre, planing hull, with two inflatable tubes either side, that are not unlike a displacement hull shape. If you remove the two tubes, the boat will still plane. I've seen this done - it's just not very stabe and is very wet! Put the tubes back on. The speed is still essentially the same, and clearly the boat is on the plane.
So here we have a centre planing hull with two stabilising tubes, which are basically of displacement form. They remain in contact with the water, so are providing lift to the boat as a whole, both in the form of displacement and hydrodynamic lift."
I don't think so. I don't think the stabilising tubes are doing any displacing in this mode. If they are in contact with the water I think they are planing too.
Same would apply to the floats of a trimaran planing ddw or under power, the only thing lifting the hull is hudrodynamics.
According to def 1, anything skimming across the water is planing.
According to def 2, only something supported entirely by hydrodynamic forces is planing.

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### Raggi_ThorNav.arch/Designer/Builder

It's just linguistics, I think

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### ianfarrierJunior Member

I guess the old saying that there is none so blind as those who cannot see is actually true.

If a video of an F-9R center hull with the bow right out of the water and a power boat like wake/rooster tail out the back is not enough for skeptics to believe it is planing, then even a video from the side would not convince either.

But there's one of those on my web site also - take a look at the Video entitled 'F-27 Action Sailing' and you will see some sequences of an F-27 planing. You can actually see it lift and accelerate in one sequence just before it passes a mono.

Apparently, that this planing may be caused by the wind, which not unnaturally causes a sailboat boat to heel, which causes the main hull of my boats to lift and plane, is somehow cheating, or 'marketing hype'. But putting a 100HP on the back of a power boat hull to lift it on to the plane is apparently okay, but planing caused by wind power assistance only is not.

Now it seems that Chris Ostlind thinks that my trimaran center hull planing could mean the end of life as we know it on this planet, and I have to be stopped. Perhaps his time may be better addressed to the real problem in multihulls at present - the claims by some that their boats make great cruisers, yet they are so overpowered that one even has a capsize ratio of over 70%.

Chris I think you are spending way too much time indoors, and you really need to get out more, and get a life. Go for a sail on one of my boats, and when you can feel the boat lift and accelerate while flying along at 18 knots with the bow clear and that long rooster tail out the back, you can either chant "this is not planing, this is not planing....or maybe you will finally see the light, as can over 2000 owners.

Ian Farrier

Farrier Marine (NZ) Ltd
Farrier Marine, Inc.

1 person likes this.

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### Dan SJunior Member

With respect,

It does not matter if the F-9R, or the F-27 can plane, the boat in question is the F-22 (see the first post of this thread).

Also I think it safe to debate if the acceleration is because the hull started to plane, or because the main hull lifted out of the water (caused by heel), thus reducing drag.

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