Oct 29, 2011
Dave Culp and Water Ballast in Multihulls by Joseph Ostercomments regarding the Yahoo! groups proa mail list:
Moderating the Proa List May 18, 2008 Open Letter to Wade Tarzia May 12, 2008 Dave Culp and Water Ballast Oct 29, 2011
On Friday, October 28, 2011, on the proa_file forum in post #30390, Dave Culp said:Water ballast is never optimal in multihull design.
On July 5, 2009, on the Multihulls mailing list [MHml], Dave Culp said:As I recall, that discussion concluded that; when beam is constrained, water ballast *can* be an advantage. 90' beam on a 90' LOA boat sounds pretty "unlimited," but it is in fact constrained.
On February 2, 2005, on the boatdesign.net forum, Tom Speer explains why water ballast makes sense on the Spitfire hydrofoil catamaran:Water ballast isn't needed until there's enough heeling moment that the lee hull or foil is supporting the whole craft. After that point, one can use down-force on the windward hydrofoil or an equivalent amount of water ballast in the windward hull. If you elect to use water ballast, the lift on the lee hydrofoil has to increase by an equal amount, which will incur a drag penalty. If you elect to use hydrodynamic down-force, the lee hydrofoil still has to oppose the down-force and incur the same drag penalty. But in addition, the windward hydrofoil has its own drag penalty.
On March 18, 1996, on the Multihulls mailing list, John Shuttleworth discussed water ballast and said "Once the windward hull is flying, then water ballast would improve speed as the wind increased - provided it did not put the hull back into the water." - full email:-------- Original Message -------- Subject: Water Ballast Date: Mon, 18 Mar 1996 12:48:44 +0200 From: email@example.com (John Shuttleworth) Reply-To: firstname.lastname@example.org (John Shuttleworth) To: email@example.com > Clearly monohulls have used the concept of ballast with great > effectiveness, yet every expert concludes that a multihull is > always better without ballast... There is a mystery here for > me. Is ballast only effective (as in monohulls) when it is more > than 40% of total displacement? What about that area where the > ballast is only 10..20% of total weight and on a long multihull > lever arm? Especially on the Pacific proa where such a shift > brings righting moment to that of a heavier catamaran? > Thanks in advance, Joseph Oster I haven't actually done the calculations for a Mono, but logic tells me that it power could be increased if the rig of a Mono was more upright. Adding ballast - crew (as in the NZ America's cup attempt in '88) or water clearly works. In a Multi particularly a wide one with large volume ourtiggers, the improvement in L/D by changing the heel angle from say 10 degrees to 5 degrees by adding weight, does not pay off. In a Cat the heel angles are less, and the beam is less so water balast is even less worthwhile here. The pacific proa is a different case. Water ballsat would definitely reduce speed unless the limit of stability had been reached. Water would only add to the displacement and hold the windward hull down into the water - increassing wetted surface area. Once the windward hull is flying, then water ballast would improve speed as the wind increased - provided it did not put the hull back into the water. Of course all this discussion is about pure speed and has nothing to do with how well you can sleep on a cruising boat at night!!! If I want to sleep well I choose wide beam and nice big outriggers (150% of total Displacement minimum), and no water ballast, and put in a reef before retiring. I have done it - in fact I once reduced to storm jib and two reefs just to get a sound nights sleep after bashing to windward for a week. John Shuttleworth ------------------------------------------------------------------------ This mail list is managed by the majordomo program. To unsubscribe from this list, send the following message to firstname.lastname@example.org: unsubscribe multihulls For help, send the following message to email@example.com: help Do NOT send administrative requests to firstname.lastname@example.org. Thanks. -ben ------------------------------------------------------------------------
On Friday, October 28, 2011, in the same post #30390 mentioned above, Dave Culp said:Fact #2: I'm not at all sure that functional water ballast exists aboard any multihull *not* designed and built by Russ Brown. Try this: Google "water ballast multihull."
Eat crow Dave
It takes very little effort to prove this statement is false. Spitfire and Hydroptere both use water ballast - 500 kg and 800 kg respectively. Culp mentioned the Gougeon 32 but not Jan Gougeon's latest effort Strings, which also uses water ballast.
On October 27, 2010, in the Multihull Anarchy forum, Ian Farrier said:Next step is to add water ballast to stern, so as to keep main hull stern down when required, and a stern ballast tank is standard on the F-85SR and F-32SR, with float sterns tanks optional. This weight again can be got rid of for the 90% of the time when it is not required.
And of course, water ballast was used in the 33rd America's Cup by both Oracle and Alinghi. From Bernie Wilson:Both carbon-fiber giants feature engines to run hydraulic systems that trim their sails and move water ballast from one hull to another, a first in America’s Cup history.
This list certainly isn't exhaustive, but is enough to prove Culp wrong. And it wasn't an innocent mistake on Culp's part since he knew better. This was a deliberate effort to discredit Russell Brown by implying that all experts agree that "Water ballast is never optimal in multihull design", which clearly isn't true.
UPDATE: Culp later tried to spring a little trap and qualify his assertion by bringing attention to the small print in his original claim: "No AC boats ever carry(ied) water ballast in order to increase RM". He says: "Call it a technicality if you like, but I'm gonna put this one in my "win" column." - typical ploy, Dave, but no cigar. Trying to win "the game", as you call it, instead of unambiguously and truthfully informing, means you lose, along with your audience who suffers from your style of disinformation.
From a sail-world.com article by Richard Gladwell:Firstly, Alinghi carries water ballast to provide original righting moment as required.
same article, statement by Tom Ehman, BMW Oracle/GGYC spokesperson:Competitors will be able to use water ballast in the coming 33rd America’s Cup commencing in Valencia on Monday, provided that the amount used to benefit performance is also in position when the boat is measured. This verdict of the International Jury was made tonight following a hearing in Valencia. 'It puts the onus on the measurer to guarantee that the amount and location of ballast aboard for measurement is solely to enhance performance, not circumvent the waterline requirements of the Deed of Gift,' said GGYC spokesman Tom Ehman.
Dave Culp has long enjoyed arguing both sides of many issues related to proas, perhaps to demonstrate his skill at debate. This is also known as obfuscation or speaking with a forked tongue:The phrase "speaks with a forked tongue" means to deliberately say one thing and mean another or, to be hypocritical, or act in a duplicitous manner. In the longstanding tradition of many Native American tribes, "speaking with a forked tongue" has meant lying, and a person was no longer considered worthy of trust, once he had been shown to "speak with a forked tongue".
Yep, I'm talkin' to you, Dave.
Another example of Culp arguing both sides - on June 4, 2001, on the Multihulls mailing list, Dave Culp said:Harry is a particularly extreme and un-seamanlike Pac proa, IMO, but he's a Pac proa, nevertheless (OK, that should guarantee a slag from *both* Joe and from Rob. My work is done... I'll argue long and hard that a "traditional modern" Pac proa (Oster) optimizes the construction, sailing and seakeeping qualities a cruising or long-distance racer wants in a boat, at lowest reasonable cost and highest reasonable performance level, but Rob will disagree, and his points are as valid as mine or Joe's.
Emails to the Multihull Mail List from Joseph Oster, discussing proa water ballast, March 1996Other Proa Pages