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Author Topic:   Whaler Drive

TransAm posted 04-02-2008 01:19 PM ET (US)
Is there some hard data out there regarding the performance differences between comparibly equipped Whaler Drive and non-Whaler Drive boats to determine more precise effects of the whaler drive unit itself? I have read discussion regarding its significant drag effects and other
However, owning one myself, I have always looked at it as a hull extension rather than a giant trim tab or other impedance. Sure it weigh 250-lbs and extends the hull two feet, but these factors alone seem insignificant. A couple thirty gallons of gas will add over 300-lbs. I will say I am certainly not an engineer or one who can opine with any degree of authority, but I would observe the following.
In looking at other "performance" boats, it seems they all now incorporate a "stepped" hull design. Why precisely, I don't know, but it must have to do with going faster. My Whaler Drive seems to step up from the termination of the main transom. These performance boats also seem to have a flattened keel or "pad" (usually 10 or 11 inches) presumably to keep the boat more buoyant and thus riding on top of the water rather than in it. The Whale Drive also has a flattened keel on the WD unit.
With that said, the Whaler hull is inherently slow due to its construction and shape and certainly not a real speed boat, but properly equipped, it can provide some impressive performance numbers. Does the Whaler Drive really detract that much from overall speed, or does it perhaps help?
jimh posted 04-03-2008 08:54 AM ET (US)
According to the designer of the Whaler Drive, Bob Dougherty, with whom I spoke recently on this precise subject, the initial purpose of the Whaler Drive was to provide additional buoyancy to counter the weight of twin V6 outboard motors. When twin V6 motors were mounted on the transom of existing Boston Whaler boats, the static trim was altered and was down in the stern. The Whaler Drive was designed as, in Bob's words, "a buoyancy box."
Tohsgib posted 04-03-2008 12:22 PM ET (US)
Uh...30gals of gas is more like 200lbs.
Whaler drive also gives you a full transom which is sweet but also adds weight over one cutout. The interior space gain and HP gain are also very significant.
TransAm posted 04-03-2008 12:36 PM ET (US)
Sorry about my math; 30 gallons x 7lbs/gal = 210 lbs. Its just when I add gas, I usually add beer/ice as well.
I agree the utility pick-up of the WD far outweighs any negative impact, percieved or otherwise. I was just curious if there was some hard data other than anecdotal.
Peter posted 04-03-2008 12:44 PM ET (US)
The WD simply makes for a bigger boat. A 22/25 WD version has 2 feet of additional waterline length. A 27 WD version has 3 feet of additional waterline length.
If you try to compare a non WD versus a WD version, you are really comparing apples to oranges.
TransAm posted 04-03-2008 01:21 PM ET (US)
Perhaps, but the actual wet surface in a 25' vs a 27' would likley be significantly less than the 2' in increased lenght, perhaps half of that be it that only half (just guessing) of the boat is in the water on plane and even less at WOT. All things being relatively equal, that difference (less than 12" of increased wet surface would be almost negligable.
My curiosity was to determine if the WD unit had some affect (drag or other) other than adding a small amount of wet surface. Since it is stepped up from the main hull, and the keel of the WD is flat, it would seem to me the wet surface is actually reduced (at the hull/WD transition)over a true 27' hull and a flat pad is created on the WD unit much like performance boats. Maybe that is the theory in performance stepped hull configurations?
JMARTIN posted 04-03-2008 05:51 PM ET (US)
Seems to me as though fuel economy suffers a bit with the Whaler Drive. I have no idea on speed. John
jimh posted 04-03-2008 10:24 PM ET (US)
The design of the Whaler Drive is also unique in that the outer portions of it are not attached to the transom and create an air gap. This allows air to be drawn into the stream of water coming off the hull and under the Whaler Drive. So the Whaler Drive runs in very airy water. The water coming out from under the Whaler Drive is more aerated than water coming out from under a typical V-hull boat.
I don't know if the airy water makes the drag increase or decrease. I believe it may decrease the drag. I think the introduction of some air under the hull is part of the intention of a stepped hull design. Perhaps this is analogous in the Whaler Drive.
TransAm posted 04-09-2008 08:06 AM ET (US)
I was also wondering if anyone has tried to fashion trim tabs on the back of the 2' whaler drive. My old BW brochure shows a picture of a 27 whaler drive with trim tabs. I know these drives are bigger (3') than the one I have. It looks as though the larger drive may have been molded to accept a factory apply tab. I can steady and level my load pretty well by adjusting either engine trim, but tabs would help, especially at higher speeds.
Peter posted 04-09-2008 08:23 AM ET (US)
I have the 27 Whaler Drive. The tabs are integral to the design. The Drive has "tab pockets" which allow the tabs to form part of the running surface in front of the WD transom. In other words, the hinge point for the tabs is forward of the WD transom in contrast to the typical tab mounting on a notched transom boat where the hinge point for the tabs is at the transom.
TransAm posted 04-09-2008 09:06 AM ET (US)
Yeah, that looks like a slick application; would have liked to seen that on the smaller WD's. I don't see tabs as a viable option, at least not without a fair amount of modification.

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Author	Topic: Whaler Drive
TransAm	posted 04-02-2008 01:19 PM ET (US) Is there some hard data out there regarding the performance differences between comparibly equipped Whaler Drive and non-Whaler Drive boats to determine more precise effects of the whaler drive unit itself? I have read discussion regarding its significant drag effects and other However, owning one myself, I have always looked at it as a hull extension rather than a giant trim tab or other impedance. Sure it weigh 250-lbs and extends the hull two feet, but these factors alone seem insignificant. A couple thirty gallons of gas will add over 300-lbs. I will say I am certainly not an engineer or one who can opine with any degree of authority, but I would observe the following. In looking at other "performance" boats, it seems they all now incorporate a "stepped" hull design. Why precisely, I don't know, but it must have to do with going faster. My Whaler Drive seems to step up from the termination of the main transom. These performance boats also seem to have a flattened keel or "pad" (usually 10 or 11 inches) presumably to keep the boat more buoyant and thus riding on top of the water rather than in it. The Whale Drive also has a flattened keel on the WD unit. With that said, the Whaler hull is inherently slow due to its construction and shape and certainly not a real speed boat, but properly equipped, it can provide some impressive performance numbers. Does the Whaler Drive really detract that much from overall speed, or does it perhaps help?
jimh	posted 04-03-2008 08:54 AM ET (US) According to the designer of the Whaler Drive, Bob Dougherty, with whom I spoke recently on this precise subject, the initial purpose of the Whaler Drive was to provide additional buoyancy to counter the weight of twin V6 outboard motors. When twin V6 motors were mounted on the transom of existing Boston Whaler boats, the static trim was altered and was down in the stern. The Whaler Drive was designed as, in Bob's words, "a buoyancy box."
Tohsgib	posted 04-03-2008 12:22 PM ET (US) Uh...30gals of gas is more like 200lbs. Whaler drive also gives you a full transom which is sweet but also adds weight over one cutout. The interior space gain and HP gain are also very significant.
TransAm	posted 04-03-2008 12:36 PM ET (US) Sorry about my math; 30 gallons x 7lbs/gal = 210 lbs. Its just when I add gas, I usually add beer/ice as well. I agree the utility pick-up of the WD far outweighs any negative impact, percieved or otherwise. I was just curious if there was some hard data other than anecdotal.
Peter	posted 04-03-2008 12:44 PM ET (US) The WD simply makes for a bigger boat. A 22/25 WD version has 2 feet of additional waterline length. A 27 WD version has 3 feet of additional waterline length. If you try to compare a non WD versus a WD version, you are really comparing apples to oranges.
TransAm	posted 04-03-2008 01:21 PM ET (US) Perhaps, but the actual wet surface in a 25' vs a 27' would likley be significantly less than the 2' in increased lenght, perhaps half of that be it that only half (just guessing) of the boat is in the water on plane and even less at WOT. All things being relatively equal, that difference (less than 12" of increased wet surface would be almost negligable. My curiosity was to determine if the WD unit had some affect (drag or other) other than adding a small amount of wet surface. Since it is stepped up from the main hull, and the keel of the WD is flat, it would seem to me the wet surface is actually reduced (at the hull/WD transition)over a true 27' hull and a flat pad is created on the WD unit much like performance boats. Maybe that is the theory in performance stepped hull configurations?
JMARTIN	posted 04-03-2008 05:51 PM ET (US) Seems to me as though fuel economy suffers a bit with the Whaler Drive. I have no idea on speed. John
jimh	posted 04-03-2008 10:24 PM ET (US) The design of the Whaler Drive is also unique in that the outer portions of it are not attached to the transom and create an air gap. This allows air to be drawn into the stream of water coming off the hull and under the Whaler Drive. So the Whaler Drive runs in very airy water. The water coming out from under the Whaler Drive is more aerated than water coming out from under a typical V-hull boat. I don't know if the airy water makes the drag increase or decrease. I believe it may decrease the drag. I think the introduction of some air under the hull is part of the intention of a stepped hull design. Perhaps this is analogous in the Whaler Drive.
TransAm	posted 04-09-2008 08:06 AM ET (US) I was also wondering if anyone has tried to fashion trim tabs on the back of the 2' whaler drive. My old BW brochure shows a picture of a 27 whaler drive with trim tabs. I know these drives are bigger (3') than the one I have. It looks as though the larger drive may have been molded to accept a factory apply tab. I can steady and level my load pretty well by adjusting either engine trim, but tabs would help, especially at higher speeds.
Peter	posted 04-09-2008 08:23 AM ET (US) I have the 27 Whaler Drive. The tabs are integral to the design. The Drive has "tab pockets" which allow the tabs to form part of the running surface in front of the WD transom. In other words, the hinge point for the tabs is forward of the WD transom in contrast to the typical tab mounting on a notched transom boat where the hinge point for the tabs is at the transom.
TransAm	posted 04-09-2008 09:06 AM ET (US) Yeah, that looks like a slick application; would have liked to seen that on the smaller WD's. I don't see tabs as a viable option, at least not without a fair amount of modification.