New pontoon, new project detailed description

DVW

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The original goal for the project was to increase speed with modest power. I was not after record breaking top speed just more efficiency. During development I used improvements in top speed as a way to measure improvements in efficiency and drag. The potential for drag reduction was first noted when I looked under the deck of a pontoon boat at speed. The hulls created wakes and turbulent water that become elevated when funneled thru the narrow openings at the stern of the boat. I reasoned that eliminating the center tube or center transom would prevent water from being funneled into the remaining narrow space. The result would be less wetted surface area and associated drag.

The basic plan for the drag reduction phase of the project was to replace the tubes with two modified jumbo tubes and then remount the original engine on one of the tubes. This would reduce the above mentioned drag source. I had originally focused on large diameter work boat tubes until I discovered fat elliptical shaped tubes from Bennington. I then purchased elliptical tubes from Bennington along with a boat model 22 SLX with 115 Yamaha motor.

The tubes were modified to improve planing, motor mounting and buoyancy. The elliptical tubes from Bennington came with relatively flat planing surfaces on the bottom of the tubes. I improved their ability to plane by adding reverse chines to the lifting strakes. Further improvement was made by mounting the motor 10 inches rearward from the end of the tube. The intent of this geometry is to improve the boats response to motor trimming. To compensate for the heavy motor overhang the open splash well area normally use for fuel tanks was sealed and used for buoyancy. Fuel tanks would be mounted forward on deck.

The next phase of the project involved mounting the modified tubes and testing. Bennington’s accommodation for different tubes made this task practically bolt-on. With the center transom removed and the motor relocated off to one side a wide space was created between the two tubes. This completed the drag reduction phase of the project. With no change in power the change in speed was a significant 46%.

The next phase of the project was adding another engine on the other tube for more aesthetic balance. In addition to balance I also wanted another throttle lever in my hand just because it felt right. Considering that I had doubled the power the change in speed was a only 31% but when added to drag reduction the boat got to 50 mph. This speed was achieved despite low cost aluminum propellers and no under deck sheeting.

I am not a speed freak but what I got is a boat that moves thru the water with less effort at normal cruise speeds. A brisk pace does not interrupt conversation. I am happy with the result.

Questions or comments?
 

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SEMPERFI8387

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I hate to ask the cost involved. Let’s just say, did you price a dual motor setup and what was the final spread in that cost vs. your modded toon, and what kind of labor hours was involved?
Very impressive setup though.
 

DVW

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I hate to ask the cost involved. Let’s just say, did you price a dual motor setup and what was the final spread in that cost vs. your modded toon, and what kind of labor hours was involved?
Very impressive setup though.
In the beginning I did cost out upper end boats with ESP hull(s) so I could use the hull(s) but surprisingly service part cost was cheaper. Saving money by doing it yourself was never my intent. You totally missed the point. It was a labor of love and in the end very gratifying. Current pontoons achieve good speed by overcoming excessive drag with excessive power. I wanted to demonstrate a more elegant approach. To do more with less.
 

Vikingstaff

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Very interesting! Thanks for sharing your experiment.

I’m very impressed with the thoroughness you went to to test out your hypothesis. The results are very intriguing, and raise other questions in my head. Thanks for sharing the details and pictures that you did with everyone else on here.
 

DVW

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…I’m very impressed with the thoroughness you went to to test out your hypothesis. The results are very intriguing, and raise other questions in my head…
Please feel free to ask the questions in your head. Obviously I strived to make a better boat for myself but in the process I was very impressed with the design of the Bennington boat. It reflects a customer focus and responsiveness to the very requests that can be seen on these pages. Within that context I was very impressed.
 

SEMPERFI8387

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In the beginning I did cost out upper end boats with ESP hull(s) so I could use the hull(s) but surprisingly service part cost was cheaper. Saving money by doing it yourself was never my intent. You totally missed the point. It was a labor of love and in the end very gratifying. Current pontoons achieve good speed by overcoming excessive drag with excessive power. I wanted to demonstrate a more elegant approach. To do more with less.
Oh trust me, I’ve modded more cars than probably most people have owned in their lifetime. I just wondered what the $$$ value would be as a inquisitive thing. If I had every dollar I lost on cars and mods I’d already be retired at 55. :p
 
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Bill N

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It looks odd to see the motor on one side vs the center, but it certainly makes sense in regards of hydrodynamic drag.
I will be following the progress of this thread!

On a side note, Did you custom order that furniture layout? I like it.
 
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Bill N

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Oh trust me, I’ve nodded more cars than probably most people have owned in their lifetime. I just wondered what the $$$ value would be as a inquisitive thing. If I had every dollar I lost on cars and mods I’d already be retired at 55. :p
Yes, but I bet you would not make that trade. Experiences & memories are more valuable than dollars!
 

DVW

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It looks odd to see the motor on one side vs the center, but it certainly makes sense in regards of hydrodynamic drag.
I will be following the progress of this thread!

On a side note, Did you custom order that furniture layout? I like it.
The off center motor offended my eye. I could not live with it despite the fact that for the most part the boat operated normal. On occasion I did experience boat rotation from off center thrust when maneuvering next to the dock.

The furniture layout was a custom order.
 

LaurencetheAdventurer

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Love This - thank you for sharing!!! I am amazed at the increase in speed - I would have expected something in the 10 to 20% range - max, so 46% in impressive and WOW. Now I wonder about performance in turns and stability. No idea how that would be measured, but I sure enjoy the high speed turns and tubing fun the triples provide with the ESP package. That would be an interesting shoot-out - same boat dual elliptical vs the TriToon. I am "sure???" you can't get the elliptical tube out of the water on a turn like the ESP. I also wonder how much speed is sacrificed off your top end by sticking with the same motor mount centered / not enclosing the transom. So Much Fun! Bennington needs a DIY play lab.......right!
 

DVW

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Love This - thank you for sharing!!! I am amazed at the increase in speed - I would have expected something in the 10 to 20% range - max, so 46% in impressive and WOW. Now I wonder about performance in turns and stability. No idea how that would be measured, but I sure enjoy the high speed turns and tubing fun the triples provide with the ESP package. That would be an interesting shoot-out - same boat dual elliptical vs the TriToon. I am "sure???" you can't get the elliptical tube out of the water on a turn like the ESP. I also wonder how much speed is sacrificed off your top end by sticking with the same motor mount centered / not enclosing the transom. So Much Fun! Bennington needs a DIY play lab.......right!
I am sure that a contest could be created that would bias one design or another. My boat behaves like a Twin Elliptical. It leans like a car or any twin tube pontoon. As such it does carve a turn like a TriToon. While the boat is underway if I tilt one motor up and the other down the boat will list to one direction and then it will veer off to that direction. It is a great parlor trick.
The biggest increase in performance came when I got rid of the drag down the middle.
 

Michiman

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Wow! I’m mighty impressed with your engineering prowess and mechanical abilities. Looks like you got extra helpings when you went through the line. Enjoy…
 

CLDave

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Great job! I'm glad you added the second motor, as I'm sure having a motor on one side would put a ton of stress on the decking and maybe even tear the boat itself apart. At least Bennies are built strong!
 
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