The Dark Side

[Bamby]

Yeah Malcolm used to tell me it'd make my Party Cruiser "fly" Yeah, ok. My max speed WOT is 18 mph. Strakes or Flap Tins won't do a damn thing for me.

I'm actually kind of surprised you're not getting a bit more speed out of your setup. Though I don't own a gps to actually get my top speed I'm almost certain I'm at least getting the same performance with my 90 and am also certain that I'm also a bit heavier than you are too.. Makes me feel a bit better about the performance of my rig though.

[slingshot]

Dan L:

Lifting strakes basically turn your pontoons into a flat hulled boat of sorts. As with a flat hull boat the straked boat has to "step up" onto plane when it starts to ride on top of the water instead of through it as a regular pontoon will do. Once the boat is on plan the resistance is greatly reduced and will allow the boat to get much more top end speed with the same amount of HP. The fact that they used the same pitch prop on both boats was a disadvantage to the straked boat. That's why it hit the rev limiter on that Yamaha because the boat was starting to get on plane or just on plane and needed more prop in order to take advantage of strakes.

[margaritaman]

Dan L:

Lifting strakes basically turn your pontoons into a flat hulled boat of sorts. As with a flat hull boat the straked boat has to "step up" onto plane when it starts to ride on top of the water instead of through it as a regular pontoon will do. Once the boat is on plan the resistance is greatly reduced and will allow the boat to get much more top end speed with the same amount of HP. The fact that they used the same pitch prop on both boats was a disadvantage to the straked boat. That's why it hit the rev limiter on that Yamaha because the boat was starting to get on plane or just on plane and needed more prop in order to take advantage of strakes.

That was done on purpose to make the crap fin look good.

[badmoonrising]

Yeah Malcolm used to tell me it'd make my Party Cruiser "fly" Yeah, ok. My max speed WOT is 18 mph. Strakes or Flap Tins won't do a damn thing for me.

I'm actually kind of surprised you're not getting a bit more speed out of your setup. Though I don't own a gps to actually get my top speed I'm almost certain I'm at least getting the same performance with my 90 and am also certain that I'm also a bit heavier than you are too.. Makes me feel a bit better about the performance of my rig though.

PC's don't come with speedos so that's my GPS confirmed top speed. I'm running the correct prop/rpm as well. Also 28 inch logs...

[Dan L]

Slingshot,

Thanks for the reply

And yes, I understand that on plane (with the strakes) that the boat takes less power to move at a given speed. (or you could just buy the Eroca that comes with a flat bottom tube)

But, again, given the same boats, props and loads, how can the boat with the higher engine (prop) speed, which per below, takes less power to move, be at a slower boat speed?

Assuming that both props have the same “bite” on the water (or slip), the one with the higher rpm should have a higher boat speed.

The only thing that makes sense to me is that from 5800 to 6100 engine rpm, the prop suddenly loses it’s “grip“ on the water and slips more, ie, starts to cavite. Yet it would surprise me if the prop designers were designing the standard alum (assumed) props this close.

Something about the numbers just doesn’t add up for me.

Dan

ps, I’m not disagreeing that the straked boat should have had more prop, clearly it needed more.
pss, I’m also not disagreeing that this product may be snake oil, as I’d be surprised if it could generate “lift” to be noticeable.

“Lifting strakes basically turn your pontoons into a flat hulled boat of sorts. As with a flat hull boat the straked boat has to "step up" onto plane when it starts to ride on top of the water instead of through it as a regular pontoon will do. Once the boat is on plan the resistance is greatly reduced and will allow the boat to get much more top end speed with the same amount of HP. The fact that they used the same pitch prop on both boats was a disadvantage to the straked boat. That's why it hit the rev limiter on that Yamaha because the boat was starting to get on plane or just on plane and needed more prop in order to take advantage of strakes.”

"The blue lifting strake version reached 6100 RPMs at a top speed of 23.5 miles per hour.
The tan TAP Fin Sweetwater topped out at 5800 RPMs at (a top speed of) 25.0 mph".

[slingshot]

Hi Dan:

I think what happened is that perhaps the straked boat was not on full plan yet. For example, lets say you have a straked pontoon and a regular pontoon w/ the same hp but propped out correctly. If you take both side by side and punch it (WOT) you'll notice that the regular pontoon boat will be ahead of the straked one till almost it's top speed. Once the straked boat gets up onto plane it will blow right by the regular pontoon. This is due to three reasons. 1) the regular pontoon boat will have a lesser pitch prop and have more holeshot torque. 2) The regular pontoon boat is a displacement type hull and designed to go thru water more or less. 3) At a certain point the straked hull uses much of it's horse power to lift the boat on top of the water instead of going through it (step onto plane). In PDB case I think the straked boat was at the step up point and couldn't get all the way up onto plane due to the rev limiter hitting. Thus, the hulls where plowing the water leaving you with an engine spinning at 6100 rpm and speed topped out at 23.5 mph.

I think the video that I saw this comparison on used a Bennington or tracker but it was obvious that the stakes on pontoons give you higher top end but lessens your hole shot given the same hp and hull length. Don't know if any of this made any sense but I've got a headache now and I think I'm going to take a little cruise on the toon to take the edge off. Peace out.

[Dan L]

Thanks for helping me think through this.

Enjoy your ride and have one for me.

Dan