lifting nacelles for pontoon boats

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radiodave
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lifting nacelles for pontoon boats

#1 Post by radiodave » Tue Nov 06, 2018 9:27 pm

Another topic for pontoon boats.
Yes, a newbe.
The idea is simple enough to have been tried, figured all you old mariner could shed a little light.
Facts you taught me already.
Pontoons are displacement hulls.
Not planing hulls.
Can behave somewhat like a planing hull with 80 grand in horsepower, brute force.
Some with strakes, or v bottoms kind behave like a planing, if you inject enough power in the equation.
Pretty much end of story.

In avaition we had the 4 forces of flight.
Thrust must overcome drag to acheved lifting speed.
Lift must overcome weight to fly.
Never land in Phoenix in a heatwave.
The drag of the wheels will not allow lifting speed.
Yer geounded!

radiodave
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Re: lifting nacelles for pontoon boats

#2 Post by radiodave » Tue Nov 06, 2018 9:35 pm

So you can lift the front, provided speed and hotsepower is right, negate some drag by having it out of the wet stuff.........very little reduction.
The ass end of the boat is still buried deeper than Jimmy Hoffa, and that where the story.

Cause there is no lift.
Displacement Hull.

If you could shallow plane the stern, she would fly.
But thrust typically cannot overcome a displaced stern.

If it could, the extra speed would allow the front to lift more.
So forth and so on.

So if you added a nacelle between the logs, just on the surface at the back, shaped like a jonboat or toboggan, there would be no drag penalty.

When you increased speed, the extra prow wash would hit the smooth bottom, providing lift.

radiodave
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Re: lifting nacelles for pontoon boats

#3 Post by radiodave » Tue Nov 06, 2018 9:41 pm

I'm talking something with a low aspect ratio.
To me a 8 foot beam pontoon boat with 24 I inch logs has 4 feet between the logs.
If only 4 foot fore to aft was planing 6 inches, you have a 16 square foot surface displacing 8 gubic feet of water, at 62 pounds per cubic feet.
Any extra speed moves the wall of water further forward, increasing displacement, and raising the back.

Has this been tried?

boocat
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Re: lifting nacelles for pontoon boats

#4 Post by boocat » Wed Nov 07, 2018 5:43 am

Yep, It's all very simple with pontoons. Big tritoons with big power go fast, two toon boats with moderate to low power go slow.

willy13
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Re: lifting nacelles for pontoon boats

#5 Post by willy13 » Wed Nov 07, 2018 7:02 am

Sounds like a fun idea to try and as far as I know it has not been tried yet.

The industry currently is using lifting strakes (what the industry calls them) to make pontoons into a semi-planing hull. It does not require a lot of HP to see a difference, 115hp on a 22ft or less should be enough to see the benefit of lifting strakes.

The v-bottom marketing refers to having the center toon lower than the side toons. I have never driven this setup but I am told it is more for turning sharper than lifting. Though lifting strakes are also used, so there certainly is also lift but I do not believe it is any faster than non "v" tri-toons.

Some people are into boating because they like to fish, I am into boating because I like to water ski. I have slalom skied behind v bottom boats that are labeled "planing hulls". But at 30 mph they are still throwing a decent wake, so I like to call them semi-planing hulls because they still a displacing water at 30mph. Otherwise there would be a much smaller wake. :lol3

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Bamby
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Re: lifting nacelles for pontoon boats

#6 Post by Bamby » Wed Nov 07, 2018 8:48 am

You're pretty much describing a "deck boat". For the few among us here who have owned them were seeming glad to be rid of them and back into a pontoon again.
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guy48065
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Re: lifting nacelles for pontoon boats

#7 Post by guy48065 » Wed Nov 07, 2018 9:50 am

Bamby wrote:
Wed Nov 07, 2018 8:48 am
(deck boats)...who have owned them were seeming glad to be rid of them ...
In the years I've been on this forum I don't believe I've ever seen a discussion on why deck boats get a bad rap. My boss at work is considering a used one--what should I tell him?
Mark
1996 Sweetwater 180EX + Johnson 40
Rush Lake, Atlanta, MI

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FLOUNDERPOUNDER225
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Re: lifting nacelles for pontoon boats

#8 Post by FLOUNDERPOUNDER225 » Wed Nov 07, 2018 10:34 am

guy48065 wrote:
Wed Nov 07, 2018 9:50 am
Bamby wrote:
Wed Nov 07, 2018 8:48 am
(deck boats)...who have owned them were seeming glad to be rid of them ...
In the years I've been on this forum I don't believe I've ever seen a discussion on why deck boats get a bad rap. My boss at work is considering a used one--what should I tell him?
Deck boats get a bad review mostly from previous owners who have moved on to other vessels (hull designs). I had a deck boat when I was in my teens (a long time ago) the design of the hull is a very low deadrise (the V you see looking at the bow or stern of a boat) the less deadrise there is on a mono-hull boat the less HP it will take to move the boat along, and it will have great planing characteristics. The down side, is when in heavy chop or wakes the boat is very uncomfortable, and will pound the teeth from your head. They have their place, inland water ways, or calmer sea states. pontoons ride soft because they are a displacement hull and don't get airborne like mono hull boats. Tritoons ride better because there is really no flat surface coming down into the water if it does get a little airborne off a wake. And now that Tritoons are competing speed wise with Deckboats its really no choice for most folks with experience.
Pensacola FL
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radiodave
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Re: lifting nacelles for pontoon boats

#9 Post by radiodave » Wed Nov 07, 2018 1:17 pm

Makes me wonder if it would behave like a RIB Boat.
Anyone have any knowledge on how they perform?

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Re: lifting nacelles for pontoon boats

#10 Post by radiodave » Wed Nov 07, 2018 1:25 pm

You just answered my question.


I had a deck boat when I was in my teens (a long time ago) the design of the hull is a very low deadrise (the V you see looking at the bow or stern of a boat) the less deadrise there is on a mono-hull boat the less HP it will take to move the boat along,

I am describing a low deadrise on the rear half to two thirds of the pontoon, and just at the waterline.
Its purpose is to convert the prow wakes to flotation when you are moving above a few miles per hour.
If it is there, and it passes under at the higher elevation, seems based on Archimedes principle is that it would rise.
If it rose, less stern is buried, you go faster, more wave

radiodave
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Re: lifting nacelles for pontoon boats

#11 Post by radiodave » Thu Nov 08, 2018 7:01 am

I'm tempted to buy a old jonboat, but don't have a clue as,to how I would noun it up to the joists.
Any ideas?
If I. Had no flooring, it would be easy

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Re: lifting nacelles for pontoon boats

#12 Post by Bamby » Thu Nov 08, 2018 10:30 am

Now you're off describing a water glide more or less. It's another gimmick that's parted some people of their money, of which there's no shortage of. :lol3 . I'm aware of some trying it with frustrating success, but then again they didn't want to admit they'd been snookered... :rofl
Respect Our Recreational Resources
Leaving Only "The Footprints of Your Passing"

Boating the Muskingum River
1972 35' Crest Pontoon Houseboat
2007 90 hp. Yamaha
Consider Visiting: http://www.pontoonhouseboatodyssey.com/

radiodave
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Re: lifting nacelles for pontoon boats

#13 Post by radiodave » Thu Nov 08, 2018 7:28 pm

What is a water Glide?

radiodave
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Re: lifting nacelles for pontoon boats

#14 Post by radiodave » Thu Nov 08, 2018 7:29 pm

What is a water Glide?

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Re: lifting nacelles for pontoon boats

#15 Post by riplipper » Fri Nov 09, 2018 4:39 am

Bamby wrote:
Wed Nov 07, 2018 8:48 am
You're pretty much describing a "deck boat". For the few among us here who have owned them were seeming glad to be rid of them and back into a pontoon again.
That was maybe the single biggest mistake of my life.........they ride like a piece of plywood.........absolutely horrible, my wife hated that thing.
I am the guy at the boat ramp that gives you dirty looks when you are a complete idiot and too stupid to know it.

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