Tapered Pontoon stern

[RadioDave]

I am new to pontoons, and learning.
Something I notice is there is a large amount of wake left behind, as the toons are blunt in the rear.
Has anyone considered of seen a toon with a tapered tail.
As inefficient as toons are for moving through the water, I would think it would inprove the laminar flow of the toon, and increase efficiency, speed.
Any thoughts?

 

[ahicks]

If you look at some of the older 'toons, you may see some that are tapered. ALL of the newer 'toons, ones I've seen anyway, are flat or nearly flat.

As far as efficient, you see no attempt on the part of power boat manf's to do anything to taper the back. There, 90 degree (+-) sharp exits are the norm.

The only attempt I've seen at anything close to "laminar" might be with sailboat design, on hulls run at displacement speeds.

 

[RadioDave]

[No message]

 

[HotTommy]

RadioDave,
I suspect the taper on the boat in your image has more to do with allowing the propeller to access water than with reducing drag. It's been almost 50 years since I got my degree in Aero Engineering so my recollections may not be perfect. But I think there are some fundamental differences in the way compressible fluids like air flow, and the way incompressible fluids like water flow. I'm not sure that water reacts to an abrupt rear surface like air does. In any case I suspect boat builders would offer the tapered rear you suggest if they could show a performance gain that would justify a higher price. It appears that lifting strakes offer a more consistent performance gain.

 

[ahicks]

Regarding the design of the boat in the drawing, methinks it might be designed for speeds well in excess of what we might even dream of when considering pontoon boat design.

 

[Scott Danforth]

A pontoon boat is a displacement hull..... Your governed by the physics of a displacement hull

 

[RadioDave]

Thanks, I'll study on the lifting strakes.

 

[Scott Danforth]

Thanks, I'll study on the lifting strakes.

and you may need a third log....... and a whole lot more power than you most likely have.

unless you have over 150hp, dont even bother with the lifting strakes

you have a displacement hull. to get the hull to plane, you need significantly more power than a planing hull.

 

[ahicks]

You can argue that "planing" point all day long if you like, but I have seen and owned 24' 'toons that will plane easily, achieving speeds well in excess of what a typical "displacement only" hull might achieve. So, at 15 mph plus, with just 40 and 50 hp engines, you can say that 'toon is planing, or you can call it something else. Suit yourself.

Further, there is nothing special about these boats. No lifting strakes or 3rd toons. See the speed vs. hp chart in this document on page 3. These are plane old boats, and typical speeds which can be expected of them. It should be easily seen these speeds would not be achievable in a displacement hull.

Point being, you don't need 150hp or lifting strakes, or a center toon, to plane a toon.

View attachment pontoonspeedchart.pdf

 

[Scott Danforth]

yet people cant match the speed that Reed Marine published in that one chart.

Been around 'toons since I have been boating., you are right, there is nothing special about them.

here is a chart from a database of pontoons taken from actual test data [h=2]Pontoon Boat Speed Chart[/h]

Bass Buggy	18 feet	60 hp	17 mph
Bass Buggy	20 feet	60 hp	18 mph
Sweetwater	24 feet	90 hp	18 mph
Sweetwater	24 feet	115 hp	21 mph
Gigantic	30 feet	115 hp	21 mph
Suntracker	22 feet	70 hp	21 mph
Starcraft	20 feet	23 mph	23 mph
Party Barge	18 feet	75 hp	24 mph
Suntracker	22 feet	115 hp	25 mph
Tritoon	21 feet	90 hp	27 mph
Tritoon	21 feet	90 hp	27 mph
Crest III	26 feet	90 hp	28 mph
Tritoon	26 feet	175 hp	35 mph
Berkshire Sport RFX9	25 feet	300 hp	50 mph
Bennington QR27	28 feet	250 hp	51 mph
Premier Pontoons 290	29 feet	600 hp	52 mph
South Bay Super Sport 925	27 feet	600 hp	57 mph
Manitou 25 X-Plode XT SHP	26 feet	300 hp	62 mph
Harris Crowne SL 250	27 feet	350 hp	63 mph
PlayCraft X-Treme 3110	31 feet	400 hp	65 mph

Pontoon Type Pontoon Length Horsepower Top Speed

 

[ahicks]

Well, even though that chart doesn't include 40-50hp outboards, it looks to me like that chart makes about the same point I was making. Using your chart, 60 hp will take a boat WELL beyond what most would consider "displacement " speed (9 mph tops?). Beyond that common sense would tell you that as you add power your speed is going to increase. Until you get to a certain point anyway. Then all you're doing is burning more gas with very little extra to show for it.

 

[Scott Danforth]

still displacement speed for a multi-hull boat. (same reason a catamaran sail boat is faster than a mono-hull)

not the old 1.34:1 ratio, however closer to 2.8:1 on a pontoon.

 

[5150abf]

With all that is going on in front of the endcaps don't kwow that the shape of the end caps would make much if any difference.

The underside of a toon at speed is a mess with the wake of 2-3 tubes trying to occupy the same space, they are just horribly inefficient.

There are a lot of chine design that attempt to deal with this but don't; know that any endcap design would improve performance at all.

 

[ahicks]

]still displacement speed[/U] for a multi-hull boat. (same reason a catamaran sail boat is faster than a mono-hull)

not the old 1.34:1 ratio, however closer to 2.8:1 on a pontoon.

If that's true, please explain why the front of the toon rises as the boat accelerates from a stop, and eventually levels out as the hull comes up to speed.

Regarding catamarans at speed, the reason they're so fast is reduced wetted area. Kinda like when 'toon get's up on top.

 

[RadioDave]

[No message]

 

[RadioDave]

Simple truths.
Wife gave up boating 16 years ago.
after 33 years of marriage, lost her to inflammatory breast cancer March 12th.
kids brought up boating again.
wanted to try a toon this time.
1996 Suntracker 20 feet.
garage kept almost never used.
sold 1996.
new owner had to service the fuel system.
he got a few trips, wife left him took the kids.
furniture, deck, carpet, looks all new.
decals shrunk.
runs like new after sea foam once.

 

[RadioDave]

Bought the boat, motor, trailer for 6k.

1996 sun tracker.
2 20 foot 25 inch toons.
16 feet of playpen.
40 horse tracker with tilt.
45 pound Motorglide trolling motor.


was garage kept, factory tires even looked new.
ran a tank of sea foam, behaves like new.
flooring, furnature look new.
first time out, 9 to 11 mph on gps.
serviced tilt, added Stingray wing to motor from my old boat, can lift nose with 2 fatties in front.
11 to 13 mph.
I notice the tach breaks 5000 rpm from the start and stays there.

how do you tell the pitch?

perhaps I need a different prop.

17 mph would be a dream.
I would go 13 mph, save fuel.

 

[ahicks]

The Tracker engines are renamed Chrysler engines that were developed back in the 70's, or maybe I should say they stopped developing them back in the 70's. Mercury was supplying them to Tracker mounted on top of Merc. lower units. Anyway, they're built like a truck, but not very popular from a performance standpoint. Single carb and Merc lower unit makes them easy to work on.

For best performance available from that engine, you want to prop the engine to turn at the upper rpm limit the Manf. recommends for that engine. We can make suggestions for the right size if we know your target max rpm, what the engine is turning now, and what pitch prop is on it now (info will be on the prop somewhere).

After that, you need to keep the boat light if speed is of any importance. Carry only safety equipment and stuff you'll be using frequently - don't carry stuff you "might" need!

And congrats on your find. That boat should treat you right for a long time!

 

[RadioDave]

It seems we were nearly fully loaded

 

[RadioDave]

22 gallons of fuel probably 200 pounds of gear, full livewell, 5 people.
135 pounds a person?
about 900 pounds worth.
bet the bimini top is an option, too.
around 90 percent loaded would be a good guess.
hell, that Motorguide x3 45 probably 60 pounds alone.
11 miles per hour.
I'm told if I take care of the motor, it could outlast me, just turned 60.
bouts gonna diet, retest.