Will Strakes Lift My Pontoon Boat?

[NNYBoater]

I have a 1990 Lowe Suncruiser TR240 Trinidad that weighs about 2500 lbs
with a full 18-gallon gas tank and is propelled by a 70hp Evinrude 2-Stroke.
The pontoons are 23 inches by 24 foot 3 inches with the 3 inches sitting aft of the stern. Since a Sun Tracker Party Barge 21 footer with lifting strakes and which weighs several hundred lbs less than the Suncruiser and has pontoons with perhaps 740 lbs less buoyancy will stay on plane with difficulty using a 60hp 4-stroke, I am wondering if my Suncruiser will lift and plane with the 70hp and stay on plane using lifting strakes of the same gauge and ends but the correct length for my pontoons. These strakes are on the insides and the outsides of the pontoons and 5 1/2 inches across the bottom

Thanks!

[PAR]

The short answer is no, you boat doesn't plane, nor does the example party barge you describe. It might look like planning, but it's really more like plowing. Most of the things that look like lifting strakes on pontoons are really spray rails.

It would be helpful for you to describe what you want, how you're currently equipped and how she currently runs. Then we can address options to get you toward your goals.

I'll assume you boat doesn't preform very well or at least as well as you think it should and maybe some extra bumps on those pontoons might get you there? Unfortunately, the round shape of a pontoon is about the worst thing for generating lift. Some have tried fat strakes, but the real preformance boost comes from weight reduction. Weight is the preformance killer of all small boats.

From just a quick set of guesses, your boat is likely under powered. The typical TR240 Trinidad comes with a 115 HP up to 150 HP and the weight is listed at closer to 2,700, which is about right for a 24' pontoon boat, but lets call it 2,500. Once a couple coolers full of beer and a crew shows up, now you're looking a over 4,000 pounds on a 70 HP.

[NNYBoater]

Okay, thanks. I understand that round pontoons are displacement hulls and not planing hulls. My Suncruiser is a 1990 and has a motor rating of 100hp. I don't put much more than 600 lbs of weight on it (passengers). With two of us aboard, it travels at 18mph and with 600 lbs of passengers, at about 16mph. I cruise at around 12mph and get 4.2 mpg. The package weight of the Fishin' Barge 21 is about 2100 lbs. Here are a couple pictures of the lifting strakes. As you can see, they are placed so that the planing surfaces are just below the bottom of the pontoons. The Sun Tracker Fishin' Barge 21 manual states that the speeds with a 60hp run from 19-26 mph and with a
90hp 25-38 mph. Bill, who has a 2009 Fishin' Barge 21, told me that with 60hp and he and his son aboard, it went up on plane and reached 28mph. He was over 30mph while alone. With four people in choppy water, it kept falling off plane. He reports that with a 90hp it reaches 38 mph on GPS. He didn't say how many were on the boat at this speed. I would guess he was alone.
He couldn't get these top end speeds on a pontoon boat with 60hp or 90hp unless he were on plane. So, I am convinced that the strakes are designed
and installed properly, and are working

I would like to plane at at a lower speed. I looked thoroughly into the Pontoon
Water Glide and I know that with it, I can plane at about 14mph. That is my main goal. My speed increase would be only about 5mph. I would be on top of the waves and get a smoother and more secure ride. I know this from questioning a man on Cayuga Lake in Ithaca who had the Water Glide under his Sun Tracker. His reports agree with many other pontooners who have the Water Glide and with Pontoon and Deck Boat Magazine's test in Iowa. But, as
an alternative, I am investigating the use of lifting strakes

Thanks, NNYBoater

[gonzo]

If you build enough of a flat surface, it will plane. It will also pound more. The whole structure will be more stressed and may fail

[NNYBoater]

Thank you, Gonzo. I am not sure if the Sun Tracker strakes would be wide enough to make my Suncruiser plane using only 70hp. With 90hp they would work without a doubt. But I don’t want to replace the motor.

The strakes extend from aft of the nosecones of the pontoons to about 3 foot short of the back of the pontoons. They appear to be 1/8” aluminum. They are 5 ½ inches wide on the bottom. I have included a couple pictures. These are on a Party Barge 25. I am told the same strakes are used on the Fishin’ Barge 21 and just shorter. The pontoons are the same 0.080 gauge aluminum

NNY Boater

[u4ea32]

Looks like a simple way to improve high speed performance.

A more efficient and high tech approach would be to use one or two horizontal foils spanning the pontoons.

The fundamentals: Planing speed is all about lift to drag. The higher aspect ratio the foil, the better the lift to drag (more lift for a given amount of drag). A planing bottom is effectively a lifting foil, but all lift is created by pressure on the bottom, no lift created by suction on the top.

A very high performance soaring airplane (glider) may have aspect ratios in the 30:1 range. Birds with great soaring ability (e.g., also with excellent lift to drag ratios) have aspect ratios in the 3:1 to 5:1 range.

Typical planning boats have wide hulls that have short immersed length when planing: perhaps a 1:1 aspect ratio (width to length). Stepped bottoms work because they greatly reduce the length of the wetted bottom, while leaving the width the same: perhaps a 2:1 aspect ratio. Lifting strakes, while they certainly provide lift, have an aspect ration of about 1:50, so have very little lift for the amount of drag produced. Lift, yes, but lots of drag.

Some builders of multihulls have had great success with adding a hydrofoil that spans the gap between the hulls. Such foils are intended not to lift the boat clear of the water, but to simply reduce the effective displacement of the boat that is carried by the hulls. Therefore, such foils do not have to be large, and they do not need to have any controlled surfaces. Documented results of adding foils to existing power catamarans include a 40% reduction in power required for a given speed. Typically, one puts a single foil between the hulls near the center of gravity. Simple, efficient. There exist

Look up articles on "foil supported catamarans" or hysucat, also the Corsair Foiler 2200.

[NNYBoater]

Thanks, David. You have added to my understanding of planing, which I seek to learn more about before attempting a practical solution to my problem.The pontoon water glide is a narrow foil between the hulls at the center of gravity and seems to work quite well on boats of varying lengths and weights, with different pontoons diameters and engine horsepowers.

It won't give me as much increase in speed as lifting strakes, but at least I know that I have enough hp already to get results with it and my 70hp may not make the strakes operate

[Knut Sand]

hmm, just thinking,

The welds will/ may cause the material to "harden" somewhat. Increasing the possibility for some fatique failure. If the strakes are built with thinner material than the hull material, you decrease the possibility for that failure, (less heat applied to weld), AND; should failure occur, you increase the possibility of failure to take place in the strakes, not the hull.. You'll live longer/ better with a dent in a strake than a hole in the hull.

Also.... Do you have the full spec for hull material, in order to weld it properly?

Glue?

[NNYBoater]

Thanks, Knut Sand

I wondered about this myself. I don't have specs. The material used by Sun Tracker for strakes appears to be 0.125". The maker and welder of these strakes would be a metal shop owned and run by a mechanical engineer. He could assess the strength of hull before making the strakes

But the boat may be underpowered using 70hp and it wouldn't plane at a lower speed. So I will probably set aside plans to do this

[WoodenPontoon]

NNYBoater I share your interest in improving the performance of a pontoon. Lifting strakes I believe will help some. I would caution about using them on both sides of the pontoons. I have heard of and seen some difficulty in handling with outboard strakes. The boat can't "lean" into the corners.

I would give serious thought to the WaterGlide. That third hull will not only provide some planning surface, but will also give extra bouyancy.

Good Luck!

[War Whoop]

Put a pad on the bottom,You can play with the width a little.

[NNYBoater]

Thanks, WoodenPontoon

I know about the strakes on the outsides of the pontoons. I would slow down for turns, though. I have thought for some time about the Water Glide, read the posts and emailed extensively with the owner. It would do what the strakes probably not do: get the Suncruiser on plane at 14mph and keep it there. A Water Glide owner on a nearby lake was able to ride 4 foot waves smoothly. This mean more to me than speed enhancment. But I am also concerned about getting it correctly installed. As a rule, 60" in front of the stern will work on a 24 ft pontoon boat. The height is critical. I have neither trailer nor hoist, so I need to place it at the correct height the first time or else pay a trailering fee in two directions