Modding the front of a pontoon boat?
 

My mother in-law has ordered a pontoon boat, for the family to use. She doesn't get around as easily as she used to, so a ramp to cover the space between the dock and boat will be useful.

Originally, I thought to get one that we can move around. However, thinking again, I decided that mounting it to the front of the boat on a hinge could be handy.

Rather than having the flat front fence of the pontoon, do you guys think there is any aero advantage to having it affixed to the front and leaning back about 30 degrees would help the horrible aerodynamics up front? The front corners of the fencing are radiused, but where the door is located...it's completely flat.

Here is a random pic of a ramp similar to what I'm considering, plus a couple of pictures of the front of the boat being built. I marked up one to show how it would work. If done, I'd secure it so it won't flop around while on driving around.

Thoughts?

I don't think this is any way relevant, water is about 1000 times more dense than air and so aerodynamics barely matter on a boat compared to water drag assuming a displacement hull.

This is a tritoon (3 logs) with lifting strakes. It works in displacement mode to around 13-15 mph, then it works in a planing mode. Top speed is around 50 mph, though it will spend most of it's life between 18 - 30 mph. The underside of the deck is skinned, except approx 20% nearest the bow.

It's a brick. I'm just wondering if mounting a slanted ramp (around 30 degrees backward slant) at the front of this brick has an aero advantage over the flat fence that is perpendicular to the deck. IE, does it make it less brick-ish?

I do agree that hydrodynamics are more important. However, I need a ramp and am wondering if how I mount it may have any benefit. I did try to google the effect of lean or angle of attack on a flat surface...I didn't find anything useful.

.

You can forget aero with a pontoon boat. They’re basically like a low height sail that you use a motor to push air out of the way with.

About the only thing you can do is make sure the boats gauge package includes a way to monitor GPH (gallons per hr) use of fuel. Most new boat motors are capable of this by way of the ECM. Just make sure the gauge package is capable. Then it’s just a matter of finding the sweet spot between trim angle and throttle input to get it dialed in for maximum fuel efficiency.

:)


>

.

boat nose
 

Seems like any potential gain at the nose would be lost due to the open, walk-around deck. Without a 'roof' on the boat, there's nothing but turbulence up there.
As the boat goes on plane, inclining, separation increases and the situation only worsens.
And that folded overhead sunshade makes a pretty good impersonation of a parachute.
When Rumpler enclosed his 1921 open touring car, converting it to a 1924, closed car limousine, the drag dropped by about half.
Even 'cigarette' boats suffer on plane. The upper body needs to be designed to be streamlined when on plane, not parked at the dock.

A quick back of the envelope calculation says that a three foot high by six foot wide flat panel pushing air at 20 MPH will require almost exactly one horsepower. A realistic streamlining of the flat front could save about half that, while an angled ramp would save even less.

Compare that to the size of motor needed to push a tritoon to 50 MPH.

I bet it doesn't hit 50mph except maybe on glass water with a single occupant and just a few gallons of fuel. Well that's not true, on the trailer it can probably do 80mph LOL! We had an older pontoon built with welded aluminum pontoons that looked more like two small boats than pontoons that would get up on a plane with 1 or 2 people. Now we didn't have a 350HP motor strapped on the back, but we did have a 115 and I doubt we ever saw 20 mph on the water. What we did do was suck the gas at any speed. It only carried 2x12 gallon portable tanks but that 24 gallons would only take us maybe 3 hours or maybe 45 miles probably less.

That does look like a super nice pontoon, and it will be a blast, but ramp or no ramp is not going to change how much fuel is burns. Technically up on a plane with 3 big pontoons it's going to have quite a bit of frontal area. I assume the ramp is only a small 3'x3' area of that but angling it should help a little, but i doubt measurable. I'd mount the ramp so it's sturdy and easy to deploy and not worry about a few gallons here or there on a $70,000 boat.

I was just thinking that I would build my ramp in the most aerodynamically efficient way as possible.

Thank you JRMichler for taking the time to actually throw out some rough numbers.

I was a little surprised that a group of people who will discuss the tiniest advantage of taping body panels on a Prius didn't feel it worthwhile to even try to help someone hoping to gain a small advantage on what would be 6-9 square feet of frontal area. While no huge gains are apparently possible, what is wrong with trying to get some small ones? No matter what I'm driving, I still try to drive it in the most efficient manner....which to me seems like what Ecomodder is supposed to be about.

I might just mount the ramp on the side via a hinge. That will be the most convenient place to put it. I was only going to do the front if there was an aero advantage. Tough call! The front would be nice when we park straight into a dock. The side will be better when loading from the boathouse. I have 10-14 weeks to decide where to put it and get all the materials together.

Moving on. This toon was ordered with the 350hp Mercury Verado. We don't plan to run around the lake at full speed, but want to have the reserve power for when the boat is fully loaded and we are pulling people on the water (tubes/skis/etc). Like a car, having access to more power doesn't mean you have to use it all the time.

Most driving will be done around 18-25 mph, which should be the sweet spot for this motor. I did research data on the Mercury website where this engine was tested on other tritoon boats of the same length and similar weight. 2500-3500 rpm is the most efficient.

Prop selection is key, and I've begun researching what size and pitch will give the best midrange efficiency. From the factory, props tend to be sized for a better holeshot with full weight. This boat is rated for 15 people, normally it will carry 5-8 (with 2-4 being kids). Our 80-90% use case will be far lighter that full rated capacity, so a numerically higher pitch should give an advantage. The Mercury data indicates a top speed between 46-52 mph from the factory...as well as info from other owners of identical boats on brand specific forums.

We'll probably never run at 50 mph, as we didn't buy it to be a speedboat. I'm sure on some random day when I wake up early and the water is glass smooth...I'll take it out just to see what the gps says is top speed. A same sized but slightly heavier tritoon with the same motor drinks 5.4 gallons of fuel per hour at 18.5 mph. At full throttle, it drinks 25 gallons of fuel per hour and runs 50.9 mph. At 20-25 mph, we should be able to stay on the lake all day with factory 54 gallon fuel tank. There will be plenty of times when we'll zip to a cove, drop anchor, and float/play with the kids. That won't use any gas while we do that!

Possibly there's less collective experience to draw on?

For, you know, planning purposes. ;)

That may be part of it. Certainly, the back of the envelope realization that no matter what I do...it may only offset 1 hp...was an eye opener. Any spirited runs will surely be done for research and planning purposes only. lol.

I will drop the bimini top all the way down when it isn't in use. That is an easy and free thing to do.