Noticed that with my front bimini deployed, my cruising MPG went from 2.7 to 2.8 yesterday. I was rather surprised. Anyone else experience this? My gut says the bimini provides lift that reduces the wetted surface of the boat, without generating excessive drag. I know for a fact it does generate lift because it tightens dramatically while underway. There's obviously lower pressure on the top side than there is on the bottom.

Too many variables to account for .1 mpg increase.

Unless you are cruising at 70mph, I can't imagine a bimini supplying enough lift to "reduce the wetted surface" of a 6500 lb boat.

Could have been any number of other factors: temp, current, wind, weight in boat (i.e decreasing fuel weight), dumped the water from the cooler overboard, etc.

Dave,have you been on a diet lately? Lost a few pounds maybe?

I get plenty of lift!

I say "no way" --- like has been said -- there are a lot of variables -- including the instrument itself -- but as an aerodynamic body itself, I would think the drag induced by the bimini would at least equal the lift ---

Did you compared both in the same half hour more than once?

Hard to believe, so many other things that would have to be equal... Even a small change in wind speed or current direction could account for that change. Not to mention instrument accuracy.

Ain't no way a bimini is going to give my boat any lift.

You should try your experiment several times, to rule out any other factors.

Come on Al, you just need a bigger Bimini. Think Spruce Goose

it should work the other way, that lift is caused be catching the wind, causing drag, check you top speed, I'll bet it drops.

Hmmmm....maybe were gonna see spoilers on the back of our boats in the future?

I get an increase in mpg when the kids remember to pull the ladder up!

and the Chinese women's Olympic Diving team swear they have absolutely never used steroids,
and although they have never looked that aerodynamic, they keep on getting sleeker and sleeker scores !

perhaps we need to give your boat a pee test ?

When Dave sez he saw a difference, I belive him. I don't want to pile on and be a nay-sayer, so I do want to offer some thoughts as to maybe why Dave saw a difference.

Dave, were you able to replicate the situation - for instance, travelling the same direction and speed, did you alternately try to put the bimini up and down, and did the MPG change consistantly between the two configurations?

Might there be other factors that could cause the MPG difference?

One thing I thought of:

With the bimini up, you increase the drag on the boat, pushing the rear down, which changes the angle-of-attack on the boat.

This could change the wetted surface as well, causing the change in the MPG reading. But it is caused by angle-of-attack from pushing the rear down rather than lift.

So might it be possible that the improved MPG be caused by a different attitude, and that attitude is changed by the bimini dragging on the rear of the boat which might mimic a different trim tab or outdrive trim setting.

Thought I posted this earlier but don't see it. I get better gph with my bimini up, cuz I drive slower! Mine flutters at higher speeds, and I hate that.. So I go slower!