Air drag while towing an open boat

[Thalasso]

Re: Air drag while towing an open boat

That's what I'm thinking. 350 pounds is the average weight of an ex-wife, that car should be able to drag one of those around on a piece of plywood and still do 28 mpg...

Almost peed myself reading this

 

[Silvertip]

Re: Air drag while towing an open boat

I've made my own boat covers for years and if you look at this one you see no straps to hold it down. At freeway speeds this cover actually sucks down rather than blowing up. Pay attention to the "nose bra" and the sides of the cover. The nose bra keeps air from getting UNDER the cover which is why they balloon. Wrapping the cover around the rail prevents air from getting under the cover as well. There is ample exhaust area for air to get out from under the cover as a slight vacuum is created at the stern around the engine. The boat prior to this one is now 18 years old and although not used much in the last couple of years, is still in use and in one piece with no patches. It is all about design, tightness, and keep air from getting under the cover.

And another (picture is several years old)

 

[mrdancer]

Re: Air drag while towing an open boat

It would be interesting to hear a comparison of your bearings, wheels, tires, etc. between the two trailers. Worn bearings, poor lube, tire design/width, bias vs. radial, psi, it all adds up.

If you wanted to go whole hog, you could mount some trailer bunks inside an enclosed travel trailer that is just big enough to hold your boat.

I don't doubt your power/mpg numbers at all (having followed VW tdi info over the years). You've plenty of power to pull any realistic load, but, as mentioned, not sure you have the weight in your tow vehicle to safely pull loads over a couple thousand pounds. Of course, much of that can be mitigated with good driving technique, but its always nice to have a big safety margin.

Btw, I've a '02 Accord with four-cyl/5-spd, gets 33mpg ave., best is 40mph on a road trip averaging 66-67mph (meaning speeds of 70-75mph over long distances) with A/C on and loaded with luggage. Not bad for a gasser...:lol:

 

[glenn property of pam]

Re: Air drag while towing an open boat

It's a VW Golf GTI stage 2, it's a 2.0 liter turbo, mine is making 300hp@4000 RPM and 350 torque@2500RPM.

The car is rated to tow 1850# if the trailer do not have a braking system and 3500# if the trailer has a braking system. It's the official manufacturer limit on towing capacity.

It's a 6 speed DSG transmission and Direct injection engine.

It's the power of the turbo, I got enough boost to accelerate without any problem and when I'm at the cruising speed on the highway the turbo are not in use and it's very efficient. The problem is that if the trailer has too much drag or is too heavy then they turbo will have to work a lot and the fuel efficiency is a lot worst.

wrong way around the engine runs better at higher rpms with the turbo spooling that it will at lower rpms with the turbo laging. My mini turbo has better mpg at 3k rpm with little throttle that at 2k rpm with more throttle. It the same with all engines thats why they put overdrive lock out on autos and no one said that you have to use all 6 gears

 

[Captain Caveman]

Re: Air drag while towing an open boat

I was wondering if adding a cover on a boat would make a big difference on the air drag while towing a boat.

Depends on the tow vehicle. Yours is struggling, hence your findings, so a cover will make a difference. As others stated, unless you have a custom, high quality cover that thing will act as a sail and actually reduce your fuel efficiency.

I used to tow without a cover. Then I bought several (never custom though) trying to gain fuel efficiency, spending $100-$200 each time. The cover always caught the wind, no matter how meticulously I tried to tighten things down. If it's not custom it will have extra material to make it a universal-use cover. I also ended up building a "horse" to hold up the cover...take away the slack. Then I had something else to deal with at the landing and it wasn't perfect. Water would still pool up.

I know cover my new boat without a cover. I don't see the point. I spend $150 in gas roundtrip each time I head to the cabin. It doesn't bother me to spend an extra $10-$20 but not deal with the hassle of a cover. I'm much happier

 

[steelespike]

Re: Air drag while towing an open boat

By the way the pickup tailgate Myth has been busted by Myth busters.Trucks did better with the gate closed and no soft cover.
Apparently the air built up a cushion in the bed that let the slip stream slide over.
I wonder if a boat with a full windshield might behave the same.

 

[mrdancer]

Re: Air drag while towing an open boat

If your boat is small (like, 350lbs small), here's an idea that is "out-of-the-box", whatever that means...

Find another boat, exact same model as yours. It doesn't have to be nice because all you need is the hull. Remove EVERYTHING from the interior of the hull, put some rubber bumpers on the gunwales, and fasten it upside down on top of your trailered boat, like a mirror image. You are now towing one of the most aerodynamic tow loads around!

Btw, it would probably be more aerodynamic if you could put the boat on the trailer backwards in this configuration (think "pivoting axle'). I know, I know, the expense and hassle isn't worth it, unless you're in a competition. Then it's the principle of the thing...