Experience reducing Aero drag while trailering?

[Thaniel]

Hi All. Looking to see if anyone has attempted to reduce the Aero drag of their boat while towing and if the efforts were noticeable. I understand the type of things to do to reduce drag but I'm wanting to know if anyone has tried it and seen a significant difference in gas mileage. Originally I had big plans but now thinking it may not be worth the time to remove things and put them back on.

(I expect to trailer my boat a minimum 2 hours and up to 12 hours (at freeway speeds) each time I take it sailing. )

Thanks for an experiences people can provide.

Thaniel.

 

[sail sfbay]

I towed a tandem trailer ski boat, albeit not much windage, for many years and not aware of anything you can do to reduce the drag other than mount a wind deflector like you see on some commercial trucks towing trailers. I would also follow the safety recommendations in this article.

Boat Trailering Guide: How To Trailer Safely - Boat Trader Blog

More than 90% of recreational boats are trailerable, which means that trailering your boat becomes an integral part of your boating experience. Knowing

www.boattrader.com

 

[Justin_NSA]

Wouldn't that create a lot of downforce on the rear of the tow vehicle?
Boats are streamlined by design

 

[sail sfbay]

The wind deflector panel extends at an angle behind the rear end of the vehicle that deflects over the trailer and reduces the gap between the truck and the trailer, which reduces aerodynamic drag.

 

[Benny17441]

I would think waxing and polishing the hull would yield the best results by reducing air friction. They use it in NASCAR. Sailboats in general already have fair aerodynamic shapes.

 

[Rick Webb]

The wing is to move the turbulent air further back
The Mast, bow rail, stern rail seats all that stuff sticking up above the boat is going to dirty up the airflow behind the boat. The only way around that would be to make a cover so the air moved around or over the top of the boat.

Drag increases exponentially with air flow (speed). Best solution is to slow down, find a tail wind, or a big truck to draft.

Drafting semi trucks actually works. In college I had a VW Beetle Convertible. I would get behind one coming out of Austin headed south on 35. You get up real close to where you feel the air blowing your hair forward rather than back take the car out of gear and the truck'll drag you right along with it. Not something for the faint of heart or those terribly bright. The truckers didn't like it much either.

 

[TRWXXA]

The easiest way to reduce drag? Reduce your towing speed.

Drag increases by the square of speed. The power required to overcome the drag increases BY THE CUBE! Double your speed = 4 times the drag = 8 times the power. So even a small reduction in your speed yields a big increase in efficiency.

Theoretically, just driving 70 mph instead of 65 would reduce your MPG by over 20%.

Probably not the answer you were looking for, though.

 

[Thaniel]

I understand the type of things to do to reduce drag but I'm wanting to know if anyone has tried it and seen a significant difference in gas mileage.

Thanks for the ideas. Was hoping for some quantified experiences. Noone has experimented?

Theoretically, just driving 70 mph instead of 65 would reduce your MPG by over 20%.

Yes this is true and on the 5 hour tow home I experimented with how much the speed affected the mpg. However if I reduce the coefficient of drag that will improve the mpg at ALL speeds. It's not an either or. Both can be done. But driving significantly below traffic speed is unsafe and for me, it is not worth the safety risk to save a few bucks.

Boats are streamlined by design

Yes the hull is quite good. But on the deck there is tons of stuff sticking out. While at 6 knots it's not a huge deal at 70 mph well... Then on my trailer it has guide posts which stick out farther than the boat (obviously). There is a lot that could be removed to clean up the shape. And the fender overhangs on the tires seem excessive etc.. But if The changes don't have a notable effect, which is my fear, it's not worth the time.

 

[rgranger]

When I tow my H26, the mileage on my truck drops from about 18 to 13. Let’s analyze a two hour trip of approximately 100 miles. I will burn two extra gallons of gas towing my boat. At today’s gas prices that is about $5. Let’s say your efforts to reduce drag improve that by 30%..... your efforts will save you $1.50 in gas....
Extrapolate that to a 600 mile trip and you have saved $9.

Seems like a lot of work to save $9. What is your time worth?

 

[TRWXXA]

Thanks for the ideas. Was hoping for some quantified experiences. Noone has experimented?


Yes this is true and on the 5 hour tow home I experimented with how much the speed affected the mpg. However if I reduce the coefficient of drag that will improve the mpg at ALL speeds. It's not an either or. Both can be done. But driving significantly below traffic speed is unsafe and for me, it is not worth the safety risk to save a few bucks.


Yes the hull is quite good. But on the deck there is tons of stuff sticking out. While at 6 knots it's not a huge deal at 70 mph well... Then on my trailer it has guide posts which stick out farther than the boat (obviously). There is a lot that could be removed to clean up the shape. And the fender overhangs on the tires seem excessive etc.. But if The changes don't have a notable effect, which is my fear, it's not worth the time.

As rgranger pointed out, you can go off into the weeds (metaphorically) doing drag reduction -- removing deck hardware, shrink-wrapping the topsides, etc.. But anything you do has to be undone down the road (literally). 20 minutes spent taking stuff off, is at least 20 minutes putting it back on. 40 minutes would that would equate to driving 10 mph slower on a 4 hour drive. 40 minutes that could be spent listening to tunes and enjoying the scenery, instead of skinning your knuckles and cursing while removing stubborn hardware.

Easy stuff you can do are things like getting that mast as low and level as possible, securing the standing rigging as tight to the mast as possible, and making sure all tires are inflated to their correct pressures. Put your boat and vehicle on a diet. There's probably a few el-bees of unnecessary stuff aboard each that could be spared.

 

[Thaniel]

Seems like a lot of work to save $9. What is your time worth?

My time is worth about the same amount as when I'm fixing up an antique boat (many would say fixing it is a waste of time). If I ever get to the point where a free $9 is unattractive to me I won't be working a day job

Don't forget burning more gas requires more time to replenish it. On my way to pickup the boat I burned one tank of gas to get there. Gas mileage was cut in half on the way back requiring an extra stop for fuel. How much time did that extra gas stop waste? And I would 100% rather spend more time tidying up the boat at the lake if it'll reduce the number of min and $ spent at gas stations a noticeable amount.

When I did the test float at the lake 15 min away I disconnected as little as possible. The next trip is planned to be over 800 miles there and 800 back.

As rgranger pointed out, you can go off into the weeds (metaphorically) doing drag reduction -- removing deck hardware, shrink-wrapping the topsides, etc.. But anything you do has to be undone down the road (literally). 20 minutes spent taking stuff off, is at least 20 minutes putting it back on. 40 minutes would that would equate to driving 10 mph slower on a 4 hour drive. 40 minutes that could be spent listening to tunes and enjoying the scenery, instead of skinning your knuckles and cursing while removing stubborn hardware.

So far working on the boat has been more fun then sailing it. Adding in a few more min of fun and saving some coin and stops at the gas station., not seeing a downside anywhere. Different people like different things. I get it, most people don't like what I do.

 

[sail sfbay]

Thaniel...........if your primary interest is to reduce fuel consumption consider these tips, which I have used when towing a 5,000 lb tandem ski boat trailer and 16,600 lb fifth wheel trailer.

1. Match the vehicle’s tow rating to trailer weight. Had to replace my Ford Explorer with a Ford Bronco and later Ford Expedition for towing my ski boat.
2. Tow with a diesel truck with a moderate gear ratio. My diesel tow vehicle of choice is a Ford F350 dually, which I tow a fifth wheel trailer.
3. Maintain proper tire pressure on the boat trailer and tow vehicle. Low tire pressure can drag both the vehicle and trailer, reducing fuel mileage.
4. Maintain the proper tongue weight. The boat trailer’s tongue weight should be between 5 to 7 percent of the total tow package, which should include the weight of the boat, all loaded gear and the trailer weight. This helps the trailer tow properly by reducing swaying or “fishtailing” which can drastically reduce the rig’s miles per gallon.
5. Adjust your trailer to fit the boat. Make sure the boat is level on the trailer and the trailer/boat is level when hooked to the tow vehicle. This will also reduce wind resistance.
6. Check trailer bearings for proper lubrication, install buddy bearings and top them off with grease prior to each trip.
7. Maintain constant speed and accelerate slowly and steadily from complete stops.

 

[LloydB]

"Thanks for the ideas. Was hoping for some quantified experiences. Noone has experimented?"

Yes I did. And sure enough just as my high school instructors forced me to calculate I found by experimentation that in fact they were right. During the gas crunch I was forced to put experimentation into practice on odd numbers days when I could not buy gas. The results were still true. Still have my lab reports in the garage someplace and I have my slide rule sitting on the shelf next to my E6B but I don't really need them because I've got Google and YouTube. I have also played 'my bug gets better gas mileage than your bug' but only at an amateur level after all who needs a gas gauge anyway. Off hand I would guess that you will get better results out of paying attention to your tire pressure because rolling friction is greater than aerodynamic drag at 63 miles per hour. Maybe fill your tires with nitrogen? I don't know just had a CDL friend that said I'd be better off and took him at his word. Just a recollection don't remember exact but someone said up to about 60 miles an hour streamlining doesn't reduce drag much then by just inspecting velocity VS drag charts on Internet seems to bear that out as that's the speed where most curves start.(excepting boats and bicycles of course) Might plan on leaving 2 hours early every trip, it's a $ailboat you may find gain in unexpected places besides location and time. Here it's one vector or another we all chase

 

[sesmith]

FWIW, I notice a difference of about 1 or 2 mpg (lower) if we have a headwind. At least I don't have to tack the truck, though.

 

[Crazy Dave Condon]

As a former dealer with too many miles pulling boats, there is not much to reduce drag. I found if you sit back and slow down, you will save alot of money on gas consumption for example 55 vs. 75 miles per hour. That is what I would recommend for a Hunter 26 as I pulled too many of those from Florida and up and over mountianous regions in WV, NC, VA
Maintenance is another issue which like all things is part of trailer and boat too.

 

[Thaniel]

As a former dealer with too many miles pulling boats, there is not much to reduce drag.

Any chance you can share what you tried to reduce drag that didn't work?

 

[Crazy Dave Condon]

Tthanio

I was surprised you asking that as I sent you my number plus I live near you
Simple advice. Check tires pressure and make sure axles are greased. Go 10-20 miles and pull over and check hubs. Some heat is normal but excessive heat indicates trouble. Slow down to save gas and enjoy the ride. As for drag there is not much you can do other to waste money on gadgets that really do not work. That is based on boats like yours which I have pulled

 

[Rick Webb]

One thing that might be worthwhile.

Leveling out the mast so that it poses less of a frontal area. You could segment the mast crutch support pole and lower the mast at the stern of the boat that would certainly reduce a lot of the drag. Enough to make a significant difference? Not likely on a 400 mile trip but maybe after 100 of those trips.

You could cut the support and sleeve it to make it easy to add the segment back in and even add another segment so that when you raise the mast you could start out three or four feet higher starting out where it starts to get easier to raise.

 

[Crazy Dave Condon]

Rick;
Engineers at Hunter, Catalina and others did not think of the mast being alot of drag but your suggestion to lower and level the mast is a great idea as it will lower the highest point on the trailer and boat downward and in some areas that is crucial. Don't mean to argue on the other but experience teaches me to go slower making sure tire pressure to proper inflation, grease the hubs, checking every so often for excessive heat in the hubs and so on to include tie downs. I was in the midst of hauling a large boat from Baltimore to Tampa on the interstate, when a car was flashing lights only to see one hub on fire. Learned the hard way.

 

[rgranger]

when a car was flashing lights only to see one hub on fire. Learned the hard way.

I always try to be a good Samaritan on the highway. Sometimes people just don't want help. This past weekend a KIA (one of those cube shaped cars) pulled up behind me on the interstate and I noticed his headlights were very VERY dim. So I'm guessing his alternator is dead and he is about to have a really bad day. As he starts to pass me, I roll down my window so I can tell him ... he ignores me.... I signal to him to roll down his window... he shakes his head and pulls out in front of me....

Oh well.... I tried. He probably figured out why I why I was trying to talk to him about 15 minutes later.