Trailing efficiency steps?

[Avendit]

Hi all,

I've been trailing my boat around for the 4 years that I've had my m3p- quite happily, but this year I'm planning many more trips up and down the country. This made me wonder, is it worth a little more thought on the efficiency side?

What can be done to a skimpy combi boat trailer to make it more efficient to tow? I already pack it to be as aero as possible (I think), but are there fancy bearings I could get to help? Can you convert from 8 to 10 inch wheels so they do less rotations? Is anything worth it, or is a 5-10% reduction in range totally reasonable and I should just shut up?

 

[philip295]

That's one thing I don't like about my old S, can't have a towbar.

 

[Foxsbiscuits]

a 5-10% reduction in range totally reasonable and I should just shut up?

Probably this my dude.
Bigger wheels are worse for EV efficiency, I assume the same for trailers. I took a ~10% hit by choosing the 19s over 18s. Then if the wind is blowing in the wrong direction I can lose another 10%!
If you're stopping to charge anyway and don't need it for one super long hypermile run then I'd cast it from your mind.

 

[Avendit]

Probably this my dude.
Bigger wheels are worse for EV efficiency, I assume the same for trailers. I took a ~10% hit by choosing the 19s over 18s. Then if the wind is blowing in the wrong direction I can lose another 10%!
If you're stopping to charge anyway and don't need it for one super long hypermile run then I'd cast it from your mind.

You're probably right. Just aware of the savings tesla made by changing the bearings on the Raven S.

You lose range going to bigger wheels as they are less aerodynamic and heavier and compliant with the lower ratio tyres, but that is all because you keep the same overall rolling size. For a trailer if you go from 8" to 10" wheels its the whole package you are changing - the rolling radius is now a chunk bigger and the wheels are turning slower at a given speed.

Its less about need an extra or longer stop, more about a bit of extra flexibility to choose the stops, go a little faster, or arrive with a little less urgency to get plugged in as the absolute first thing.

Or like you say I'm over thinking it. I've been towing around Scotland and Northern England for the last 4 years and this has gently niggled at the back of my head as something to look into. This year I have multiple trips further south planned, including the south coast (from Edinburgh) so those 5-10%'s will start to add up.

 

[Foxsbiscuits]

You're probably right. Just aware of the savings tesla made by changing the bearings on the Raven S.

You lose range going to bigger wheels as they are less aerodynamic and heavier and compliant with the lower ratio tyres, but that is all because you keep the same overall rolling size. For a trailer if you go from 8" to 10" wheels its the whole package you are changing - the rolling radius is now a chunk bigger and the wheels are turning slower at a given speed.

Its less about need an extra or longer stop, more about a bit of extra flexibility to choose the stops, go a little faster, or arrive with a little less urgency to get plugged in as the absolute first thing.

Or like you say I'm over thinking it. I've been towing around Scotland and Northern England for the last 4 years and this has gently niggled at the back of my head as something to look into. This year I have multiple trips further south planned, including the south coast (from Edinburgh) so those 5-10%'s will start to add up.

Good info, didn't know about that, not a physicist
It's hard to ignore the numbers when we're given so much detailed data but I think it's better for peace of mind and calm journeys
Maybe someone can help you improve it but it seems unlikely that a trailer will have zero effect.
Now the more important question when you're planning, can you predict the weather?...!

 

[MovingSouth]

Hi all,

I've been trailing my boat around for the 4 years that I've had my m3p- quite happily, but this year I'm planning many more trips up and down the country. This made me wonder, is it worth a little more thought on the efficiency side?

What can be done to a skimpy combi boat trailer to make it more efficient to tow? I already pack it to be as aero as possible (I think), but are there fancy bearings I could get to help? Can you convert from 8 to 10 inch wheels so they do less rotations? Is anything worth it, or is a 5-10% reduction in range totally reasonable and I should just shut up?

Sounds like you are already doing a good job of aero efficiency. A 5% to 10% reduction efficiency is low for towing anything.

For reference, towing a boxy trailer gives a far bigger hit:

He also finds that the weight of the trailer load has little effect, so the hit comes from aerodynamics.

 

[Avendit]

Sounds like you are already doing a good job of aero efficiency. A 5% to 10% reduction efficiency is low for towing anything.

For reference, towing a boxy trailer gives a far bigger hit:

He also finds that the weight of the trailer load has little effect, so the hit comes from aerodynamics.

Yea - a small high performance dingy is pretty aero - 4.5m long, only 1.5ish wide and 80cm on its trailer in towing configuration. Also, I drive a bit slower when towing which gives you quite a lot back in terms of range to make up for the added drag. I've a photo in a really old thread somewhere, but no idea how to find it.

 

[looseend]

Just having bikes on the back of my MY is at least 20%, and closer to 40% this weekend driving into strong southerly wind and rain. So sounds like you're getting really good efficiency.

 

[Avendit]

Just having bikes on the back of my MY is at least 20%, and closer to 40% this weekend driving into strong southerly wind and rain. So sounds like you're getting really good efficiency.

Oh, the bikes are terrible. With 3 on the back, and 1 + a roof box on the top we were probably 40% down - we were very fully loaded that day. In comparison the boat sits behind the car, under the boot lip height so I suspect turns the whole thing into a single aerodynamic unit mostly. But always more to be done! (or not)

 

[Adopado]

Is anything worth it, or is a 5-10% reduction in range totally reasonable and I should just shut up?

5-10% looks like a great result when towing ... I think you must be pretty close to ultimate optimisation. Anything you improve isn't going to get back to zero range reduction so you've little left to gain. I suppose it comes under "law of diminishing returns".

 

[Jason71]

There are 3 main factors,
Aero
Weight
Rolling resistance

You say you have optimised the aero and not much you can do about weight without leaving stuff behind or buying a lighter trailer.

Yes good bearings are important but so is
tyre width, as narrow as possible
tyre type, low RR
tyre pressure ( as high as possible)
aero covers?


I assume it has mud guards but what would probably be good would be some enclosed ones like the GM EV1. I doubt anything like this exists to be purchased but they could be made

I imagine the benefits would be minimal though