Calculating tow weight - back of the napkin math

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hart
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Calculating tow weight - back of the napkin math

Post by hart »

I have a new tow beast, and I’ve been playing with trailer weight numbers. It’s been a long while since I’ve done it and it’s pretty eye opening. Anyone with more experience calculating this I’d love you to check my numbers, or let me know if I’m forgetting something.

I’ve been driving a 2006 Honda Ridgeline and using it to tow our 26x. After 225,000 miles it was time to let her go. So I recently bought a Jeep Gladiator. The Ridgeline has a max towing capacity of 5000 lbs. The Gladiator package I bought has a stated max towing capacity of 7700 lbs. Of course there’s more to towing than that (like dealing with GWVR/GWCR) but let’s keep it simple for now, my brain is getting overwhelmed.

Starting with the basic weights:

Macgregor 26X - 2350 lbs (not including gear)
Dual Axle trailer - 1050 lbs (found on the VIN plate)
Mercury outboard - 205 lbs (found online, so iffy?)
Gas 12 gallons. - 73 lbs

3,746 lbs

And that’s before adding any gear on board. I really have no idea how to guesstimate that. Grill, safety gear, anchors, toys, sails, etc etc etc. What would you call it, Let’s say 500 lbs?

The last long trip we took, there were 5 of us. 2 adults, one teenager and two smaller children. Taking a wild stab, I’m going to guess 200 lbs of “stuff” for each person (food, drinks, clothing, etc) and call that 1000 lbs.

If those numbers are remotely close, I’m at 5246 lbs. Overweight for the Ridgeline, and not even looking at GWVR including passengers/gear in the truck. Glad I didn’t get in an accident.

While Jeep claims 7700, I want to stick with 80% of that as a safety factor. So 6160 lbs ends up being my max. Do you supposed my figures have a 900 lb margin of error? Hmm. I hope so.

Next mental exercise is to figure out how much weight I’m carrying in the Jeep and add that in to the gross vehicle equation. We may need to start taking two vehicles, or doing two trips to the ramps for our heavier trips.

Bottom line, I’ve justified towing with the Ridgeline for years and to be fair it’s done great. Tows the boat well, no issues stopping etc. But we tow short distances and down here on the Alabama/Florida coast it’s pretty flat. However, I think I was taking chances I shouldn’t have, just didn’t realize it. Time to rethink a few things about how we tow.

Conclusions:

I’m going to go through the boat and get rid of the dead weight. I bet I have a ton of stuff in there I don’t really need to carry and can ditch. I’m also basing my “personal gear” numbers on a long trip. I don’t think we are carrying 200 lbs of stuff/per person for day trips or weekends.

The ramps we use are typically within a few miles of the house. If we’re going to Pensacola Bay sometimes we’ll drive about 30 miles to Big Lagoon State Park. I have a general rule of spending more miles sailing than driving. Seems to make the trips more fun. So we aren’t doing long or hard towing. With that said, I still want to maintain a reasonable safety margin - which apparently I haven’t been doing.

I’ve never gone to a scale and weighed our setup. I’ve just assumed I was good since the Ridgeline “felt” fine towing the boat. I think I should go get weighed. All this napkin math is fun, but I’d like an actual number to work with.


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dlandersson
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Re: Calculating tow weight - back of the napkin math

Post by dlandersson »

Ditto 8)

" I bet I have a ton of stuff in there I don’t really need to carry and can ditch"
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Re: Calculating tow weight - back of the napkin math

Post by C Buchs »

I don't see anchors or batteries in your calculation. You should include them in your estimate.

For getting rid of extra stuff, we've been emptying the boat every every season (except this one) for the last few years. Take everything out, give the boat a good cleaning, and decide if you need the stuff you put back.

We towed for 5 years with a 2005 Mercedes ML500 (5.0L V8 gas engine, 12-13 mpg towing the boat) that had a 5000 lbs. towing capacity. We made multiple trips that were 250+ miles away from home. The only issue we ever had was a broken fan belt. We now have a 2015 GL350 (3.0L V6 diesel engine, 16-17 mpg towing the boat) that has a 7500 lbs. towing capacity. Both of these vehicles have air suspension. The 2005 had an option to put the suspension in sport mode. This mode stiffened the suspension and towing was nice. The 2015 is bigger and has a higher capacity, but doesn't have any modes for the suspension. It tows great, but it's a luxury SUV. So it just feels softer. The only issue we've had with the 2015 is when we had the extra kicker motor on the back and we didn't have enough tongue weight. As soon as we got to 60 mph, it started to sway a little. We got off the road and moved the kicker inside, the problem was solved.

Jeff
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hart
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Re: Calculating tow weight - back of the napkin math

Post by hart »

Jeff,

Good call. Currently carry 2 Fortress anchors so I’m not that worried about them. But the two batteries add a fair amount.

Sounds like you’ve got a nice setup!

I keep thinking I’m overestimating but a scale will truly tell.
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Wyb2
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Re: Calculating tow weight - back of the napkin math

Post by Wyb2 »

I don’t trust Roger’s advertised boat weights at all. The 25 is listed as 2,100 lbs (iron swing keel, so no wet and dry displacement). Anything else in this size range with a keel weighs at least 700 lbs more. So here are some pictures of my attempt at figuring this out on my end. A shop crane, scale, and one very heavy piece of pipe. Since I was lifting ahead of the axle, the tongue weight during this was almost nothing, so I can could ignore that and I was lifting right about half the load.

IMG_2796.jpeg
IMG_2797.jpeg
The math came out to about 3,700 lbs, so a boat weight of maybe 2,700-3,000 lbs. Incidentally very similar to a few others in this size range with a swing keel. A pretty big difference from 2,100. I guess it would be about right if they weren’t including the keel, but I think they knew better than that.

Edit: That was a little bit of a tangent. My point was if anything that 2350 lbs could be low.
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Starscream
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Re: Calculating tow weight - back of the napkin math

Post by Starscream »

There have been a couple of 26X owners who have weighed their boats. The Jill Kristy came in at just over 5000 lbs, and Richard posted the details here. From memory, I've seen posts of 26Xs weighed at 4800 and 5200 lbs.

I've always decided to own tow vehicles with rated towing of at least 6k lbs. The Nissan Pathfinder is one of the very rare "normal" size/price SUV with a tow rating of 6,000 lbs, so it's been our choice of tow vehicles. Most are rated at 5k lbs, and I don't want to ever have to worry about some lawyer finding out that my tow rig was undersized.
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hart
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Re: Calculating tow weight - back of the napkin math

Post by hart »

WYB2, that’s fascinating. And I’m not surprised to be honest.
Starscream wrote: Fri Jun 21, 2024 5:04 am I don't want to ever have to worry about some lawyer finding out that my tow rig was undersized.
Exactly my thought. The Ridgeline never struggled, but looking back - If I’d been in a wreck, yikes.

And for that reason I won’t be going too “Jeep” with mods on my new truck either. Jeep seems to be pretty particular about this setup to get the max tow rating. The other trims the max towing capacity starts dropping, some a little, some a whole lot.
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kurz
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Re: Calculating tow weight - back of the napkin math

Post by kurz »

My :macm: incl Trailer, 2 axles, is around 5000 lbs
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Be Free
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Re: Calculating tow weight - back of the napkin math

Post by Be Free »

Boat, trailer, batteries, fuel, and outboard are about 3700 pounds for me. Food, water, and miscellaneous tools and gear add about another 1000 pounds for a week-long trip. My towed weight is between 4500 and 5000 pounds for most trips.
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KevinGD
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Re: Calculating tow weight - back of the napkin math

Post by KevinGD »

A wise person (my wife with many years of towing horse trailers) pointed out “it’s not how much you can tow, it’s how much you can stop that matters”
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Be Free
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Re: Calculating tow weight - back of the napkin math

Post by Be Free »

KevinGD wrote: Tue Jun 25, 2024 4:44 am A wise person (my wife with many years of towing horse trailers) pointed out “it’s not how much you can tow, it’s how much you can stop that matters”
A wise woman and a lesson I learned many, many years ago. :wink:
My boat trailer is set up to carry (and stop) 7000 pounds.
Bill
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