Trailer capacity; a cautionary tale

There must be a mechanical engineer in the C-Dory family who can en- lighten us on weight transfer issues. Say a 22' cruiser on the trailer weighs 3,000 lbs and the trailer another 1,000 lbs. Unhooked, that combination obviously puts 4,000 lbs on the axle components and tires.
But when the trailer is hooked to the towing vehicle, some of that combined weight is transfered to the hitch and vehicle frame. How much would probably depend on the kind of hitch. Any engineer out there in C-Dory land who would address that issue? Another variable to factor in.

John
 
Average tongue weights run about 10% of total trailering weight (boat + trailer), so in your example of a 4,000 lb rig, 10% is 400 lbs. With this configuration (again, this is very typical), you'd have 3,600 lbs on the axles and tires, 400 lbs on the hitch being supported by your tow vehicle.
 
Yellowstone said:
Say a 22' cruiser on the trailer weighs 3,000 lbs and the trailer another 1,000 lbs. Unhooked, that combination obviously puts 4,000 lbs on the axle components and tires.
But when the trailer is hooked to the towing vehicle, some of that combined weight is transfered to the hitch and vehicle frame. How much would probably depend on the kind of hitch. Any engineer out there in C-Dory land who would address that issue?

After the trailer is hooked to the vehicle, the weight on the hitch would be almost exactly what was on the trailer dolly wheel, about 10%, so the axle weight would still be about 3600. The change in the "levelness" of the trailer before and after hitching up would affect the weight transfer more: tongue down, heavier on the hitch; up, lighter. Of course a weight-distributing hitch would put some of that hitch weight on the trailer and vehicle frames.
Click to expand...
 
Well, if anyone is still monitoring this thread (or maybe just for posterity), here's an update to my original post. I'll try and keep it short, but...

1. I reweighed my rig at Cat Scales (as suggested) to confirm accuracy. Original weights confirmed although some of the conclusions are now different - see below.

2. My boat is not "overloaded", assuming the 4500 on the water limit is correct. More below...

3. My King trailer is not overloaded, but close (within 170 pounds) to the 4000 lb load limit.

4. The tires on the trailer are not overloaded (a change in my original post) - assuming the load distribution on any of the two axles does not exceed 2860 pounds - it does not.

5. The winch on the trailer (2000 lb) is, in my opinion (and experience) under capacity. This will necessitate a swap out at about $75-100.

7. I weighed each and every item on my boat (but for stuff which is attached). For anything not weighed, I obtained weights from manufacturer's product specifications or, in some cases, had to estimate. My final calculations, using all scale weights indicate I was over in my load weighing by only 47 lbs. I use the more conservative weighed weights below.

8. The gear on my boat weighs 1907 pounds. This includes EVERYTHING but the dry hull. If you want to see an inventory, here is a copy of the Excel worksheet (in PDF format):

http://www.squareknot.net/weights.pdf

Warning this will make your head hurt.

I have a seperate column on this worksheet for loading using only "essential" items, ie, engines, fuel, and basic gear - first aid kits, safety equip, batteries, electronics, and a reasonable amount of fishing gear, etc. The "essential" load weight total is 1750 pounds. There is nothing on my boat that does not have a place/storage spot. There is nothing on my boat I do not use. Maybe there is a difference between typical near and off shore salt water and inland boat loading??

8. According to Jeff at the factory, the basic hull (ONLY - no engines, no batteries, no floorboards, no water or gas, etc etc - JUST the dry hull) has a load capacity of 2000 pounds. I am 93 pounds under this, but over this by about 400 pounds when I load trip gear and people. If I load only the "essentials", I am about 250 pounds overweight when I load trip gear and people.

9. My boat, fully loaded for transport (without people and trip gear) weighs 3830 pounds (hull and gear only). The 4000 model King is rated for 4000 pounds. This weight is under the capacity by 170 pounds, but will be pretty close when I load 100 pounds of trip gear (ice, food, clothes, TV, Tivo, refer - just kidding on the last three).

10. The boat, (full) load and trailer weigh 4920 pounds. This is the towing weight of the package. This is under the combined tire load rating (a correction to my original post). However, this is about 98% of the trailer's GVWR. As previously discussed in this thread, some indications are that only 85% of a trailer's GVWR should be used. I also see different reference to trailer GVWR including the trailer weight and others including only the boat and load weights. If the latter, the actual vs. GVWR is fine (about 86%). If the former, this is stretching it pretty thin.

11. Per the original post, the front axle carries more weight than the rear. This may or may not be an issue - no clear input on this one although King says it's OK so long as I rotate the tires frequently. The front axle, as loaded, is not over the rated tire capacity or the axle capacity. My only question - per the original post- is whether this contributes to poor handling on rough roads. No clear answer here. Maybe more experimentation will give the answer.

BOTTOM LINE: As far as I can tell:

My boat on the water is at or slightly over the factory-recommended limit. (Jeff made the point he has loaded his 22 over 2000 pounds before...) My winch is too small (no comments please). My "towing package" may be close to the GVWR and over the 85% "safety zone" - I can't be sure, but time will tell.

I still recommend that new buyers get sufficient information about their boat and trailer weights and capacities at delivery. Also, run your rig over the scales when you are fully outfitted. I think it is pretty easy to UNDERestimate the weight of gear loaded on a boat. I also recommend that buyers get at least a 3000 lb. winch.

Hope this helps.
 
Had a request for the Excel version of the spread sheet I created and used for this.

It can be downloaded from:
http://www.squareknot.net/weights.xls

Note this sheet is not very refined for use by others. Be sure you understand the formulae. It also assumes the percent calculation for GVWR includes hull, load and trailer.
 
Falco, thanks for the follow up on this. As a future C Dory owner, I found this to be an interesting and informational thread. Additionally, I want to give you credit for being forthright enough to admit the corrections in your original assertions. I know plenty of boaters who would have just let this whole thread lay, especially with some of the commentary that flew when you first posted your concerns. :thup :thup :thup
 
Certified scale weighing today:

C-Dory C-22, two topped off fuel tanks, 1/2 tank water, normal day trip "stuff"

Tandem axle Pacific trailer, spare tire removed

Tongue weight 230 lbs, trailer tires carrying 4550 lbs, total 4780 lbs

Yes, tongue weight is light. Re-mounting the spare will increase the weight as will moving the boat forward a bit. Nevertheless, when towing with either the 6 cyl 4Runner or the Duramax long bed, the boat and trailer behave well so I'll go by the "If it ain't broke, don't fix it" rule for now. It's rare to have fuel topped off on longer trips and that too will influence tongue weight.


Don
 
Hi Folks,

This is a great thread.

A few years ago, I had the chance to use the scales at the local dump. I weighed the Explorer and the trailer, and then went back with the boat on the trailer. Result was the boat with the old engine (83 70 HP Johnson) and equiptment weighed about 2700#. I went on the C-Dory site and gave the info, and everybody said I was about right. I have since changed engines to a 75 HP Yamaha four stroke, but took off the 7 HP Johnson. I figure I might be about 3000# now. I do not know how heavy the trailer is, but at 500# ( might be light), I am running the trailer at about the 3500# Gross weight.

When I drive, as long as I stay about 50 MPH or under, and stay way over on the right when the semi's and buses come, I am all right.

I know I need a bigger tow vehicle, one with brakes which I do not have, but it is not in the budget at this time.

The longest I have towed the trailer was from the west end of the Erie Canal to Hingham MA. It took twelve hours, and many stops to fuel me and the car, and check the tires and wheels. No problem.

Just adding this as my story for information. Keep the info coming.


Fred
 
One comment after reading Sneaks':

For tandem trailer owners, I think it's important to also get the weight of each axle. This will tell you the distribution of weight along the trailer (which theoretically should be equal on both axles (meaning the center of weight lies right in between both axles) and indicate whether any one axle is overweight, given its rated capacity, per design/spec and/or tire load rating. Assuming the weight per axle is not equal (and it probably won't be), but within load specs then you might still keep a closer eye on the "heavier" axle and tires and rotate them often. Also give "special" care to the bearings on that heavier axle... If one axle is over-spec then I think it's real important to do something to redistribute some of the weight to the other axle.

This distribution between axles might also indicate when to shift weight onto the ball, eg, if the back axle is heavier than the front, and tongue weight is less than the "recommended" 7-10%, you might consider more seriously shifting weight forward on the trailer, be it moving the boat toward the hitch, shifting load aboard the boat (move the beer to to fo'casle), or even checking level-ness of the trailer on the tow vehicle and if high, lower it.
 
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