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 Formula to calculate tongue weight?
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Tainui

RO# 26562

Posted - Dec 02 2008 :  15:36:19  Show Profile  Reply with Quote
Just wondering if there is a guideline to determine tongue weight on my trailer. Somehow I don't think the bathroom scale will cut it.

The boat is 2860 Pursuit denali 7200 lbs dry. Trailer is a Venture tri-axle bunk. Maybe the pictures will provide some insight?


Morgan
Pursuit Denali 2860 - SOLD

Homeport:

Msibley

RO# 16534

Posted - Dec 02 2008 :  15:40:24  Show Profile  Reply with Quote
weight of boat and any equipment, fuel, etc, plus trailer weight (call mfgr for that - or, sometimes trailer weight is listed on the title)= Gross vehicle weight. recommended 10% is tongue weight. Make sure your hitch and ball are rated for the weight.



Mike
"War is cruelty. There's no use trying to reform it, the crueler it is the sooner it will be over."
"I hate newspapermen. They come into camp and pick up their camp rumors and print them as facts. I regard them as spies, which, in truth, they are."
- Maj. Gen. William Tecumseh Sherman, Commanding, Union Armies-Military Division of the Mississippi

Edited by - Msibley on Dec 02 2008 15:42:23

Homeport: Melbourne, FL Go to Top of Page

jrpar

RO# 11343

Posted - Dec 02 2008 :  15:49:55  Show Profile  Reply with Quote
I measured tounge weight using a bath scale and a fulcrum. I'll try to dig up a pic and the dimensions, but picture a placing two blocks on either side of the tounge which are connected by a piece of 4x4. A bath scale is placed under one end of the 4x4. When the tounge is placed on the 4x4, it's positioned closest to the non-bath scale end of the 4x4. With the offset, the majority of the weight is not on the scale as it has a mechanical advantage. You just need the exact mesurements to convert the portion of the weight read from the bath scale into the full load.

John



Edited by - jrpar on Dec 02 2008 15:50:31

Homeport: Palm Coast, FL Go to Top of Page

pauld

RO# 1369

Posted - Dec 02 2008 :  15:50:05  Show Profile  Reply with Quote
Here's a way to use the bathroom scale.
http://www.etrailer.com/faq_trailertowtips.aspx


"Ugly Duckling" 1991 Shark 34'
"Lazy Daze" 1986 Chaparral 28'
"No Name" 1987 Starcraft Runabout 19'

Homeport: Covington, KY Go to Top of Page

Msibley

RO# 16534

Posted - Dec 02 2008 :  15:54:00  Show Profile  Reply with Quote
Take it (the whole rig) to a truck scale...it's official and accurate. Bathroom scales are not valid for trade.




Mike
"War is cruelty. There's no use trying to reform it, the crueler it is the sooner it will be over."
"I hate newspapermen. They come into camp and pick up their camp rumors and print them as facts. I regard them as spies, which, in truth, they are."
- Maj. Gen. William Tecumseh Sherman, Commanding, Union Armies-Military Division of the Mississippi

Homeport: Melbourne, FL Go to Top of Page

jrpar

RO# 11343

Posted - Dec 02 2008 :  15:59:54  Show Profile  Reply with Quote
I think we have two interpretations of the original question...
If the question was asking how to determine the actual tounge weight, then pauld found the info I was trying to describe.
If you are looking for accurate weight of the rig to determine what the tounge weight should be, then Mike's spot on..




Homeport: Palm Coast, FL Go to Top of Page

Sandy

RO# 1159

Posted - Dec 02 2008 :  16:08:21  Show Profile  Reply with Quote
You can have your boat and trailer accurately weighed at many landfills and most large gravel suppliers. You may be suprised at it's true weight.

You can use a bathroom scale if you have the tongue resting about 1/3 from the end of a 4x4 which is solidly blocked up (fulcrum) so the 4x4 is approx level , then put the scale blocked up at the other end at 3/3 the total length . Since leverage is allowing 2/3 of the weight of the tongue to press down on the block only end & only 1/3 of the tongue weight on the scale end, just multiply the scale reading by 3 to get the tongue weight. ( Or use 1/4 & 3/4 lengths & 4x scale,.... 1/10 & 9/10 length & 10x scale , etc., as works best for your boat & trailer vs. scale used.)

If that calculation is too much or too little, adjust the boat on the trailer moving the winch post, or the axle placement, to get the desired tongue weight for safe towing according to Mike's % above. .

If I have this a bit off , feel free to correct. It's been a long time since high school physics. .


Sandy

Edited by - Sandy on Dec 02 2008 17:50:53

Homeport: The Vineyard Go to Top of Page

pdecat

RO# 842



Posted - Dec 02 2008 :  16:21:57  Show Profile  Reply with Quote
Im sure some trailer gurus will weigh in with a better solution but just for giggles I figured I would try to come up with a cheap solution. Here is one attempt.
Set up a Rube Goldberg weight divider on a bathroom scale. Place one end of a 4x4 about 5' long on the scale and the other end on a block a few inches higher than the scale such that the 4x4 only touches the scale and block at a sharp edges. Set it up with 50 between the point touching the scale and the pivot point on the block. Place the trailer tongue on the 4x4 at a point 5 from the pivot edge of the block. The scale should now read 10% of the tongue weight.



Bruce



Homeport: Gulf Coast FL Go to Top of Page

pdecat

RO# 842



Posted - Dec 02 2008 :  16:23:23  Show Profile  Reply with Quote
Sandy beat me to it.


Bruce



Homeport: Gulf Coast FL Go to Top of Page

Sandy

RO# 1159

Posted - Dec 02 2008 :  17:13:57  Show Profile  Reply with Quote
& 4 other posters beat me to it as I was slowwwly replying! [:-D]

Sandy

Homeport: The Vineyard Go to Top of Page

Tainui

RO# 26562

Posted - Dec 02 2008 :  17:30:37  Show Profile  Reply with Quote
With all the good explanation and the graphic from Pauld's link I think I see how I can figure this out.

Thanks all.


Morgan
Pursuit Denali 2860 - SOLD

Homeport: Go to Top of Page

rbmitchell

RO# 3641

Posted - Dec 02 2008 :  17:36:21  Show Profile  Reply with Quote
If, at 60 mph, your tow vehicle fishtails and you run off into a ditch, then your tongue weight was too low. Move the boat forward and try again.

Nice rig!


"The solution to this problem, when found, will be obvious."

Homeport: Beach Haven NJ&KeyWest FL Go to Top of Page

thataway4

RO# 10872

Posted - Dec 02 2008 :  17:43:04  Show Profile  Reply with Quote
I weigh the boat with axels on the scale, and truck off the scale. Then back up the trailer, and weigh the entire boat, with wheel jack down, on the scale. Subtraction gives the tongue weight. Also it is a good idea to weigh the truck and the entire rig-(Cat scales)--that way you can be sure that you have not esceeded your tow or gross vehicular combined wieght capacity.

For a load that big I use an equalizing hitch (yes they will work with surge brakes)--but electric over hyraulic is preferable with that size trailer. Even with a projected weight of 7200 lbs, I suspect that with gear, trailer and liquids, you are going to be at 10,000 lbs.


Bob Austin

Homeport: FL Go to Top of Page

Veebyes

RO# 11224

Posted - Dec 02 2008 :  19:01:38  Show Profile  Reply with Quote
It will be interestinng to see how much your pin weight actually is. I suspect that it will be much less than you think. Your outdrive & engine/engines are behind your rear axel. Fuel tanks are above the fwd 2 axels. Not much boat, weightwise fwd of the front axel.

I'd try the bathroom scale trick for fun then take the rig to a commercial scale & compare.

Just a few inches position on the trailer make all the difference. We have had this one on the trailer perfectly balanced. Nothing on the pin.



The boat weighs 18,000#. Hyraulic trailer is most likely another 4,000#. Amazing how much weight can be shifted by adjusting hydraulic pin & stern pads.



Edited by - Veebyes on Dec 02 2008 19:11:36

Homeport: Bermuda Go to Top of Page

32carv

RO# 24150



Posted - Dec 02 2008 :  19:21:59  Show Profile  Reply with Quote
Veebyes,
Do you tow your boat with that truck on the open road?



Homeport: Sacandaga Lake Go to Top of Page

32carv

RO# 24150



Posted - Dec 02 2008 :  19:22:15  Show Profile  Reply with Quote
Veebyes,
Do you tow your boat with that truck on the open road?
Jim



Homeport: Sacandaga Lake Go to Top of Page

mandm1200

RO# 29581

Posted - Dec 02 2008 :  19:52:22  Show Profile  Reply with Quote
I am not sure what 'nothing on the pin' means. If you are talking about tounge weight, I certainly would tow like that. Out first boat while trailering would sway the tow vehicle side to side. The dealer moved the boat forward for more tounge weight and the problem was gone.

"If you're not the lead dog, the view never changes."

Homeport: Lewisberry, PA Go to Top of Page

Veebyes

RO# 11224

Posted - Dec 03 2008 :  07:22:45  Show Profile  Reply with Quote
32carv, yes we do however we don't have any more than a few miles to travel & all of it is done at about 15mph with an escort to clear traffic as needed. 20 years of seasonal trailering my large boats to & from storage. No incidents.

No pin weight means just that. We miss judged the positioning by just a few inches & had the boat perfectly balanced on the trailer wheels.



Homeport: Bermuda Go to Top of Page

Tainui

RO# 26562

Posted - Dec 03 2008 :  11:39:18  Show Profile  Reply with Quote
Veebyes, You must have a friend at the Jeep dealership (in addition to the one upstairs). The Liberty is only rated to tow 5,000 lbs. I think that's 440% over capacity.

Is it pretty safe to assume you're not using a ramp for launch?


Morgan
Pursuit Denali 2860 - SOLD

Homeport: Go to Top of Page

JeffR

RO# 19718

Posted - Dec 03 2008 :  12:21:17  Show Profile  Reply with Quote
Excuse me for asking the obvious (or not), but why use the fulcrum and go through all the calculations? Why not simply weigh the tongue directly, either by lifting the scale to the height of the hitch, or putting the scale on the ground and putting something between the scale and the tongue? What am I missing?


Homeport: Chicago, IL Go to Top of Page

onthecreek

RO# 11208

Posted - Dec 03 2008 :  16:04:11  Show Profile  Reply with Quote
...you'd need a REALLY big scale to show 10% of 20,000 lbs


Homeport: Go to Top of Page

JeffR

RO# 19718

Posted - Dec 03 2008 :  17:07:35  Show Profile  Reply with Quote
Oh, okay, it's simply for capacity reasons; that makes sense.


Homeport: Chicago, IL Go to Top of Page

jtybt15

RO# 3300

Posted - Dec 03 2008 :  20:28:19  Show Profile  Reply with Quote
I wish I could click on the link!




Charlie

There is much to be said, in a world like ours, for taking the world as you find it and fishing with a worm.-Bliss Perry, 1904



Homeport: Ca Go to Top of Page

SCORPIO

RO# 4810



Posted - Dec 03 2008 :  21:26:06  Show Profile  Reply with Quote
Tianui, what is the beam on your boat? Which Venture model do you have? Did you have any problems getting the bunks aligned on your hull? I have a VATB 12625 for a 300 Searay and had difficulty setting the bunks far enough apart to miss the strakes. I'm still working on getting it setup. My beam is 11 feet. Also, how far above the frame cross members is your keel? Got any close up pics of the boat resting on the trailer you'd care to post? I really want to get my trailer setup and some pics of a similar trailer and hull would really help.
Thanks
Chris


Chris USPS AP

Homeport: Lewes, Delaware Go to Top of Page

Sandy

RO# 1159

Posted - Dec 03 2008 :  23:53:14  Show Profile  Reply with Quote
quote:
Originally posted by onthecreek

...you'd need a REALLY big scale to show 10% of 20,000 lbs



Well....If you really need/want it , they are available for this specific pupose in several max weight ranges from 0-1000,-2000 or -5000lbs tongue weight : http://www.sherline.com/lm.htm


Sandy

Homeport: The Vineyard Go to Top of Page

Don B

RO# 11333

Posted - Dec 04 2008 :  13:33:16  Show Profile  Reply with Quote
veebyes, the problem w/ zero weight is that the load can and will toggle back-and-forth. setting the weight slightly forward also provides additional load to provide traction

Don
'91 Thompson

Homeport: Menasha, WI Go to Top of Page

blouderback

RO# 24057

Posted - Dec 05 2008 :  09:26:36  Show Profile  Reply with Quote
OK, what you need to do is get a bunch of instant jello and a bathtub. No, wait, that's for determining the prop pitch....

-Bob-
.................................................................
"Annabo": 2005 Larson Senza 206 w/5.0L Bravo III

Homeport: Chalfont, Pennsylvania Go to Top of Page

Tainui

RO# 26562

Posted - Dec 05 2008 :  18:40:31  Show Profile  Reply with Quote
quote:
Originally posted by SCORPIO

Tianui, what is the beam on your boat? Which Venture model do you have? Did you have any problems getting the bunks aligned on your hull? I have a VATB 12625 for a 300 Searay and had difficulty setting the bunks far enough apart to miss the strakes. I'm still working on getting it setup. My beam is 11 feet. Also, how far above the frame cross members is your keel? Got any close up pics of the boat resting on the trailer you'd care to post? I really want to get my trailer setup and some pics of a similar trailer and hull would really help.
Thanks
Chris



My boat has a 9.6 beam and the trailer is a VATB1060. I took a few pictures today to give a bit of perspective but the angles are tough.

I did not have to realign the bunks from the previous owner (Striper 2901). I have about 5-6 inches of clearance before the keel reaches the cross members. My only concern was lining up on the Stbd side of the trailer to allow for my depth sounder. It doesn't sit perfectly flat but I'm okay with it and ther is no safety concern.




Transducer is just right of the bunk....




Morgan
Pursuit Denali 2860 - SOLD

Homeport: Go to Top of Page

SCORPIO

RO# 4810



Posted - Dec 05 2008 :  19:48:52  Show Profile  Reply with Quote
Thanks Morgan! That helps more than you realize! I was worried about that verticle clearance on the frame members but see others have it too. I talked at length with the an engineer at Venture and he told me that the boat should not rest on the cross member. Flexing while going over bumps would cause the boat to shift on the trailer. Also, the axles travel up and down a few inches and need clearance to prevent hitting the keel. He told me that if I need to, I can replace the bunks with the next size smaller dimensional lumber to lower the boat a bit. I have taken measurments of my strakes now that the boat is on blocks so I can properly align the bunks to miss the strakes.
Do you block your boat after she is home to take load off the trailer? I was thinking that would be a good idea.
Thanks again
Chris


Chris USPS AP

Homeport: Lewes, Delaware Go to Top of Page

Tainui

RO# 26562

Posted - Dec 06 2008 :  10:02:58  Show Profile  Reply with Quote
I'm not sure if it's necessary to block the boat or not. I heard a horror story about damaging the springs and tires by having the weight on them for the winter so I opted against it. The boat really is on the trailer and only additionally supported along the centerline by blocks.

Morgan
Pursuit Denali 2860 - SOLD

Homeport: Go to Top of Page

tugboat kevin

RO# 24998

Posted - Dec 07 2008 :  09:36:54  Show Profile  Reply with Quote
well you could always use redneck engineering and place a budweiser can (easy to obtain as the cooler on the swim platform is usually full) under the tongue on top of a block of wood if it crushes the can you gots to much tongue weight....: )


Homeport: oswego ny Go to Top of Page
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