So today we raised the trailer frame under the boat and started
to figure out where the axels should be to get optimum tongue
weight. Here's some of what we found / figured:

We figure the boat will be about 3800 lbs and the trailer about
1400. So that's 5200. Most people and books recommend 7%
to 10% tongue weight, so that's 365 to 520 lbs. The truck
we have is rated for 500 lb tongue weight. So we were shooting
for 400 or 450 lbs.

The boat is 22 feet. The side rails of our trailer come together
at the tongue at about 23.5 feet. And we have 6.5 feet more of
tongue there, deciding where to cut it off.

So we placed some blocks at 5' from the back of the
trailer and we setup the scale at a point that would
give us 3' of tongue. The weight was 680 lbs.

Blocks= 5' Tongue= 3' Weight= 680

Then we did this:

Blocks= 5' Tongue= 4' Weight= 680
Blocks= 6' Tongue= 4' Weight= 600
Blocks= 7' Tongue= 3' Weight= 480

So you can see that the leverage of a longer tongue
gave us almost NO change. But moving out blocks
(axel point) up change things pretty dramatically.


Now our gas tank is right at the back of the boat. For the
above measures the tank was mostly empty (maybe 5 gallons)
so I decided to sit back there to simulate some gas. (Some
might think that's an appropriate use for me.) Anyway, my
170 or so lbs didn't change the tongue weight at all. Maybe
a pound or two, but nothing we could really notice. Hmmmm.

Now that we were zeroing in on our target weight we set our
spare tire plus a 50 lb concrete block up near the tongue
area. That's where the spare will really go and the concrete
was to simulate the jack, bow-stop post, and winch that
will eventually go there.

So with everything in place we got these numbers:
Blocks= 7' Tongue= 3' Weight= 540
Blocks= 7' 2" Tongue= 3' Weight= 480


Now that's what we wanted. 480 is a pretty good number. We have to add
16 lbs to that for the actuator, but can also subtract 3.5' worth of tongue
that we can cut off. The tongue material is 9.4 lbs/foot so that's 33 less
lbs. Anyway, 33lbs - 16lbs = about 17 lbs. ~ So our 480 number should
end up being more like 465 lbs.

Ok, so I've been all exact here and, of course, things will change. We
don't
have the final bunks on the trailer, the concrete block to represent the
jack and stuff was just a guess, etc. But generally, I think we found
our axel point: 7' 2".

Actually, I'm thinking maybe trying 7'3" tomorrow. I don't want too little
weight on the tongue, but I'd rather have just a slightly larger margin to
play with in case something is wrong.

Ok, any one that's read this far is obviously bored...

On Mon, 26 Jan 2004 00:59:40 -0500, "Gary Warner"
wrote:


So today we raised the trailer frame under the boat and started
to figure out where the axels should be to get optimum tongue
weight. Here's some of what we found / figured:

We figure the boat will be about 3800 lbs and the trailer about
1400. So that's 5200. Most people and books recommend 7%
to 10% tongue weight, so that's 365 to 520 lbs. The truck
we have is rated for 500 lb tongue weight. So we were shooting
for 400 or 450 lbs.

The boat is 22 feet. The side rails of our trailer come together
at the tongue at about 23.5 feet. And we have 6.5 feet more of
tongue there, deciding where to cut it off.

So we placed some blocks at 5' from the back of the
trailer and we setup the scale at a point that would
give us 3' of tongue. The weight was 680 lbs.

Blocks= 5' Tongue= 3' Weight= 680

Then we did this:

Blocks= 5' Tongue= 4' Weight= 680
Blocks= 6' Tongue= 4' Weight= 600
Blocks= 7' Tongue= 3' Weight= 480

So you can see that the leverage of a longer tongue
gave us almost NO change. But moving out blocks
(axel point) up change things pretty dramatically.


Now our gas tank is right at the back of the boat. For the
above measures the tank was mostly empty (maybe 5 gallons)
so I decided to sit back there to simulate some gas. (Some
might think that's an appropriate use for me.) Anyway, my
170 or so lbs didn't change the tongue weight at all. Maybe
a pound or two, but nothing we could really notice. Hmmmm.

Now that we were zeroing in on our target weight we set our
spare tire plus a 50 lb concrete block up near the tongue
area. That's where the spare will really go and the concrete
was to simulate the jack, bow-stop post, and winch that
will eventually go there.

So with everything in place we got these numbers:
Blocks= 7' Tongue= 3' Weight= 540
Blocks= 7' 2" Tongue= 3' Weight= 480


Now that's what we wanted. 480 is a pretty good number. We have to add
16 lbs to that for the actuator, but can also subtract 3.5' worth of tongue
that we can cut off. The tongue material is 9.4 lbs/foot so that's 33 less
lbs. Anyway, 33lbs - 16lbs = about 17 lbs. ~ So our 480 number should
end up being more like 465 lbs.

Ok, so I've been all exact here and, of course, things will change. We
don't
have the final bunks on the trailer, the concrete block to represent the
jack and stuff was just a guess, etc. But generally, I think we found
our axel point: 7' 2".

Actually, I'm thinking maybe trying 7'3" tomorrow. I don't want too little
weight on the tongue, but I'd rather have just a slightly larger margin to
play with in case something is wrong.

Ok, any one that's read this far is obviously bored...

Actually, no - that's some pretty fair "kentucky windage" type
engineering.

Is there anyway you can manage to borrow a set of truck scales to
measure the weights?

Later,

Tom
S. Woodstock, CT
----------
The years will bring their Anodyne,
But I shall never quite forget,
The fish that I had counted mine
And lost before they reached the net.

Colin Ellis, "The Devot Angler" quoted
in A. R. Macdougall, Jr's "The Trout
Fisherman's Bedside Book" (1963)

"Short Wave Sportfishing" :


Actually, no - that's some pretty fair "kentucky windage" type
engineering.

Is there anyway you can manage to borrow a set of truck scales to
measure the weights?


Well, we did take the boat to the truck scales before we did the
restoration.
That's how I figure it's about 3800 lbs. Things might have thanged a little
from the work we've done. But things might also changine a little depending
on how she's loaded with gear at any time. We're just looking for a range.

We surely will take the trailer to a sacles when she's done. But it's kind
of chicken/egg situation because we need the wheels on to do that.

Anyway, I think the estimates of weight are pretty close.

Thanks for reading.

Why not mount your springs and shackles on pieces of angle iron so that you
can move the axle back and forth till you find the sweet spot. Many trailers
are set up that way.
Jim
"Gary Warner" wrote in message
...

So today we raised the trailer frame under the boat and started
to figure out where the axels should be to get optimum tongue
weight. Here's some of what we found / figured:

We figure the boat will be about 3800 lbs and the trailer about
1400. So that's 5200. Most people and books recommend 7%
to 10% tongue weight, so that's 365 to 520 lbs. The truck
we have is rated for 500 lb tongue weight. So we were shooting
for 400 or 450 lbs.

The boat is 22 feet. The side rails of our trailer come together
at the tongue at about 23.5 feet. And we have 6.5 feet more of
tongue there, deciding where to cut it off.

So we placed some blocks at 5' from the back of the
trailer and we setup the scale at a point that would
give us 3' of tongue. The weight was 680 lbs.

Blocks= 5' Tongue= 3' Weight= 680

Then we did this:

Blocks= 5' Tongue= 4' Weight= 680
Blocks= 6' Tongue= 4' Weight= 600
Blocks= 7' Tongue= 3' Weight= 480

So you can see that the leverage of a longer tongue
gave us almost NO change. But moving out blocks
(axel point) up change things pretty dramatically.


Now our gas tank is right at the back of the boat. For the
above measures the tank was mostly empty (maybe 5 gallons)
so I decided to sit back there to simulate some gas. (Some
might think that's an appropriate use for me.) Anyway, my
170 or so lbs didn't change the tongue weight at all. Maybe
a pound or two, but nothing we could really notice. Hmmmm.

Now that we were zeroing in on our target weight we set our
spare tire plus a 50 lb concrete block up near the tongue
area. That's where the spare will really go and the concrete
was to simulate the jack, bow-stop post, and winch that
will eventually go there.

So with everything in place we got these numbers:
Blocks= 7' Tongue= 3' Weight= 540
Blocks= 7' 2" Tongue= 3' Weight= 480


Now that's what we wanted. 480 is a pretty good number. We have to add
16 lbs to that for the actuator, but can also subtract 3.5' worth of
tongue
that we can cut off. The tongue material is 9.4 lbs/foot so that's 33
less
lbs. Anyway, 33lbs - 16lbs = about 17 lbs. ~ So our 480 number should
end up being more like 465 lbs.

Ok, so I've been all exact here and, of course, things will change. We
don't
have the final bunks on the trailer, the concrete block to represent the
jack and stuff was just a guess, etc. But generally, I think we found
our axel point: 7' 2".

Actually, I'm thinking maybe trying 7'3" tomorrow. I don't want too
little
weight on the tongue, but I'd rather have just a slightly larger margin to
play with in case something is wrong.

Ok, any one that's read this far is obviously bored...

".JIMinMA." :

Why not mount your springs and shackles on pieces of angle iron so that
you
can move the axle back and forth till you find the sweet spot. Many
trailers
are set up that way.
Jim

What we have is a torsion axel (no springs, just a straight steel tube with
all
the suspension on the inside). That axel comes with brackets the is bolts
to.
The bracket is supposed to be welded to the traier. Though, as you
suggested,
the bracket could probably be bolted. ~ It's not a bad idea. It would
also
make the trailer more adaptable to other loads/boats. It really is a good
idea. But we decided to make a custom trailer just for this boat. With all
the work we've put in this boat, I don't think we plan on selling her
anytime
soon (or making any major weight changing modifications to her). So welding
it on in place is OK.

But I do get your point - and thanks for suggesting it.

On Mon, 26 Jan 2004 13:27:23 -0500, "Gary Warner"
wrote:
The bracket is supposed to be welded to the traier. Though, as you
suggested,
the bracket could probably be bolted. ~ It's not a bad idea.

==========================================
I would go with bolts, at least for the first iteration. Until you
actually get the boat on the trailer, measure the actual tongue
weight, AND take it for a test ride at highway speed, you won't know
for sure that you've got the right configuration. It's also a good
idea to leave room for the forward post to be adjusted fore and aft
because that's an easier way to make the final adjustments on tongue
weight.

"Gary Warner" wrote in message
...

Blocks= 5' Tongue= 4' Weight= 680
Blocks= 6' Tongue= 4' Weight= 600
Blocks= 7' Tongue= 3' Weight= 480

So you can see that the leverage of a longer tongue
gave us almost NO change. But moving out blocks
(axel point) up change things pretty dramatically.


Hey, we had a major discussion (argument) that predicted this outcome a
couple of months ago!

Anyway, my 170 or so lbs didn't change the tongue weight at all.

How far behind the blocks were you sitting?

I am not sure I have the geometry right: Blocks are 7' forward of the very
back. The base frame is 23.5 feet long, so there is 23.5 - 7 = 16.5 feet of
frame ahead of the blocks. The tongue extends 3 feet beyond that, or a
total of 19.5 feet

If you were sitting at the very, very back, then your weight would create a
moment about the blocks of 7' x 170 lbs = 1190 ft-lbs. Due to its
leverage, the tongue will see this as 1190/19.5 = 61 pounds.

I would have expected that you would notice that. If you weren't all the
way to the back, or you did this when the blocks were farther back, then the
difference would be much less.

Another issue you should be aware of is the size of your blocks. If your
block is a 12"x12" you could be introducing a significant error in your
measurements. As the trailer flexes and the scale depresses the trailer
frame will rock forward on the blocks, which can shift the contact point on
the block to the forward edge, effectively moving the pivot point forward up
to 12 inches. This would make a huge difference.

A better way would be to place a piece of pipe between the blocks and
trailer frame so that the contact point is well defined and the block itself
is not creating any moment in the frame. You may want to place a piece of
heavy steel between the pipe and trailer frame so that the pipe doesn't dent
the frame (center the piece of steel so that it is roughly balanced and it
won't effect the measurements).

Rod

"Rod McInnis" wrote:


Anyway, my 170 or so lbs didn't change the tongue weight at all.

How far behind the blocks were you sitting?


I was sitting on the transom of the boat which is directly over the
farthest back part of the trailer. Maybe MY center of gravity was
in 6" or 8" or however big half my ass is? The blocks were at 7'


I am not sure I have the geometry right: Blocks are 7' forward of the
very
back. The base frame is 23.5 feet long, so there is 23.5 - 7 = 16.5 feet
of
frame ahead of the blocks. The tongue extends 3 feet beyond that, or a
total of 19.5 feet


Yes, that's it.


If you were sitting at the very, very back, then your weight would create
a
moment about the blocks of 7' x 170 lbs = 1190 ft-lbs. Due to its
leverage, the tongue will see this as 1190/19.5 = 61 pounds.

I would have expected that you would notice that. If you weren't all the
way to the back, or you did this when the blocks were farther back, then
the
difference would be much less.


I was all the way at the back, maybe in 6 or 8" or so. I'm also 90% certain
we
did this test when the blocks were at 7'. But everything is still there in
the shop
so I think I'll go down there tomorrow and double check because I too was
surpried that my weight didn't have any effect.


Another issue you should be aware of is the size of your blocks. If your
block is a 12"x12" you could be introducing a significant error in your
measurements. As the trailer flexes and the scale depresses the trailer
frame will rock forward on the blocks, which can shift the contact point
on
the block to the forward edge, effectively moving the pivot point forward
up
to 12 inches. This would make a huge difference.


Yes, the size of the blocks was about 7". I can see what you mean and think
I'll try it again. The axle that goes across (well, I guess we've
determined that
shouldn't really be called the axle - but I don't know what to call it)
ANYWAY
that tube is about 3" or so wide. So it seems to me using a 3" block would
be
about the same thing.


Rod,

Thanks VERY much for the comments and taking your time. I think some others
here know as much, but the way you explain it - and some of your
suggestions -
make sense to me.

Gary