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Old 11-30-2004, 03:35 PM   #15
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1968 17' Caravel
Battle Ground , Washington
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Don't you think the forces on the trailer in motion would be down forces? If you think about how the air will come over and around the truck, and then over the rounded shape of the trailer, I think the forces would be mostly downward. Not that that would excuse the need for a solid floor to frame connection.


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Old 11-30-2004, 03:54 PM   #16
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I think any coefficient of lift calculations would be very complex, due to the turbulence induced by the tow vehicle, and further complicated by the angle of attack due to various hitch heights.

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Old 11-30-2004, 08:39 PM   #17
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1973 31' Sovereign
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It is all so complicated...

Here is some food for thought:

I was wondering just how much load the body was applying to each foot of the bottom of the body channel. On my 31' AS I estimate that I have something like 65' of channel around the bottom of the body. So here is what that means:

Formula: body weight / 65' = lbs per lineal foot

if the whole body with its attachements weighs 1000 lbs this would work out to be 15lbs per lineal foot of channel. If the body and all of its attachements (windows, AC, wiring, etc.) weighs 2000lbs then it would be 30lbs per lineal foot. It is hard for me to believe that the body could weigh in at anything more than that (does anyone know for sure?). If I assume the 30lbs per lineal foot then that means that each outrigger end would be supporting 60lbs since the outriggers are on 24" centers. Since a lot of my floor is off I decided to try to get a feel for what an outrigger could support. With the body sitting on it I decided to see what would happen if I added my weight to it too. It was a good thing it did not break I guess. Of course I could not get my weight all the way out at the end but it did not have any trouble supporting my 230lbs and the body. That roughly means that just the outriggers can support at least 5 times the dead load of the body without any help from the floor.

So what kind of forces are needed to actually break an outrigger I wonder? I had one that was broken that was just in front of the wheel well on the curbside.

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Old 11-30-2004, 09:00 PM   #18
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Putnam , Connecticut
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I remember seeing somewhere that Wally claimed the trailers weigh less on the road because the aircraft wing shape created lift and took some of the load off the axel, making for better gas mileage and easy towing. He was some kind of marketing guy.

I do know that if I don't tie my canoe on the canoe trailer that it well "fly" off.

My point was in installing new floors one must consider that they need to take into account both forces. One pushing down and one pulling up. As I have been considering self tapping screws this has caused me the most concern. Try standing in the back of the truck holding a 4x4 sheet of plywood while your spouse picks up speed. The front of an AS is more like 50-64 square feet.

Is this one of those square of the increase deals. Twice as fast gives you four times the force? I think it is. That's alot of force at 60mph. Maybe that's why elevator bolts are needed. The hold the whole thing to the frame and keep it from flying away.
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Old 12-01-2004, 11:05 AM   #19
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Out riggers don't usually break.

But they can and do fatigue crack because of lack of proper running gear balance.

As in your case, the fatigue cracking takes place near the axles, because of the vibration.


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