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that is for an circumference going from 24 to 25.

For diameter you would get....about 8% ha ha.

so a 1500lb capacity goes to 1620 lbs. Not that much unless you are right on the edge of capacity.
 

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LOL!

Actually you'd want area (pi * r * r) since the length is the same for the volume calculation)...

= 1962.5/1808.6 = about 10.5% more volume
 

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Discussion Starter #5
So Sotar told me that their recommended load capacity of the 16' X 25" tubes is 975lbs. Seems a little light. Thoughts?
 

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So Sotar told me that their recommended load capacity of the 16' X 25" tubes is 975lbs. Seems a little light. Thoughts?
I think my Maravia 14 X 24 is 980 lb.if I remember right.
All that math makes my head hurt ;)
 

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that is for an circumference going from 24 to 25.

For diameter you would get....about 8% ha ha.

so a 1500lb capacity goes to 1620 lbs. Not that much unless you are right on the edge of capacity.
Tubes Are not spec'd in circumference. If so, 25" would be a circus clown balloon

The diam changes by 4%, not 8. Volume is a rough function of cross sectional area, so your area would increase by 1.04^2 or 8% more volume in the completely cylindrical part of the tube

If Sotar says less than 1000lb then I would believe them. If there is a lot of rocker then you will have a short waterline, maybe 9 or 10'. People think you can load up a cat but I wouldn't knowingly exceed 1200lb on my leopard and that has 18x26.5 tubes

Mostly cause I don't want to put my self in a situation where I can't maneuver it and have to figure out how to unpin the boat
 

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Which Sotar design? I went from a 19" to 23"x 14' Sotar ST this year- Big difference, but maybe not quite as much as I originally thought it would be. I wouldn't think you'd notice a difference between the two-
 

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Which Sotar design? I went from a 19" to 23"x 14' Sotar ST this year- Big difference, but maybe not quite as much as I originally thought it would be. I wouldn't think you'd notice a difference between the two-
That's a 46% increase in cross sectional area

Like going from 24 to 29"
 

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So Sotar told me that their recommended load capacity of the 16' X 25" tubes is 975lbs. Seems a little light. Thoughts?
I think my Maravia 14 X 24 is 980 lb.if I remember right.
All that math makes my head hurt ;)
That's what I was telling you about weight ratings. Maravia gives "max optimal" weight ratings, allowing for 1/3 of the tube to be submersed. If you take 15-20% of that weight off it'll perform like Papushka the dancing bear!
And that likely gets you into the weight range that Sotar is recommending.

As for diameter, BackwardsRaft, the design of the tubes plays a huge role too. NRS or AIRE Lion tubes are also 25" and carry a lot more weight because they are full diameter for much more of the length and have a longer water line to support the weight. They just won't be as sporty, even loaded lightly.
 

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draft vs load for Jacks cats

I would like to jump into this conversation.

Because of our proximity to major multiday river expedition opportunities like the Grand Canyon, and Smaller more technical stuff like the Upper Animas, We decided that long straight water line was more important than a rockered design. That has shifted slightly with the introduction of the Royal flush that has a more rockered section on the ends, but still has a bit more capacity than a daddy cat with a heavy load. We were trying to provide a good all around boat for these two extremes. Keeping in mind that cargo takes priority over empty performance, because the majority of our customers purchase these two boats for multi day trips. That being said, have a look at draft VS load for some of our most popular cataraft tube models.

The idea is that the weight is evenly balanced so the tubes sink evenly in the water, and the inch measurement on the left is determined by the weight that each boat can carry, in the particular column.

We did this to help our customers make informed choices on which boat to purchase. The Royal flush has become our best over all multi day cataraft, that is still nimble enough to do something like the upper Animas.
 

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Thank you very much for this "unsolicited testimonial"

Now with that said, I want to show you what AAA inflatables in Denver is having us build. There is a urethane double bottom placed on these tubes by AAA, so it is a co-op effort. The baffle is off set, but we have a large cone shaped baffle that allows the baffle to expand into the larger chamber if necessary. Our all time most popular design, the Daddy cat has had an offset baffle since it was brought out in 1988.
 

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I forgot to mention that it is a 24.5 inch diameter tube.

I do not have the capacity figured out for this, but the system we use to do this is to use our design software to determine the buoyancy or weight of the water displaced when the boat sinks a certain distance into the water.
 
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