>Flotation Chart

Flotation (or buoyancy) is critical in the design phase of your cat, so pay attention.

There are four sizes of PVC pipe that will work for a RebelCat 5:

8" - 21.75 lbs / foot

10" - 34 lbs / foot

12" - 49 lbs / foot

15" - 76.5 lbs / foot

Example: With two pontoons, each 10 feet long (total 20 feet of pipe):

8" x 20' = 435 lbs flotation

10" x 20' = 680 lbs flotation

12" x 20' = 979 lbs flotation

15" x 20' = 1530 lbs flotation

How to Use These Numbers

Formula: Add the weights of your boat, crew and cargo, then double it - that is the flotation you need. Why? Because you must have at least HALF of your total flotation out of the water.

Let's Try to Calculate Our Flotation and Pipe Length:

Boat Weight (RebelCat 5): approx 250 lbs
Crew Weight (two adults 150 lbs each) = 300 lbs
Cargo (camping gear, food, water) = 50 lbs

Total Weight = 600 lbs

Flotation Required: 1200 lbs (600 lbs x 2)

How do we create 1200 lbs flotation? We select a pipe diameter and length.

10" diameter x 18' (x 2) = 1224 lbs flotation (34 lbs/ft x 18' x 2 pontoons)
12" diameter x 13' (x 2) = 1274 lbs flotation (49 lbs/ft x 13' x 2 pontoons

Why Do I Have to Calculate Flotation? Doesn't the DVD tell me that?

No, because a RebelCat 5 can be made using PVC pipe 10" or 12" in diameter and in any length. Also, you have to decide your total weight, based on boat, crew and cargo.

My suggestions:
1. Build your cat with extra flotation. It is far better to have too much than too little. You might want to have a guest on board or carry more cargo. You may have to rescue someone. Strong wind will always try to push your leeward pontoon under water. In flotation, more is better.

2. Make your cat longer than 10' (not counting cones). The longer your pontoons, the more gentle your ride. Short boats have to go up and down over each chop and wave. Longer pontoons can ride on two or three chop waves at a time, keeping the boat almost level. If you like rodeo rides, go with short.

My RebelCat 5 is 10" pipe, 21' long, including cones aft. It rides like a Cadillac. (see video on the Home Page) Sure, it turns slower than a short cat, but I'm not usually in a hurry to turn on a dime. Your call.

If I were to make another RebelCat 5, I would use 12" pipe at about 17' long. That would give me plenty of flotation for three to four people and enough length for a gentle ride. The reason I used 10" pipe was because I could not find traffic cones 12" in diameter (someone has since informed me that the Home Depot in his city has them that large), and I wanted to use materials that most peopel could buy locally. So I made my RebelCat 5 as a demo for others.

My next RebelCat 5 would be made from 12" pipe, and I would either locate those 12" traffic cones or I would  heat-shape the aft end of the pontoons (similar to RebelCat 4 - see RebelCat Evolution here). Traffic cones may appear unprofessional or unusual, but the fact is they perform better than anything I have tried. They allow the water behind the cat to close with very little turbulence or wake, which means that little of the sails power is transformed into swirling water (which required energy). The video of RebelCat 5 sailing fast on the home page demonstrates how well traffic cones work.