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Old 28 September 2018, 12:21   #1
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Zodiac Futura Speed tube mod? Thundercat

I have a Futura w/max HP and I wish the round speed tubes would lift more. If you look at the ThunderCats the small tubes that are in contact with the water are flattened out with what looks like rubber molding. This creates far more lift I suspect.
The Futura's tubes seem to be the same size as the Thundercats but are round.
Has anyone tried this or if you have a thundercat talk about the bottom tubes construction. Futura tubes are about 6" round and 8' long. They taper forward blending into the main tubes about 2/3 from stern.
thx
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Old 28 September 2018, 15:53   #2
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The thundercat ones taper in slightly towards the bow as well. What pressure do you run in the futura? It makes a big difference on the thundercat, we run 12psi in the hijackers and 6psi in the tops. There is a bit of a flat on the bottom of the hijacker, its just very hard rubber

The biggest difference is the height of the hull from the bottom of the hijackers, the higher that is the more air goes beneath the deck and the more lift you get
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Old 28 September 2018, 22:57   #3
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Officially the futura gets 3.4psi. But my dealer says he puts 4+ psi in his. He says itís definitely faster but at 5.2 psi expect a rupture.
I gave it some thought today. I think if I fabricated two 5Ēwide, at rear, tapering towards the front polycarbonate sheet 1/4Ē thick with well radiusís edges. It would follow the speed tube taper. These can be slipped into the fabric pockets under the tubes. Then inflate the speed tubes. This would just be a test configuration to see what happens. This material is what bulletproof windows are made from. Far less brittle than acrylic sheet, it cannot crack!
If it improved things enough then figure out how to add the flat bottom permanently to my speed tubes. Mounting the rubber to the outside bottom of the tubes will be higher the the test version, providing more lift.
This will be a fun mod to test.
As far as height to catch air for lift. I think air can get squeezed under my boat, some. The bow curves up enough to get some amount of ďground effectsĒ. Just need more speed.
It just seems a shame that at 37 mph running solo the main tubes & hull skin are still in the water causing drag. Even if only 4í of it
In North America I donít think there any dealers of any brands of inflatable cats.
Iíve never even seen one in person.
The river I boat at would love those catamaran inflatable boats. Most of the boats are cats. 24í to 40í high performance ones. Iím the only inflatable except for sea-tow and the sheriffs boat.
-Lake Havasu-
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Old 29 September 2018, 10:59   #4
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Sounds like a cool idea, would make an interesting project for sure although definitely easier to buy a ready made one
There is a Ceasar dealer in the US I think, Ceasar Inflatable Boats, US - Home
Or contact Jacques directly via the south africa ceasar site, he's a nice guy easy to deal with. He'll ship anywhere and will probably work out cheaper than from the dealer
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Old 29 September 2018, 22:17   #5
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Ceaser inflatable boats is now only selling a fiberglass cat the same scale as the inflatable ones.
Thanks for the other lead.
The testing will be for next season. I’ll update test results then.
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Old 30 September 2018, 02:58   #6
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Looks further out than a zap-cat to me!!!
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Old 01 October 2018, 00:33   #7
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Originally Posted by maverick58 View Post
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Looks further out than a zap-cat to me!!!


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Old 25 October 2018, 13:49   #8
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Ceaser inflatable boats is now only selling a fiberglass cat the same scale as the inflatable ones.
Thanks for the other lead.
The testing will be for next season. Iíll update test results then.
I just re-read my reply I posted and it was written wrong. "Ceasarinflatable boats.us" no longer sells inflatable boats. But instead is manufacturing a 13' fiberglass version in Lake Havasu, Arizona, usa
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Old 16 July 2019, 13:11   #9
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I completed the Futura speed tube bottom flattening experiment.
First, specs on my boat.
2013 Futura MKll with a 60HP Evenrude Etec 2 stroke 19P Alu prop . Top speed before test 37 mph. Plane time about 5 sec. Top speed 20 sec?

Here are the results of the experiment.
The planning time was shorter by almost half. It felt like something lifted the transom right up. This was not expected at all and could be a big plus if you have a more modest engine and planing time is slow. The speed increase was only 1 mph. I am sure its due to the fact that after flattening the speed tubes they are even shorter and plenty of hull is still wet at planning speed. The main tubes were only 2" higher than the bottom of flat speed tubes and probably the same height as the keel. Lastly the boats stability at speed was diminished quite a bit. It's more twitchy, just not as stable going strait. Though the ability to slide when turning was fun to have back, I always enjoyed that feeling in my traditional hulled sibs in the past. Futura's do really hook tight turns.
My conclusion is for my boats setup the factory design is best, but the test was fun to try. If anyone has a MKll and is sporting around a 20 hp this mod could really make an improvement since the instability happens above 25-30mph. And time to plane was impressive.
The material used was 3/16" Polycarbonate (unbreakable). The finished parts were 6" shorter than actual speed tubes and 1" slimmer. If any Futura owners are close to me and want them PM me. (So Cal.) You just deflate and slip in, re-inflate.
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