Lighter Weight JAE 21

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BobBonahoom

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Mar 6, 2009
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494
We recently attempted to build a lighter JAE 21, but have not been able to test it since the water got hard here. I wanted to build a light boat but still be able to paint it with PPG Concept single stage car paint even though that adds a few ounces of weight.

It came out fairly good at 3.40 lbs, with everything but fuel. We used a GT kit because I really like how easily it goes together with the laser cut and notched parts, but we think the G2 geometry has some advantages. So we cut the bait box off the GT, used the Tommy David mods on the front sponsons, and made the ski a little wider at 1-1/4". I have had very good success with a strutless 0.062" wire drive setup in my 12 JAE, so I set the 21 up with a strutless 0.078" wire drive and ball bearings. Its using small high voltage servos from Pro Modeler and a high voltage Futaba S-Bus receiver. That allows use of a small and light 200 mahr LiPo RX battery with no voltage regulators.

A 3.0 lb 21 hydro still eludes us, but we are getting closer! Of course getting it too light may create a whole new set of handling problems on the course.
 

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BobBonahoom

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Mar 6, 2009
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494
Good question. Not sure how to do that. Is it lighter than 1/16", 1/32" and 1/64" wood?

Let's hear from others on how to do that and where you get the materials, thickness, areal densities of the carbon fiber, etc. compared to wood, etc.
 

KenOlvis

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Oct 10, 2014
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20191202_200220.jpg

Use both carbon fiber an wood!!
.21 size hull less than 3lbs is very do able base on the info I'm getting for my Glen Quarles Twin Texan .12 glen told me its is .21 size boat just wider for the twin .12
 

Richard Dahlheimer

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Jan 30, 2005
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1,011
Hello Bob, i like your build. I have the same motor, just heat cycled and the wind came up so never ran it. I hope to see your new hydro next season. Richard
 

Lay26

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Dec 11, 2003
Messages
994
thats a pretty light build.....i was watching some artists on YouTube got alot of ideas on how to approach this.
 

BobBonahoom

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Mar 6, 2009
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494
Bob i see some work on the cooling fins and are you running 3ed channel?
Butch,
Yes, I milled some off the fins on both sides and between the mounting holes to take out a little weight. The engines are running too cold anyway.

I'm going away from 3rd channel needles on my smaller boats. I just set it by ear and its usually right where I want it. The 3rd channel just tempts me to go to lean, adds weight and more stuff that's heavy and can fail. I'm probably the only one who thinks that way about 3rd channel needles, just old school I guess.
 

brad nichols

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May 10, 2010
Messages
2,490
I have built a couple of boats out of carbon sheet with an end grain balsa core as the tub sides and bottom and top sheet was ply. One had an OPS 90 and ran very well until it lost it's life, running at speed a dog distracted the driver. His 67 powered boat is very fast, boats are the JAE 90-101. They say you should not bend the cloth at 90 degrees because it breaks the fibres.

Brad
 
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