Building gas cat

[Boris Mazor]

I'm busy to prepare for my winter project.

It will be a gas cat, made from aircraft grade plywood a little bigger than aeromarine cat. The project dimensions are: 48 x 20". Closed cockpit. Full mod Zenoah 260.

Did anybody have plans for cat this size?

What is center of gravity, % of length from the transom?

Thanks. Boris

 

[Ian Webster]

Plan from Holland here, Maxcat

Build thread (one of a few) here

Ready cut frames available from RBC Kits

It is slightly larger than you are after at 1450mm (57") but you could scale the plans down.

 

[Ron Olson]

Boris, with a full-mod Zen I'd put the CG close to 33% forward of the transom.

 

[Boris Mazor]

Boris, with a full-mod Zen I'd put the CG close to 33% forward of the transom.

Thanks, Ron! Usually I keep 31 to 35% on all my projects. Boris

 

[jeff baham]

here you go scratchbuilt cat 43'' long and a 8" tunnel 260 zen is 14 1/4" from transom, 11 1/2lbs less fuel.

 

[Boris Mazor]

here you go scratchbuilt cat 43'' long and a 8" tunnel 260 zen is 14 1/4" from transom, 11 1/2lbs less fuel.

Hi, Jeff! It is good idea to use whiplash cowling on cat. Do you have plans for this boat? How fast it run, and how stable?

Thanks. Boris

 

[jeff baham]

here you go scratchbuilt cat 43'' long and a 8" tunnel 260 zen is 14 1/4" from transom, 11 1/2lbs less fuel.

Hi, Jeff! It is good idea to use whiplash cowling on cat. Do you have plans for this boat? How fast it run, and how stable?

Thanks. Boris

no plans, just out of my head, as of now don;t know the speed, it is flying in the back strait ,plus i have murphy law under my tent, first weekend had radio problem, found out it was the receiver, second weekend my hard tank problems, need pressure for it to work, went to gas bag,it gave me trouble, found out that the bag was slideing under motor and kinking the line, install bag holder, third weekend adjusted strut to keep from flying in back strait, then lossed the screw for the throttle, so in the next weekend or two i'll try agian.

 

[jeff baham]

here you go scratchbuilt cat 43'' long and a 8" tunnel 260 zen is 14 1/4" from transom, 11 1/2lbs less fuel.

Hi, Jeff! It is good idea to use whiplash cowling on cat. Do you have plans for this boat? How fast it run, and how stable?

Thanks. Boris

forgot to add yes it is a whiplash cowl, and the hull is wood over foam lot of cutting and sanding.

 

[gary cuppels]

Boris, with a full-mod Zen I'd put the CG close to 33% forward of the transom.

Ron: How do you measure % are you taking the loa at 100% fwd Of the transom an example would be for a 60"loa hull the distance from the transom to the spark plug should be 20". If I am right about this how do you know what % to use?

 

[jeff baham]

gary, measure the length of hull, from transom to front of hull and divide by 3. this is great for monos and catamaran hull, hydroplanes and outrigger is determined by the center of gravity.

 

[Boris Mazor]

Boris, with a full-mod Zen I'd put the CG close to 33% forward of the transom.

Ron: How do you measure % are you taking the loa at 100% fwd Of the transom an example would be for a 60"loa hull the distance from the transom to the spark plug should be 20". If I am right about this how do you know what % to use?

Usually spark plug position is close to CG, but position of spark plug and CG is not the same!!!!!

You have to find CG by balancing the ready to run boat on the piece of wood .5 inch wide. It is not so hard for cat.

The middle of this plank very close to CG.

Now measure distance from transom to CG, divide for the length of hull, multiply by 100 and you got %CG.

If it is different from you goal add weight to front or to transom to correct. My two penny. Boris

 

[Ron Olson]

Boris hit it. You can't simply just figure that the CG is going to be at the spark/glow plug. The weight of all of the radio gear, transom hardware and exhaust system can vary a lot which can throw everything off.

 

[gary cuppels]

Boris hit it. You can't simply just figure that the CG is going to be at the spark/glow plug. The weight of all of the radio gear, transom hardware and exhaust system can vary a lot which can throw everything off.

Ron: so if I find the c/g all out and have the boat balanced that is all there is? simply move stuff around till the boat balances at the point jeff thru out using my 60" example the c/g should be set so the boat balances at a point 20' from the transom.

 

[Ron Olson]

What the gas boaters are doing and if you have the room to play with it is to move the radio box around if you already have the engine in place. This helps to keep it more "lead-free" so you don't have to add weight to the nose. I don't mind having to move the engine back once the boat has been run but moving it forward is harder to do as you can make the flex cable shorter. Some do use the center of the engine as a locating point reference but things I mentioned in the above posting will have a factor. I recently had a mono hull that was set up at the prefered amount of inches as far as location went but the boat rode extremely wet. I had ot move the engine back 1-1/2" to get it to run looser.

 

[Boris Mazor]

Plan from Holland here, Maxcat

Build thread (one of a few) here

Ready cut frames available from RBC Kits

It is slightly larger than you are after at 1450mm (57") but you could scale the plans down.

Hi, Jan! Your advise is priceless!I have download MaxCat and print it. I made full size test frame to see how will I like it and decide to make some changes.

I scale plans to 48" long and made center part 8.5" wide. Now all stuff will fit in the center part, like I did in all my DEEP-V mono. I put riding skin (1/16" plywood) and will mount motor, radio box and IV bag.

 

[Boris Mazor]

Plan from Holland here, Maxcat

Build thread (one of a few) here

Ready cut frames available from RBC Kits

It is slightly larger than you are after at 1450mm (57") but you could scale the plans down.

Hi, Jan! Your advise is priceless!I have download MaxCat and print it. I made full size test frame to see how will I like it and decide to make some changes.

I scale plans to 48" long and made center part 8.5" wide. Now all stuff will fit in the center part, like I did in all my DEEP-V mono. I put riding skin (1/16" plywood) and will mount motor, radio box and IV bag.

It is more progress on my cat:

I made a heated room 2"x 1.5"x60" with electric heater and can work now in any weather condition.

I skinned bottom of sponsons and center part. Protect the entire assembly with West Coat Epoxy. All hardware, engine, IV bag and radio box are installed for test fit. Boat is ready to skin the top. I hope to put it in water about 2 week later.

 

[Ian Webster]

Happy you found it useful Boris. You seem to be getting along nicely with the build. One of the beauties of building from plans is the ability to adjust the boat to what you want.

Is that a RCMK you are using?

 

[Boris Mazor]

Yes, this is RCMK-254 EVO.

If you dont ming shoot me your e-mail address. Thanks. Boris.

[email protected].

 

[Ian Webster]

If you dont ming......

Don't think I "ming" You have mail.

 

[Boris Mazor]

A few more pictures of my cat. Now I'm ready to finishing. Finally I found

the way to make good looking canopy with less trouble. Boris