.15 Nitro Aggressor 23" Cat

[Hammerhead]

Re:Hull Ideas for Nitro .12 Cat

What do you think the results would be if you cut the sponsons like this?

 

[Eric Perez]

Re:Hull Ideas for Nitro .12 Cat

But if I do that then it would be a Hammer Cut I wanted to try this idea first, then convert to a Hammer Cut and see what the differences are. This is R&D on a budget - Eric style!

The flat portion near the front of the cut was left there to try and keep the front end from hooking when the CG is moved forward for rough water running.

As I mentioned before, the spoons on the larger cat will not be finished until I get some data back from the test mule.

You know this new cat is large enough for a 21. Just need to find the sweet spot on the CG for it.

On the question on the CAT dims:

The Nitro Aggressor 19 was built with a 2:1 ratio. The length of the sponsons are exactly double of the boats width.

The Nitro Aggressor 23A is more like 2.2:1 . A longer hull, with more tunnel area and with thinner sponsons. The CG of the new boat will be more toward the front than the old one. The plan is to make more lift in the tunnel and reduce the wetted area to allow the boat to run in rougher water.

My boats run quite flat as a result of the tunnel design.

 

[_laxmasta2039]

Re:Hull Ideas for Nitro .12 Cat

hammer,

what's an REX .21 like?

.049....jeez, what would you use for a driveshaft?? i've got some plastic .9 nitro props, let me know if you end up doing that and i'll send 'em to you, you might be suprised.

eric,

ya, i went back and looked at it again, it must be the camera angle. what engine are you using? i still kinda want to give a small nitro cat a try, just matt and i got fed up trying to make light, sturdy, true sponsons after the third try, i've got a perfectly nice tub lying around.

you might want to try putting the engine as close to the transom as possible while still leaving room for a radio box, then you can easily move the fuel tank farther forwards or back to find the right CG. just a thought.

Joe

 

[GTR]

Re:Hull Ideas for Nitro .12 Cat

Hi Lax,

A REX 21 is an awesome motor made by Nova Rossi under a different design team - 7 port liner and slightly different crankcase from the others.

Nova, TOP & REX all top Nova Rossi designs. There are off course others like JP, Mugen & Serpent Mega motors also. All have a slightly different approach to the same overall outcome - arguably the most powerful 21s around. I'm a fan.

GT ;D

 

[_laxmasta2039]

Re:Hull Ideas for Nitro .12 Cat

sounds awesome!!

hammer, is that engine for sale? [i did notice you mentioned it at the same time as the OS .21s, crossing my fingers here] :

Joe

 

[Eric Perez]

Re:Hull Ideas for Nitro .12 Cat

Lax the reason for the bowing sponsons is that the thin foam pieces don't have enough support when you start installing the skins. The longer the parts the worst. What I'm going to do to address the bowing is to install a graphite arrow shaft inside the foam to keep the bow down to a minum.

 

[Hammerhead]

Re:Hull Ideas for Nitro .12 Cat

Sorry Lax! Not for sale. Can't get the short stroke version anymore. I can get parts, so I want to hang on to it. If you wanna long stroke, I can get you one new and shipped for about 270 dollars. I think the long stroke is a dog compared to the short stroke. I'm not sure that the 13mm stroke is the problem. It might be other issues such as the porting configuration. I know that the REX here in Japan is made exclusively for boats. By the way, The REX short stroke holds the .21 oval record here. The are great engines if you get a good one. They do have a pretty bad hit and miss factor like the old Picco P5s did.

Hammer

 

[_laxmasta2039]

Re:Hull Ideas for Nitro .12 Cat

oh, darn. it'll probably be better to get a more common .21 racing engine anyway because i can easily get parts, advice, etc.

eric,

what are you thinking about as far as what's gonna go where in the cat? what's a good starting point for CG in a cat?

Joe

 

[Hammerhead]

Re:Hull Ideas for Nitro .12 Cat

Here you go Lax! If you want it, send 50 bucks to Ron Olson, when he says he's got it, I will send you the Engine. I thought about it, and I decided to buy a VX-M

This engine still runs good. It comes with an O.S 4E carb, and flywheel. The bearings for the RX-M or other O.S .21s will fit in it, if you feel you need to change them in the future.

Hammer

 

[Hammerhead]

Re:Hull Ideas for Nitro .12 Cat

Hey Eric! Sorry to hijack your thread to sell my stuff

Hammer

 

[nitro junky]

Re:Hull Ideas for Nitro .12 Cat

you can order longer ply from balsausa.com

 

[Hammerhead]

Re:Hull Ideas for Nitro .12 Cat

Hey lax! Look at Pg.2

Hammer

 

[Hammerhead]

Re:Hull Ideas for Nitro .12 Cat

This is the current .21 oval record holder in Japan. As you can see it has a short stroke REX350 in it. It is the round water jacket version though. The one I have is square.

Hammer

 

[_laxmasta2039]

Re:Hull Ideas for Nitro .12 Cat

looks sweet,

is that one of those german EVO riggers?

btw,

i replied to your email! '

Joe

 

[Hammerhead]

Re:Hull Ideas for Nitro .12 Cat

Nope! This boat is was made by the driver. Dr. Otagaki.

It is made from scratch. All wood.

Hammer

 

[Eric Perez]

Re:Hull Ideas for Nitro .12 Cat

oh, darn. it'll probably be better to get a more common .21 racing engine anyway because i can easily get parts, advice, etc.

eric,

what are you thinking about as far as what's gonna go where in the cat? what's a good starting point for CG in a cat?

Joe

A good starting point is 32% of the length of the boat [starting from the transom] This way you can add lead under the canopy to balance the hull to the wind conditions. This # will depend on the amount of tunnel lift, the weight of the boat and the angle of the strut. I like running the bottom of the strut even with the bottom of the sponsons. This is the way I start the initial runs.

On the new cat the engine rail will be 2" appart. They will run the entire length of the engine bay. everything will get put on the boat except the engine. I then put the center of the fuel tanks at the 32% mark and move the engine back and forth until the hull balances at the 32% point.

Note: engine will not be mounted on the rails like the original CAD drawings. I will bolt the engine down using an RC car mount through the bottom of the tunnel. The flywheel will sit below the floor of the tunnel. Just like the Nitro Aggressor 19 hull.

I will start the project with a Modified TRX 15-Pro and will eventually change it out for the new Traxxas 2.5 engine -when I get a new flex-hex that will fit the IPS shaft.

I will use the same layout as in the picture. I will probably start the new boat with the CG at 35% so I expect the engine to be a little more toward the front.

 

[Eric Perez]

Re:Hull Ideas for Nitro .12 Cat

Finally I was able to cut loose at the pond with Nitro Aggressor CAT. Worked on the pipe and lowered the head clearance on the engine. Now I can get the engine to "turn on" at a lower head temp.

Still running X432 with a .12 engine. The prop looks super small compared to the S215 that I run on my .12 rigger, but the hulls and the engines are very different.

The day was real windy, the water was not too bad. I moved the CG forward, now it's 6 1/2" from the transom. The boat flies nice and level not a single blow-over...but still had to work the throttle.

With the CG at 35% the boat runs good and it's predictable in the straights.

Tried the Y535 even with the pipe slid away from the coupler but the engine had a hard time staying on the pipe all the time. I will do an engine swap this Sunday and see what can be done with a little more power...

Still looks like I can reduce the rear sponson width, I will remove 1/4 to the rear, so it will go from 1-1/4" to 1".

 

[Eric Perez]

Re:Hull Ideas for Nitro .12 Cat

More build pics

 

[Eric Perez]

Re:Hull Ideas for Nitro .12 Cat

More build pics

Hardware is placed up-side down for CG checks before the engine mount is bolted in place.

Note: 6-sided sponsons are tapped to hull

 

[Eric Perez]

.15 Nitro Aggressor 23A CAT

Here are more pics of the power-plant a Traxxas TRX2.5 with flywheel and the 5mm smooth-bore .130 flex hex adapter.

I've also made a small bell-crank mechanism from a Hi-Tech servo horn to work the slide carb.