Slow build - 8S Twin Cat

[photohoward1]

Hopefully we can get together this year larry. I have competition for you!

Hello Alain
I am not sure what OFNI is,
But yes 2 X 56106 TP motors, 1,066m Cat, 8S- 6000 mHa per motor.
This is for racing in IMPBA S+T or Open Cat, or Open Hydro classes.

Larry

[Alfa Spirit]

Hello Alain
I am not sure what OFNI is,
But yes 2 X 56106 TP motors, 1,066m Cat, 8S- 6000 mHa per motor.
This is for racing in IMPBA S+T or Open Cat, or Open Hydro classes.

Larry

In english OFNI is "unidentified floating object" ...

[TRUCKPULL]

In english OFNI is "unidentified floating object" ...

Larry

[TRUCKPULL]

Hopefully we can get together this year larry. I have competition for you!

Howard
It will be fun. What you got?

Larry

[jaike5]

Photohoward1, ....how about a photo, Howard !!
J.

[photohoward1]

Big Singles.....

Howard
It will be fun. What you got?

Larry

[TRUCKPULL]

Big Singles.....

Three or four big singles in one boat?

[TRUCKPULL]

Well I got my package from OSE this morning.

In the mean time I have been busy, I filled all the holes on the hull. A crack in the joint on the
inside of both sponsons, The window area was damaged by a flip at over 70 MPH three years ago.
I reinforced it with Carbon Fiber, sanded it all down,, applied Epoxy with Micro Balloons.
Then sanded - sanded - and sanded again. then wet sanded the hole thing.
I also installed two hatch locks at the rear of the hatch.
It is now ready for primer.
Sponsons bottom edges were sharpened and blue printed also.

Larry

[Alfa Spirit]

Hello Alain
I am not sure what OFNI is,
But yes 2 X 56106 TP motors, 1,066m Cat, 8S- 6000 mHa per motor.
This is for racing in IMPBA S+T or Open Cat, or Open Hydro classes.

Larry

Hi Larry,
OFNI means Unidentified Floating Object in french and UFO in english ...

[TRUCKPULL]

I got my two water pumps installed, These are flow through pumps,
This means that when the water flow is higher then the output of the pump, It flows with no restriction.
The flow on these little pumps is over 1 US Gal per minute.
https://bc-robotics.com/shop/12v-4-2...rushless-pump/
There draw is only 0.400 A, so for the two of them is only 0.8A
To power these I use a
https://www.pololu.com/product/2855
This will take up to a 36V input - with a 12V at 2.2A output.
I ran two of these pumps in my 6S twin all last year with no problems.
Last fall I put one of these pumps in my humidifier it has been running steady for six months now with No problems.

[TRUCKPULL]

I installed two 1/4" X1/4" carbon square tubes
along the top of the inside bottom at 5 1/2" apart
This will add some rigidity and align my servo mount plate and my ESC mounts.
The Push -Pull system, Is made up of two HS5645MG Digital servos.
When placed facing each other, servos will always work opposite to each other.


Larry

[Jesse J]

I hope you didn?t glue in the ballast, Larry; me thinks you won?t need it!

[TRUCKPULL]

I hope you didn?t glue in the ballast, Larry; me thinks you won?t need it!

Jesse The lead blocks and the mag-blocks, were just to hold them down untill the JB dried.
I had drilled each rail with a 3/32" drill, every 3/16" for the total length, to get the JB into them.

If it is too heavy when I am done, I will use balloons, with helium in them for floatation.

Larry

[Jesse J]

Thanks, buddy, that makes me feel better!

[TRUCKPULL]

This Cat is 41 1/2" from transom to the tips.
From the tips to the props is 46"
This boat is no feather weight by any means, Right now I am pushing 22LB ready to run.

What should my CG be? I am thinking 13.5" to 15" from the rear.

Larry

[TRUCKPULL]

OK guys I have got to have a better idea about the CG.
Once I glue down the ESC trays, I will be restricted to how much I can move my batteries, to adjust the CG.

Larry

[jaike5]

Don't use battery trays. velcro on the floor with small tab of velcro on each end of the batteries , wedge a pool noodle between the deck and the batteries and they stay put. lots of room for adjustment, great for windy days and ruff water.
J.

[TRUCKPULL]

Jay -I do that with my 6S twin Cat, But I have had a battery unplug in a flip and stuff.
The batteries in this one are heaver, so I would like them to be anchored a little better.
I am asking about the ESC trays, Once I glue them in, I will only have about 1 1/2" of movement in the Batteries
because of the short wires on the ESC's

Right now The best I can get is 13 1/4" to 14 1/2" from the transom

This why I am asking about the CG on a large CAT.

Larry

[fweasel]

I measure my CoG from tips to the rear of the ride pads and start at 30%. Your long drives and rudder arm are definitely going to add more stability, but that hull looks wide and tall. I suspect it's going to pack a lot of air. I end up running my long skinny hulls way over 30% (HPR, Genesis, Rivercat) to keep them on the water at SAW speeds. The 48" Zelos G I converted to electric, was a wide, tall hull. It packed a lot of air and I just couldn't keep it glued to the water after a certain speed threshold was passed. I was worried I was starting with my CoG too far forward in that hull. Painted myself in a corner, and had to run the two 6S packs pushed all the way back just to hit 33ish %. I ended up pushing them farther forwards every pass as I figured out how the hull responded to the power I was throwing at it.

If you're copying a tried and true setup, glueing everything in makes sense before testing. When you're blazing your own trail, I'd leave as much adjustment as possible before the initial runs start. Skip the battery trays until you know what you want. Since the ESC wires are a limiting factor, I'd also hold the ESC's down with some type of temporary fashion, couple dabs of aquarium silicone or something like that. Lots of foam on top to cushion them if they let loose in a blowover. It really won't take much time on the water to quickly sort out where you need to be weight wise.

[TRUCKPULL]

I measure my CoG from tips to the rear of the ride pads and start at 30%. Your long drives and rudder arm are definitely going to add more stability, but that hull looks wide and tall. I suspect it's going to pack a lot of air. I end up running my long skinny hulls way over 30% (HPR, Genesis, Rivercat) to keep them on the water at SAW speeds. The 48" Zelos G I converted to electric, was a wide, tall hull. It packed a lot of air and I just couldn't keep it glued to the water after a certain speed threshold was passed. I was worried I was starting with my CoG too far forward in that hull. Painted myself in a corner, and had to run the two 6S packs pushed all the way back just to hit 33ish %. I ended up pushing them farther forwards every pass as I figured out how the hull responded to the power I was throwing at it.

If you're copying a tried and true setup, gluing everything in makes sense before testing. When you're blazing your own trail, I'd leave as much adjustment as possible before the initial runs start. Skip the battery trays until you know what you want. Since the ESC wires are a limiting factor, I'd also hold the ESC's down with some type of temporary fashion, couple dabs of aquarium silicone or something like that. Lots of foam on top to cushion them if they let loose in a blow-over. It really won't take much time on the water to quickly sort out where you need to be weight wise.

Ryan
That sounds like a plan, I can live with.
13 1/4" is 32%
14 1/2" is 35%

Larry

[srislash]

Keep the weight back Larry. I am pretty sure I?m 30-32% on my R42. These bigger hills do pack the air but won?t likely be much over 70 and they are heavy with packs and gear. One usually wants to run it as light on the water as you can. Bigger gas hills are usually designed to run wet because then they stay glued into the water in a race situation.

[jaike5]

Only one battery came un plugged thats pretty darn good on a 60plus mph flip. Batteries in the sponsons lower cog and spread the weight. My insane G3, 10s 2p
44" hull is right at 30%.
J.

[Jesse J]

I agree with Ryan on 30% start cog. In new to me boats, I like 2-3% wiggle room forward and aft.
Desired application, speed, hull design (lift) and other factors play into the equation.
Agreed lighter is better, but ultimately handling at desired speed is the most important. I am not against a little ballast if I just can’t arrive at the correct cog. I’m sure some will cringe at the thought of adding even more weight.. not first option, but not the end of the world.
On the other hand, if you just cannot get cog far enough forward, one can add a small air dam to reduce lift.

Ideally, layout should allow 2-3% around the target 30%.

[TRUCKPULL]

Thank You very much guy's

So it looks like my next project is all the wiring
water pumps, Servos, ESC's, BEC, Radio.

Then Paint

Larry

[TRUCKPULL]

I have figured out a way to get the CG down below 30%
This is a rabbit hole that I don't want to go down.
So hopefully my set up at 32% turns out OK at testing time.


Larry

[ray schrauwen]

Just keep cranking the props down, lol.

[TRUCKPULL]

Just keep cranking the props down, lol.

My setup right now is 3 3/4 degrees down. This should be a good starting point seeing my Q is at 2 1/2.

Larry

[Doby]

Started the cg on mine at about 30%.

Running mine on 10S2P with a big Neu 2215 in it.

Just got it tuned in at the last Michigan race I went to..its a beast, heavy as a tank, but moves nicely.

Went with dual rudders on mine.20220127_003702.jpg20220127_003713.jpg

[Doby]

.....another pic...fbcat.jpg

Think this was taken in London...Chris K's cat in the background.

[Jesse J]

It’s all about the upright fins, that’s why you are ahead!
Great looking boat and I love the action shot!