Simon's Balsa Cat

[Simon.O.]

Sorted!
It still has a small pitching motion but is a lot smoother than it was.
Turning is still very sharp.
I have the strut set so the top of the shaft is at the bottom line.
I will now poke in the 23t and spin a few different props to see if a 540 or 600 is better.
The 600 on a 438 is good.
Let's see if we can get more.
Back tomorrow.

[rcflyer55]

Nice craftmenship. The cat looks great.

[Simon.O.]

I have now found that the surfaces I fitted calmed down the the pitching / bouncing behaviour that was present with the 600 + 438 prop.
Now I have trialed a 23t (27.5krpm) 540can + 535 prop, all sorts of handling issues have arisen.

I now believe that I have too much aerodynamic lift as a result of the tunnel.
I have a few options here as I see it.

1. Reduce the lift of the tunnel .This can be achieved by reducing the intake of air among other measures.
2 Reset the strut so that the shaft has positve thrust and lifts the tail, this could get interesting !!
3. Put the 600 back in with the 438 and .............wtf sort of plan is that ?

I will have a go with strut angles and depths before I have a go at changing the lift properties of the tunnel.

My brain is full of some amazing ideas and derived formulae at the moment so I am off to have a beer and contemplate the next move for this hull.

The rigger is nearly ready

[Stealth Assassin]

You can try adding a pod In the tunnel to slow air flow. There are several differant things you can do with a pod...

[Simon.O.]

Right !
I did a few more tests today with some very interesting results.
I have currently got a Super Stock 23t ( 27krpm) can in there spinning the 531 prop. 6 IB4200’s push the electrons round.
The strut is set so the shaft is level with the sponson bottom line and at 0 degrees.

It goes like a cut cat !
Nice ride attitude with the nose up and running 25-30% wet.
Acceleration is insane and it looks great on the staright.

BUT ! with any rudder input the bow drops and therefore speed comes off. Cornering is spectacular but this nose drop is a bit of a problem.

I have read loads about the rudder caster and how it affects this behaviour but I am still a little lost.
I am tempted to reduce the chord of the rudder so that it is long and narrow.
At the moment it is about 1” front to back.

Any other bright ideas?

[Simon.O.]

Right !!
I got this caster thing sorted.
I set the rudder up so that it pulled the rear down with serious turning input and guess what. It rocks !!
It will now keep its nose high on the staright even with steering corrections, and will turn round ( 180 deg ) in less than 4 ft radius at wot.

Today I gave it a spin with the 30 krpm can from the hydro and it was not a success. I now feel that 30k is a bit quick for the 5 series octuras that I run.
With the SS motor (27 krpm) this hull screams, that extra 3k seems a little too much for the prop.

I will now get another SS can for this hull and throw the Reedy 30k motor into my little red mono on a gear drive that drops it to 20k with more torque than me.

Oh you guys have not seen the little red boat yet have you ?? or the big yellow one ??

Standby as more threads are about to appear from me !!

[Stealth Assassin]

What did you do to change the rudder? Post some video of her running, a pic of the changes and the set up Inside the hull.

[G Doggett]

Hey Simon

When are you going to bring some of these amazing homemade boats down to the lake at Wattle Downs ?
We would love to see them.
Actually having said that, don't be in too much of a hurry as the council have drained the lake to kill the weed.
We are all getting stir crazy without our 2 weekly dose of model boating.
Graham.

[Simon.O.]

Hey Simon

When are you going to bring some of these amazing homemade boats down to the lake at Wattle Downs ?
We would love to see them.

With the price of motion potion now trips down there are going to be a little pricey.
I do want to come down in the summer as even my wife is interested to see what some real boats can do. I keep showing her vids of those crazy euro cats!

I live in Birkenhead and Chelsea pond is only 5 mins away.
I have seen Chris down there once too with his SV, man that is impressive.
Come summer and I'll get hold of you guys and come down for a day.
Cheers.

[Simon.O.]

Old thread dragged up as the hull is now altered, again.

I now get 70+kmh out of this baby.
When the strut parts company the wire-drive makes a mess of the rear.
http://forums.offshoreelectrics.com/...ead.php?t=4492 Post#5

It was time to cut out the rear and go for a rebuild.
The hardware is a bit of old and a bit of new and I have gone for a J-tube water pickup as I now think these look a lot smoother and cleaner than some of the others that I have seen and tried.

The drive dog is now a bit further back at 15% and I am aware that this will alter the handling and setup a bit. It was at 11 % before.

This is where the fun is for me. Make radical changes and then adjust, evaluate, record and have fun !!

Here is the old and new.

[Jesse J]

Interesting, what was the motivation for these modifications? was it for looks? or to add stability?

I notice you have a short rudder, what do you think the consequences of too long of one would be?

Any vid of this beauty? Great work Simon, I always like your threads/posts.

[Simon.O.]

The work was as a result of damage caused by a broken strut that let the wire loose and the prop took chunks out of the back.

I resoldered the strut and it was on the water the next day. The setup was fine but as a result of the cosmetic work that needed to be done I decided to do more and change the setup and appearance.

The long prop to transom distance will change things a lot and the rudder may be too short. If so then I have a couple of longer ones.

It will be a few more days before I get pond time so for now it waits.

[Simon.O.]

Step time !!

This cat's butt has had more cosmetic surgery than Cher, although she has a nice butt too !!

The last setup was a long flat (front-rear) bottom with about 7deg deadrise and a 20mm (3/4") wide flat ride pad.
This was able to run just like a OPC tunnel on the last 2"of the rear. Blowovers were normal.
I took the pads off, blowovers still.

With either setup the options were limited.
1. Stuck to the water like velcro and moderately fast
2. Insanely unbalanced and blowovers at 40+mph

I have decided to step it. I have read a lot about steps on cats and have seen a few first hand, model and full-size.

I have now chopped the cat so that I have a clean slate to work with and can begin my step building from here.
As it is now it will (should) run a bit like a 3 pointer.
I can then feed in another step or 2 if needed, I would prefer to do only one extra per side.
I have seen the Baby Frear(sp) cat that Adrian sold to Danny. It had a very nice step setup.

My plan now is to run it as a 3-pointer and then put a pair (1 each side) of ride shoes like some of the riggers have. This will allow me to run it on 4 ride surfaces and then release the shaft from lift duties to straight power duties.

Enough of my theory and rambling.
Here is todays handy work.

Feel free to offer advise and even "draw"on a pic to show where steps may go.

[ED66677]

Simon,
you really are Mister Scratch Buid!
you remind me when I was young, I was building a plane almost every week!
you now have to learn to use a CAD software and share you creation with the rest of the world!

[Simon.O.]

Simon,
you really are Mister Scratch Build !
I scratch my..........um..........head a lot while I design / draw
you remind me when I was young, I was building a plane almost every week!
I could build a hull in a week flat too, but my wife would not be too keen.
you now have to learn to use a CAD software and share you creation with the rest of the world!
I scribble on paper occasionaly ,

I am keen to see what is a good idea.

1. Run it as a Hydro-Cat. It would not be the first
2. Run it with steps and loosen up the prop