ScaryKat By Paul Thomason

[Bob Abell 2Participant @bobabell2]

With the two hulls connected together with a parabolic hull….How can it be called a Kat?

Bob

[Gareth JonesParticipant @garethjones79649]

Invisible Mike,

I am intrigued by your choice of brushless motors for this beast. They are rated at 1800 kV and you are planning to use 5s LiPo batteries which will give you around 15 volts. The free running speed will therefore be around 27000 rpm which is pretty fast for a boat propellor. Have you some inside information that Paul is going to suggest some sort of exotic fast electric surface piercing propellors on the back end, perhaps to complement the exotic bow mounted rudders?

Gareth

[mike farrellParticipant @mikefarrell21522]

More info , cannot get my head around this idea .Go for it Michael

[lnvisiblemanParticipant @lnvisibleman]

Gareth

I am only using 4s lipo as stated earlier.

I think a fast racing prop will be order of the day. And Diede will have to wait just like me. 

Mike twiddle twiddle

Edited By lnvisibleman on 30/08/2014 20:11:54

[lnvisiblemanParticipant @lnvisibleman]

Paul

That is looking MEAN !

Second thought awaited eagerly

Mike

[Gareth JonesParticipant @garethjones79649]

Sorry Mike, my mistake, 4S LiPos will give you around 21600 rpm which is still pretty fast.

Gareth

[Gareth JonesParticipant @garethjones79649]

Hang on Mike,

I have just had third thoughts and realised where I got the numbers from. My 3S LiPos when fully charged give me around 12 volts. 4S LiPo packs should therefore give you around 16 volts so you are back up in the  >27000 rpm range. Still it should be exciting, make sure you have some good thick wiring, maybe Bob can spare a bit from his mobility scooter charger.

Gareth

Edited By Gareth Jones on 30/08/2014 20:28:33

[Diede van AbsParticipant @diedevanabs87670]

4S LiPo is 14.4V nominal and 27000rpm unloaded is pretty much OK for a surface piercing prop, maybe a bit high but nothing too bad as long as your prop protrudes far enough behind the hulls.

Racing cats routinely run at these RPMs and Hydros even go up to the 32000's – although that tends to be pretty much the limit for most props; a little jump or a leaf in the water will be enough to snap off one or more blades.

Note that at these RPM's you will need a well balanced fixed coupling between motor and propshaft; a cardan coupling will simply explode when loaded.

The 16V Gareth is referring to is "gone" after the first blip on the throttle stick, dropping to the 14.4V nominal. I'd say you should be fine but once again make sure the props are running about 10% of the hull's length behind the hull and the shafts should be as horizontal as possible. Take a look at the fast electric racers how they set up this kind of stuff.

And indeed; exciting will be the name of the game here, and that is great!

[lnvisiblemanParticipant @lnvisibleman]

Died

I'm guessing that Mr P's design does not call for props to be behind the hull so what would you suggest if it is a more conventional set-up. Bearing in mind that the prime objective from this constructer is the need for speed

Mike

 

Edited By lnvisibleman on 30/08/2014 21:01:00

[lnvisiblemanParticipant @lnvisibleman]

I have just had a great idea !!

We need to find someone that can produce a virtual water tank to test all the prop/motor possibilities.

Any volunteers ?

[Diede van AbsParticipant @diedevanabs87670]

For fully submerged props try to stay below 15000rpm.

[Amy jane SeptemberParticipant @amyjaneseptember49770]

Hmmm, I think I shall enjoy this thread……..Wanna race my birthday boat? ( You'd jolly well had better beat it!)

[lnvisiblemanParticipant @lnvisibleman]

There you go Paul, it's official !!

Scarykat has true global interest !!

Hi Amy Jane, if you think I'm coming over there to race you then think again . Unless I can drive all the way.

Mike

[lnvisiblemanParticipant @lnvisibleman]

Just been looking for Scarykat's crew and found this !!

[Bob Abell 2Participant @bobabell2]

Nice one, Mike

Is this Fatman and Bobbin?

Bob

[lnvisiblemanParticipant @lnvisibleman]

Good morning to you Bob

A lovely sunny day here, hope you have the same.

You do realise that I shall need some of your crafty building tips when Scarykat gets going.

Mike

[Bob Abell 2Participant @bobabell2]

No problem, Visi

It will be very interesting to see your model gradually take shape and fly!

Bob

[lnvisiblemanParticipant @lnvisibleman]

Hmmmm , Visi, I like that !

It's better than Sible – – –

Edited By lnvisibleman on 31/08/2014 12:10:27

[Paul TParticipant @pault84577]

Bob

Its not a parabolic hull…..its a parabolic hydrofoil wing that spans between the two sponsons.

Paul

[Bob Abell 2Participant @bobabell2]

Paul

Can`t see this parabollick wing thing in the plan view?

I would like to see the prop stuff….Out back, SloMo style and an animated driver of course

What size is this craft and why is it so stunted?

Bob

[lnvisiblemanParticipant @lnvisibleman]

[ashley needhamParticipant @ashleyneedham69188]

I take it this bit is in the water?? It looks very thin if so (sweeping statement not knowing how big the rest is of course)

AND it is straight and not curved so less of it stays in the water at high speed?? waterjets or surface piercing props?

##### OR ANOTHER NEW DESIGN !!! ######

Ashley

[lnvisiblemanParticipant @lnvisibleman]

waterjets sound good if you know where they can be purchased at a reasonable cost

[Paul TParticipant @pault84577]

Second thought

[Dave MilbournParticipant @davemilbourn48782]

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