Cat experts--Questions

[hinchy]

Hi

Interested in learning about the workings of cats,not interested in starting a brand war,just looking for intelligent input to some questions.
1. Is there an optimum length to breadth [beam] ratio?.Would a say 6m cat with a 2.4m beam perform better overall than one with a 2m beam?

2.Do cats with a single motor operate as effectively as those with twin motors i.e.what effect does a single engine driving in the middle of the tunnel have on the performance of the hull?

3. Does the width and depth of the tunnel effect the overall performance?

I realise that these questions have some very technical aspects,however some of the members with a lot of experience in boating may be able to shed some light on the subjects.

Kind Regards

Hinchy

[Noelm]

I guess the answers are 1: yes, 2: no, 3: it must do. I will give a further more in depth (my thoughts only of course) later.

[coucho]

Hi Hinchy
I don't know too much about cats but my thoughts would be thus.
1 the wider the hull seperation the more stability the vessel would have but it would be heavier.
2 I have never seen a cat with a single engine down the center and I don't think it would be a good option as the prop would tend to lift with the boat and would have too be faily deep to make sure it stayed in the water. would also be a pain in the rear end to stear
3 no idea but I don't think so

[tin can marlin]

People say once you go in a cat you never go back.

[julian1]

hinchy, can i ask why all of these questions ?
are you planning on building one or just buying one of the many availbale on the market ?
if you are trying to establish what makes the best cat hull then you will get a lot of different thoughts from alot of people, but the models that have stood out over the years with the best combination of tunnel height width beam etc would have to be the Sharkcat 23 or in the smaller range it would be the 5.2 Kevlacat

cheer's

Julian

[tin can marlin]

Hi julian i know were your coming from a all cats ride different very valid point you are makeing.

[Fish Guts]

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[tin can marlin]

Hi fish guts i have driven only 4 and they all acted different i found the power cat the pick of them haveing said that i'am still a mono man. I don't like the feeling you get in a side sea. Have you found that and what is you fav make. Regards mark

[business class]

Hi Hinchy,
My thoughts on this as i fish in one quite often are.
1. yes the more beam the better ride.
2. me personally have never seen a single engine on a cat as i think it would create drag in the tunnels.
3. Yes it does matter of the size and width of the tunnel in your cat. The greater the width and depth of your tunnel is, which becomes very important in multihulls as the tunnel dimensions adjusts just how much air flow is running through the hulls, with having greater tunnel depth and width helps give you a greater volume of air running through the hull, which then creates a pocket of air which makes the ride alot smoother. also with a narrower tunnel in depth and width would take away the hole riding on a pocket of air theory and make the ride alot more stiffer and give you that pounding feeling instead of that soft landing as it normally would. narrowing the tunnels would make it hard to get that constant flow of air which multihulls depend on and would change the whole ride completely which why would you want to do? There just my thoughts hope they sort of answered your questions.

Cheers
Matty

[mirage]

Hinchy just sold a 5.2KC. So I don't think he's looking for one of those.;D

In answer to question 1. In VERY general terms nothing compares to overall length of a boat to soften the ride and I guess the wider it is the more stable it will be.

As for 2 and 3 I agree with all the others. Only cat I know with one engine is the Webster Twinfishers. They aparently perform quite well but most cats wouldn't. Most struggle to get up on the plane on one engine, if at all. (I have a KC2400)

Cheers.

[Noelm]

there has been lots of attempts to fit a single Engine on a cat, Markham Whalers tried, Websters, some Sharkcats had a single stern drive, Noosa made a single Engine Centre Console, and a brand called a Seacat, later became Barjumper, all had a go at it, all are OK, but none are great, twin Engines on a Cat are the best option, end of story!

[boatboy50]

Hi

Interested in learning about the workings of cats,not interested in starting a brand war,just looking for intelligent input to some questions.
1. Is there an optimum length to breadth [beam] ratio?.Would a say 6m cat with a 2.4m beam perform better overall than one with a 2m beam?

2.Do cats with a single motor operate as effectively as those with twin motors i.e.what effect does a single engine driving in the middle of the tunnel have on the performance of the hull?

3. Does the width and depth of the tunnel effect the overall performance?

I realise that these questions have some very technical aspects,however some of the members with a lot of experience in boating may be able to shed some light on the subjects.

Kind Regards

Hinchy

Hi Bob,

All you need to do is study and meaure a 5.2 KC and you will get all your answers :P Now, where will you find one of those!

Seriously, heres your answers.

1. Yes, not sure what that ratio is, but I am sure the aforementioned KC and 23 Shark Cat carry the same ratio, in smaller amounts. All others are still trying to work it out too:P

2. I have done hundreds of hours in a single engine 5.5 Noosacat, and others. I can tell you that it never works 100% Never driven a Webster, but I doubt very much it would be any better. Only solution to single engine is on hull, not pod, but even that has it's weight distribution issues.

3. Yes, dramatically. The higher the better, and should not be too wide. In fact it should probably be as wide as it is high in a small boat.

Regards

Darren

[hinchy]

Hi Gents

Thank you all for the input to date

Julian 1

I will answer you question by advising that I have secured moulds for a 4.1mtr fibreglass cat with 500mm pods [overall 4.6mtr] with a beam of 1.95mtrs.

Mirage

It is not a matter of brands as I was very happy with the KC 5.2 except that it was too heavy to tow over very long distances

I am considering experimenting by adding another 1 mtr to the hull length plus 500mm pods [overall 5.6mtrs] whilst leaving the beam at 1.95mtrs.Am I wrong in believing that the boat would be more easily driven by smaller more economical motors without compromising stability underway and at rest?
Or am I better advised to widen the hull to 2.2mtrs or 2.4mtrs to ensure enhanced stability overall?

I have moulds for both single or twin motor installations,however I have never been in a cat with a single motor and have no idea as to how they behave.

kind Regards

Hinchy

[lenm5]

Hi Bob,

Your old 5.2m cat (minus pods) (2.4m approx beam) has a length to width ratio of 2.16

Your new 4.1 cat (minus pods) (1.95 approx beam) has a length to width ratio of 2.10

So your new small cat has basically the same length to width ratio as your old cat if not even slightly more beamier than the 5.2.

I personally wouldn't lengthen anything without upping the beam I recon it would be to roly poly.

Lenny

[Fatenhappy]

Hey Hinchy ...

We've got a 23' Shark Cat single diesel leg stern drive.

There is no argument that the twin o/bs or twin stern drives are far better than the single set up for manuvourability "when not on the plane" or up close..

What I simply mean by that is, as soon as you're back to displacement speed with twin hulls then stands to reason there is twice the amount of hulls to turn and hence a greater resistance to making the turn. With twin power units not a problem with a single takes a bit of getting used to.

After a little experience at this you tend to make the necessary alteration a little earlier and most times all is sweet.

Cheers
Greg

[Noelm]

some older Whalers even had a single Motor mounted on one side, now I reckon that would be a dud, anyone who has tried to turn a Cat with only the "inside" motor will remember that it is not a great experience, can be done, but is quite a large turning circle, also, try getting your Cat to plane on one Motor, (on the side that is) almost impossible!

[Crocodile]

I have a 4.3 Webster, single engine with a splitter in the tunnel.
Very efficient, no cavitation or aeration, plenty of trim range.
As for the Whaler with a single side-mounted motor, refer to Seamedia for test, apparently no performance shortcomings.
On the smaller cats the complexity/expense of twins is not warranted, on the bigger cats the cost is less obvious on a percentage basis.
Bigger cats go further offshore so twins are more appropriate.

[Noelm]

as mentioned, single Engine Cats go OK (well most do) BUT NONE of them are anywhere near as good as a twin Engined one, been in enough of them to form that conclusion a long time ago, including a Webster, they are fine, some even far better than a Mono of that length, for some reason, 5.5 (18') and a 2.4 (8') beam seems to be a good reference, most of the smaller ones 4.1 and 4.9 Whalers and the like, are no where near as good as the 5.5 Whaler, and most of the 5.5's are better than the 6.5M, not too sure why, but it just happens like that.

[reidy]

Hi Hinchy
I don't know too much about cats but my thoughts would be thus.
1 the wider the hull seperation the more stability the vessel would have but it would be heavier.
2 I have never seen a cat with a single engine down the center and I don't think it would be a good option as the prop would tend to lift with the boat and would have too be faily deep to make sure it stayed in the water. would also be a pain in the rear end to stear
3 no idea but I don't think so
Good day,
I think the Webster twin hulls run a single up the centre.
Cheers
Reidy
Sorry should have read further