Canadian alloy cat!

[Napa Mike]

I thought you all would enjoy this. I like the boat, but I wonder about the bluntness of the front of the hulls (meaning the relatively flat deadrise at the bows).

http://www.youtube.com/watch?v=tG5KfM9POqA


Cheers,

Mike

[dawgaholic]

To my highly untrained and in need of extreme vision corrected eyes, looks to me as if that is a Displacement design that is plowing the water with brute force. I just examined a 35' mono open cab design powered by the brutish 480 hp. of the Cummalong 5.9 TD and it exceeded 50 knots and cruised at 28 @ 2.7 MPG.

Got my Mad Money that sez that Cat can't touch those numbers with a ten foot pole. Kinda...Sorta....

[JETTYWOLF]

To follow up on what dawg said.......

anything allloy with 600 HP better "step and fetch" no matter what. Or should we be surprised, "via the discription of the video".

[Chaps]

That looks like an asymmetrical hull, kind of like taking a monohull, splitting it down the middle, swapping the two pieces and joining them at the rubrails or in this case separating the pieces with a spacer to create a wider tunnel. Good performers, see it more in the plastic cats.

[kmorin]

I agree with Chaps this hull looks, as much as can be seen in the video, as a "split monohull with a bridge over the two halves".

Where the design totally fails is the forward third of the hull. Cats are a design challenge and this one will probably be fine in the flat calm bay of the video but will be a barge in the open sea in a swell; following or on the bow.

Most high speed cats are decked or bridged between the hulls high enough off the waterline to allow the two hulls (ama's) to enter the water almost as though they were two very narrow and sharp monohulls. This means the entry is soft and there is little impact until that hull is in a combined motion and seaway where the combination results in slam or pounding.

The combination is both speed and sea state or wave height. Forward rate of travel enters the bow into ANY wave, so the waterline start up the hull based on the time that hull travels enough to convert headway into pitch up by the bow. So a very sharp, narrow angle by the bow, deep forefoot boat will be able to have a 'smoother' transition to lift from forward than a flat bottom jon boat (extreme case) because the jon boat's bow makes the change all at once! That is the ultimate slam.

The old WWI Destroyers with their vertical stems and 15 degree (plan view angle of the bow [entry] at the waterline) meant they could hold their full/top speed in any sea since they were 'knifing' through the seas.

Now that there are the full slam and the never slam bows - above- we could consider this bow's performance and see that if the seas are 'flat' it can go top speed without slam. But what would happen to that same bow when it runs into a 4' head sea? Well its plain that it will slam the entire boat into a wave face therefore I think the design is limited, like the jon boat, to certain waters and sea states or it will have to run the two big outboards at an idle and 'walk' like a barge.

the only high speed cat hulls I've seen that 'worked' were bridged high enough to allow the majority of at least a 3' if not a 4' sea to run under/between the hull(s). This meant those hulls wouldn't slam unless they were trying to run at planing speeds in a 5' swell where the bottom of the bridge or flat part of the hull was actually getting wetted with a 'wave top'.

These hulls all have two different curves in profile, one is the forefoot of the two ama's and the other is the much higher up and much more 'flat' curve of the bridge (under deck) and those two curves allowed the hull's performance. This hull seems to have a very deep bridge between two very low ama's or side hulls, and therefore both these sets of surfaces seemed ramped up like a huge jon boat, and I suspect she will perform in a head sea like one too?

If the video were a little brighter, and showed under the bow more clearly maybe the shape is less barge like than it appears? But from what I can see the designer made some serious open water performance problems for this boat.

Cheers
Kevin Morin

[Napa Mike]

Here is additional information from the designer, Scott Jutson. See if this changes your opinion of the boat.



http://jutson.ca/blog/page/2/

Cheers,
Mike

[kmorin]

Mike, the other pages confirm my suspicions about the boat's intended waters: flat, inland, calm.
Notice the same designer has a very high deck/bridge panel 40' and 44' cats on the other pages? These are more open sea boats so I'll suspect he doesn't intend this cat to go outside sheltered waters, at least not at the speeds it can deliver in flat inland waters. Clearly he knows what he's doing (design-wise) so that bow was intended for inland or protected waters.

The photos show this hull is essentially a derivative of the Hickman Sea sled of the 19-teens. http://en.wikipedia.org/wiki/Hickman_sea_sled. The hull's tunnel effect or ground effect cushion is what the designer wanted not an open sea boat for waves. These hulls can trap a bow cushion when landing on a wave- reducing the slam to an air cushioned landing- but the forward speed is slowed pretty fast, and the boat is literally awash from the bow's forward throw returning over the cabin and decks.

The wetted area change when this hull runs over a 4' wave at any speed will "put your face on the instruments" sort of head shock from speed reduction, even with a cushion of air under the hull. Maybe they've installed 'air bags'?

Nope, no change in my opinion, but a lot more clarity on where the boat is intended to be used. Seeing the taller hulls with the flatter bridge between the hulls on the other designs says the steeply ramped bow is for a purpose; highest speed over high speed in all sea states.

cheers,
Kevin Morin

[speedboats]

Just a comment on asymmetric hull form, they do help to reduce alot of spray onside the tunnel which in turn does help reduce hull noise while underway, an important consideration as the wing deck / bridge does appear so low. Lift in the forrard 1/3 can be helped with the placement of a foil between the hulls (and below the waterline). While this does create more drag it can be offset by lifting the vessel further out of the water reducing overall drag.

However, that bow section is something only a Mother could love...

[dawgaholic]

Insofar as Cat designs go, speedboats sez it all:

However, that bow section is something only a Mother could love...

Check out the many Freeman Cat videos as I feel that that is the quintessential plastic haul azz Cat. The vid of a 33' blowing a 42 Quad Vrod Intrepid out of the water in 4-6's is all the proof you need concerning what CAN be done with the design. The one in question had twin 350's and topped at 62, operating range of over 600 nm if memory serves. A very seriously build Carolina pelagic getter, appropriately equipped SOTA everything and the price to prove it.

[CTMD]

Scott has been designing cats for a long time and has spent quite a bit of time tank testing and developing his preferred hull shapes. What is of interest here is these hulls have a least one transverse step and because it is so far forward is suspect it actually has at least 3. In theory this will make the boat more efficient, but it also means the boat will always run very flat which is ok on lakes and rivers but means you wont be able to play with trim much to adjust the ride in waves. 50 MPH for 2x300hp on a 32' boat is a little slow this one does 46 with a pair of 245HP and from memory (its 8 years since we drew this boat) this one from Roger Hill did similar with a pair of 250 Suzukis both are very much offshore capable.

Heck, when it was first lauched (ie built light in New Zealand as the Black Cat) the Arrowcat (30') would do 44 MPH with a pair of 150HP Optimax outboards and 2x175 would get it up to 50 MPH.

[Napa Mike]

Kevin and Chris:

Thanks for your comments. It is great to get the straight scoop from folks who really know the score!

Mike

[dawgaholic]

Kevin and Chris:

Thanks for your comments. It is great to get the straight scoop from folks who really know the score!

Mike

What score would that have been?????

[CTMD]

23/18

[dawgaholic]

23/18

Who won the Gran Prix?

I woulda done better staying at home and watching it because we couldn't even get a bite today. Unreal but we failed to factor in the early Spring effect which has the fish in a tissy here. We could nearly noodle giant Bass cruising the shallows but they would not pay anything any attention though a yearling did chase one of our live baits for a bit, was quite exciting actually since we had NO other activity.

Oh well, it was stunningly beautiful, a Chamber of Commerce day except for the Yellow Air this time of Year. As in pollen and this is the Home of the World's worse pollen season. The surface of both Lakes were a light chartreuse and lures cast out came back caked in the stuff. Yuck.

[CTMD]

[Quote]Who won the Gran Prix? [\Quote]

Who cares? I was just using it to give you a land mark.