AeroCat power cats, opinions?

[Alik]

Originally Posted by Krauthammer

Just being polite; "qualified" as in seriously educated naval architects with a full portfolio of proven successful designs.

Having researched the field extensively I was surprised to see how few of the currently marketed cats in the US come from a "qualified" drawing board. For instance the company of the OP draws its designs from an individual without any credentials whatsoever.

In US, 90% of boat designers do not have any engineering degree. Why are You surprised?

I believe designing powercats is still much about opinions, preferences and experiences. I was doing seminar with M&M guys two months ago on powercat design and we found that sometimes we have different answers/approaches on same questions.

[Krauthammer]

Originally Posted by Alik

In US, 90% of boat designers do not have any engineering degree. Why are You surprised?

For the same reason if I were to uncover that 90% of the buildings were designed by carpenters.

Originally Posted by Alik

I believe designing powercats is still much about opinions, preferences and experiences.

Same with sail multihulls and the last America's Cup gave us a great display of differing approaches.

Getting back to the single drive multihulls, are we saying that a Tri would be the only acceptable solution?

[Mr Efficiency]

Is the Glacier Bay 22 a symmetrical sponson boat ? The only ones of the brand name I have seen weren't, and I did note they were pretty full at the stern. "Disastrous" is probably a bit exaggerated for the description of its handling, reviews are pretty subjective, I would say if the boat in question is being used in large numbers in difficult offshore conditions, there would be no dire vices.

[Krauthammer]

Originally Posted by Mr Efficiency

Is the Glacier Bay 22 a symmetrical sponson boat ?

Yes they are, all of them are. See their website on design:

http://www.glacierbaycats.com/site/design/hull-design/

Originally Posted by Mr Efficiency

The only ones of the brand name I have seen weren't ...

You are obviously confusing them with something else.

Originally Posted by Mr Efficiency

"Disastrous" is probably a bit exaggerated for the description of its handling, reviews are pretty subjective ...

Not exaggerated in the least. Magazine reviews in the US are typically "puff" pieces intent on keeping advertisers happy and a critical review like the one on the 22' is very rare and a caution flag. Disastrous, yes when one considers the numerous reports of occupants in the 22' being tossed around at speed and sometimes overboard. It was bad enough for the 22' to be discontinued and eventually the original company to go into receivership.

[Alik]

This is our 6.2m cat... Never heard any problems mentioned with this one, besides I owned one of them (open version) for over 3 years and used it quite intensively as family boat in the Gulf.
Note amount of spray underway...

[Krauthammer]

Originally Posted by Alik

This is our 6.2m cat... Never heard any problems mentioned with this one, besides I owned one of them (open version) for over 3 years and used it quite intensively as family boat in the Gulf.
Note amount of spray underway...

Nice. Is it a single or a twin? Didn't see it in your website.

[Alik]

Originally Posted by Krauthammer

Nice. Is it a single or a twin? Didn't see it in your website.

Twin; on this one I believe they use 2x115HP. My boat had 2x85HP that is more then enough.

[Krauthammer]

Originally Posted by Alik

Twin; on this one I believe they use 2x115HP. My boat had 2x85HP that is more then enough.

Are you categorically saying that a 25' X 8'6" cat can not be designed to work efficiently with a single OB in the 90-140 hp range and to perform flawlessly in open water conditions?

[Alik]

Originally Posted by Krauthammer

Are you categorically saying that a 25' X 8'6" cat can not be designed to work efficiently with a single OB in the 90-140 hp range and to perform flawlessly in open water conditions?

No, I am not saying this. We can do it if we get such design request, but what is speed range?

[Krauthammer]

Originally Posted by Alik

No, I am not saying this. We can do it if we get such design request, but what is speed range?

25 kts cruise, 35 knots max., with usual average loads. The intent is to save the cost of buying and rigging the second outboard and, equally important, to produce much lower mpg at cruise.

The economics of running such a boat an average of 500 hours/year should yield eye opening savings. Considering that outboard engines require replacement after ~1,500 hours, the savings keep piling up and over a 10+ year useful life of the hull should be stunning.

It must be a stable platform without rocking at rest (the Glacier Bay 22' was the worst offender here) and capable of trimming and running "through" a healthy chop without slamming and dousing the crew. It must leave a clean wake at trolling speeds and not have noisy hull slap when idling up to fish.

The design should provide for construction with liner and alternatively with rolled gunnels.

[Alik]

Originally Posted by Krauthammer

25 kts cruise, 35 knots max., with usual
It must be a stable platform without rocking at rest (the Glacier Bay 22' was the worst offender here) and capable of trimming and running "through" a healthy chop without slamming and dousing the crew. It must leave a clean wake at trolling speeds and not have noisy hull slap when idling up to fish.

Rocking - this is quite usual for cats, but making cat relatively wider solves the problem. Increased beam reduces the roll amplitude. BUT this contradicts with trailerability requirements.

In general it is feasible, if we can make it wider the problem with single engine blocking the tunnel will be solved. We can make some tricks on hull and tunnel for efficiency but those I will not share in forum

[Krauthammer]

Originally Posted by Alik

In general it is feasible ...

See PM

[Mr Efficiency]

No rocking allowed ? This thread is turning silly. Why are there no 25' offshore cats with 25 knot cruise, fitted with just a single 90-140 outboard ? Easy question, it is too difficult, by far, to meet those specs, for a number of reasons.

[Wavewacker]

What happens when you use a single OB on a center mounted "pod" say three feet behind the stern....moving the engine back further in the center?