power problem

[beau]

Thank you for your advise but I have studied naval architecture and no where does it say that a fine angle of entry plus a flat wide stern will "defeat" the OLD rule of squareroot of waterline Etc.
YET I have proven in 15 ft prototypes that I can go well beyond the "rules" of displacement theory and achieve 20 knots with NO bow wave or stern wave with VERY low power.

i know what I have done wrong, the design is overloaded, I just have to consider the least expensive way to correct it.
Thank you for your comments.
I will keep you all informed of progress.

[waikikin]

Old yachty, Beau is having a red hot go at doing something that is different, without this mankind will stand still for fear of falling off the edge of the world, I think you maybe should read your own tag line, NA is indeed a complex topic but now & then whats considered a "black art" advantage proves itself in phisics & the ideas man is held as a hero, good on ya Beau for havin' a go. All the best from Jeff

[Pelagic]

Hi Beau,

Unfortunately, as your gut is telling you, the weight issue is killing the flow and you’ve lost that sweet spot

I understand your frustration as I have had similar experiences project managing light weight (Kevlar/carbon fibre) power cats for Superyachts and the “extras” put on board, made her too heavy and killed the design.

The first thing I did was strip off everything I could, to bring the waterline down to design draft and then tested it. (Performed beautifully).

Now with everyone encouraged, we made some temporary modifications at the chine and stern sections with glassed over foam strips to increase buoyancy and tested again with more weight.

In the end it will be a compromise between increasing buoyancy and decreasing weight.

Good luck…. Nick

[beau]

Thank you all for your support.

Nick, your dead right, and i will be doing as you suggested.
The biggest problem is, I have 4 X 200 amp batteries too far back.
I will remove two of them completely and move one well forward plus
remove spare anchors and chain etc as well.
I am able to "push" down the outriggers (with spacers) at the rear which will give me more buoyancy at the rear, but I will then have to extend the waterline length to get a good water flow. (no problem just extra work)

The bow can be immersed a bit more without affecting the water flow and that may even be beneficial by changing the angle of water flow to the stern.
On the prototypes I never had a bow wave but I did encounter a substancial stern wave at first, but with extra power the boat seemed to lift ever so slightly, the stern wave then flattened out and the boat took off.

To answer other comments, i do not believe I am getting any wave interference from the outriggers. The flow is very smooth with very little induced wave action. Absolutely no formation of a bow wave or the beginning of a bow wave even at 8.5 knots (you would expect some bow wave formation to form at 6-7 knots for a 39 ft waterline)

It also could be that the boat just needs more power for what I am trying to do. The problem is the cost of new motors and what to do with the old ones plus we then have extra weight.

On a positive side being able to move the outriggeres in an out has allowed the boat to be moored in a much cheaper and more available monohull berth. The boat is very stable at anchor or cruising because of the 20 ft beam. Downwind it is a dream, though I havn,t had time to set up the sails yet. The boat can sit on the mud, with a flat bottom and a draft of only 1 ft.

[OldYachtie]

A straight-sided wedge for maybe 3/4 of its length terminating sharply and suddenly in a square not far forward from the stern with a transom that is the widest point of the waterline doesn't look anything like any boat I ever saw, nor like any boat I ever saw a drawing of. It looks like a form that would give a very high resistance to me, and apparently, it is giving high resistance. Some pretty unusual ideas have worked out in practice when it comes to boat design, but they were developed incrementally, by people who had thoroughly studied naval architecture. I've done some pretty unusual things myself, but I did all of my homework first. I've seen a lot of attempts to innovate by people who didn't bother to do their homework first, and they were all disasters. For fast power cat design showing some amazing innovation, see Malcolm Tennant's article at
Catamaran Comparisons by Malcolm Tennant

[beau]

There are two forms of resistance, wetted surface and bow/stern wave formation.
reducing wetted surface can only be achieved by lifting the boat free of the water planeing or hydrofoils or hovercraft all use large amounts of power.
A planeing design requires a minimum of 50 hp /ton.

Yes, my design has wetted surface, maybe slightly more than a wide hull design.
In a displacement type hull you need 5hp /ton to reach displacement speed. squareroot of the water line etc.
With motors idleling my boat design does 4 knots.

Once a displacement boat approaches its "hull speed" another drag factor comes into play which is the bow/stern wave where the boat tries to climb up over the bow wave, which uses considerably more power.

Narrow catamarans/trimaran hulls can escape or delay the formation of a bow wave if there hulls are very narrow. (Malcolm tennant designs and many others)
However THAT concept is not very suitable for craft under 20 meters.
By the way I manufactured boats like that 25 years ago.

What I have found (with over 25 years of theory and practical experiments) is that there is ANOTHER way.

I have had many well know Naval architects look over my work and agree that I might be on to something. Not one has critized the basic theory that I am following.

Your comments suggest that there is ONLY one way of discovering new ideas and that apparantly I don't fit your idea of an innovator.
By the way I have many successful Patents in my name.

What is the point of being so negative, everyone else on this forum tries to help, not critizise, particularly where it is not warranted.

[OldYachtie]

Hi, Beau - It will surprise and perhaps outrage owners of multi-hulls under 20 meters to read your view that narrow hulls don't work well to lessen resistance in boats of that size. ( See Southwinds - January 1999 ) Since you are keeping your new theory of resistance to yourself, I can't comment on it. I might not have anything to say if you did describe it, for that matter. Your drawing looks like a slice of pie on top of a cube, and it looks in no way, shape, or form like any planing boat or displacement boat I have ever seen. It has been said that water doesn't like surprises, and I think the shape you have drawn must surprise the water quite a bit. I think this hull must make some major eddies, and I would think that this eddy-making process must consume a lot of energy that you want to go into moving the boat forward. If you do invent a drastically new hull type that is more efficient that all existing types, based on an inventive new theory of resistance, I will be the first to applaud. However, I am not going to be holding my breath until this happens.

[Ex-Calif]

OY said - "I've done some pretty unusual things myself, but I did all of my homework first. I've seen a lot of attempts to innovate by people who didn't bother to do their homework first, and they were all disasters. "

This might be an unfair characterization of Beau's efforts. If you read this thread in it's entirety you will see that he has been working on this for quite a while. He has also made scale models.

We are all loking forward to further reports and I am sure at some point a YouTube video would be awesome.

I am a bit sceptical myself but I am fascinated with the innovation and encourage Beau to press on.

The only alarming thing I am reading is Beau's suggestion that it could be intimately related to weight. This is scary because I don't know any boat that loses weight after launching....

[OldYachtie]

Hi, Dan - I can see how my remarks might seem harsh. I am not trying to be unkind. Beau has designed an unusual boat that goes against a lot of the conventional wisdom of yacht design. He says he has a new, different theory, and apparently this is the theory that guided him in his design. Then he says that his boat is working out as well as he had hoped. Well, it seems to me that the likely explanation is that his theory is wrong and the dozen yacht design books on my bookshelf are right. Call me conventional, if you like, but it is a charge I rarely hear directed at me. I mistakenly leaped to the conclusion that he wasn't familiar with conventional yacht design. He says that his is, and is ignoring it deliberately. Well, good luck with that. Only by succeeding will Beau prove that he is right and the design "establishment" is wrong.

[OldYachtie]

Then he says that his boat is (OOPS, TYPO-I MEANT ISN'T) working out as well as he had hoped.

If I had to guess, I'd guess that the previous prototypes were very light and very flat on the bottom, and that they planed despite rather than because of the other features of the design.

[Ex-Calif]

OY - In the land of irony you could be right but for now I'll follow the advice in your tag line - LOL

[OldYachtie]

Dan, I feel obliged to point out that there is a difference between "doing" as quoted in the tagline, and attempting to do. I didn't tell Beau it wasn't going to work out, he told us it wasn't working out. I suggested that maybe the reason it wasn't working out was because his theory was wrong.

[beau]

The prototypes did not plane and they were heavily loaded for their size.

For a start, there are no eddys or turbulence along the hull sides, which is why there is no bow wave, it is the turbulence/friction that causes the bow wave.
Also i never said the design is NOT working, just not as well as I hoped.

I have already shown the improvement over conventional design with this concept. A conventional displacement design can not do what this boat has already achieved.

However there is no doubt that further speed can be extracted without having to resort to a planeing hull, it is just a case of fine tuning, which is what I am doing.
I am sharing my experience and design with others so that everyone can benefit. and getting some wonderful support and assistance.

Old Yachtie why do you think everything has to come out of a manual. Why is old conventional wisdom always the only way.
Why can't new things be invented.

The fast catamaran ferry concept was only developed 30 years ago and that was also against naval architeture theory at the time.

Also by the way the US Navy has ordered two destroyers,(one is already in the water) from a Western Australian company "Austral" which have developed a very similiar design, which is fine entry,flat bottom and wide stern. (I was allowed to see the plans and a model)
So maybe your theories are just behind the times.

[bill good]

Some of those streath bombers look very ordinary but the do the job!! Beau will get there. help were you can!!

The only time practice & theory are not the same is when knowledge is not complete.

Bill Goodward

[Ex-Calif]

In theory practice and theory are the same. In practice they are not.