Banshee

[Paul TParticipant @pault84577]

[Paul TParticipant @pault84577]

Banshee is a super light and screamingly fast hydrofoil catamaran.

The project came into being during a discussion at Bobs big Haydock event where the concept of a high speed catamaran with tilting hulls was first envisaged.

The thoughts have been rumbling around in my head ever since and so I have decided to put the ideas onto paper.

At the moment the prototype is just over 750mm long, the hulls are variants of the Brutus design (take Brutus and split it into 2) connected to the fuselage body by aircraft type lifting wings.

Motive power will be brushless and hopefully some home engineered water jets.

More to follow as the design progresses.

Paul

[Dave MilbournParticipant @davemilbourn48782]

**LINK**

Might save some time.

Dave M

[Paul TParticipant @pault84577]

Thanks Dave

Its a good site and the kit is cheap enough to play with.

I'll get my platinum card out

Paul

[Colin BishopModerator @colinbishop34627]

You are a modelling hooligan Paul!

Still, why not?

Colin

[Bob Abell 2Participant @bobabell2]

Shop floor to Captain Scarlet………….Otherwise known as Red Leader

Just to get the show on the road………..

What makes Thunderbird 10 go any faster than a plank with the same motive power?

Why water jet?

Why the wobbly rock n roll action?

Can we use the existing brushless motors with the prop inside a Venturi?

Can't see any motors on your layout

Is this the result of your new medication?

Bob……Still lurking in the depths, not having risen to the bait

[Diede van AbsParticipant @diedevanabs87670]

Bob,

Allow me to answer all the "WHY"-questions for Paul:

BECAUSE HE CAN.

Having said that, I am still sceptical about the tilting hull steering thingie. I guess there is only one way to find out (and no, I am not going to do that, I already have waaaaay too many projects on hand)

Design looks quite interesting and futuristic, may I bring out a vote for a matte black and high gloss chrome paint job?

Brushless motors should not be an issue if they are a close match to the recommended brushed versions.

Having a prop in a venturi will probably be not the best of ideas, this brings quite a bad efficiency and excessive drag in fast moving vessels. Better stick with either jets or surface prop drives.

Edited By Diede van Abs on 03/12/2014 11:53:54

Edited By Diede van Abs on 03/12/2014 11:54:28

[Paul TParticipant @pault84577]

Colin

Modelling Hooligan….Perhaps but it adds some excitement to the lake side in a form that cant be banned by the elf & safety people

Bob

What makes Thunderbird 10 go any faster than a plank with the same motive power?

The same reason that any boat goes faster than a plank with the same motive power…a decently designed hull, the question should be 'what makes Thunderbird 10 better than any existing high speed boat'

Why water jet?

Water jets are supposedly faster than prop driven craft and they operate on the surface…..besides which I still fancy home engineering my own version.

Why the wobbly rock n roll action?

The tilting hulls will enable the boat to 'dig in' to the corners as the boat turns. Think how skiers takes curves as they travel across the snow…..its similar to how a motorbike banks as it makes high speed turns. The science is all about centripetal force and inertia.

Can we use the existing brushless motors with the prop inside a Venturi?

A Venturi is possibly the wrong description but a 'prop' inside a tube is basically the same principal as a water jet

Can't see any motors on your layout

That's because I haven't developed the drawings that far.

Is this the result of your new medication?

Possibly but didn't some of the greatest inventions of the last century come about as a result of 'medication'

Diede

Black and chrome…….nice idea…..a bit like a 1950s motorbike

Paul

 

Edited By Paul T on 03/12/2014 15:51:07

[Bob Abell 2Participant @bobabell2]

Paul

How about putting the ski edge on the outside?

For extra stability

Bob

[Dave MilbournParticipant @davemilbourn48782]

Paul
While I can just about grasp your theory of tilting the hulls to make a turn at high speed, how effective will that be at lower maneuvering speeds? I reckon you'll need to use split throttles on the waterjet drives, or a steering mixer on the two speed controllers.
Dave M (Doubting Thomason)

[Paul TParticipant @pault84577]

Bob

As the boat turns the hull on the inside of the turn digs in to the water

Just like a skier ….so the ski effect that Bob mentioned comes into effect.

In theory this gives the boat something to 'grip' as it makes the turn instead of simply skipping over the water.

Dave

Slow speed manoeuvring comes from rudders on the rear of the fuselage (that can just be seen on the plan drawing) and from vertical ailerons/rudders mounted on the front of each sponson (hull)

Blue sky idea or pie in the sky thinking……..I don't know……the science stacks up but its a long way from theory to actually working.

 

Paul

 

Edited By Paul T on 03/12/2014 18:44:11

[Bob Abell 2Participant @bobabell2]

The skiers edges dig in on the inside, because the skier leans that way

With a boat, won`t centrifugal force work the other way?

Bob

[Paul TParticipant @pault84577]

Bob

Sorry but there is a slight misunderstanding about the ski analogy as I only used the skier to demonstrate how the boat operates in a turn by leaning into the corner.

I was trying to explain how the mass of the boat moves in a way that Kevin could understand without clouding the issue with centripetal force mumbo jumbo, but you will be pleased to know that your comment about centrifugal force (which is really the direction of inertia) would apply in the ski analogy.

Paul

[Bob Abell 2Participant @bobabell2]

Are the rudders fastened to the floats or the top section?

I still say the ski edge should be on the outside

Bob

[ashley needhamParticipant @ashleyneedham69188]

The "because he can" bit is the most pertinent bit here.

I can see that this is a bit like the tilting train . The top of the boat will remain level when turning which will be very unusual indeed.

It may not necc be as efficient at yer normal boat, but that will not be the point.

To get this to work well will be a feat of engineering indeed, the tilting mechanism will have to be very quick acting I would say. Not sure the jets would be be the best thing for this due to the inlets presenting a different angle to the water in the turns ?.. I would think normal high speed props would do. Surface piercing is the way to go for very high speed of course, the rear of the sponsons would have to be contoured to suit at different angles..

Centre of gravity will have to be kept right down. Interesting shape, very interesting and of course MORE interesting than could be achieved with a normal cat.

Ashley

[Paul TParticipant @pault84577]

Bob

Using the ski edge sounds intriguing but I'm not quite sure what you mean so, and only if you have the time, could you explain your thoughts and include a sketch or two.

Ashley

The reaction time of the tilting mechanism will need to be fast and also very strong as it will have a lot of different forces acting on it.

At the moment I am thinking of using a heavy duty servo in each sponson to manage the tilting equipment, I am hoping that these servos will be fast enough to work in tandem with the steering servos and be strong enough to resist some of the lateral forces…although it has to be said that I don't expect the heavy duty servos to do all of the work and there will be some basic mechanical fixings between the two hulls simply to prevent them from 'doing the splits'

You are probably right about water piercing props being a better option that water jets, I intend to make the fulcrum point of each sponson coincide with the C/L of the motor/shaft arrangement.

This means that the motive power is always in full contact with the water and will work very well with a surface piercing system but a jet drive does present extra problems in needing a scoop arrangement to ensure water is always available for the pumps.

The centre of gravity (or gravities) is more of a problem and apart from keeping it as low as possible I still have to work out all of the different permutations.

Kevin

Sorry about the techno mumbo jumbo and I will try to make things easier to understand as I produce the designs.

There is no such things as silly questions or daft ideas and I welcome any and all comments so please feel free to 'pitch in'

Paul

[ashley needhamParticipant @ashleyneedham69188]

I wonder if the submarine self-levelling devices work quick enough ??? probably.

The centre hull could underhang more, as it will not be in contact with the water, so lowering c of g. Batteries could then be lowest place poss

Do the sponsons need to be much more than surfboard type arrangements? A small bulge can accomodate the brushless motors…flexidrive takes up no above-water space.

Locically the drive could be central portion that stays upright, removing any complication from the sponsons, which could then simply be glassed over foam.

Ashley

Edited By ashley needham on 05/12/2014 08:26:59

[Paul TParticipant @pault84577]

Hi Ashley

The self levelling devices should work quickly enough………I don't think the reaction speed will be the issue as the major problem will be getting the hulls to work in unison.

After playing around with the design of the centre hull it appears, at the moment, that it is in the best position to work with the lifting wing but this could all change as the design develops.

The design of the sponsons has been through various incarnations to reach their current shape. A surfboard profile proved to be to thin and had the tendency to flip the boat when turning into a wave.

Putting the drive into the central fuselage isn't really an option as it would reduce the motors from two to one and, quite unexpectedly, put the mass of motor/battery in the wrong position. I think that it is more likely that the central fuselage and wing will be glassed over foam rather than the sponsons.

Paul

[Paul TParticipant @pault84577]

One of the biggest design problems is preventing the sponsons from collapsing either inwards or outwards.

At the moment I am relying on the tilting mechanism and the forward hydroplane to stop this happening but I'm not sure that the hydroplane will be strong enough to lift the boat and resist the sponsons from collapsing.

Paul

Edited By Paul T on 05/12/2014 17:05:51

[Paul TParticipant @pault84577]

This is a view showing the aerodynamic lifting areas of the project (sponsons removed for clarity)

The thinking behind using an aerofoil is to provide extra lift and stability at high speed, the aerodynamic shape of the central fuselage also helps provide lift.

When moving at speed the combined lift provided by the wing and hydrofoil should raise most of the boat out of the water leaving only the hydrofoil and bottom edge of the transom in the water.

The hydrofoil is formed as a curve between the sponsons and is very slender so I am thinking of using a laminated carbon fibre to construct the foil.

Paul

[Bob Abell 2Participant @bobabell2]

Why do the sponsons wobble about?

I must be missing something?

Bob…..Not convinced at all

[Paul TParticipant @pault84577]

Doubting Bob

The sponsons aren't supposed to 'wobble' about.

I intended the drawings to show the problems that could arise if the sponsons are not properly restrained and to demonstrate the forces that would be acting on the hulls.

Paul

[Bob Abell 2Participant @bobabell2]

Thank you, Paul

Still as clear as mud!

How about a sleek hull with outriders that form part of the hull for straight running, but pivot out when the rudders are activated…………..?

It would look impressive and novel………Coupled with an animated driver and a back seat driver that turned his head, Archie Andrews style?

Bob

[Paul TParticipant @pault84577]

Hello Bob

Sorry that is clear as mud…………I'm not very good at explaining things so I must try harder.

Your proposal of a sleek hull with outriders and animated driver is a non starter as your hull configuration would create a trimaran and completely change the basis of the experiment.

Paul

[Paul TParticipant @pault84577]

Dear Kevin

As I am sat waiting for info on the Ghost project I decided to do a little more work on the Banshee, the design has changed ………..just a bit…..as the concept has been played around with.

The twin sponson style hulls still 'lean' into the turns as the boat corners.

Paul

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