Super cavitating very high speed stealth surface vessel

[Bob Abell 2Participant @bobabell2]

We need to exploit the artist`s licence for my suggestions to work!

Chunky pivot area, as large as the motors, to house the pulleys, with boxy legs to house the Brushless motors and batteries

We can`t make a scale model, but we can adopt the features of pivoting legs, contra props and space age shape

The pivot mechanism could be a screw thread driving a rotating nut on an arm with about 45 degrees of movement

Say a 40" hull with a hull 12" wide x 8" deep

10" radius legs with the sponsons….4" dia x 30" long

One normal propshaft inside a tube with a second prop fixed to the tube

One pulley for the propshaft and one for the tube

This would be my starting spec

Any good?

With the space age Brutus style, it may look ok?

Just thinking out loud and can`t really get down to the nitty gritty till the VGC is finished, but once we agree on the design, I`ll work with you

Bob

[Paul TParticipant @pault84577]

Back to the design work

One of the things that have to be identified are structural changes that have taken place over the life of the boat. For example on the Ghost boat a couple of changes jump straight out.

The addition of cowls to the cooling inlets (Red) and the new stubby wings (Yellow)

The images on the left show the boat in its original condition and the images on the right show the additions.

The cowls and wings are very obvious changes (but how many of you spotted them……be honest) but there are other far more subtle alterations that have been made.

When working on a design for a model of an existing boat it is important to identify which period of the boats life you wish to concentrate on and then include, or exclude, the relevant components.

As Bob is the 'client' it will be his choice as to which version we build………although based upon recent experience this simple decision is likely to be fraught with many complications: lol

Paul

[Paul TParticipant @pault84577]

Its Question and answer time again

Bob

We need to exploit the artist`s licence for my suggestions to work!

The original instruction was for a scale model so artistic licence is out.

Chunky pivot area, as large as the motors, to house the pulleys, with boxy legs to house the Brushless motors and batteries

See the above answer

We can`t make a scale model, but we can adopt the features of pivoting legs, contra props and space age shape

We can make a scale model using the design features that I have already worked out, the model will perform exactly as its full size parent. We cant make a scale model using the design constraints that you seem hell bent on using.

The pivot mechanism could be a screw thread driving a rotating nut on an arm with about 45 degrees of movement

This is a good idea and might be better than my plan to use twin heavy duty servos

Say a 40" hull with a hull 12" wide x 8" deep

Thank you for the dimension request unfortunately due to the constraints of scale we can only adopt one of your proposed dimensions…….I would suggest that we explore the 40" as an overall length and see how the rest of the model scales to this length.

10" radius legs with the sponsons….4" dia x 30" long.

If we are working to an overall length of 40" then these dimensions will become evident as the 'scale' model is drawn up and detailed.

One normal propshaft inside a tube with a second prop fixed to the tube

This is another good idea and might prove more cost effective than my gearbox proposal

One pulley for the propshaft and one for the tube

As above

This would be my starting spec

A specification……..be careful Bob or people will think you know what you are doing

Any good?

Some of this is good and some is just 'pie in the sky' as you are fond of saying

With the space age Brutus style, it may look ok?

The parent boat does have a unique style and is proving to be a challenging subject

Just thinking out loud and can`t really get down to the nitty gritty till the VGC is finished, but once we agree on the design, I`ll work with you

I like your thinking aloud even if it is done in crayon

[Bob Abell 2Participant @bobabell2]

I didn`t think you had started the design work……How far have you got?

Your design is based on motors and batteries inside the sponsons

How do you propose to have a reliable easy sealable opening for access to the stuff inside?

Bob

[Paul TParticipant @pault84577]

Hi Bob

Ever since I first looked at the boat I had envisaged using plumbing plastic drain pipe and fittings for building the sponsons, this type of pipework comes in various diameters and have a mixture of welded joints and best of all rubber sealed threaded fittings.

Paul

[Paul TParticipant @pault84577]

Back to the design process.

There are a few different ways of getting the information necessary for producing drawings.

The best and most accurate method is to find templates or blueprints of the subject and I always visit The Blueprints.com **LINK** to see if they have a set of blueprints that I can use.

But for most of my design work I end up tracing images from photographs although it should be mentioned that the photographs must be 'square on' so that details aren't lost in the perspective.

For example these images are suitable for tracing some details of the front and side elevations

The tracings don't have to be super neat as they will be straightened up as the design is worked up. To get sufficient information for the entire boat you might need to copy a few photographs and be inventive in the places that aren't covered by photos. I know it sounds complicated but the eventual results are 95% accurate.

NB

Whilst I have done this on a computer the same work can be done with a photocopier or scanner and home printer (it takes longer but it can be done)

The next stage is to overlay and compare all of the tracings to ensure all of the components are picked up and then begin to work up the sketches into working drawings, even with a computer this part of the process can take some time.

Paul

 

 

Edited By Paul T on 05/01/2015 18:21:06

[Bob Abell 2Participant @bobabell2]

You`ve copied that well!

From your earlier posting, the sponsons look about 50% longer that the hull and tapered at both ends

Can`t see us doing that with a plastic drain pipe

A scale model looks like a bridge too far………Prefer a simplified semi scale version….Said the Client

Bob

[Paul TParticipant @pault84577]

Questions and answers

You`ve copied that well!

I was trying to show that the tracing doesn't have to be perfect but all will become clear when the drawings are produced

From your earlier posting, the sponsons look about 50% longer that the hull and tapered at both ends

Yes that's about right

Can`t see us doing that with a plastic drain pipe

Maybe you cant ….but I can and I can show you how to do it

A scale model looks like a bridge too far………Prefer a simplified semi scale version….Said the Client

I didn't expect you to give up at the first stage. But don't worry, if I cant design it you won't have to build it.

Paul

[Bob Abell 2Participant @bobabell2]

How can the sponsons stay submerged at speed?

They either float or they don't?

Bob

[Bob Abell 2Participant @bobabell2]

We could make the sponsons from drain pipe material with solid wood tapered ends

We could flood the sponsons if required

Have the motors in the hull, but fit the props below the hull, level with the lowered position of the sponsons on a support with a pair of rudders. They wouldn't be seen and makes life easy

Any good?

With widespread wings, can't see it being unstable

I can see motors in the sponsons, easily enough, but the batteries in the hull for accessibility

Bob

Edited By Bob Abell on 05/01/2015 21:15:07

[Andy CParticipant @andyc56856]

I do love a good mystery. Also been interwebbing super cavitation, very interesting topic. Looking around though it is not the motors wot make it fast but the way the thing sits in its bubble. So a very normal brushed motor sitting in the sponsons with the correct cavitation forming nose cone should work. Servo powered hinges connecting the "wings" to the hull, to stop them moving too much and Bob's your aunties uncle, there you have it. If the Russians could do it in the 60's we must be able to come up with something nowadays.

Back to the shadows again. My man cave now even has wifi.

Andy

[Bob Abell 2Participant @bobabell2]

Hello Handy Andy…..Your excelling yourself tonight?

It's encouraging to hear your positive comments

I'm tempted to abandon the pivoting wings, but they are an essential desirabell feature and will be great fun to play with on the water

Call again

Bob

[Bob Abell 2Participant @bobabell2]

Paul…..Can we make use of the magic words….Super cavitation?

I would have thought that super cavitation would be inefficient?……Normally, cavitation is to be avoided?

Is the propellor belting round in fresh air?

Paul is in his Bat cave at the moment, how he gets to sleep, hanging upside down, I've no idea?

If we use brushless motors, we could use those super lightweight batteries in the hull?

Bob

[Paul TParticipant @pault84577]

Bob

I am looking at the super cavitation system at the moment but no the props don't run in fresh air.

Super cavitation is very effective: the company that built Ghost (Juliet Marine Systems) is claiming very high levels of efficiency but, as yet, I haven't found any independent data to support their claims.

For the sake of avoiding any further misunderstandings it is highly unlikely that any equipment other than the receiver will be located in the cabin (hull)

Here are some preliminary dimensions for you to consider:

The overall length is 1200mm, the sponsons are 55mm dia, the cabin is 800mm long by 180mm high and the wings are approx.170mm long.

Paul

[Bob Abell 2Participant @bobabell2]

Keep up the good work, Paul, but don't overdo ithings

You've left me miles behind on this job

Hope it all works out for us……It will be a spectacular model for the Haydock show!

Bob

[Paul TParticipant @pault84577]

Bob

This is the tidied up side elevation

So now you can see how the overall model would look.

Paul

[Bob Abell 2Participant @bobabell2]

Looking good, so far, Paul

What about the props?

Where would the waterline be in this view?

Bob

[Paul TParticipant @pault84577]

Bob

I am still looking into props so I've not included them on the drawing.

The waterline is just above the sponsons.

What size brushless motors do you have in stock? (for fitting into the sponsons)

Paul

[Bob Abell 2Participant @bobabell2]

Got 4 x Turnigy D3536/6 1250 KV….1250 revs per volt

Body 35 dia x 40 long plus shaft 5mm x 16 long

They don`t look big enough

How will you keep them dry?

Bob

[Andy CParticipant @andyc56856]

Don't need to keep brushless dry. Found a few vids a while back where peeps were running them in water with no ill effect.

https://www.youtube.com/watch?v=ejRRek-4tL8

 

Edited By Andy C on 06/01/2015 23:24:22

[Andy CParticipant @andyc56856]

Sorry, you have got to see this one. Won't spoil the surprise.

**LINK**

[Bob Abell 2Participant @bobabell2]

Hello Andy C

Thank you very much for such valuable information!

It could be the answer to a very difficult problem……Sealing the motors!

It certainly has made the job easier

The super cavitation video is also very interesting, but I don't think we cam go fast enough, for the phenomenon to come into action……Will read it again

Paul will be very impressed

Thank you very much for the info

Bob

[Paul TParticipant @pault84577]

Andy

Thanks for the links and for offering advice as both are really appreciated. I had an idea that these brushless thingies can run underwater but I wasn't sure……….and having see it happen I'm still not sure as it goes against every engineering principal that I know. I just goes to show that you are never to old to learn something new.

Bob

We don't have to seal the motors…just the prop shafts where they pierce the hull (exactly like any other boat)

The model is theoretically capable of achieving very high speeds especially if we can get the legs to work correctly so the cavitation system is a distinct possibility.

Paul

[Bob Abell 2Participant @bobabell2]

Is that a typo?…..Where the prop shafts pierce the hull?

If our brushless motors are too small, why not make the model size suit the motors?

Bob

[Paul TParticipant @pault84577]

Good Afternoon Bob

No it isn't a typo: The propshafts pierce the hull of the sponsons at the front (where the props are)

But before Kevin starts to get confused with the names of the major component parts I think that we should stick to the following descriptions.

 

 

Re brushless motors and the size of the model……………..someone, I cant remember who, requested that the model be about 44in long and so the design is being done to suit this request.

Kevin

You might find it easier to think of this project as a cutting edge catamaran rather than a futuristic stealth boat 

Off for a cream cake and a coffee.

Paul

 

Edited By Paul T on 07/01/2015 15:25:22

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