Super cavitating very high speed stealth surface vessel

[Bob Abell 2Participant @bobabell2]

It might have been……10-33?

Bob

[Paul TParticipant @pault84577]

Dave

Don't go blaming me as I wouldn't know my 10-33 from my 8.21 to Eastbourne. But I do know about loosing expensive models to the selfish antics of these 'good buddies'

Paul

[Len Morris 2Participant @lenmorris2]

Dave,

10-4

Len

PS

What's the code for "Would anybody like to talk about Model Boats again"!

[Dave_PParticipant @dave_p]

[Paul TParticipant @pault84577]

Hello Bob

You were right about the elastic band system.

I have been testing and it failed three times out of twenty so I think it's best to use the servo controlled system that you recommended.

Paul

[Bob Abell 2Participant @bobabell2]

Hello Paul

We only just got back from Betws y Coed……Nice day out after being stuck in for three months!

Sorry to hear your Lacky Band idea has fallen by the wayside!……But very noble of you to confess the fact in publick

So are you going for the two washing gear segments with one driving pinion, now?

Any news from Stateside yet?

Bob

[Paul TParticipant @pault84577]

Hi Bob

We agreed that every design twist and turn would be reported on the forum, in this way kevin can see how the project develops and why certain decisions are made.

There will be a two segment and a single drive pinion, which is the most weight effective system, operating the wings.

No replies to my TQs yet.

Paul

[Paul TParticipant @pault84577]

Hello Capt Bob

I've started drafting the working drawings.

For your information the sponsons are 950mm long, 50mm dia. the internal diameter of the sponson tubes is 45mm. Obviously this dictates motor size and the model will be restricted to can dimensions of 45mm or less.

Distance between the sponsons at the widest point is 600mm

I will keep the information coming.

Paul

Edited By Paul T on 25/01/2015 19:48:38

[CookieOldParticipant @cookieold]

Hi Bob , Sorry to change theme but did you have a good time at Betws Y Coed i bet you went to the 7 and a quarter railway is that 15 inch britannia still there .

Dave

[Bob Abell 2Participant @bobabell2]

Hello Cookie

So you know the area, then?………Pleased to hear it

I`ve not been in the museum for a few years, but I have seen the big Britannia. It must be worth an absolute fortune!

A few years ago, Colin had a young chap, build two large Loco`s based on a Beyer Peacock theme…..In a Guards van! We used to visit him regularly on our trips to the Caravan site next door…..The Riverside

Small world….eh?

Bob

[Bob Abell 2Participant @bobabell2]

Thank you, Paul

A nice sized model……..Don`t want to put the mockers on your creation, but just don`t like the idea of motors and batteries inside the sponsons

Do we have to build an exact replica?

Keep talking

Bob

[Paul TParticipant @pault84577]

Hello Bob

I am sure that Kevin would love to know why don't you like the idea of having the motors and batteries in the sponsons.

If we are not building a replica then we are avoiding the challenge……what is the point of building it at all.

Paul

[Bob Abell 2Participant @bobabell2]

Hello Paul

Motors on the sponsons means we`ll need totally reliable prop shaft seals………Not practical, without a proper engineering solution

The 4600 batteries won`t fit inside a 45 mm bore tube and if we could fiddle it, connecting up the wires and sealing the wire holes would be a heck of a job

The only easy bit would be the end caps

In my opinion, a scale model is out of the question

You and I are not seeing eye to eye on this very difficult project and I wish to be excused from further involvement

By all means, continue with the design and I will watch with interest, but with a jaundiced eye, I hasten to add

We are not falling out one little bit, but being in the middle of the VGC build, my mind is on the current project

I`m very sorry to have let you down, old chum

Bob

[Paul TParticipant @pault84577]

Hello Captain Bob

Fair enough.

The design will carry on (in the best Sid James manner) I shall continue to post as the work progresses and hopefully change you opinion.

Paul

[ashley needhamParticipant @ashleyneedham69188]

I am with Paul on this; a craft this unusual needs the appropriate engineering.. personally I would make some slight adjustments for practicalities normally however so far the dimensions of the craft seem to preclude having to do this.

The sponsons are very long and 45mm is quite sufficient to put batteries in if the pack as a single cell stick. A brushless motor at the front would be my answer to the drive, and this could be running wet; a bulkhead could be used to seal the batteries in and so forth.

Ot is only the batteries that are the big weight so they need to be in the sponsons.

I am not convinced one would obtain supercavitation, but unless you try???

There woild be no doubt that the craft will be fast however, and so the cavitation thing is all to play for.

Bob. Unusual craft need some outside the box thinking and going against accepted engineering principles. I say stick with it, you may be suprised. I would not say this is a difficult project at all, just different to the same old same old. The build should be straigtforward, getting it to run in the appropriate manner will be challenging, and thats the best bit.

Ashley

[Bob Abell 2Participant @bobabell2]

Ashley to the rescue?

Will reserve further judgement pending Paul`s final design studies

(I had forgotten that Brushless motors can run wet!)

That makes a big difference

Well done, Ashley……Carry on up the Creek, Paul

Bob

[Trevor HollowayParticipant @trevorholloway99134]

As a change from the run of the mill watercraft – its worth the challenge of designing out any forseable hurdles and designing in adjustments.

I'd be tempted to put a brushless on each end of the sponsons running flooded. The sponsons would take a 12 stick of sub-c's in each sponson. The light bits can go in the body.

Still must be a darn sight easier than building a full size one !

Ashley to the rescue – only if Paul can design it in hardboard.

[Paul TParticipant @pault84577]

Ashley, Bob, Trevor

The intention is to use AA batteries in four x 4 pack holders wired in parallel and mounted on sliding trays in each sponson, the ESCs will also be on these sliding trays. The sponsons are 50mm plastic waste pipes and will be sealed with plastic welded threaded caps

The receiver and compressed air supply will be in the cabin.

I'm not at the brushless stage yet but I don't want to run the motors 'wet', I will be using a home engineered propeller shaft connected to an air supply to ensure positive pressure to keep the water out and to provide the cavitation bubbles.

Difficult to explain with out diagrams but I'm in the process of detailing the GAs and will be able to post them soon.

Not going to use hardboard but I am going back to balsa for this project.

Still going up the creek but thrown the paddle away and now using the outboard.

Paul

[Trevor HollowayParticipant @trevorholloway99134]

Slight positive pressure behind lipseals on the propshafts will work.

Is the propshaft to be hollow to bubble in front of the blades ?

[Paul TParticipant @pault84577]

Hi Trevor

I intend the bubbles to exit the tube to the rear of the blades, the quantity of air being released will increase as the boat increases speed.

The prop tube will be divided into 2 sections, the forward section will be pressurised and the rear section will have a traditional seal and loaded with grease.

Paul

[geoff abellParticipant @geoffabell49720]

Hello Bob

Just managed to sort out the membership enrolment

Geoff

[Bob Abell 2Participant @bobabell2]

Welcome aboard, our Geoff

Bob

[ashley needhamParticipant @ashleyneedham69188]

Paul. AA sticks only good for about 7 or so amps max draw and thats that. Would recommend sticking to normal sub-c or even 2/3 c to get the desired current for the high speeds envisaged.

Ashley

[Paul TParticipant @pault84577]

Hi Ashley

I know that my usual building style involves heavy amp eating boats but with the Ghost I am opting for a lightweight build and using helicopter/aircraft building techniques.

With this lightweight approach I hope to reduce the amp draw and be able to use the 4 x 4 AA packs (16 batteries per sponson)

I am in a quandary as I cant decide between using compressed air canisters or a lightweight compressor as the air supply, both have advantages and disadvantages.

Paul

Edited By Paul T on 27/01/2015 17:09:19

[Trevor HollowayParticipant @trevorholloway99134]

I'd go for the compressor, rather than have stored up gas under pressure in cannisters and pipes. Compressor can be adjusted to regulate the max output and zero at rest.

Any leaks should be less dramatic with the compressor option.

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