Super cavitating very high speed stealth surface vessel

[Trevor HollowayParticipant @trevorholloway99134]

Assuming NiMh around 2200mAh – would the extra oomph from the bigger cells make up for the lack of volts ?

16 x AA@ 21g each = 336g

10 x 4/5 Sub-C @ 35g each = 350g

[Paul TParticipant @pault84577]

Hi Trevor

I am leaning toward the compressor option as it offers a greater range of control, the downside is the extra weight that the compressor adds to the upper superstructure.

Thinking of using a small and simple electric tyre inflator.

Re the batteries: I opted for the 4 x 4 AA for the ease of moving the individual packs inside the sponson whilst adjusting the ballast and trim.

Paul

 

Edited By Paul T on 27/01/2015 17:51:46

[Bob Abell 2Participant @bobabell2]

Hey, Paul……Are you winding me up?

What`s the compressor for?

Bob

[Andy CParticipant @andyc56856]

Hi Paul

I'm pretty sure that brushless motors and lipo batteries would bring the weight down. Brushless motors also don't mind a bit of water too, as we saw in an earlier post. Would that not be worth investigating?

Andy

[Mark Jarvis 2Participant @markjarvis2]

Hi Paul

Like the idea of the tyre type compressor, they dont weigh a great deal but they dont have much output, it takes for ever to inflate a tyre. Surly you only need low volume and pressure???

Andy C has the best idea with LiPo batteries and brushless motors, aircraft ESC,s are very light as well, only need forward control.

Mark

[Len Morris 2Participant @lenmorris2]

Hi Paul,

Think I know where you are going with this one but am still concerned about buoyancy if the sponsons are to remain submerged. Will comment on this later, however for now suggest you forget compressors and gas cylinders (that's submarine thinking). Think Hovercraft. High volume air flow, very low pressure. Even if the sponsons were 6 inches under water you only need a quarter of a psi. Easily achieved by a small radial fan unit with the high flow rate you need. Build the fan and casing out of half mill ply (or balsa), it'll weigh nowt and on the end of a decent light weight motor will blow you away. Tyre inflators, will never give you the air flow you need and gas cylinders won't last a second (and be heavy and expensive for your job).

Why bother making a water proof prop shaft? Robesch make them for little money with lip seals and roller bearings. You could not make one for the price and when you see one the are beautifully engineered. Why not fit a large sleeve around the shaft and flow the air into that? Mi Resurgam has an 8 mill Robesch fitted down the middle of 13 mill domestic water pipe. Have a look somewhere around the mid postings. It was never intended, happened during the development and the sealed cavity created is redundant on my model. But, I could easily blow air into it, drill a few holes at the stern and have bubbles galore! Also, it would keep the functions separate, propshaft and bubble system. Combine the two and I think you are in for a world of pain. Design philosophy, one bolt one job, happiness. One bolt two jobs, misery. Some thing long forgotten in our let's save a penny world of today! (Sorry. starting to rant again!)

Hope all this helps Paul

Len

[ashley needhamParticipant @ashleyneedham69188]

Would not want to put Lipo in the submerged hulls…….

Hmmm… a, or a paiir of 40mm EDF may indeed create sufficient pressure for bubbles as stated, and you also get the gas turbine whirr noise as well!

Ashley

[Bob Abell 2Participant @bobabell2]

Paul

The geared segments, I suggested, would make ideal subjects for 3D printing!

Take a look at the examples on this 3D printer thread…..

**LINK**

Our friend, Matthew may be a handy contact?

There could also be more shapes suitable too

It`s a brave new world out there!

Bob

[Paul TParticipant @pault84577]

Hello Bob

It is a brave new world out there but before you rush out and buy a 3D printer you should bear in mind that the downside with new technology is knowing how to use it.

Having a 3D printer seems like a wonderful solution to all sorts of problems but to make the printer work you need a firm grasp on using CAD and 3D software.

Paul

[Bob Abell 2Participant @bobabell2]

I wasn't proposing to buy a 3D printer

I was thinking that Matthew could help us out

Bob

[Paul TParticipant @pault84577]

Hello Captain Bob

Have you had any snow yet?

Sorry I wasn't suggesting that you should buy a 3D printer, I just wanted to inject a word of caution before Kevin went out and bought one.

I am sure that Matthew would gladly help but we should be careful in our requests as the poor chap still has huge amounts of school work to complete.

Paul

[Paul TParticipant @pault84577]

My balsa has just arrived and I am very impressed with the service.

I ordered a pack from Fred Aldous through Amazon on Sunday and it arrived today, very well packaged and at the right price.

I will certainly be using them again.

Paul

[Paul TParticipant @pault84577]

The latest rough GA drawing showing some major dimensions and the basis of access into the cabin area.

[Bob Abell 2Participant @bobabell2]

Hello Paul

You've made a good job of the layout

Have you made a start, with the construction?…..Having bought a bundle of balsa

Bob

[Paul TParticipant @pault84577]

Hello Captain Bob

I am making one more card prototype, this time at 1:1 scale so that I can check some of the finer details, but I expect to begin construction of the working model before the end of the week.

Not making any decisions about motor types just yet as I want to see the thing 'in the flesh' before I start specifying the main equipment.

Its been over 40 years since I last built with balsa and it might sound daft but I am a little nervous of using such a fragile material especially having spent so long bashing nails into thick plywood.

Can you seal balsa with PVA or do you still have to dope it?

I presume that I can use PVA to stick the stuff or do I have to buy balsa cement?

Paul

[Bob Abell 2Participant @bobabell2]

Hello Paul

That sounds a good idea…….Even if we don`t go ahead with the real thing, we`ll have something to show at Haydock?

I think PVA is ok for glueing Balsa….It`s easy to sand, not like Balsa cement, but don`t smell as nice

I think normal paint would be ok too

For what it is worth, I still think a semi scale model is the best option…..Using known technology and stands a good chance of working, using timing belt drives etc

Bob

[CookieOldParticipant @cookieold]

Hi Paul , I use have used bog standard fiber glass resin to seal my balsa , It,s great quick rub down , prime and finish coat job done , it also makes the balsa stiff.

Best Regards Dave

[Mark Jarvis 2Participant @markjarvis2]

Hi Paul

Would look to sealing resin, i get mine from http://www.easycomposites.co.uk they also supply light weight glass cloth, like the stuff aeromodelers use, cheap to.

You thin the stuff with Meths, mix it like water so it will sink in.

Mark

[Dave MilbournParticipant @davemilbourn48782]

For what it's worth please see my contribution about resin finishing to Gareth Jones' thread on Spyder J. I wouldn't use the very lightest cloth on balsa.
DM

[Paul TParticipant @pault84577]

Dear All

Thank you for all of the excellent advice.

The full size card prototype is half built and has already proved its worth by giving me some insight into the lateral forces acting on the wings.

Instead of the wings being hollow structures they will now be reinforced with metal tubes running from the sponsons to the cabin, these tubes will also double up as ducts for cables and air lines.

Paul

[Mark Jarvis 2Participant @markjarvis2]

Hi Paul

Have a look at this on ebay, might be what you need

171661501985 Hydraulic unit

Mark

[Paul TParticipant @pault84577]

Hi Mark

Nice kit and thank you for the lead, I have made the owner an offer but had no reply.

Dear All

An update on the design:

There has been a slight change to the overall size of the cabin simply as an expedience for common sense. I have reduced the dimensions by 2.6% to bring the cabin panel sizes into line with commercial balsa sizes.

Paul

[ashley needhamParticipant @ashleyneedham69188]

Ah ha !!! dimensions dickered with for "operational reasons" I like it.

Worried about the sponsons becoming submarines at speed or will the floatational qualities of them and the streaming air bubbles keep them up and if so what about the depth keeping going through the speed range???

I did see little "canards" on the front, could be handy.

Ashley

[Paul TParticipant @pault84577]

Hi Ash

Operational reasons win every time especially when the changes are measured in microns (well almost microns)

I hope that the sponsons wont 'submarine' I have added a few sneaky ducks (oh la la) to make sure the sponsons rotate in the correct direction and stay at the right angle as the boat rises from the water but all the theory in the world cant anticipate everything and there is a real chance that the sponsons will porpoise at speed.

At the back of my mind I am considering the prospect of having to use a quadcopter gyro system to manage the trim.

Paul

[Bob Abell 2Participant @bobabell2]

PAUL,

How will the Quadcopter Gyro system manage the trims, when you haven`t got a rudder etc?

What will it manage?

Bob

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