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I imagine you could plate spring steel as well. I looked for piano wire, but the hobby shops here seem to only sell it in short (<1=m) lengths....and much smaller sizes.

EDIT: yeah also this stuff is probably set up for torsion, even under quite extreme curvature.

 

Can I comment here?.....ok I will anyway! It can be a catch to compare underwater or even in-air projectiles with ones that are dual medium (surface) ones. Even in flat water things change, and in any sort of ripple or waves, the blunt bow begins to be a real show-stopper.

Tear-drop shaped subs are great under water, but not as good on top, either for speed or manoeuvrability and sea- kindliness.

I know all this stuff and I am not using it, so I thought I would share....

Nick

 

Hi Colin
Just a suggestion for your boat, attach two pontoons say 1-1.5 ft in dia with pointed ends each side under your boat. This will give you speed and improve the stability, turns the boat into a cat.
Ian

 

If the flex shaft is not over about 2m you can probably splice the <1=m section. That is, assuming piano wire has the same specks as the spring wire Rick uses. Seems like I remember Rick wrote something like that could be done in one of his projects. Splicing works with my fiberglass versions anyway.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXLHU7&P=0

Porta

 

Ok. Interesting. But the wire I am finding is more like 1mm than 8.

I do not understand why modellers would want 8mm rod!

 

A question folks, regarding Javaprop.

I entered a .3m diam prop, 2 blade, hub of 50mm, 300 rpm 3 m/s, 100w. I am sure it worked once, but now it says design failed try reducing prop load.

What gives? I have tried both the online and downloaded version and did set the viscosity (which I think is about 1*10 -6? but I tried all sorts of values)

to get the thing to work I had to have a 3m prop, or 2100 RPM, or some such.

Thanks for any help.

Nick

 

Hang on! I saved and loaded another value, and the thing worked, but with an efficiency of .5%, simply when I went back to the calc page. but then it fialed when I recalculated.

 

what density?

 

Sorry, Rick, yeah. density = 1. I did try others as well.


D'oooh I assumed density = 1 because water is the sort of standard. 1000 Rick..

Thanks

 

Try 1023kg/Cu.m for salt water or 1000 for fresh. Even air at NTP is 1.2Kg/Cu.m.

You are designing a prop for very thin air if you have density at 1kg/Cu.m

 

Read my "D'oooh" Rick. I realised what I had done.

Nick

 

The thinner stuff is used for landing gear. Don't know about the 9/32" = 0.28" which is just under to 8 mm. Only the tail section of the flex rod has to be spring wire and thick rigid pipe can be used for the front section that connects to the gear box in hpb application, I think.... My hobby shop had thicker than 9/32" - was claimed to be music wire, but who knows....

Porta

 

Hey All,

Thank you guys very much for your opinions - very helpful. I'm going to look into some things and I'll let you know how it goes. Thanks!!

Colin

 

Rick, been doing some reading on this and it appears that there will be cathodic corrosion when using carbon directly on steel or aluminum. One chap that built a CF bike recommended using fiberglass insulator between. Also it is not clear how much flex the CF top coat has before shattering with a flex substrate underneath.

Hope this helps.

Vic

 

Be good to hear. Comments were pretty tough, but well meant and genuine.