Metal octura vs Carbon Graupner

[TTKarl]

Ok well last night I just finished balancing and polishing my new copper x440 prop. I've been using and carbon graupner 40x1.4. Now i thought they were the same prop but......

I put it the x440 on and tossed it in. It didn't perform nearly as well. When I opened the throttle the motor would rev but it would take 2-3 seconds for it to accelerate I think it's called cavitating. So I swapped back to the old carbon prop and no more hesitating boat speed increases with motor etc. It looks like the graupner is a little longer prop but the numbers match. Anybody got any ideas?

[hydroracer]

howdy. what hull and motor is it? i'm not familiar with graupner boat props, but i can try and help you with octura prop selection.

[laxmasta2039]

the x440 wont cavitate more than a TINY bit, and probably not at all unless on a big nitro or gas engine. my guess is the x440 was too much for your boat. even if the graupner has a higher dia. it could still be lower pitched.
are you sure your needle's not slipping?

Joe

[TTKarl]

Ok, lets see. It's a cen grey thunder with a .16 running 45% nitro. Ok the graupner prop is 1.4x40=56.0mm or 2.20" which is the same as the x440 if I'm reading the octura number right. I also use a 1.4x42=58.8mm or 2.31" gruapner sometimes but I've had some other issues with that prop. I'm not sure I know what you mean by needle slipping, I'm still kinda new at this. I figured if it was too much prop I wouldn't get the same top speeds and would have overheating from the excessive load??(I dunno that's just what I figured.

[DavidJ]

Props aren't just pitch and diameter. They are just the simplest things to compare them by. There is many many more factors affecting the performance of the prop. I don't have any experience with the graupner props so I can't comment, but they may be completely different prop designs. Even Octura themselves make both a x440 and a 1440, same pitch and diameter, very different props.

I would guess that your Octura prop may not be balanced properly. That could cause the slippage you refer to. It isn't cavitating when it does that it may be slipping or ventilating. Cavitating is when high pressure bubbles literally denotate on the prop.

[TTKarl]

I think your probally right. I didn't know unbalanced props would cause slippage. Not to give you the wrong idea I did balance and polish but it isn't perfect.

[hydroracer]

start with the octura x432 and x435. and maybe a prather p215 :)

i can almost guarantee that you'll bog down with an x440 prop. you're getting into much more powerful .21 size motor territory with the x440. my guess is- it won't come on pipe because the x440 is to much prop for the boat

[TTKarl]

I wish there was some kind of method for this madness. From what I gather it's sorta a hit and miss trial and error method.

[hydroracer]

the diameter and pitch will give a rough idea of where to start experimenting. but after your efforts, you'll learn how different props perform on your boat, probably gain performance, and you'll be able to help out the next guy with advice on prop selection for that boat. as david j said, there's a heck of a lot more to boat props than those two measurements. we're pushin water, not air. different animal altogether... it does'nt compress