CNC or ABC Prop

[Speedfreek]

My question is wouldn't a CNC prop be better then a hand massaged prop, due to each prop being identical to each other in a twin set up?

[raptor347]

Not if the hand prepped props are done right.

[Speedfreek]

Not if the hand prepped props are done right.

I understand some people can do a good job which takes a lot more time and your paying more for them, when a CNC can do the same if not better and costs less.
I would like to know if anyone has done a CNC vs a Hand sculpted comparison of the same size prop.
Back in the day hand finishing props was the norm because there was no CNC or Computerized program's that simulate the prop cutting threw water or whatever, just saying technology these days is far superior then the old eye.
Your thoughts.

[raptor347]

Honestly, you won't find a CNC prop on anything really fast. Even Joerg's props are hand finished castings. CNC are a good option for those who don't or can't do prop work.

[Speedfreek]

Honestly, you won't find a CNC prop on anything really fast. Even Joerg's props are hand finished castings. CNC are a good option for those who don't or can't do prop work.

Like me
This is what i want to know
So no CNC props in the 90+ zone ?

[NativePaul]

A raw CNC prop is definitely better than a raw cast prop, to the point that a CNC prop doesn't need balancing and can be used raw, but really both need finishing, a CNC will just need he'll of a lot less work to finish, some can be bought finished but they will have been hand finished after manufacturing.

CNC props are fairly new and the companies making them generally only have 2 ranges so far, one that is a lot like an Octura X series, and one with a lot less blade area for Navigation type endurance racing, whereas Octura and ABC both have a lot more styles and pitches available.

Those with big ranges of props are more likely to have something that will work well for your application, but it is unlikely to be the ideal prop, and to get the most out of it you will have to tweak it a little, and at the moment there is a lot more experience out there tweaking Octura and ABC, having said that most CNC props can be tweaked.

Materially most cast props have an advantage over most CNC props, most cast props are beryllium copper which is fairly strong yet very ductile in its cast state and can be hardened further, whereas Most CNC props are either 6061 or 7075 aluminium and come in a prehardened state, 6061 is not good enough and should be avoided, 7075 is about as strong as unhardened BeCu, but impacts tend to crack it where the same impact would bend BeCu and the prop may be savable. Some day 7075 will crack if you try tweaking it, but it has enough ductility for the tweaks I have done. There are some outliers like Octura's aluminium which is like cheese way weaker than 6061, and chrome cobalt stainless steel CNC props that are way stronger than unhardened BeCu (I have no experience with hardened BeCu for comparison), doctor props for example come way thinner and sharper than I can get away with making a BeCu prop. I hear the chrome cobalt steel used in stainless CNC props is brittle and it does tend to crack rather than bend in impact, but I have seen some bend so I suspect that like 7075 they are ductile enough to be tweakable.

All the CNC alloy props that I have seen have an oversized blade root, and thinning it pretty severely is a worthwhile mod, I belive it is so big not for strength, but to utilise a larger ball ended milling cutter which substantially reduces the machine time and thus cost to make a prop. The stainless CNC props are much better in this regard but the price is much higher.

Theoretically they could use many thousands of passes and get a prop that doesn't need hand finishing, but it is way more cost effective to CNC it most of the way there, and finish it by hand.

I only know of 1, but I would guess that there are a bunch of 90+ boats out there on CNC props. On the other hand I highly doubt that we will ever see a competitive world record fall to a boat with a stock CNC prop.

[Speedfreek]

A raw CNC prop is definitely better than a raw cast prop, to the point that a CNC prop doesn't need balancing and can be used raw, but really both need finishing, a CNC will just need he'll of a lot less work to finish, some can be bought finished but they will have been hand finished after manufacturing.

CNC props are fairly new and the companies making them generally only have 2 ranges so far, one that is a lot like an Octura X series, and one with a lot less blade area for Navigation type endurance racing, whereas Octura and ABC both have a lot more styles and pitches available.

Those with big ranges of props are more likely to have something that will work well for your application, but it is unlikely to be the ideal prop, and to get the most out of it you will have to tweak it a little, and at the moment there is a lot more experience out there tweaking Octura and ABC, having said that most CNC props can be tweaked.

Materially most cast props have an advantage over most CNC props, most cast props are beryllium copper which is fairly strong yet very ductile in its cast state and can be hardened further, whereas Most CNC props are either 6061 or 7075 aluminium and come in a prehardened state, 6061 is not good enough and should be avoided, 7075 is about as strong as unhardened BeCu, but impacts tend to crack it where the same impact would bend BeCu and the prop may be savable. Some day 7075 will crack if you try tweaking it, but it has enough ductility for the tweaks I have done. There are some outliers like Octura's aluminium which is like cheese way weaker than 6061, and chrome cobalt stainless steel CNC props that are way stronger than unhardened BeCu (I have no experience with hardened BeCu for comparison), doctor props for example come way thinner and sharper than I can get away with making a BeCu prop. I hear the chrome cobalt steel used in stainless CNC props is brittle and it does tend to crack rather than bend in impact, but I have seen some bend so I suspect that like 7075 they are ductile enough to be tweakable.

All the CNC alloy props that I have seen have an oversized blade root, and thinning it pretty severely is a worthwhile mod, I belive it is so big not for strength, but to utilise a larger ball ended milling cutter which substantially reduces the machine time and thus cost to make a prop. The stainless CNC props are much better in this regard but the price is much higher.

Very nice reply, do you do props yourself ?
Can you recommend a prop for my new set up ?

[NativePaul]

I buy cast props finish them and mod them for myself and occasional props for close friends, but I hate it, by far ny least favourite part of FE boating, sorry but as a stranger you couldn't pay me enough, Raptor or Dasboata are your men.

Dunno, I might be able to if it is similar to something I have done before and you want a similar thing out of it.

[Speedfreek]

no problem.
What prop would you recommend for a 44 in Mystic duel TP 4070 1520Kv in CR Dual Castle XLX for SAW ?

[srislash]

no problem.
What prop would you recommend for a 44 in Mystic duel TP 4070 1520Kv in CR Dual Castle XLX for SAW ?

Talk to Brian (Raptor), he will set you up. Well as long as he is offering his services at least.

[NativePaul]

That is out of my experiance range, I have no duals and only 1 boat over 40".

[T.S.Davis]

Brian's work is pricey and worth every penny in my opinion.

[ray schrauwen]

CMDI was the only place to cnc props not needing any finishing. They stopped after a short run. I still have a 50mm x3 blade, 83mm pitch, never found a boat it ran well on... yet.

[Speedfreek]

I have PM Brian, see what happens
I did get a price, it was going to cost me $348 Australia dollars approx, way to much for two props.

[longballlumber]

CMDI was the only place to cnc props not needing any finishing. They stopped after a short run. I still have a 50mm x3 blade, 83mm pitch, never found a boat it ran well on... yet.

That could be the reason they quit making them.... just saying