prop treating

[rol243]

not sure on the availability of smaller prop sizes but have a look at what the COCR props are made from.

[Gary]

Well that's easy to answer. 30 year old tech has propelled this hull to a best of 106 mph, gps.eagle tree and radar, but not a sanctioned race. I am pretty sure it's the fastest PT 45 around. It is easy to get on plane,pulls a moderate amp draw and keeps the ESC's happy. All the other props I have tried produced some strange hull behavior and way to much time and money "chasing" issues. I am always open to new things but with this boat it took to long to get here.

[rol243]

I must say we always go back to using the original Octura and Prather props . i am using an Octura on a p limited rigger as it works better than an ABC prop.

[raptor347]

The PT45 was designed around the prather and octura props that were available at the time. They do work well on that hull, and sport hydros tend to be picky when it comes to props. 106 is really moving for a sport hull. You need to bring that thing to one of the SAW events.

There are some hulls that don't get along with the new ABC props, but not many. When you get it all dialed, they are spectacular. Example: 4 cell rigger-45mm prop (1823-19-38)- 40.5k rpm peak -141mph through the traps at Legg.

[rol243]

wow thats moving 141 mph.

[kfxguy]

They have those balances for airplane propellers that you can use with a shaft. It my understanding that they are more accurate than magnetic types, although I don’t use one, but I’m not trying to spin 45K either! This would probably work with a flex shaft, but the clearances needed to run the flex just makes balancing it a joke, IMO.

You guys got me thinking, a fairly dangerous thing! I think I would use the 3/16 hardened stub shaft, put a piece of flex on that just to make the bend. Then put a piece of straight shaft to the other end of the short flex. You’ll need a lathe to tool the hole into the straight shaft, so you can make a good brazed welded attachment. This would allow a bearing clearance for the majority of the drive line and only having it loose for the short piece of flex. What you guys think about that?

45k rpm is nothing. Balancing that whole assembly like that is a waste of time. Every time the prop blade hits the water it’s off balance. Plus the shaft and drive dog are such small diameter that balancing them too are pointless. Now, balancing the collet is a worthwhile thing to do.

[Shooter]

Interesting point. That makes sense since it is a surface running prop and only (1) blade is in the water at a time. Hmmmmmm......

[CraigP]

I’m not buying that... It only makes sense while the prop is IN the water. When it jumps out, due to rougher water, the prop overspins like crazy and that’s when balancing is the most important. There’s a reason why everyone balances their blades... Keep in mind that many people run laps, circling over the same water they just disrupted and pressing cornering speeds to the max. In that manner of running, prop cavitation and balancing is a big deal.

I have also read that Jorge, the German fellow doing 198mph in Saw, balances his entire rotating assembly as one unit. So I think it’s a relavent discussion.

[kfxguy]

I don’t ever worry about balancing my personal props perfect. I’ve seen no difference either way. Sharper and thinner makes more difference. If I sell a prop to someone it’s bakanced as best as I can do just do in case they check it then they can’t complain. My own stuff I don’t worry with it because it seems to work well for me either way. Obviously by looking at my builds I spend lots of time and details building these boats and if I felt like they needed that much attention, I would do that. I don’t like to leave any potential gain I could have out of the mix.

Bye compared a 198mph boat to sport running boats and much slower 100ish mph boats is kinda different. Just sayin.

[CraigP]

It’s not about a speed advantage, it goes to reliability, which is the topic of this thread. We all know you build a great boat, but many of us don’t just zip-zip straights, take it easy on the corners and zip-zip back again, while on glass water. This is NOT a knock on the way you and many others enjoy their boat, so please don’t get all bent out of shape. But running consecutive laps over progressively rougher water is a completely different world that zip-zipping. On most every video you have posted, you are running on glass and the prop never cavitates. On oval racing water, it is out almost as much as in the water, especially on the later laps. My data logger shows the prop rpm’s go from 32K to 42K, a big jump. The batteries unload up to a volt during these excursions. So there’s some big time dynamics in play under those conditions. That is the point I’m trying to make.

On full size hydros, props either broke hitting something in the water or on big time prop cavitation. Hardly ever when it’s hooked up proper, which concurs with what your saying. But in our style of running, we have to contend with cavitation to a big degree.

[kfxguy]

It’s not about a speed advantage, it goes to reliability, which is the topic of this thread. We all know you build a great boat, but many of us don’t just zip-zip straights, take it easy on the corners and zip-zip back again, while on glass water. This is NOT a knock on the way you and many others enjoy their boat, so please don’t get all bent out of shape. But running consecutive laps over progressively rougher water is a completely different world that zip-zipping. On most every video you have posted, you are running on glass and the prop never cavitates. On oval racing water, it is out almost as much as in the water, especially on the later laps. My data logger shows the prop rpm’s go from 32K to 42K, a big jump. The batteries unload up to a volt during these excursions. So there’s some big time dynamics in play under those conditions. That is the point I’m trying to make.

On full size hydros, props either broke hitting something in the water or on big time prop cavitation. Hardly ever when it’s hooked up proper, which concurs with what your saying. But in our style of running, we have to contend with cavitation to a big degree.

No getting bent out of shape here. I was just stating my experience based on the original posters boat. I don’t thing he’s doing oval at 105mph. Was just basing this off the original topic. I didn’t know (or didn’t realize) we gravitated towards oval boating talk. I’ll see myself out lol

[Gary]

Well Bodycote just quoted me $450.00 to do the props {3} that I have. Ummmmm...I don't think so. I will just keep a few in stock this year . LOL

[CraigP]

Holy crap! I guess that’s the I don’t want to do it price! Have you tried nitriding?

[CraigP]

Holy crap! I guess that’s the I don’t want to do it price! Have you tried nitriding?

[CraigP]

one other thought... have you tried a 3-bladed prop? I know it’s a huge change, but the harmonics are much less in a 3-bladed prop.

[bob horowitz]

Guys,
I don't think nitriding is the way to go. It is only a surface treatment, only about .005" deep. 17-4 is a heat treatable steel. It is what they call precipitation hardening. If you heat treat it at about 900* F for about 2.5 hours you can get a Rockwell C of about 46 or 47. I work for a dental instrument company and we use it all the time. If you want to try it out, I will put it in with one of our batches and do it for you. We have an inert atmosphere furnace so there won't be any scale, only a little discoloration. Let me know, there won't be any charge, you just might have to wait a bit until we run some.
Regards,
Bob

[CraigP]

Going full hard makes the most sense. Very generous offer Bob. 17-4 is a relatively low temp heat treatment and the quench cycle isn’t too fussy, so the risk to the prop is low. You might want to take that offer Gary.

[bob horowitz]

Craig,
With 17-4 and other precipitation hardening steels there is no quench. It's just a soak at the proper temp.

[ray schrauwen]

Is that a Jae 21 Rigger?

I must say we always go back to using the original Octura and Prather props . i am using an Octura on a p limited rigger as it works better than an ABC prop.

[ray schrauwen]

Steve Reesor used to just use a propane torch on a ceramic turntable to get it to the right shade of orange/yellow and then into his oven on a cleaning 600F cycle for so long. Worked fairly well for him and he was near impossible to catch before his eyes went bad and got out of it.

[CraigP]

Craig,
With 17-4 and other precipitation hardening steels there is no quench. It's just a soak at the proper temp.

At a tooling machine shop I worked at, we still considered it a quench, or returning the metal to room temp. We did 17-4 blades to cut rubber parts. I can’t remember the exact recipe, but we had the heat treat oven programmed with a temp controller and a cooling channel that dropped the temp from something around 1000 degrees to room in 6 hours or so. The oven followed a heat profile. We also had oil and water quench for high carbon steels, going full hard, around 63C Rockwell.

[rol243]

Yes Ray, motor is a low 1500 kv on 4s . but the other high kv jae,s like the ABC,s.

[Gary]

Guys,
I don't think nitriding is the way to go. It is only a surface treatment, only about .005" deep. 17-4 is a heat treatable steel. It is what they call precipitation hardening. If you heat treat it at about 900* F for about 2.5 hours you can get a Rockwell C of about 46 or 47. I work for a dental instrument company and we use it all the time. If you want to try it out, I will put it in with one of our batches and do it for you. We have an inert atmosphere furnace so there won't be any scale, only a little discoloration. Let me know, there won't be any charge, you just might have to wait a bit until we run some.
Regards,
Bob

Thanks for the offer. If I don't do anything before tour ready I will send some to you. Thanks.

[Shooter]

Well Bodycote just quoted me $450.00 to do the props {3} that I have. Ummmmm...I don't think so. I will just keep a few in stock this year . LOL

Cripes! That is way more than they charged us to do a sample run. I think it was around $75. Maybe because they were already running something else? Bummer.

[bob horowitz]

Thanks for the offer. If I don't do anything before tour ready I will send some to you. Thanks.

Gary,
No problem. I'd be glad to do it for you. I would just do one to make sure it works okay. I am assuming they are cast, and that can get hinkly sometimes. At 900* it shouldn't be a problem, but I would want to do a test.
Bob