Converted Cat from single to twins, now which prop?

[srislash]

You should be good for 45mm. I am not sure how that hull will respond to a lot of pitch but I bet 1.6 would be fine.
Perhaps more on the CNC ones. But I think the suggested ABC 17-1815's would be the ticket.

[RuntheraceAMC]

Sweet! Ordering

[RuntheraceAMC]

Update: So I have been running CNC cleaver 46mm 1.6 props and have been in the 63-65mph range. I thought those results were very promising. Runs very stable at high speed.

I ran a bent shaft rather than replacing it and blew up on of my 4074's. So I am throwing my 4092 1730kv in there and ordering a matching one.

my temps have never really gone above 70F so I believe I can still prop up. Plus I should be able to swing more prop on the 4092. I can't find cleaver style props bigger than 46mm and 1.6 pitch that come in counter clockwise and clockwise directions.

So my question is: what about 3-blade props. I tried one when I was running a BJ24 and the results were terrible. Struggled to get on plane.

But this is a very different boat. Thoughts.

[srislash]

Ok so a three blade will draw another half amount the amps of a two blade( assuming the same pitch). Running a twin you will have less cavitation than you would as a single. Many things can contribute to cavitation like too much pitch and/or not enough blade area.

Which three blades did you have your eyes on?

[RuntheraceAMC]

Well since I wanted to go up to 48mm two blade props( can't find a counter-rotating set) I didn't back off the size of 3 blade much. I already ordered the 45mm 1.8 pitch CNC but now I'm thinking that was a mistake

[RuntheraceAMC]

New prop question. So I have both 4092's in and it's now running 68-70 mph on the 2 blade CNC 46mm 1.6 pitch prop. I tried a 3 blade CNC detounged 45mm 1.8 pitch on the new set up. They ran ok. Decent whole-shot and very little cavitation but weak on the top end. I only did 61 mph on the 3 blade. It seemed like the props just really weren't working. They were hooked up but perhaps props with that kind of pitch need to run higher Rpms?? Couldn't figure out the problem and so I don't know what to try next.

I know I can push my set up further than the 2 blade 46mm, and detounged props are performing better. I like the CNC props but am limited in my options. Some have suggested running an ABC 1417 or 1517 but I have a set of 42mm 1.7 pitch props. They get me to 62mph. I just don't think that's enough surface area to push my boat. Where to next?

[srislash]

Well certainly not 14-1517's 1816,1817, heck with 4092's I wouldn't worry about any of the 19 series either but you'll be pulling all of 250 amps.

On the higher pitch props you may need to shift the CG back as they lift the transom. I have a vid somewhere where I could show you in an obvious fashion, it really just pushes the nose in. You can see it. It starts out great and at some point just flat lines.
Now on the other hand those ABC props mentioned with high rake will do the exact opposite. So huge adjustment going from one extreme to the other.

You are limited to those ESC's so maybe consider the 17 or 18 series props. I have had awesome results with the 1815's and just experimenting in the higher pitches in those props now.

[RuntheraceAMC]

That's interesting stuff about moving the CG on high pitch props. I think 1816 and 1817's might be worth a shot. I have a 1917 I could try on one side just to see if it helps or hurts speed before ordering $90 worth of props.
I'll try moving the CG back on the 3 blade 45 1.8 props and let you know my results

[MarkF]

Your running to small a prop at 45mm. I would buy the 1914s Chris offered and try them as is. If they are not fast enough, he can put some pitch into them. I went 101 mph on 2300 kv motors and 6s with 50mm prop with 1.5 pitch. Cats don't like high pitch like riggers do. I would run 47 to 50mm props with 1.4 to 1.5 pitch.

Mark

[srislash]

So I awoke this morn to Mark's post and thought 'what was I missing'! Still not real awake but for one I was wrong about the amps as I missed the 1800 kv'ish motors. With 47,48, or even 50's you'll likely only be pulling 120'ish amps. He has sound advice.

Sorry about that KV thing, I've been helping a couple people with 2100kv setups.

But try what you have as it is how we learn.
Shawn

[MarkF]

I think the logical next step would be those 1914s from Chris or a pair of Octura 447s.

Mark

[RuntheraceAMC]

What 1914's are you referring to?

[MarkF]

Look at post # 8

Mark

[RuntheraceAMC]

Thought I would update you guys on my results. I've been experimenting with 2 and 3 blade detounged CNC props. On a two blade 48mm I am seeing 70-71mph. On 48mm 1.8 3 blades I am hitting 75 but I lose some hole shot. I've been wanting to try 50mm 2 blades but both reversed and regular props are never in stock.

The latest I've tried is 50mm 1.8 3 blades. I have hit 78mph but it requires a bit of tuning from the other props because these props really force the nose down. Had to adjust the strut angle and weight back. Also noticed I have to be careful backing off the throttle on the 3 blades. If I back all the way off the throttle it drags the back end and starts dancing around. However it does handle the corners better with the three blade.

[fweasel]

The latest I've tried is 50mm 1.8 3 blades. I have hit 78mph but it requires a bit of tuning from the other props because these props really force the nose down. Had to adjust the strut angle and weight back.

Have you tried swapping sides with the props and cables and spin switch from CW to CCW or CCW to CW?