SAW propeller for Hydro 2

[Ivan Kozyakov]

Hi guys!


I am preparing my Hydro-2 for the next season with 8s SAW setup (2000 Kv SSS, 240A Swordfish). In many SAW videos I have seen that they use three bladed propellers. What are the advantages of such a solution? How do they differ from standard semi-submersible ones?

IMG-1979.jpg

[Bande1]

they slip less

[NativePaul]

For a long time Octura's V series were the only props readily available with high pitch and lowish lift, and they are all 3 bladed.

[Bande1]

For a long time Octura's V series were the only props readily available with high pitch and lowish lift, and they are all 3 bladed.

as pitch increases, rake has to increase and/or blade area goes down. the prop has less bite on the water and thus 3 blades add blade area causing less slip. As rake increases lift decreases because the thrust cone becomes narrower.

this is what the prop dudes tell me, anyway.

[Ivan Kozyakov]

Does this make sense for all three blade propellers? Or only for special ones SAW with low lift? Can I buy an inexpensive 1.8 pitch prop from Aliexpress for the first tests?

HTB1FuCWXyDxK1RjSsD4q6z1DFXaR.jpg

[Bande1]

you got to be careful because 2000kv is extremely high for 8s and youre very likely to destroy something. You really need to lower the RPM and raise the prop sizes. or get a TP competition motor rated for those RPM's. 1000-1400kv is much more appropriate outside the very specific high RPM motors that have extra kevlar around the magnets to turn that fast.

once you get that under control you need to use the prop calculator to find out where you need to be. you have to start off slower and monitor temps. thats absolutely critical to start slow.

[LibertyMKiii]

I am interested in trying 3 blades as well.
My logical conclusion is that having a blade in the water 33% more often per RPM will net a much higher load on the motor. It would be wise to start with a 2 blade and see where things are with temperatures and then move to a 3 blade.

Having a higher amperage draw will result in lower RPMs and in some cases this is why more blades = less top speed. The setup has to be optimized for 3 blades.

[Ivan Kozyakov]

you got to be careful because 2000kv is extremely high for 8s and youre very likely to destroy something. You really need to lower the RPM and raise the prop sizes. or get a TP competition motor rated for those RPM's. 1000-1400kv is much more appropriate outside the very specific high RPM motors that have extra kevlar around the magnets to turn that fast.

once you get that under control you need to use the prop calculator to find out where you need to be. you have to start off slower and monitor temps. thats absolutely critical to start slow.

Yes, I understand the risk, but I want to do this for the sake of experimentation before buying a new motor. Moreover, according to the calculator load RMP will be 49K, the maximum for this motor is 50K by manual. My current setup is 6s+46mm/1.8 pitch prop and the motor is a little warm.

[Speed2]

The abc 1820 22 45 2 blade. For saw runs you may get away with the 2000kv on 8s. You just have to make sure you have proper cooling. Also the 240amp swordfish is like not going to be good for a setup like this. The castle creation hydra is likely going to be the best esc for your goal. The hydra is an 8s capable esc that will handle well over 300amps for a saw setup.

[Veloctiykingsracing]

2000kv is absolutely fine for 8s SAW runs. As mentioned, go w a hydra, check your data. The Swordfish is much less forgiving. If the data suggests your amp load is within range for using the Swordfish, then use it.

[Bande1]

2000kv is absolutely fine for 8s SAW runs. As mentioned, go w a hydra, check your data. The Swordfish is much less forgiving. If the data suggests your amp load is within range for using the Swordfish, then use it.

you dont even know what size it is. the biggest SSS 2000kv is a 4092 rated for 23v max and 4200w peak, which is only 150A on 8s.

https://tflnorthamerica.com/wp-conte...ist-2020-2.pdf

[Ivan Kozyakov]

you dont even know what size it is. the biggest SSS 2000kv is a 4092 rated for 23v max and 4200w peak, which is only 150A on 8s.

https://tflnorthamerica.com/wp-conte...ist-2020-2.pdf

4082 2000kv, 31v Max. And even 60K RMP Max

H4800cf9311c74d02917fe17ae1cfb4b.jpg

[Veloctiykingsracing]

you dont even know what size it is. the biggest SSS 2000kv is a 4092 rated for 23v max and 4200w peak, which is only 150A on 8s.

https://tflnorthamerica.com/wp-conte...ist-2020-2.pdf

Again, it would be fine for an 8s SAW run. Do I have to buy one and prove it?

[Bande1]

you see that 3200w rating? 3200w / 28v = 114A

[Bande1]

Again, it would be fine for an 8s SAW run. Do I have to buy one and prove it?

yeah and do it with an 1820. be fun.

[Veloctiykingsracing]

Or an 1823 or 1925. Says the guy who was going to run a 36mm can in a jae 33 and just figured out they fit 4070 cans. How many saw runs have you done? Collected data? Let's see the vids.

[Bande1]

Or an 1823 or 1925. Says the guy who was going to run a 36mm can in a jae 33 and just figured out they fit 4070 cans. How many saw runs have you done? Collected data? Let's see the vids.

I will be working the clock at the official IMPBA time trials next week. stop on by and set a record.

[Veloctiykingsracing]

Only concern would be due to their crap rotors would be if the prop was able to spin airborn unloaded. Go ahead, stick with your 1400kv on 8s. And then post video of your speed. I've run 3200 kv on 8s successfully for data. I've consistently run speeds of 125 to 132mph. With that comes experience, not what written on paper. Vids are all there.

[Bande1]

Only concern would be due to their crap rotors would be if the prop was able to spin airborn unloaded. Go ahead, stick with your 1400kv on 8s. And then post video of your speed. I've run 3200 kv on 8s successfully for data. I've consistently run speeds of 125 to 132mph. With that comes experience, not what written on paper. Vids are all there.

you can prop up 1400kv. you dont need high rpm. you get less slippage and much safer rpm's. why run it on the ragged edge? furthermore, TP makes comp motors specifically for doing this. a 2319 will get in the 125mph range with that KV. you can even run 1/4 props. 6719 3 blade.

I dont run SAW but ive seen plenty of smoked motors, esc's, and batteries.

[Veloctiykingsracing]

Yes tip speed, slip all come into play. Again, I wouldn't personally use An Sss motor for a Saw run. I can come up w a lot of positive and negative remarks regarding it's use BUT to answer the question, yes a SSS 4092 2000 kv will be fine for an 8s saw run. Never said it was the best choice, never said it was optimal or the worst choice. The user has to try it in his setup and collect his own real data. Not paper data. I hit 105mph in my Pursuit(vid is online) MONO, that was using well over 2000kv on 8s. Now most would say you can't do that or it's wrong. Then again, "most" haven't broke 100mph in a mono so their point in moot.

[Bande1]

Yes tip speed, slip all come into play. Again, I wouldn't personally use An Sss motor for a Saw run. I can come up w a lot of positive and negative remarks regarding it's use BUT to answer the question, yes a SSS 4092 2000 kv will be fine for an 8s saw run. Never said it was the best choice, never said it was optimal or the worst choice. The user has to try it in his setup and collect his own real data. Not paper data. I hit 105mph in my Pursuit(vid is online) MONO, that was using well over 2000kv on 8s. Now most would say you can't do that or it's wrong. Then again, "most" haven't broke 100mph in a mono so their point in moot.

its a 4082. and nobody is saying you cant run 2000kv on 8s. Im saying that motor specifically isnt made for that. CM/SCM motors are 3000kv on 8s rated. they have special wiring and rotors to do it.

[Veloctiykingsracing]

4082 or 4092? Either way, don't use a SSS motor for SAW would be the best answer. Use a TP.

[tbonemcniel]

I am interested in trying 3 blades as well.
My logical conclusion is that having a blade in the water 33% more often per RPM will net a much higher load on the motor. It would be wise to start with a 2 blade and see where things are with temperatures and then move to a 3 blade.

Having a higher amperage draw will result in lower RPMs and in some cases this is why more blades = less top speed. The setup has to be optimized for 3 blades.

That's not the case, like, at all. It's a general rule of thumb that a 3-blade will have a slightly higher load than a 2-blade, but typically by one prop size. So to have equivalent load moving from a 2-blade to a 3-blade, prop down one size and the load is similar.

Again, just a rule of thumb. A few months ago I had a 39" 6S Mono I was running a 1917 2-blade on. I moved over to a 1917 3-blade prop without making any other changes to the boat. Left COG, strut settings, and trim tabs where they were, and guess what. Amp draw went down, temps went down, top speed went up, and the boat was more stable.

[fweasel]

4082 or 4092? Either way, don't use a SSS motor for SAW would be the best answer. Use a TP.

With your SAW experience, what do you prefer to use prop wise, in reference to the OP's original question? I've only ever found 3 blades to be useful on problematic monos where I needed more prop but couldn't continue to increase diameter. 2 Blades have always been a more efficient option for my SAW boats, but I don't have any hydro experience.

[Veloctiykingsracing]

Use a 2 blade. More efficient and less drag. Aside from what is written on paper, one would have to really do trial and error to see if they would make gains w a 3blade for the conditions and hull setup. Each prop will have its sweet spot w a hull and given conditions. It really boils down to getting out there and put in the time with a setup, a bunch of props and collecting the data. Many can suggest what would be best but the truth and reality will come from one's own testing. Save your data logs, write down your observations. Review and assess after testing. When my mono hit 105 and many runs over the 100mph point, it required alot of testing. No one could suggest an answer or prop that would be the best, despite them also maybe owning a Pursuit. Acquire some props in the ball park area, test and assess.

[Ivan Kozyakov]

Guys, thank you for the hot discussion and advice. I have ABC 1817 and 1917 2 blades and I'll start with that. Does it make sense to buy the 1717 or is it too small for my setup?

[LibertyMKiii]

Guys, thank you for the hot discussion and advice. I have ABC 1817 and 1917 2 blades and I'll start with that. Does it make sense to buy the 1717 or is it too small for my setup?

Specs online say the Hydro-2 is 990mm long (38.9").
I know the JAE 33 FE likes the 1817 prop and is only 33" so I would suspect the 1717 might be small for this boat? Ultimately the diameter is something you would change depending on how it is running. You will have to test and see how it runs and then make decisions from that point.

This is where an ESC with data logging comes in handy to help you make educated decisions instead of guessing.

[NativePaul]

Which Hydro2 is it Ivan?

While I don't have a JAE33 to compare I did have the old JAE.21FE that I ran in hydro2 for a while and it was the heaviest and hardest to push Hydro2 I've had, so while hydro2s have grown since then so has the JAE and I should imagine that while it may be bigger Ivan's boat will be lighter than the JAE33, it likely has fatter ride surfaces, is more aerodynamic and has aero lift too, all of which make it easier to push.

Personally I like to start with as small a prop as I think will work, tune the boat on it and work my way up tuning as I go, which reduces the likelihood of running a super wet setup pulling a lot of power which can burn things up, or worse a loose setup at very high speed that can result in a big splash and the loss of your boat the first time out. Props are always useful to have and are cheaper than ESCs, motors or hulls. I'd buy a few props and start with a 1614, with the end goal being 1819 if it has the temps to get there and the hull to do it.

On the subject of aero lift nearly all Hydro2s have it to some extent or another in order to maximise efficiency and minimise lap times for 6 minutes with limited energy, Naviga racing has a very different hull requirement than SAWs, and for SAWs you may well have to find ways to ditch some of that lift.

[Ivan Kozyakov]

My boat is Dr.Super Evil from Hydro&Marine (890mm) with custom SAW sponsons. My result in this season is 134 kmh at setup:

4082 2000Kv SSS motor
180A Seaking ESC
6s 5000mAh 100C battery (2*3s)
1817 ABC prop
Weight with batteries 1980g.