General discussions - FAST RC boat

[Sargent_Horse]

@LibertyMKiii Looks like the JAG rigger has some top rudders, presumably for stability. Any concern for any thing like that? Also wow, the actual run distance to get top speed is incredibly short compared to what I was thinking in my head.

 

[LibertyMKiii]

@LibertyMKiii Looks like the JAG rigger has some top rudders, presumably for stability. Any concern for any thing like that? Also wow, the actual run distance to get top speed is incredibly short compared to what I was thinking in my head.

The "Grip" is pretty impressive on these and the acceleration. It only needs a short distance to build up to full speed. The only slow part is starting from a stop when the prop is cavitating and fighting to get the boat planning on top of the water. One of these days i'd like to mount my GoPro with telemetry to the mono hull that runs 60 mph and see how fast it can jump from 5mph up to 60. It feels like only 1-2 seconds but probably is more in reality.

I don't know if I will ever go out for a sanctioned run like that. The plan is to do my own thing with a GPS unit at the local spots.

I will likely add a vertical in the rear. It will also function to streamline the air around some of my hardware for the rudder. FYI I started a separate build thread here about my boat build as to leave this thread more about general RC boating.

 

[Homebrew]

Anyone know where I can find some parts for this Blackjack 26? Mainly the antenna, and radio box cover, etc.

https://www.horizonhobby.com/product/radio-box-cover-bj26bl/PRB3304.html

 

[SARRT8]

Any you guys have any experience with the blackjack 24 catamaran? I have a opportunity to buy one thought I would check in here first.

 

[jkflow]

Blackjack 26 - no idea but if you seal the cover with tape you won't have any water intrusion or at least it's negligible.
I use hockey tape (clear, other use true boat cover tape for 3x the price, but it's the same at the end of the day.
https://smile.amazon.com/gp/product/B01HSPHKQ6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Edit: Google to the rescue:
https://www.lprcs.com/radio-box-cover-bj26bl

Blackjack 24 - no real experience either, but I did look at it in length. It's ok at the right price. It will bounce a lot as the bottom is not straight. Takes a lot of work to get it to go right but as long as you keep it stock it's ok.
Check out this guys channel and specifically the BlackJack24 in the link.

 

[LibertyMKiii]

I have a few pro boat plastic props in the box of junk I got if anyone needs them.
I can dig them out and get specifics if anyone is interested.

 

[jkflow]

85mph multiple passes today. Encounter with a small Gator that could have ruined my day for sure.
So much to learn, but it's worth it. Then again, not a ton to learn, just re-applying it differently. Tiny adjustments make a huge difference.
One stuffing tube was slightly misaligned from the factory and that created a lot of friction heat. Replaced/re-seated, and now she runs like greased lightning.
40mm CNC prop - 75mph
42mm CNC prop - 85 mph
next will be 44 CNC,

The problem in my area is access to good places where you can run, lakes are either private or totally overgrown. This one has a very steep bank, but where there is a will, there is a way. If I'd hit that Gator, my boat would have been severely damaged, I doubt the Gator would have noticed even though it was a small one.

 

[Doom!]

@jkflow I doubt my knee would let be navigate that river bank, your not kidding about steep. Other than that it looks like a decent spot, barring gators of course.

 

[LibertyMKiii]

85mph multiple passes today. Encounter with a small Gator that could have ruined my day for sure.
So much to learn, but it's worth it. Then again, not a ton to learn, just re-applying it differently. Tiny adjustments make a huge difference.
One stuffing tube was slightly misaligned from the factory and that created a lot of friction heat. Replaced/re-seated, and now she runs like greased lightning.
40mm CNC prop - 75mph
42mm CNC prop - 85 mph
next will be 44 CNC,

The problem in my area is access to good places where you can run, lakes are either private or totally overgrown. This one has a very steep bank, but where there is a will, there is a way. If I'd hit that Gator, my boat would have been severely damaged, I doubt the Gator would have noticed even though it was a small one.

That is a good pond for tests like this.
85 mph is great!

We took our 42" v-hull out Saturday night. Moving the batteries back a little I picked up 1 mph but it was getting too much bounce with the weight distribution like that. New PB of 62mph.

I am going to start modifying the pitch on the prop just to see what works and what does not in preparation for the rigger build.
My son found this little guy at our pond:

 

[LibertyMKiii]

Anyone here dabbled in modifying their own props?
I am ready to start bending more pitch into my Octura x447 to see what it does. Any recommendations where to start?

I have already de-tonged and sharpened the leading edge.

Original 47mm diameter 1.4 pitch on 6s the 42" mono ran 61 mph on 6s.
I made a tiny bend in the outside tip of the trailing edge and the boat went 62 mph.

I think I am ready to make a real change in the prop now... For this size boat and the HobbyWing esc, I think it would be great if I could break into the 70s with this 47mm prop.

My thought is to focus on the trailing edge area and add some "cupping"

Been reading over this a few times also:

 

[jkflow]

I thought something was odd but didn't realize what happened until I looked at the footage.
I believe this was my last run at this place I can handle 5-6 ft gators but this one is easily 12-15ft.

It's a short video, enjoy

 

[LibertyMKiii]

I thought something was odd but didn't realize what happened until I looked at the footage.
I believe this was my last run at this place I can handle 5-6 ft gators but this one is easily 12-15ft.

It's a short video, enjoy

No kidding and during the run towards the other end of the pond you have your back turned to where it was.
Better safe than sorry!
Boat appears to be picking up speed!!!

I tried a modified prop over the weekend and lost some speed, but I believe it was because the boat was running too wet. I had also shifted weight to the front and over-did-it.

 

[ABabyEater]

I tried a modified prop over the weekend and lost some speed, but I believe it was because the boat was running too wet. I had also shifted weight to the front and over-did-it.

Remember, 1 variable at a time! The lake seems MUCH faster to test on than finding a good speedrun road; you don't need to rush any changes

 

[LibertyMKiii]

Remember, 1 variable at a time! The lake seems MUCH faster to test on than finding a good speedrun road; you don't need to rush any changes

Yep I agree 100%
Luckily it was just a battery placement that I changed, so it is easy to put it back.

I'll get back and test again. It may be that I made the prop inefficient. I'll know for sure when I re-test.

 

[jkflow]

I made one change and run was at 83 vs 85.Nice little secret in my back pocket. Different and lighter lipos with same CG and it was 78, tiny changes.

Next it's a new location, I won't go back to this one followed by larger props. Still running 42 CNC props and I can bash in the 80 MPH range. 44 is next.

 

[Speed/267]

I made one change and run was at 83 vs 85.Nice little secret in my back pocket. Different and lighter lipos with same CG and it was 78, tiny changes.

Next it's a new location, I won't go back to this one followed by larger props. Still running 42 CNC props and I can bash in the 80 MPH range. 44 is next.

44 is a sweet spot

 

[Streeter69]

Anyone here dabbled in modifying their own props?
View attachment 165835

I have had good luck on Figure3, progressive change from center to the outer edge. Figure5 worked the majority of the time. Just need a Dial indicator and a note pad to keep up with prop tweeking

 

[jkflow]

Propped for 85mph. Going for larger props tomorrow, pending weather and nerves.
Killer shot from yesterday.

 

[LibertyMKiii]

Propped for 85mph. Going for larger props tomorrow, pending weather and nerves.
Killer shot from yesterday.

View attachment 167547

Very nice action shot!
I just put the XLX2 in mine and going up to 8s. Nerves are hitting me hard as this Mono is already sketchy on 6s LOL

 

[1coopgt]

The whole stuffing tube/flex shaft thing has me worried when pushing big power. I agree the methods used seem to be ancient.

The idea of using 14s with a high power boat ESC sounds fun, but honestly I doubt they truly push more power in total watts than the XLX2 in the end.

Assuming this is for your Rigger you want to build .If you're planing on 8s you'r going to have to go with a 1/4" flex , a piano wire drive or a solid drive shaft.

How does the turbine work with propulsion? I see a prop but not sure how it all connects. Wouldn't it be better to use something similar to a jet ski? I really have no clue how these things work....hey! stop laughing!

They have a gear driven transmission off of the output shaft of the turbine which connects to the flex shaft.