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Thread: On a quest for the fastest bj 24 ever

  1. #1
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    Default On a quest for the fastest bj 24 ever

    sorry for the long post Sooo.... my wife bought me a BJ24 for my birthday in July and I've got the RC bug again bad. I use to own nitrous cars 10 years ago but in that time rc electric boats have come very far.

    I almost regret that I am confined to the blackjack 24 in my quest for more speed but seeing as how my wife won't let me get the 29 I am stuck. As a consequence I am making my 24 as fast as possible. I have made a few mistakes along the way but I feel like I am headed in the right direction now. I've learned a lot in the last 2 months but I know there are tons of more knowledgeable guys out there. I would like to share where I've been and where I am headed with the boat in the hope that those Knowledgeable people will come out of the woodwork and save me a lot of time and money.

    Of course the stock set up didn't last long, I went to a 3s 45c battery and over propped it and the motor fried in the first week. I ordered a leopard 3650 2450kv, went to 4s, swapped the stock esc for a seaking 120a and added 3 water pick-ups (for a total of 4) and I instantly had an out of control boat. I noticed the water flow still wasn't great for the two lines I had running to the engine so I ordered 9/16 hoses, wider "y connectors" and wider outlets. I even bored out the esc cooling tubes and the water jacket nipples. Replaced everything and it was running super cool. Then I dealt with the instability caused by going to 4s with trim tabs (ose-80069). I know this is unconventional for a cat, but they really allowed me to dial in the boat. The only problem was that I liked it crazy and now it was stable again. There could be only one solution....

    I ordered a leo 3660 2750kv and jumped up to 5s 4500mah 25c batteries (this is where the experienced folks are shaking their heads). Now I know this set up is pushing my batteries and esc, but man is it fast. At first it rain too wet and I had to slide the esc and batteries back. Dialing in the strut took time and a lot of flips before I got it right. Once I got it stable the power of my set up began to show...... in the form of several broken props after 2 seconds of full throttle and a completely twisted flex shaft that ripped my stuffing tube in half. After upgrading to an aftermarket strut, bj29 flex shaft and bj29 prop It became reliable. BUT I wanted more so I bought a pulse 5s 4500mah 45c battery. I also upgraded the wiring to 10 guage and the connections from ec3's to some much better connection who's name I can't remember. Now the boat spends all its time bouncing from the last 2 inches of the hull to just the prop in the water. I have no idea how fast the boat is going but I would guess 45-50 mph. I've got this set up nailed so I decided to go a different direction in the quest for more...

    I just ordered a leo 4074 motor 1800kv, Rader 150a esc, several octura props 38-42mm (1.5-16. pitch) which I think might be too small??, and a revoelectrix 5s, 70c 5000mah battery. I have no idea what this will do to the boats speed. I think I am stuck with the newbee thinking that higher kv is better, time will tell. And I suspect I will be running 6s in this set up before long. The question is, am I heading in the right direction????

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  3. #3
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    Right direction going to the 1800kv Leo on 6s? Probably. I ran the 4074 2000kv and a 2200kv in a BJ29 on 6s. Went just under 70 until the motor went and took my seaking180v3 with it. Hindsight I would have been better off with the 1800kv.. The revo pack? Will not disappoint!... This little thing is going to be flying. Id look for more ESC, headroom is your friend.... And dam dude, much more spent on this you could have had a Zelos twin.

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    Put a plastic washer on the z bend rudder push rod at the servo horn to take up the steering slop, or change to a straight push rod with a through style attachment on the servo horn. The rudder also has a pretty blunt leading edge that can use some sharpening, and angle the bottom like the rudder on the bigger proboats.

    Funny, I started about the same time as you, same boat, but my wife has been a little more lenient with the hobby expansion.
    Vac-U-Tug Jr (13mph)

  5. #5
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    I did the sharpening of the rudder. Even to the blunt edges off of the joints and skeg on the strut. I get the concept with what you said about eleminating the servo slop but I have to be honest, I don't understand how to execute what you described.

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    If you started the same time I did and now have four boats.... Ya she's a keeper

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    Quote Originally Posted by RuntheraceAMC View Post
    If you started the same time I did and now have four boats.... Ya she's a keeper
    Indeed, but it's all about baby steps. I bet if the 24 suddenly disappeared and was replaced with a 29, she'd never know. And then it's all about scale, a new boat only slightly bigger than a 29 is easier to pass off vs. a 24.

    Quote Originally Posted by RuntheraceAMC View Post
    I get the concept with what you said about eleminating the servo slop but I have to be honest, I don't understand how to execute what you described.
    Vac-U-Tug Jr (13mph)

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    Awesome. I'll give it a try. What about more speed. Know where to find some!?

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    My 24 runs 33mph on 3S with a S&B stainless BJ29 prop like yours (composite one is in the picture). My strut (Kintec with the bushing) is only a few mm above level with the sponsons and no trim angle. I sanded the flexshaft and propshaft in a drill with 400 grit and scuffed up the rear ride pads with 600. It would be fun to make it faster, but it runs so stable and reliable, I think it's right where it needs to be. If I keep it, I'll add another water pick-up underneath to cool the motor and ESC separately.
    2016-08-11 19.27.55.jpg2016-09-17 11.02.33.jpg
    Vac-U-Tug Jr (13mph)

  10. #10
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    I agree that pushing it more makes it less reliable and stable. That's why I added the trim tabs. It made it capable of taking so much more power. Reliability... That's another conversation.

  11. #11
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    I recently upgraded my BJ24 with a Leopard 3650 2750kv motor and I am running 3S. Man, talk about a screamer but it's still stable. I'm probably getting about 35+ MPH or so. Also running an Octura M440 prop. I'm also using the upgraded OSE shaft for this boat and it seems to be holding up to the increased RPM with no problems at all. I figure I'm getting around 30,000 RPM in the water with this setup.

    Very pleased with this setup. I don't feel I would need to run 4S or more.

    In the near future, I'll probably upgrade the Seaking 60A ESC I'm currently using to a Seaking 120A ESC for a bit more headroom and I might grab one of those new Revolectrix 70C 3S lipos OSE is now selling as well.
    Current boats
    Aquacraft Cajun Commander, Aquacraft Mini Alligator Tours - brushless, ProBoat Blackjack 9, ProBoat Impulse 9, ProBoat Recoil 17, ProBoat Blackjack 24, ProBoat Shockwave 26 BL V3

  12. #12
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    I just got in my Leo 4074 1800KV in and installed it with my new esc and oh... My.... God.... I can't wait to run this beast.

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    Watch the ESC temps.

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    Quote Originally Posted by Erroneous View Post
    Watch the ESC temps.
    Every prop 42mm and smaller it runs very cool. I put a 47mm composite prop on 5s yesterday and had a complete yard sale.

    I was running it at top speed near the shore and it started to head for shore. I tried to turn it away and it just launched straight in the air, flew at least 30-40 feet and hit a tree on shore. The hull was shattered 😢

    Lucky for me I had another hull. I transferred everything over last night and ran it today. Dialing it in each time. Good gravy it is fast (for a 24 inch boat) Definitely over 50MPH. Maybe 55

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    Id try a prop with more pitch vs more diameter. A Octura 645 would be insane. I see 65. ESC is going to go poof if not carefull though.

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    I think it's got room to run a 45mm prop. It's running so much cooler than my previous set up. Just warm, never got.

    I ordered a x642, m445 and m545 already. I can order the 645 next. Although I don't think it will stay on the water up to 65mph. It is having trouble staying in the water now and I have an air dam in the tunnel.

  17. #17
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    The next time I run my BJ24, I plan to do a speed run. I downloaded a speedometer app on my phone and plan to seal the phone in a zip-lock bag and see what I get.

    Running a Leo 3650 2750kv motor with an Octura M440 prop on 3S. Hoping for about 35+ MPH.
    Current boats
    Aquacraft Cajun Commander, Aquacraft Mini Alligator Tours - brushless, ProBoat Blackjack 9, ProBoat Impulse 9, ProBoat Recoil 17, ProBoat Blackjack 24, ProBoat Shockwave 26 BL V3

  18. #18
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    Quote Originally Posted by DBJr View Post
    The next time I run my BJ24, I plan to do a speed run. I downloaded a speedometer app on my phone and plan to seal the phone in a zip-lock bag and see what I get.

    Running a Leo 3650 2750kv motor with an Octura M440 prop on 3S. Hoping for about 35+ MPH.
    I can see 35. What esc are you running?

  19. #19
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    Quote Originally Posted by RuntheraceAMC View Post
    I can see 35. What esc are you running?
    Hobbywing Seaking 60A for now. Gets a bit warm but hasn't gone into thermal shutdown mode. I do plan to upgrade to a 120A in the near future though. I also use a Dynamite Reaction 50C 3S lipo.
    Current boats
    Aquacraft Cajun Commander, Aquacraft Mini Alligator Tours - brushless, ProBoat Blackjack 9, ProBoat Impulse 9, ProBoat Recoil 17, ProBoat Blackjack 24, ProBoat Shockwave 26 BL V3

  20. #20
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    Quote Originally Posted by DBJr View Post
    Hobbywing Seaking 60A for now. Gets a bit warm but hasn't gone into thermal shutdown mode. I do plan to upgrade to a 120A in the near future though. I also use a Dynamite Reaction 50C 3S lipo.
    Do yourself a favor, I had the seaking 120 and it's a step down from the Raider 150. Plus it's more money for the 120. Grab the 150. You'll thank me. But remember you'll need to run two water lines to it

  21. #21
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    Quote Originally Posted by RuntheraceAMC View Post
    Grab the 150. You'll thank me. But remember you'll need to run two water lines to it
    Nope. In on one side, looped from one nipple to the other on the far side, and back out the original side.
    Vac-U-Tug Jr (13mph)

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    Or that too.... Lol

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    Good price for a 150A ESC. I will probably consider it.

    My only questions are will it fit into the confines of the BJ24 tray and will a Hobbywing program card be able to program it or will the OSE program card be needed???
    Current boats
    Aquacraft Cajun Commander, Aquacraft Mini Alligator Tours - brushless, ProBoat Blackjack 9, ProBoat Impulse 9, ProBoat Recoil 17, ProBoat Blackjack 24, ProBoat Shockwave 26 BL V3

  24. #24
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    Quote Originally Posted by DBJr View Post
    Good price for a 150A ESC. I will probably consider it.


    My only questions are will it fit into the confines of the BJ24 tray and will a Hobbywing program card be able to program it or will the OSE program card be needed???
    I bought the programming card so I couldn't say for sure. As for the esc your going to have to mount it higher than the plastic sides of the battery/esc tray. I prefer that because I don't want it to sit in water if it gets wet inside. I used some foam (actually it was foam from inside the box my leopard was shipped in. I epoxied it to the tray and put Velcro down so I could easily remove the esc when I'm working on the boat. I'll send you a pic

  25. #25
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    Quote Originally Posted by DBJr View Post
    Good price for a 150A ESC. I will probably consider it.

    My only questions are will it fit into the confines of the BJ24 tray and will a Hobbywing program card be able to program it or will the OSE program card be needed???
    Here are some pics. In your leopard box there should be a long piece of foam cut it to the size you want for your tray. It should be thick enough to to sit above the plastic rim. Glue the GSM down and do Velcro on top. This way you have easy removal of the esc and as you increase or decrease battery size you can shift your esc side to side to help offset battery weight for each run.

    Having trouble posting pics

  26. #26
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    here are the pics

    in the second pic it's hard to see the foam because it is covered by Velcro. the third pick is the leopard box. the loan piece of foam is missing because I used it.
    6S with raider 150.jpgfoam block covered by velcro for esc.jpgfoam from leopard box..jpg

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    Well, i wreck the boat bad today. Ran 5s on a new 642 prop. Lightning fast. But ran well. It looked like the strut was angled up to much so I adjusted it slightly for a bit more nose down before switching to 6s. That was my mistake. It started porpoising at 3/4 throttle and instead of recognizing that I nailed the throttle. It bounced until it finally flipped and pieces of the boat started flying. Thankfully it landed right side up so I could limp it in. Hull cracked for the full length. Deck shattered. Lid shattered. Electronics are fine. I think it's time to get the BJ 29.

  28. #28
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    If/when you upgrade to the 29, I would start with some hull reinforcement before it even hits the water. Based on your past, shared experiences here anyways
    Vac-U-Tug Jr (13mph)

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    Good tip. I did reinforce the 24 hull but I think I was just asking too much of that little boat

  30. #30
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    I just ran my Shockwave at 44mph today on 4S and all I could think about was it launching onto shore and smashing into pieces like yours. Little boats going too fast is fun, regardless.
    Vac-U-Tug Jr (13mph)

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