On a quest for the fastest bj 24 ever

[RuntheraceAMC]

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????

[RuntheraceAMC]

146665146666146667146668146669

here are some pics

[Erroneous]

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.

[fweasel]

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.

[RuntheraceAMC]

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.

[RuntheraceAMC]

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

[fweasel]

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. :banana:


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.
http://forums.offshoreelectrics.com/attachment.php?attachmentid=144954&d=1470369941

[RuntheraceAMC]

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

[fweasel]

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.
146670146671

[RuntheraceAMC]

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.

[DBJr]

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.

[RuntheraceAMC]

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.

[Erroneous]

Watch the ESC temps.

[RuntheraceAMC]

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

[Erroneous]

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.

[RuntheraceAMC]

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.

[DBJr]

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.

[RuntheraceAMC]

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?

[DBJr]

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.

[RuntheraceAMC]

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

[fweasel]

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.

[RuntheraceAMC]

Or that too.... Lol

[DBJr]

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???

[RuntheraceAMC]

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

[RuntheraceAMC]

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

[RuntheraceAMC]

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.
146787146788146789

[RuntheraceAMC]

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.

[fweasel]

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 :rockon2:

[RuntheraceAMC]

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

[fweasel]

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.

[RuntheraceAMC]

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.

Couldn't agree more. I put humpty dupmty back together again and am headed to the lake right now. If it flips I would be shocked if it holds together.

[DBJr]

I made 40 MPH with my Blackjack 24 earlier today. I can't believe it.:rockon2:

[RuntheraceAMC]

I made 40 MPH with my Blackjack 24 earlier today. I can't believe it.:rockon2:

That's awesome man. What did you change to get there?

[DBJr]

That's awesome man. What did you change to get there?

I used the Leo 3650 2750kv motor and the Octura M440 prop. Definitely a HUGE change over the 2000kv stock motor.

Nice calm water as the water fountain in the pond is not currently working. A perfect opportunity to attempt a speed run.

The app I used is DigiHUD if anyone is interested. Seems to be accurate. I tested it out in my truck yesterday driving down the highway at 50 MPH. Was right in line with what my truck speedometer said.

[NativePaul]

Hull cracked for the full length. Deck shattered. Lid shattered. Electronics are fine. I think it's time to get the BJ 29.

I don't understand why you would want another RTR. You still have all the upgraded gear from the last one, why would you waste your money on something that is too weak again, and that comes with gear that's worse than what you already have? A quality hull would be no more expensive than a RTR, transfering your gear over is no harder than stripping gear out of a RTR reinforcing it and reinstalling it, and you would have a much better boat at the end of it.

[RuntheraceAMC]

I don't understand why you would want another RTR. You still have all the upgraded gear from the last one, why would you waste your money on something that is too weak again, and that comes with gear that's worse than what you already have? A quality hull would be no more expensive than a RTR, transfering your gear over is no harder than stripping gear out of a RTR reinforcing it and reinstalling it, and you would have a much better boat at the end of it.

Can you suggest a cat hull for less than $250 that will let me get into the 60's and 70's?

[NativePaul]

Hydro&Marine Agitator, Freya, Supercat, Maritimo. Chinese splashes of the Agitator and Freya are available if you are really cheap.
MHZ BTM Marine, Mystic C5000.
Aeromarine Mean Machine, Sprintcat .21/45. More roundy round than zippy zip so may take more tuning, but people have had both into the 70s.
HPR LMT99. Slightly over budget at 270 but worth every penny.

[RuntheraceAMC]

Hydro&Marine Agitator, Freya, Supercat, Maritimo. Chinese splashes of the Agitator and Freya are available if you are really cheap.
MHZ BTM Marine, Mystic C5000.
Aeromarine Mean Machine, Sprintcat .21/45. More roundy round than zippy zip so may take more tuning, but people have had both into the 70s.
HPR LMT99. Slightly over budget at 270 but worth every penny.

I've been looking at the Delta Force Explorer 36. I hear it's not good for racing because it doesn't corner well at speed but I'm just doing sport running and I like speed. Seems to fit that. What do you think?

[NativePaul]

I don't know that hull, my first thought is that 36" sounds very big for 4s, but the Freya and its clone are 37" and so narrow that they go well on 4s.

[RuntheraceAMC]

I'm running 5 and 6s

[kfxguy]

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.

44 is cake for the shockwave. I had mine at around 64. Probably close to that hills limit lol.

I know someone who has a 70+ mph bj 24 (geico). I'll try to find a video of it. 50 should be pretty easy.

[kfxguy]

Here's the video

https://youtu.be/G16ujPtHpME

[RuntheraceAMC]

Hydro&Marine Agitator, Freya, Supercat, Maritimo. Chinese splashes of the Agitator and Freya are available if you are really cheap.
MHZ BTM Marine, Mystic C5000.
Aeromarine Mean Machine, Sprintcat .21/45. More roundy round than zippy zip so may take more tuning, but people have had both into the 70s.
HPR LMT99. Slightly over budget at 270 but worth every penny.

Went with the delta force explorer 36. It looks incredible and I saw some videos of it running on the Same motor I have. Seemed to corner fine and handle the straight line slows very well. Bought everything I need to build it. So long blackjack. Great boat but After breaking 3 hulls I've learned my need for speed was writing checks my hull could not cash.

[MCcrawlers]

how do you install the thru hull water pickups? Im sure you used some type of epoxy in order to seat them. Have you ever had one come loose?

[RuntheraceAMC]

Used a dremel tool to make the initial cuts and made small corrections till I could force it into a snug fit then epoxy or JB weld from the inside. Most thru hills are made with a notch to allow it to sit on the inside of the hull but be flush with the exterior

[MCcrawlers]

Used a dremel tool to make the initial cuts and made small corrections till I could force it into a snug fit then epoxy or JB weld from the inside. Most thru hills are made with a notch to allow it to sit on the inside of the hull but be flush with the exterior

Ok thank you!! I just ordered a bj24 and wanted to install these thru hull pickups. One for motor and one for esc. I like this the best because they look clean. Just wasnt to sure how you guys were installing them!! Thanks again!!

[MCcrawlers]

RuntheraceAMC

Do you have a vid of the leo 4072? I just ordered the ose raider 150 and the motor will be my next purchase. Was thinking about the 2200kv but read where u went with the 1850 i think? Would u make the same purchase again or go with the higher kv? My prop is the x642.

[RuntheraceAMC]

What hull? Bj 24?

[MCcrawlers]

Bj24

[RuntheraceAMC]

Idk dude. I made a lot of mistakes with my bj. If I had to do it all over again I would do a 3674 Leo at 2200 or a TP 3630 (36mm by 61mm)at 2540kv. This for several reasons. Yes it was stupid fast on the Leo 4074 on 5s much less 6s but there were several problems: weight (of the motor and the battery), fitting the motor, balancing weight side to side, keeping the prop in the water and too much torque leterally twisting the boat's position in the water.

I think the max the boat can handle would be the 3674 or TP 3630. The TP would keep the weight to a minimum and I would never do more than 4s. Get a battery rated for 40c/ 4000-5000 mah. Don't go more than 5000mah or the battery will weigh too much. Prop? The 642 would be a nice choice or 640. I have become fond of the CNC props but I wouldn't do more than a 1.6 43mm, smaller props for longer runs.

That raider 150 is a beast for the money. I have about 20 runs on my DFE 37 with twin Leo 4092s running 1.6 46mm props. No issues so far.

If you are going to drop this money into your bj 24 I would reinforce the sponsons as far forward as you can to the transom with thin strips of fiberglass in the joints of the sponsons. A couple bad blow overs and the joints will split.

I have trouble downloading videos here. Pm me your number and I will send you videos of my bj 24 on a Leo 3660 and 4074

[MCcrawlers]

I have ordered the x642 prop. it will be balanced, sharpened and polished. Im really not looking to run 6s but want the option just to say that i can and if i get a wild hair i might even try it on 6s. But im really looking at only running 4s. What do you think about the Leo 3674 2200kv vs Leo X2 3674 2650kv. The x2 is only 5 grams heavier, is there a noticable difference in the X2 motors? Also is there plenty of room for the 74mm can and can you use the existing mount or do you have to buy other parts to mount these motors to the flex shaft? Also do you have your vids on youtube?

now that i look more into the TP's im leaning toward them. IDK which one im going to go with. Do you think the TP3630 at 2540kv could handle 6S?

[fweasel]

Someone stop the insanity. The Blackjack 24 is not, nor ever intended to be a fast boat. I started with one, made a few fun upgrades, and quickly realized it was time to move on to a bigger, stronger hull. As already demonstrated in this thread, you can stuff all the money you can handle into that hull, and at any time, it can all go up in flames or simply sink to the bottom when the hull disintegrates.

[MCcrawlers]

Man its all for fun. Its a risk you take when upgrading anything. Its all about seeing how much something can handle and when you reach the peak, enjoy it. When you get tired or want to go more then upgrade your base. If it fails, oh well, build another one that is the great thing about this hobby!

[RuntheraceAMC]

The x2's are actually down in max wattage by 20-30%. Wattage equals horse power so I would stay away from the X2's

The TP is actually less wattage but it's also a smaller motor. The next size up in the TP would be rediculous. I would not do more than the Leo 2650 or more than the TP 2540. You'll lose torque and the Rpms will be so high you'll need to upgrade to a .187 flex shaft. Believe me I've tried.

As for videos I don't have anything on YouTube but I can text you videos of different setups. Just private message me

[RuntheraceAMC]

As for fweasal's comments. I agree to an extent. That was my experience and I had fun with the black jack but I am having more fun now putting more speed into a hull that can handle it.

That said I can appreciate wanting to make that little BJ fly because I was caught up in doing that myself

[alex clark]

were did you get trim tabs