BJ29 Pilots, what is your setup to avoid the bouncing?

[dre414]

dre414, where did you have the batteries positioned, fwd or centered or back, in their trays? I have a spare (new) 60A PB esc (part number PB4018, parts list part number for the Mystic) and the package says "with reverse" ???? Programming card for those controllers doesn't have a setting for turning reverse "off". Does the dynamite 80A programming card have that option? Would love to know how to disable reverse on the one I have, if anyone knows, as a side note.

I had them pushed forward almost half way off the tray and angled in so that the half of the battery that was off the tray was resting on the center deck. Prop strut was set high (within a quarter inch of touching the bracket) and angled flat. As for the ESC, I may be wrong but the programming card (DYNM3821) has a reverse setting.. the instructions indicate this is to turn off/on the reverse.. again, I never tried it (now wish I did and forgot to set it back) but I assume thats what it's for? Unless it's to reverse the motor direction? If that's so then it's redundant seeing as you can just swap a couple of motore leads.. Don't know about the ESC you have, sorry.

[tlandauer]

I had tried to move the batteries as forward as possible and another stick of Nimh in front of the motor as dead weight, NO USE! Then I thought it was time to blue print and true the pads---something I was trying to avoid all along.
Well, it helped a great deal and I wish I had done it sooner. There is a seemingly threshold relationship between bounce and No bounce. On mine ( 4s2p, m445, Leopard 4082, 2200kv) .
Once I am in the last 20% of throttle, the bounce decreases, but below mid to above mid throttle it will bounce. ( this before truing the pads)
If you true your pads I believe you will see improvement, this comes from a one time non-believer.

[scrillamil]

Dre did you sort your bounce out? When we are running (2) 2s 5000mah 60c was no problem but as soon as I jumped to (2) 3s 5000 30c it really woke up but tryin to keep in the water w/o flipping is my issue

[dre414]

Hey Guys, sorry its been a while.. Happy New Year!

Over the holidays I replaced my blown stock motor with a Leopard3674 1900Kv and while I was at it, I decided to upgrade the ECS to a SeaKing 180 ESC V3 (extra caps) just to be safe. While waiting for the parts, I got around to blueprinting the sponsons.

Man was that allot of work squaring and sanding, I never realized how quick filler sets.. Anyhow, to my surprise it came out pretty well, all surfaces are square and very flat.. I however wish I had done a better job of painting.. the clear coat seems to stick to the foam on my boat stand even after a few days of drying upside-down. As of now I have lightly sanded the sponsons, partly b/c I can’t stand the smudged finish and partly b/c my LHS guy told me that lightly sanding the finish will create turbulent flow and stop and sticking to the bottom. Anyhow below are pics of my work.. I noticed a small crack near the prop tube so I filled and painted a bit there as well.

This weekend I ran the new motor and ESC setup on both 4s and 5s with the stock 1.6x2.5” (~ X640) prop in the morning and then in the afternoon with some more wind and it ran great in both conditions! No heat on the motor, esc, whatsoever even on 5s. It feels like 6s will be no problem (although I probably won’t bother).

The handling was much improved with a tighter turning radius and very crisp cornering (no sliding on the surface). It spills lots of speed on the turns but is very fast on the straights. Most importantly, although not gone completely, the height of the bouncing (amplitude) was dramatically reduced and the frequency was also considerably less such that I don’t notice it as much. On glass water, it’s still there but much less frequent and not as choppy. In slight ripples and upwind, the air gets under the hull a bit more and kills the bouncing altogether. Blueprinting does help! LOL.. During my last 5 s run the wind picked up and I got her in the air.. luckily for me she got enough air to backflip completely and land right side up.. drove her back, looked her over and back out she was (slower on the throttle in that direction however).

In all runs, I still had the prop strut set as high up (to the waterline) as I can without touching prop to strut bracket. The prop angle was slightly pointing down. Both batteries were far up on the tray and angled in pretty much resting on the center of the hull and touching the Styrofoam block.

I bought a few more props of varying sizes (time to perfect my sharpening/balancing skills) to see how they affect speed and bouncing. I should probably get some GPS telemetry for speed measurements. I’ll keep you posted..

[CHIEFY_44]

Dre414 I suggest you try a octura m445 prop that's what I have found to work best for me, I also trimmed the bracket of the strut for more clearance. With basically the same setup except I use a Leo 4074 2200kv with 4s2p it rides great, I agree the faster the boat runs the less bounce you get the magic figure seems to be 50mph at this it just flattens out and runs awesome

[scrillamil]

Nice work👍 looks good. Going to repair my old hull and work on blue printing. Awesome input

[dre414]

Dre414 I suggest you try a octura m445 prop that's what I have found to work best for me, I also trimmed the bracket of the strut for more clearance. With basically the same setup except I use a Leo 4074 2200kv with 4s2p it rides great, I agree the faster the boat runs the less bounce you get the magic figure seems to be 50mph at this it just flattens out and runs awesome

Thanks Chiefy, question on the motor.. I was considering the 4074 but wasn't sure if it would fit.. may I ask what the difference is b/t 3674 and 4074 besides the size of the can? Does it have more torque? I was also considering 2200Kv however wasn't sure if that would be reliable on 5s.. Ill try the M445 or sure.

Oh yeah I forgot to mention, I noticed the tips of my prop after a few runs were dull and almost rounded out.. I was thinking the prop tips squeezing all that incompressable water between tip and the bracket would do a number on the prop tip. Cutting the bracket will be my next modification.

[CHIEFY_44]

Sorry about the delayed reply dre, but I work at a hobby store and its been hectic, not really sure of the difference between the motors, but I really don't run anymore than 4s voltage in any of my boats, my rigs are quick enough in this configuration and reliable that's what I want for racing, to win you have to finish. I just do a lot of testing and tweaking of my rigs to get the best out of them, not just slap 5 or 6 cells in and hope the electronics survive I have gd temps when I setup for 7 laps and 20-30% left in the cells.

[dre414]

Sorry double post.. this one was deleted.

[dre414]

Thanks Chiefy, I managed to get allot of time this past weekend to sharpen/detounge some props and try them out on the water. I tried a X642 and an M445 both in 4 and 5s configurations.. I have concluded that my favorite prop is the M445. After running the M445 it feels/sounds like the stock 640 and 642 props are churning allot more water than pushing it. With the 445 it sounds quieter and the boat has allot of acceleration. The problem is that at full throttle on the M445, the boat gets too much air and flips out of the water... I had a pretty bad crash that ended up with a shattered canopy; thank God I had a spare and it was close enough to shore to recover the boat. Overall the motor I have works really nice and reliably, so the motor can size to me is not a non-issue.

Regarding the 4s and 5s debate, from the posts on here this is quite a hot topic. Whereas the insane speed of 5s was cool it was a concern to be sure not to flicp back or overheat. I noticed one of my battery connectors kept disconnecting and had arc burns.. don’t know if it was a loose connector or the amount of current passing through it but the little exposure I had to this made it apparent 5s is not as reliable. Temperatures were not an issue.. but as you said, the key is to finish (or in my case not get stuck out in the center of the lake). So whereas I think this setup could run 5s all day (with a better connector), I’m sold that a high performing reliable 4s setup is golden..

Back to the original post topic.. the bouncing was still there but still nowhere near as much and as frequent as before blueprinting the sponsons and upgrading the ESC/Motor/Prop.. still more bounce on glass water than ripples and more bounce on 4s than 5s (probably the weight) but nominal. I don’t know if it will ever be gone altogether at all throttle ranges.. There is however a sweet spot in the throttle range that does't have any bounce at all but I know there is more juice left.. so hard to not go too fast when you know it will go much faster.

More of the questions…

1. Are you able to run your setup (4s M445) at full throttle? If so do you have additional weight besides the battery or should I just calm the heck down and expect to not give it full throttle till the batteries have died down some?
2. With the couple of nasty crashes I had, one of my battery trays came loose.. I read on here that many boaters just pull the trays off and Velcro their batteries to the sponson deck. Would anyone recommend the same for a MG/BJ29? Do you think this will further dial out the bounce?

[CHIEFY_44]

DRE WATCH THIS VIDEO AND I'LL POST THE SET UP LATER

http://youtu.be/rexRB9LXKEw

[CHIEFY_44]

I can run at full throttle and never let off unless it looks like flipping, no additional weight just set cog at 33% and I'm golden.
As to trays mine came loose and I re glued them in at a angle to ease battery installation, another thing I did was fill the front part of sponsons upto about 1-2 inches from the canopy opening, this help stop the hull splitting in a bad flip, then I strengthen the seams with extra fibreglass, remove water outlet and move to top deck that's all the mods I have done. I have a video on you tube if your intereste

[olwarbirds]

My buddy and I finally did the motor and esc swap.... leopard 4082 2000kv 180 amp seaking xtra caps...stock prop on 6S it screams ... added onto the battery trays and moved the 2 11.1v 5000mah 65c lipos forward...the back of the lipos is now where the front would of been in the stock location....no bounce probs at all...cant wait to try a better prop...will get vid up when I get the chance... DJ

[dre414]

DRE WATCH THIS VIDEO AND I'LL POST THE SET UP LATER
http://youtu.be/rexRB9LXKEw

Ok my boat is nowhere near that smooth and stable at full throttle.. I definitely need some more tweaking.

[dre414]

I can run at full throttle and never let off unless it looks like flipping, no additional weight just set cog at 33% and I'm golden.
As to trays mine came loose and I re glued them in at a angle to ease battery installation, another thing I did was fill the front part of sponsons upto about 1-2 inches from the canopy opening, this help stop the hull splitting in a bad flip, then I strengthen the seams with extra fibreglass, remove water outlet and move to top deck that's all the mods I have done. I have a video on you tube if your intereste

Thanks and after seeing your video I know I don't have it dialed in.. I thought I did but there is clearly room for improvement. When you say you filled in the sponsons.. are you talking about the 2 part expanding foam they sell on OSE? Also you said about 1-2 inches from the canopy opening I take it you mean 1-2 inches short of touching the original battery tray locations? Would you say the additional wieght of the foam is what helps?