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

[dre414]

Im running a stock BJ 29 with a sharpened and balanced stock prop on 2S and cannot seem to get the bouncing (porpoising) to stop.

I started with the Prop strut flat to the bottom of the boat (placed boat on a flat surface and adjusted the strut so it was also flat on the surface) and the batteries at the front edge of the trays.

The closest setup I have gotten is with the batteries pushed all the way up on the the tray (almost falling off) and the prop strut really high such that the prop is almost touching the bracket. Although the bouncing has reduced some (however still bounces) the rooster tail is very high and it seems the prop is half submerged in the water. This can't be the right setup.

I looked around on the MG forums but I didn't get a clear answer besides having to buy an offset rudder or buying a faster drive system. Any help or tips would be greatly appreciated!

BTW I'm usually running on a very calm lake with the occasional 5mph wind on one direction.

[MAMBA2200]

These hulls are good at bouncing you will find that a cat hull will be smooth then bounce and then smooth out again once you get fast enough. What i have done to calm mine down is set the strut about 1mm above level and angle it down about 1mm. But what you must take into consideration is that no matter how hard they try every hull is different so it will be different for every boat out there on setup. So try to use my setup and see if it works for you it might it might not but it is a starting point. Hope this helps you

[CHIEFY_44]

I agree with mamba2200, every hull can be sorted in different ways, but the most important is making sure you dont have any concavement on the ride pads, these act like suction cups, what I did was blueprint the hull, taking all the concavement out of the pads and making them level with each other, then I made all the edges and things sharp and 90degrees. This helped a lot on my gieco, hope this helps, you can see step by step instructions by Darin Jordan in the miss gieco thread,

[tlandauer]

I agree with mamba2200, every hull can be sorted in different ways, but the most important is making sure you dont have any concavement on the ride pads, these act like suction cups, what I did was blueprint the hull, taking all the concavement out of the pads and making them level with each other, then I made all the edges and things sharp and 90degrees. This helped a lot on my gieco, hope this helps, you can see step by step instructions by Darin Jordan in the miss gieco thread,

My MG had a bounce that just would not go away until I blue printed the riding pads. It really makes that much of a difference, at least with mine.

[mtbenjamin77]

My MG had a bounce that just would not go away until I blue printed the riding pads. It really makes that much of a difference, at least with mine.

Yeah mine has a pretty bad hook in one of the sponson, it's not flat. That can create a bad bounce. I've found if you add lift at the transom the bounce tends to settle. set your strut at nuetral like you had it and score a line on the strut at the top of the bracket. this will give you a mark for reference. if you find a adjust ment that lessens the hop mark it. I'd say try lowering the strut to about 1.5mm below neutral keeping the strut flat. also try different props or add a slight cup to the one you have 1.2" to 1.7 cup. this will also improve your top end.

[dre414]

Thanks guys for the good advice! the Darin Jordan thread was excellent information.. whereas I’ll probably blueprint and true the sponsons, It appears I have some more adjustment and trial and error to get the bouncing out regardless.. Mamba your advice got me really close so far (not too much time to test). I’m embarrassed to say that I didn't even know you can angle the prop as well as raise/lower the strut.. that just added about a thousand more combinations to try out..

What is good news is that having the strut all the way up such that the prop almost touches the bracket is ok.. I may have to grind the bracket a bit but at least it’s been done before.

Thanks guys I didn't think there was much to be done by way of tweaking a boat but after this thread there's tons to try and tons to still learn!

[bob_t]

On my bone stock , other than PB SS prop, MG29 V1, (same hull) I found that the further fwd I moved the batteries, the "bounce frequency" (# of bounces per second, as I will call it for lack of a better term) got shorter and shorter, with more or less same bounce height, or amplitude, but never settled and ran "flat". For my particular hull (I know each is a "little different") it wants to ride "bow high" ... not excessive, but not flat like what you typicallysee/expect for cats. So, I started moving my batteries back, and the "bounce frequency" got longer between bounces, and now, althought it rides slightly more "bow high" than I would like, it doesn't bounce. The boat seemed like it was trying to carry the bow, but it would "drop" due the batteries (really, the COG) being too far fwd, then it would lift the bow again, would try to carry itself, drop again, and keep repeating this cycle. Strut is set with centerline even to slightly ~ 1/32 - 1/16 above rear ride pad. I'm using a PB SS prop that has been balanced, blade matched and slightly sharpened .... which brings up another point ... my friend had a brand new Mystic - it comes stock with the PB SS prop, but they are not balanced! His was so far out of balance that it rather quickly destroyed the aft most bushing in the strut due to vibration. It was significantly out of balance ... the hub was not drilled straight! With a lot of work, it is now static balanced (he has since then also bought a new one, and that one wasn't too bad - it was drilled straight and is now balanced extremely well). Not saying that my setup is ideal, as I would love to see it run fast and "flat" (someday it will probably have an unfortunate "blow-over" event), but it seems to perform well in the wind protected ponds where I run it.

[dre414]

Thanks Bob agree with the frequency based on the battery location.. I found the same thing when I moved them al the way up.. faster bounce but not as high. Although not static balanced I did balance and shapen the stock prop. I howevr never looked at the shaft bore being straight. I have a few extra batteries coming in today and I pulled out my calipers so this weekend (wife's honeydo list permitting) Ill be doing some methodical testing.

I took a quick look at the hull and although my right sponson is nice and flat the left sponson is somewhat cupped and tapered towards the center of the tunnel. I plan to bluprint and flatten but not till I get it smoothed out as much as I can.

[ray schrauwen]

I find the combination of blueprinting sponsons, homemade offset and extra weight settled mine down very nicely. Too much weight and the motor will burn up though!

[dre414]

Update, I tried every variant I could get and still come back to the setup I described in my OP. Prop almost touching the rudder bracket and the batteries all the way forward falling off the tray.

Bob, I got it to settle w/ the batts back far however the bow rides way too high and almost blows over at speed (esp. upwind), IMO I'd rather have the higher frequency bouncing instead... thanks for confirming the behavior!

Ray when you say extra weight.. what did you use? where and how much? I was thinking about using fishing weights to see if that would balance things out further but ran out of batteries and daylight yesterday.. if it worked, I would switch out to those self sticking airplane weights..

I'm sure blueprinting is required but I'm hoping to get as close as possible to balanced before I go there.

Thanks!

[dre414]

Guys so I finally dialed it in without bluebrinting.. I set the prop to the best I could get it on 4S and then popped in 5s for the first time.. boy did it run fast! and it settled down allot!! Seems that the added weight and power balanced out the bouncing effect.

I ran it for a few laps around the lake on 5s and no temp propblems.. I took it back out and unfortunatly I made the mistake of trying to reverse out of a tight spot of grass and POP there goes the motor!! Why I didn't program the ESC to remove the reverse and why I tried to reverse out is beyond me!!

So now that I have an opportunity to buy another motor (ESC seems to be working still) I was hoping for some suggestions. I really liked the 5s speed.. can you either confirm or recommend a solid 5s motor? I was thinking about either the old version of the PB 1500Kv or a OSE leopard 3650 1600Kv.. I'm using the stock ESC (80 amp Dynamite) and stock prop and am willing to get another prop if you can advise the best motor/prop combo. Thanks in advance.. can't wait to get this baby back on the water. Looks like now Ill have time to finally blueprint it..

[ray schrauwen]

I find the combination of blueprinting sponsons, homemade offset [B]and extra weight settled mine down very nicely[/B]. Too much weight and the motor will burn up though!

Imagine that adding weight settled it down, hmmm....

[bob_t]

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.

[dre414]

Imagine that adding weight settled it down, hmmm....

Thanks Ray, I tried some additional weight using wheight strips on 4s and still had bouncing.. I feel the additonal power helped as well. Any suggestions on the replacement motor??

[Doby]

I find the combination of blueprinting sponsons, homemade offset and extra weight settled mine down very nicely. Too much weight and the motor will burn up though!

Just buy an AQ Motley Crew!

[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..

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[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?