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

[olwarbirds]

I always do what tlandauer shows ....nicely done man... DJ

[AlanD]

Its the little details that make the difference. Great idea tlandauer. I'll try that.

Olwarbirds, what was your motivation to upgrade your flexcable to the OSE cable?

[olwarbirds]

Alan, the OSE cable is just better quality than the stock stuff.... DJ

[hydro_pyro]

In the 1:1 world, performance outboard catamarans such as the Skater have this same porpoise tendency. We call it "clearing the bubble." Trim gives the driver some control over it. As the boat builds speed, the tunnel begins to pack air. The air lifts the bow somewhat, increasing the angle of attack and thus packing more air. As the tunnel compression lifts the rear, the bow drops and the air "burps" out the back, starting the cycle over again. Typically, the driver trims UP to keep the bow from dropping as he accelerates through the porpoise zone. Once the boat achieves a higher speed, there's enough air entering the tunnel to lift the entire hull including the stern, and the driver lowers the trim back to a near-neutral setting as the angle of attack flattens out on a bubble of flowing air.

In the case of our scaled-down catamarans:

This is why a rearward COG holds the bow high to reduce porpoise, but increases blowover risk at high speeds;

This is why hanging the batteries far forward reduces porpoise, it forces a flat ride and stops the tunnel from packing air altogether;

This is why a high strut setting reduces porpoise-- it reduces bow lift and increases stern lift.

With our electric boats, we can't overcome midrange porpoise with trim adjustment, so handling and speed are always somewhat of a compromise. The best solutions seem to involve circumventing the benefits of aerodynamic catamaran design, and trying to make the boat run more like a hydroplane.

[ray schrauwen]

Interesting...

In the 1:1 world, performance outboard catamarans such as the Skater have this same porpoise tendency. We call it "clearing the bubble." Trim gives the driver some control over it. As the boat builds speed, the tunnel begins to pack air. The air lifts the bow somewhat, increasing the angle of attack and thus packing more air. As the tunnel compression lifts the rear, the bow drops and the air "burps" out the back, starting the cycle over again. Typically, the driver trims UP to keep the bow from dropping as he accelerates through the porpoise zone. Once the boat achieves a higher speed, there's enough air entering the tunnel to lift the entire hull including the stern, and the driver lowers the trim back to a near-neutral setting as the angle of attack flattens out on a bubble of flowing air.

In the case of our scaled-down catamarans:

This is why a rearward COG holds the bow high to reduce porpoise, but increases blowover risk at high speeds;

This is why hanging the batteries far forward reduces porpoise, it forces a flat ride and stops the tunnel from packing air altogether;

This is why a high strut setting reduces porpoise-- it reduces bow lift and increases stern lift.

With our electric boats, we can't overcome midrange porpoise with trim adjustment, so handling and speed are always somewhat of a compromise. The best solutions seem to involve circumventing the benefits of aerodynamic catamaran design, and trying to make the boat run more like a hydroplane.

[olwarbirds]

Interesting stuff....yes we are giving up some handling for speed...running the BJ29 on our setup using 6S is more of a SAW running type setup as Lenny previously mentioned...2/3 throttle is max turning speed for sure and the water had better be smooth!...I cant tell you how many times the BJ has cartwheeled/flipped/barrelrolled/sumersaulted and any other none boat type manuevers you can imagine, but it has shown to be a very resilient hull...one thing I did want to point out was that we were not looking to race our BJ29, I have other cats for racing, our goal was to see what kind of topend speeds we could achieve before loosing all control...we are just insane like that

If your going to use a mtr upgrade like the Leopard 4082 using the stock motor mount, you will need to add rear motor support or get the OSE mtr mount...the way I insure not having cooling line leaks is to use Dubro fuel line clips, their a very secure seal around nippled and smooth fittings, plus I use quality cooling/fuel line.

[Barrel Roll Joe]

Any vids yet DJ?

[hydro_pyro]

I got rid of nearly all the porpoising.

-Custom tuned factory prop... Thinned, tried, sharpened, balanced.
-Three 2s hard packs in series
-COG at 7.75" from the rear edge of the running surface.
-Strut top 1/4" above the mount. Prop tips have 2mm of clearance.



Stock boat and electronics. Tiny bit of hop with GPS in the boat. :D

[hydro_pyro]

On smoother water this evening, I was not able to repeat those numbers, or the bounce-free ride. Only got 51 mph, with lots of hop. Almost blew over a few times. This boat LOVES a bit of windblown ripple-chop on the surface.

[olwarbirds]

Any vids yet DJ?

No...its been snowing here in the NC mountains again...hopefully we will have something new to show soon... DJ

[olwarbirds]

Thats the speeds we came up with for the stock setup on 6S was right around 60MPH...with the leopard setup we are in the 70MPH range.. sure looks good all sharpened and shined up ....yes on glass smooth water it does seem to like to hop more...

[AlanD]

The good news: tlandaur, your silicon tube seal on the flexcable worked perfectly. I also removed and silicon-sealed the strut. Found some water leaks there. Not a drop of water in the motor or radio area now. Great pointer. Thanks.

The bad news: I fried the wiring going into the stock Dynamite3830 motor. Ran for 8 minutes on 6S/65C see saw runs. Minimal hopping and great speeds. Proboat says the motor is rated for 6S but that wiring is totally underrated for 6S.

I guess I'll be moving ahead with my leopard 4082 upgrade sooner than expected. Olwardbirds, what motor mount did you order from OSE for your Leopard upgrade?

DSC06444-1.jpgDSC06445-1.jpgWaterSeal-1.jpgDSC06441-1.jpg

[hydro_pyro]

The electronics can handle 6s. However... Inconsistencies in the quality of the physical connections can be the weak link. I did numerous top end runs on 6s, and the only things I experienced we're a little bit of burnt smell from the motor (Horizon tells me this is normal, just breaking-in the winding enamel), and flinging all the grease out of the flex-shaft.

The failed motor connections aren't happening to everyone running 6s.

[tlandauer]

The good news: tlandaur, your silicon tube seal on the flexcable worked perfectly. I also removed and silicon-sealed the strut. Found some water leaks there. Not a drop of water in the motor or radio area now. Great pointer. Thanks.

The bad news: I fried the wiring going into the stock Dynamite3830 motor. Ran for 8 minutes on 6S/65C see saw runs. Minimal hopping and great speeds. Proboat says the motor is rated for 6S but that wiring is totally underrated for 6S.

I guess I'll be moving ahead with my leopard 4082 upgrade sooner than expected. Olwardbirds, what motor mount did you order from OSE for your Leopard upgrade?

DSC06444-1.jpgDSC06445-1.jpgWaterSeal-1.jpgDSC06441-1.jpg

Good to hear the water issue is gone, 8 min. run is extremely long and on 6s it is not surprising for something to fail. Assuming that your run was continuous. The wiring and especially the plugs are always a joke to me, anyway.
For my curiosity: does the motor still turn or it is completely dead? I can see the insulation has suffered hight temp.

[AlanD]

The motor turns as normal but won't run. It didnt get over 120F degrees on the previous runs. I'm returning it to Horizon Hobby today.

I'm keen on the leopard 4082/2000kv with a T180 upgrade only because other posters have had success from this setup. I will only ever be running 6S since that's what I've invested in battery wise, but I'm unclear on prop choice and expected run times. I know I need to prop down so can someone recommend a sharpened/balanced prop that I can use with my proposed setup that won't fry things, still give me crazy speeds, and allow me to run until LVC?

Most of my runs are 80% + on the throttle which I understand to be less of an amp strain. Am i expecting too much?

(These questions may seem noob like, but I'm coming from a nitro background and although I have a degree in light current electronics I'm perplexed by some of the rational I'm reading on this forum :) )

[tlandauer]

HI Alan,
I understand your desire to upgrade and stay with 6s since that is what you already have. Keep in mind that the 4082/2000KV is really a 4s motor, I have a 4082/2200kv with a m445 prop and this motor is an amp hog, so I run 4s2p, with the parallel set up I have 10,000 mah and I get good run time. Yes, I can get over 6 or 7 min. continuous run time, but I always NEVER do that because of heat build up. After 2 min. I bring the boat back and check temp, then go out again. The heat build up can damage your gear, as heat builds up, the likelihood of failure grows disproportionally, and that is just talking about my set up with 4s.
If you have not bought your motor yet, I would look into the something in the 1600kv range . Are you using 6s2p? I doubt it will fit in the boat, if you plan to use two 3s, there will not be as much run time as you hope.
Also keep in mind that part throttle is HARDER on the equipment than running full throttle, I am not a nitro guy but may be in the nitro world is different. The part throttle makes the ESC work Much harder and heat builds up much quicker. So if you think in order to keep the amp draw manageable all one has to do is use part throttle, it does not work that way in reality. If you want 6s set up, get a set up so you can run full throttle all day long.

[AlanD]

I don't mean to hog this thread so let me know if I should create a new one.

It almost seems counter intuitive to go from 4S / 2200kv to 6S / 1600kv. Sort of changing your car engine from a 4 cylinder 6 speed, to a V6 with a 4 speed transmission. Am I correct to assume folks are putting in the 4082/2200kv to get blistering speeds for 2 minutes and then having to take a few minutes break to let it cool off? I understand their desire to do it I just want to understand what the implications of a setup like that imply.

So your suggestion to go with the 1600kv is to have slightly lower performance but less risk of overheating and possibly longer run times? I think I understand now.

Now that I've done some homework, that Neu Castle 1515/1.5Y is looking tempting too. I might have to refinance the house to buy it though.

[lenny]

What S would you be running the neu 1515 1y on ?

[tlandauer]

To get similar performance, if you use higher cell count and correspondingly lower kv motor, your amp draw is lower, yes, it is more reliable and desireable. I have a 12s set up on a Neu 2230 , the kv is only 725, at 32,625 rpm, the amp draw is lower than say, an 8s, 1100kv set up with 33,000 rpm.
On a Neu 1515 1y, there are 5s set ups with relatively small prop like m440 on a Mean Machine for instance. I think the Neu can tolerate this higher rpm to a certain extent, their materials ( bearings and magnets) being superior and the quality is Made in the US, I won't go for 5s on a 2200 kv Leopard.

[AlanD]

I'm assuming 6S as as described above. I'm still shopping around.
Castles web site refers to using 4S2P with it on the Blackjack. Castle doesnt mention 6S with it but a user on another forum had it setup on 6S. Any thoughts on it?

[tlandauer]

The 4 cylinder and V6 comparison is only true to a certain point: the V6 has more torque and can use a higher gear to obtain a certain speed within a given time, the 4 cylinder would have to work harder in a lower gear and turn faster to get enough torque to obtain similar speed in the same amount of time. In my mind therfore a V6 will last longer. But I could be ridicured here too for saying this.

[tlandauer]

I'm assuming 6S as as described above. I'm still shopping around.
Castles web site refers to using 4S2P with it on the Blackjack. Castle doesnt mention 6S with it but a user on another forum had it setup on 6S. Any thoughts on it?

Are you talking about the Castle/Neu or the Neu 1515, they are different motor, one is made in China and the other is made here in the US, I have the US made one in my Mean Machine and the member who was helping my build runs his with 5s set up , with a smallish m440 prop.

[lenny]

If you want a 6s setup,
Why not save a little money and try what my buddy is running in his geico.

[AlanD]

I was referring to the Castle/Neu. Didn't realize there were 2 options. I'm beginning to think there is now reliable solution for 6S.

[AlanD]

Lenny, tell me about his setup.

[lenny]

I am still testing my setup in the mystic,
And it is running on two 4s 40c 4000mah pack and nice and smooth with a gps speed of 56mph,
And that was with some old packs I picked up with a boat on hear.

[lenny]

This is his boat,
Not sure if he gps it yet.
I could find out from him,
He is using a 130amp hv seaking esc for good head room.
On 6s with this motor.http://www.hobbyking.com/hobbyking/s..._Inrunner.html
And loves it, Told me it is a great motor and he has tried a lot of setups in a lot of boats.
But cat hulls are his favorite.



Tell me what you think of it.

[olwarbirds]

We run a leopard 4082 2000KV with a seaking 180amp with cap bank on 6S with NO overheating probs...have run on the stock prop and others with NO overheating probs...OSE has had the leopard 4082 2000kv and 2200kv motors custom wound so they can handle 6S...If your looking for longer runtimes then yes drop to a 1600/1800kv ...our setup was just us trying to see just what kinda speeds could the BJ29 handle ... 6S setups on boats this size are not for everyone! Im a speed demon, I enjoy SAW runs and will be competing in future events along with other types of FE boat racing events....

Im very familiar with NEU motors from being a Jet junkie for many yrs...I use them for SAW setups...The NEU 1515 1Y is a 2200kv that is rated to a max 27v and a max 60,000 rpm, so their is no reason you couldnt run it on 6S ...I would personally NOT use it for a sport setup, thats more of a SAW setup, I would use the leopard 4082 1800kv-2000kv...each to their own madness...

Alan, this motor mount is very nice ....OSE-80610 ...its easy to install and distributes the weight of mtrs like the leo 4082 nicely, plus the price is very reasonable....

[AlanD]

Lenny, that MG is very impressive and he seems to get good runtime too. Is he on 4S or 6S?

Olwardbirds, thanks for all the good info. That gives me confidence that I can continue with a 6S setup. I would love to see photos of your setup and how you mounted the new motor bracket. I'm leaning toward the 4082/Seaking 180 combo with 1800 motor. Do you know if the 1800's are custom wound?

I since found part of my burnout problem was that the junky stock flexcable was binding in the leading edge of the strut bushing putting excessive load on the motor. I pulled the cable out after finding it didnt rotate freely, and where the flex portion joins the solid section its not aligned so its wonky when rolling it on a flat surface. OSE has an upgraded cable AND a new strut with better bushings for the BJ29 coming out in 3 weeks which is a straight replacement of the stock strut. I'll be doing that too.

Guys, thanks again for all the good info.

[lenny]

Yes on two 3s 40c 5000mah packs in series.
In the video,
I do not think he was pushing it to hard that day.
And also not hitting full throttle ether,
Just cruising power on a sunday after noon.