Supervee 27 - Balance Point

[kesso2118]

I am interested in what the balance point should be for an stock SV27 and if anyone is using a modified set up whether they have altered their balance point??

Thanks,

James

 

[Flyguy55]

If its trying to blow off or blow over , adjust the CG forward. If you try some other props and Lipos , most of us take out the wooden battery box frames and add more velcro. With a good prop and 4800 lipos , my lipos are close to centered on the motor mount. even then you'll have to sdjust the CG for water conditions

I am interested in what the balance point should be for an stock SV27 and if anyone is using a modified set up whether they have altered their balance point??
Thanks,

James

 

[M@MRacing]

Check your trim tabs to you might be able to bring them down some.

 

[kesso2118]

Thanks for the responses guys, however, I was wondering what the stock starting point would be e.g. possibly something around 30% from the transom which in theory would make it around 8 - 9 inches??

Mine is not a stock set up. The motor is mounted close to the transom, around where the radio box would normally be and I have a Feigao 540XL with a Castle Hydra 120 ESC and 4800mah Lipos. At present the balance point is around 7.75 inches.

Regards,

James

 

[David Kingston]

James

What wind motor is your XL

8, 9, 10

With the 8, i found that the x440, x442 works well.

An ABC4555 hooks up nicely, use to run that in a 29inch titan and a 120 ESC also and it went like a cut snake.

Bit hot but that was back in the day of NiMH cells. Other guys run a 26inch delta with that combo and its quick and they have 3800mAh cells so you should be safe.

Having not run a super vee i cannot say what CoG to run but 30% is a good starting point. Id move the CoG back it it really rides loose then move the cells foward just that fraction.

Dave

 

[kesso2118]

Thanks Dave, you know I'm new to these electrical gizmos, :unsure: :unsure: I forgot to mention it is a 540 8XL.

I had been running it with an X440/3 and my batteries as far forward as they could go. It was very quick but it kept blowing over. That's when I decided to check on the balance point.

I took it out for a run today with the batteries in the same position but with a teeny bit of negative in the strut and the stock plastic prop. It went much better it was still pretty fast and I managed to keep it on the water with no crashes

Now I need to find out from the experts how hot is too hot for the battery packs. When I brought it in you could feel the heat through the top of the cowl. I could put my fingers on the packs for about 5 seconds before it got a tad uncomfortable. Is this too hot????

Regards,

James

 

[Bill-SOCAL]

Most people have found that a good balance point for the SV is around 33% ~ 8.91 inches from the transom. But whatever you do, an 8XL is a lot of motor for that hull. You might try adding some weight on the keel to both move the CG and to make it heavier. I've run up to 8 ounces in mine just to keep it stable and that is with the stock motor!!

With the 8XL I'd try a m445 being careful to check temps. Speaking of which, if you plan to run FE boats get an infrared temp gauge. Try to keep the packs below 140 degrees F.

 

[David Kingston]

yep 120degF is where i am to have my packs at the end of a race, usually they creap up to the 130mark

Definatly no more than 140degF as that will kill them in quick time.

Get a temp guage - offshoreelectrics has them so does Jaycar i think

The m445 prop is another good choice but for less pitch and to let that motor unwind try the ABC4555, i think you will be surprised. Big Ash swears by it in his mono when i got him onto it. He has the 3800mAh lipos and no worries with heat. Check temps and battery capacity though after a few laps in your setup The chopper prop might also be something to look at...

Also some have great results with a x442 as well.

One other important thing is to not let you lipo packs get below 3.0 volts per cell. If the 120 has lipo cut off then i would suggest setting it before running again.

Dave

 

[kesso2118]

The ESC was set so the Lipos wouldn't run too low. When I put the packs back on the charger they started charging at 7.25v and 7.45v respectively. Is this good, bad or irrelevant??

Until I get a Temperature Gauge can someone tell me if the "finger test" i.e. holding your finger on there for 5 seconds before you go Ouch, equates to anything like 120 degrees???

Thanks,

James

 

[David Kingston]

James

The finger test is not accurate.

I can hold my 130degF packs in my hand, where as the next person might find that really hot.

I can tell you though if you are running only half mill and 5 laps with final complete the course (so 6, 1/2 lasps total) with the 8XL and 440/3 prop, with packs fully charged and warmed in sun a bit, you will not be getting over the temps. You will be between 120 - 130 at the worst.

Ive run a bigger heavier mono hull with 4500mAh packs and a hotter motor and larger prop and i was not over the temp limit.

Dave

 

[kesso2118]

James
The finger test is not accurate.

I can hold my 130degF packs in my hand, where as the next person might find that really hot.

I can tell you though if you are running only half mill and 5 laps with final complete the course (so 6, 1/2 lasps total) with the 8XL and 440/3 prop, with packs fully charged and warmed in sun a bit, you will not be getting over the temps. You will be between 120 - 130 at the worst.

Ive run a bigger heavier mono hull with 4500mAh packs and a hotter motor and larger prop and i was not over the temp limit.

Dave

Thanks Dave, I'm going to Jaycar today to pick up a gauge.

I'll probably give it another run tomorrow and let you know what I find. Now that I've managed to get it to stay on the water it's time to start trying the bigger props

Regards,

James

 

[kesso2118]

Got out to the pond today with a Temp Gauge, balance point at 8 1/8 inches, two fully charged sets of packs (I'm running 2 x 2S packs), a handful of props and perfect water.

The boat went like a scalded cat

I started with the X440/3 and it went great, put on an ABC 1614/3 and it went better and then I tried a cut down X640 (one of my Outboard Props) and it still went good. The boat was running high and dry and fast. It was a little bit wild coming out of the turns but if you were sensible it hung in there.

So now I'm happy with the balance point ^_^

BUT, when I put the Temp Gauge on the packs I consistently got 170'F on one pack and 154'F on the other pack. I got the same results when I changed to fresh packs as well. The motor and ESC were fine.

The pack that measured 170'F was always the one where I have the Positive Lead connected to the Cut Out Loop. I assume from the earlier posts this is too hot, any suggestions??????

Thanks,

James

 

[David Kingston]

James

Are you running Deans Plugs

Get rid of them and run 5.5 bullets

Make sure that the soldering is good and no dry joints...

I have never experienced a pack drain more than the other, and i have also run 2x 2s packs to make 4s, and in much hotter setups than an 8XL, so my suggestion would be to try the plugs first.

Getting rid of that y-harness...

How many laps did you do to get them that hot... Its really odd

Dave

 

[kesso2118]

James
Are you running Deans Plugs

Get rid of them and run 5.5 bullets

Make sure that the soldering is good and no dry joints...

I have never experienced a pack drain more than the other, and i have also run 2x 2s packs to make 4s, and in much hotter setups than an 8XL, so my suggestion would be to try the plugs first.

Getting rid of that y-harness...

How many laps did you do to get them that hot... Its really odd

Dave

Dave,

I'm running 6mm plugs, maybe the soldering could be done better, I was using a low wattage iron and having a bit of a problem getting enough heat. However, at the end of each run none of the wires were hot and the motor & ESC weren't hot.

I wasn't running on a marked course but I ran about 5 or 6 laps that would probably equal about 4 of our race laps.

When you say "get rid of the Y harness" are you referring to what I would have if I was using Deans Plugs or are you suggesting I bypass the "cut out loop"??

Thanks Mate,

James

 

[David Kingston]

James

Yeah basically have

2 wires from ESC with Male and female

2 wires from each 2s pack male and female

connect one negative to one positive battery to battery

Then connect the negatice battery to negative ESC

then connect positive battery to positive ESC

(I have male and female on my cells but some have 2 females, so they dont spark out, but i have caps on mine)

I would suggest that you try and solder the plugs again. Does sound like there is a problem in the soldering...

You really should be draining the packs the same.

Your running the elite cells still hay. They are good, but you need that heat under control...

Are you prewarming the cells a bit. Leave them in the sun for 20 mins to charge and wack them in the boat and see what temps you get. Boat should run slightly faster and temps should be down a bit.

Just something else to try.

Dave

 

[Tim_Duggan]

James,

You are welcome to use my soldering iron if you need a hotter soldering iron. Let me know.

Tim

 

[David Kingston]

80watts is great if you have one.

Ive got a 40 and 80 wella soldering iron. For small and big soldering. Worth it...

You can also solder up tanks with the 80watt wella. Great stuff

Dave

 

[Tim_Duggan]

I have a 100 watt transformer based super scope iron. It's a beast.

 

[kesso2118]

Thanks guys, I got myself an 80 watt soldering iron today and I will redo all the connectors.

Dave, the wiring setup you describe is the way I have mine done, with the "cut out" loop in between the Battery Positive and the ESC Positive.

I haven't been "warming up" the packs prior to running them, so I will give that a try when I go out next time.

One question I have is whether there is anything tricky in the settings on the ESC e.g. what do they mean by "Motor Timing" settings?? It was done for me by one of the guys from our club. Sounds like I better get the USB Cable and dowload the Castle software and do it myself :wacko: :wacko:

Regards,

James

 

[David Kingston]

James

Are you running a Hydra 120 ESC

Did shane do the setup on it?

Not sure what the timing should be on a 2poll motor with that ESC. but i can find out for you... In the mean time someone else might know and jump in here.

I dont currently run any Castle stuff. I do have 3 of them but have yet to put back into a boat as i am scared they will go BANG again, in setups where a less powerfull controller lasts.

Its very interesting that your packs are getting that hot....

Dave