4s versus 6s and runtime

[Erik Aa]

Ok, do you sharpen and balance alu props for racing as we do with BeCu props? Or do you race them stock?
If you balance them, do you rely on magnetic balancing tools or is this problematic for alu?

Regards,
Erik.

[NativePaul]

Some run them stock, they aren't terribly blunt out of the box and dont need any thinning or real work, personally I would give the leading edges a little tickle as they are not perfect.
I've not tried balancing one, I borrowed the only one I have used, which was box stock, it didn't make any funny noises like it was badly out of balance, but it wasn't as well suited to my boat as the heavily modified Octura that I was using, so I didn't buy it and play about. Magnetic balancers should wrk just fine but by the virtues of them being very light and CNC cut, they will need much less balancing than BeCu or stainless props.

[Erik Aa]

Alright. I'll try both some modified octuras and some alu props. Thank you so much.
I infer from your posts that you race in Britain? Do foreigners travel to Britain to race, or is it primarily/only a national thing?

Another thing. Any input on possible changes in Naviga battery rules for the 2013 season? I have seen on the Astec forum that Britain may suggest leaving the weight limit in favor of a capacity limit. When will the Naviga rules for next season be decided? Are the propabilities of a change high or low?

Kind regards,
Erik.

[NativePaul]

I do race in Britain indeed. Generally we do get a fairly large overseas contingent of racers at our nationals, mostly from Belgium but some others too, and if you wanted to come over for a race this would be the one I recommend as it is our only multi day race of the year, practice Friday, racing Saturday and Sunday, great facilities at the lakeside, is the best attended race of the year, has the most classes to watch, ( mini eco, mini mono. mini hydro, eco expert, mono1 hydro1, mono2, hydro2, supermono, supercat, team eco, and team mono1) plenty of room for camping to make it cheap, and a real party atmosphere as we don't have to drive anywhere in the morning. Let me know if you want more details.

There is zero possibility of any rule changes for the 2013 season, and I think the chances of a change for the 2014 season are low, I do want a change to a capacity limit instead of a weight limit, but don't see it happening before 2015, if we get it at all.

[Erik Aa]

Thanks again, Paul, for outstanding input.

I see that your 2013 nationals will be held at Bridlington. If time and resources permit, maybe I can make it. I will have to see.

You mentioned in one of your earlier posts that the Etti 4500s, VB 4500s and the Zippy Compact 4000mah 3s cells graph pretty closely.
I have noticed that Zippy Compacts have come recommended by a Belgian racer. Do these cells actually come closer to 4500 than 4000?

Do you have experience with these Zippy compact cells in Britain?
If they actually perform competitively in racing, they represent an interesting option at less than half the price of e.g. the Etti cells.

Kind regards,
Erik.

[NativePaul]

Sorry if I mislead you, it is the Turnegy A grade 4500s that my friend graphed and came out close to the ETTIs. quite a few of use here do use the 4000mah zippy compacts myself included for my 6s Hydro2, I don't have the graphing capabilities of my friend, but my charger says they are underrated and closer to 4500 than 4000, other racers tell me they are seeing the same thing. I have an ETTI pack too and they are better but not much and the compacts win on value hands down, I only just switched to 6s and have only 3 cycles on my compacts so I am yet to see if longevity is an issue with them, but it is for the ETTIs.

[Erik Aa]

Thanks Paul. I saw that Astec recently posted these tests on their forum as well. Excellent information.

I have two more questions.
1. The exiga setup of 1700kv with a 42 2-bladed alu prop that most racers seem to prefer, how many average amps does this setup draw for a 6 + min run?
2. How many more average amps does a 3-bladed prop at a given size (say 40 or 42) draw than a similar sized 2-bladed prop?

Thanks again,

Erik.

[NativePaul]

I think most 6s Exiga users are getting 7 minutes runtime on 4500mah which works out to about 39Amps average with throttle usage round the oval, which puts the hull right on the limits, several Exiga owners have told me they have power to spare that they cant use.

I have heard 20% extra current tauted for 3 blade props, but the only 3 bladers I have used are V series which don't compare to my usual props at all so I cant say for sure.

[martin]

Paul any idea what is the max amps their seeing with the Exigas with 1700kv on 6s.

[Erik Aa]

39 amps average! Wow, that is a lot less than what I draw in my DF 29 (86 amps average).
Paul, how many mahs do you get into your Zippy compact 4000s? Would the compact 4000s cut it for the exiga, or should I go for 4500 mach packs?
I have a feeling I should go for 4500 packs unless you manage to get 4300+ into the Zippy compacts...

Regards,
Erik.

[NativePaul]

My charger shows it is putting about 4400 into my 4000 compacts, but you always put more in than you get out and Marks figures you saw on AStec were output figures so they are not really comparable even though the numbers are similar, I don't doubt that the 4500s will offer more power, but I know the 4000s are cheaper, the Nanos came out very late in the season and there is not a huge price difference between them, had they been out when I was buying I think I would have gone for those.

I have no real knowledge of the spikes on an Exiga, but from Marks Info on his mono1 Envoy on half voltage (3s) and double KV (3400) "Current averaged 37.7A for the race duration, peaking at 76.6A on recovery from a flip or spin." looking at the graph more normal acceleration out of a turn (rather than from standstill) currents are circa 60A, I wouldn't expect an Exiga to be much different.

Mark's very helpful info.

[Erik Aa]

Paul, have you had the chance to put more cycles onto your Zippy compact 4000s? Any news on the longevity of these cells?
Here in Norway, the ponds are still all ice...

Regards,
Erik

[Punisher 67]

So what is it the 4s or the 6s . I was going to run out of whiskey reading this ......LOL

[1truckerdan]

remember....... wattage (power) = voltage x amperage .......a lower kv motor on a higher voltage uses less amperage than a higher kv motor on a lower voltage. so you should see a longer run time with the lower kv motor and higher voltage setup.

[NativePaul]

Erik, no, only a few cycles so far on the compacts for me, race season starts next week though so should get start getting some more in soon.

No worries if you run out of whiskey Peter, raise a glass of akevitt in Erik's honour instead.

Daniel, if you only want to lug around a set weight of battery say 560 grams then the higher voltage battery will have less capacity, it matters not a jot to the available energy if you have a 67A draw on 4s 6750mAh or a 45A draw on 6s 4500mAh both will give around 6 mins runtime, the advantage to 6s is that of efficiency, either you use the same ESC and wire in which case the lower current draw of the higher voltage setup will waste less energy heating the wire and FETs up, or you use a smaller ESC and wire, keeping the electrical efficiency the same but saving weight which increases the boat's efficiency. The advantage is small and a good 4s driver/boat will thrash a bad 6s driver/boat, but it is there and is noticeable if all else is equal.

The UK Fast Electric Nationals has changed dates, it is still at Bridlington but has been brought forwards due to a clash with the world championships, the new dates are June22-23, the worlds are in Gent, Belgium August 1-11.