Silly 'SAW' rules - UK

[vvviivvv]

Could anyone with a bit more experience than me chime in on this please.


I want to have a run at some UK records in regards to SAW's but struggling to get clarification - emailed the SAW's 'Officer' and didn't really get a response...

I'd rather plan in advance as the date isn't released yet and i work out the country 6 months of the year


I have a twin cat, runs 7s which is 1 batt feeding 1 esc and 1 motor / side from what i've been lead to believe this classes my boat as a 14s boat ~52votls....in reality each motor is getting half of that.

Now if i parallel the packs before the esc as there is no weight restrictions on cells i'm classed as 7s again......

Seems a bit daft adding all this extra cable / connectors when its the same as running 7s direct to the esc and motor? are these just silly outdated rules or am i missing something

This is the only info i can really find..
"In all even classes you may run one bank of cells or if you have two motors you can split the pack into two, ( ie two banks of 4 cells in an 8 cell setup one for each motor )."

Thanks guys.

[RaceMechaniX]

Sounds like the UK rules follow some of German rules which are significantly different than the US rules.

In the US for IMPBA and NAMBA you are allowed to run parallel batteries as you describe. 7S per motor and a maximum of two motors would run in the S class. 7S2P for the battery configuration.
In Germany and I gather the UK they go by the total number of cells. So a 7S2P becomes a 14 cell class boat. L14 in German rules. In this rule scenario it favors higher voltage non-parallel cells. So if you could 1/2 your KV and run both motors off a single 14S1P battery you have the same power in the boat. That's a bit of a stretch, but hopefully you get the idea.

Especially in the cat classes in Europe guys will run both motors from a single pack for the lower cell count classes. Classes go from L2 through L20 and as you guessed L20 can be 20S1P or 10S2P or 5S4P. Additionally in Germany there is a weight limit per cell so you cannot run a 12000 size cell. The mass limit ends up being around a 5000-5200mAh cell. In L12 and above you start to see more paralleling of cells.

This debate goes back more than a decade when the US and Europe parted ways on uniform battery rules. The US stuck with paralleling and Europe followed with non-paralleled. No point in arguing whose right or wrong.
If you want to run at a SAW in the UK you will run in a class where they count the total number of cells.

[vvviivvv]

I guess I’ll be investing in a 7s Sls ‘speed’ pack and some weights for balance... think burst is north of 700 amps on a 5000mah pack

We don’t have the weight issue... that was removed, so in theory I could ‘hard solder’ 2x 7s 5000mah packs creating a 10000mah 7s pack...

Guess it would be one of those open to interpretation scenarios? Don’t think there’s 100% rules on it (might be pushing my luck but I’ll try and get it in writing from the uk mbpa’ before I go investing in a specific saw batt

[NativePaul]

We in the UK along with several other European countries decided to adopt the German SAW rules for some sort of parity and comparison, to me it is perfectly fair that a twin 7s boat should run in the L14 class, as while it is technically still only 29V it is capable of putting out the same power as a 14 cell boat, so adding the voltages of each side together is to me a reasonable way to prevent single motored boats being made obsolete from SAWs.

We have deviated from the German rules in that we removed the maximum battery weights, and as I see it that allows the loophole of running a 2p pack to supply a twin, I don't believe anyone has taken advantage of it as yet, but i believe it is there. If I was records officer I sure as heck wouldn't want to put it into writing, I'd just be hoping that people carried on ignoring it. IMO whatever the rules, or even if running for fun twins should be fed from a single pack, as the inside motor is under considerably higher load than the outside and I have seen puffed packs on the inside of twin cats when the outside pack has been well within temperature range.

There doesn't necessarily have to be any extra connectors or wire when running cells in parallel, it is possible to have less of each compared to 2 separate packs, but keeping the same amount when used in parallel is may be best in SAWs from a resistance/impedance standpoint.

I am not sure I would go as far as to say the rules are silly, and I know it is the same in the USofA where these forums are based, but it doesn't seem fair to me that you can compete in the same class with a boat with 14 cells in it against a boat with only 7 cells in it. If you Find the rules Silly, I encourage you to change them. SAWs is a small subset of a small hobby, If you attend the MPBA FES AGM on the 3rd of July, and you can propose a way of filling that loophole without banning the 1p packs people are using at the moment, or the *!***!***!***!**ty (sometimes undisclosed) 2p car packs that newcomers often turn up with, it has a very good chance of passing.

[vvviivvv]

I think my grievance is more I could build a twin mono for example, plenty of space, throw a single 30,000mah pack in which would cope with most amp draws,

But for weight distribution / space in most cats it is best to run a pack in either sponson

And again... you could build a 14s boat with one massive pack to power both motors say 52 volts...

Maybe I’m missing the point / talking nonsense.. when I’m back on land I’ll try and get more involved with fast electrics in the uk.

I will try and seek more clarification from the officials, worst case is I shell out for a high discharge pack, put it in one sponson and fill the other with ballast..

[RaceMechaniX]

Just run the cat in L16 with your 7S2P configuration.
Here are the German SAW rules: http://rc-saw.de/images/articles/RC_SAW_2016.pdf

If you want to know who is really fast with FE's, take a look at the speed list: http://www.rc-saw.de/images/articles...C-SAW_2019.pdf

And if you want to know the top speeds by class: http://www.rc-saw.de/images/articles...C-SAW_2019.pdf

[vvviivvv]

Just run the cat in L16 with your 7S2P configuration.
Here are the German SAW rules: http://rc-saw.de/images/articles/RC_SAW_2016.pdf

If you want to know who is really fast with FE's, take a look at the speed list: http://www.rc-saw.de/images/articles...C-SAW_2019.pdf

And if you want to know the top speeds by class: http://www.rc-saw.de/images/articles...C-SAW_2019.pdf

Nope. Wouldn't even try i know the German league is another level...... for example there tunnel record in K8 is 145mph... Uk record stands at 55mph...

The Uk records i don't think are very well contested and reading the meeting minutes don't really draw much of a crowd... To me personally SAW's should be on voltage regardless of if its 6s1p 6s2p to me 6s1p10,000mah and 6s2p 5000(/pack) is the same...

[RaceMechaniX]

Then plan on running at a US event.

[JestDanny]

I don't know much about these rules and SAW racing, so can I ask yous guys something? If you took two identical boats / hulls, one set as a twin screw, the other as a single screw, ran them on the exact same drive line batt, esc, motor, and prop would not the twin have a big advantage in strait away drag racing? Why not separate the twin screws from the single screws in volt for volt SAW racing?

[vvviivvv]

I don't know much either about SAW's... as you can tell from my thread

But generally if you take my hull for example, its a 1.2m cat with 2x Lehner 2250/7 i guess this is the equivalent of running the same hull on a lehner 3040? which would also requie a bigger esc and higher volt count

So yes, like for like twin to single you'd be massively under powered in comparison


It's been confirmed If i run 7s1p (/ motor) i'd have to run in L20

If i run 7s2p feeding both esc/batt from both packs i can run L8

Which i fully intend to do... and maybe next year ill bump up to 8s