WW IV SV OPC Class discussion

[Flyguy55]

Hi
Dave N suggested that I start a new thread about SV OPC rules for the Race

I received this from Datin Jordan today.

Dick,

You are correct... I think 10-laps on anything less than 5000mah cells is pushing the limits... with a mill and cooldown I'd say no way...

We reduced our race to 8-laps, and things were just starting to get too warm at that point...

I think we're going to go to 6-laps for this race season and see where things are... You can't really fit 2P in these things... not at 4S anyhow... without some major cutting... Shouldn't need it anyhow...

As an example... I ran mine with 4S1P of 4350mah 20C PolyRC cells... After 10-laps, the cells were approaching 150-degrees! NOT good... I don't recall the exact mah put back in, but I remember it was well over the safe 75% guideline....

I think maybe with the newer gen cells, we could go longer, but for now we are going to limit it to 6-laps... at least at the moment...

I think also that in the next year, some of this will be moot, since I hear that 6000+mah cells are on their way... I know Brian tested the Elite 5300 cells at the SAWs and said they were excellent performers... Heck, he went 116mph on 4S1P with them!

Thanks for sharing that information concerning the rules... It would be nice if one of these days things get back on an even keel so we can all get back to just worrying about prepping boats!

Hope you are having a GREAT Day...

Talk to you later,
Darin

[Flyguy55]

Look at Darin and Pats experience with these boats.
(My wife had surgery this weekend and I didnt get to test my OPC this weekend.)

I don't think we should run over 5 laps , 5/8th of a mile , on the 1/8 mile course.

Maybe after we have mor experience we can race longer .

Dick

[jfruge]

Look at Darin and Pats experience with these boats.
(My wife had surgery this weekend and I didnt get to test my OPC this weekend.)

I don't think we should run over 5 laps , 5/8th of a mile , on the 1/8 mile course.

Maybe after we have mor experience we can race longer .

Dick

That sounds good to me. Are we running a 1/8th mile course this year @ WWIV?

if so I vote for your plan of 5 laps.

[Darin Jordan]

You could probably get by with 8-laps... which would be a mile on that course... Just keep a close eye on things at first... You'll definately need at least 4350mah packs to keep things safe... These use more mah than the SV27 hulls... At least that's been my experience and observations...

[PatrickM]

What Darin said......IMO, we can do 6-8 laps on the 1/8th easily. My TP 25C 5000's were at 125 deg after 6 laps. We'll do whatever you guys vote for....

Are we running a 1/8th mile course this year @ WWIV?

The 1/8th mile course will be easy to do at the Crossroads pond, we can probably go larger, but I'm not sure that we'll be able to fit 1/6th comfortably. A test race is planned for February 23rd, we'll nail down the exact size then.

[Steven Vaccaro]

What about running a bit smaller prop? I guess its up to you guys on if you want a few extra laps at slower speeds or less laps faster.

[PatrickM]

What about running a bit smaller prop? I guess its up to you guys on if you want a few extra laps at slower speeds or less laps faster.

I don't have enough run time on my setup to say for sure, but I strongly suspect that the amp draw and battery temperature are drive line friction issues. Not sure if propping down will help to any great degree unless its a major reduction in diameter/pitch. The same motor and battery with a similar prop, installed in a sport hydro hull, will draw half the amps. We'll know more as we gain experience with the setup...

[Darin Jordan]

I don't have enough run time on my setup to say for sure, but I strongly suspect that the amp draw and battery temperature are drive line friction issues.

Patrick,

I think you may be onto something there... The Lawless drive I have for the Mod tunnel I'm working on doesn't have nearly the drag that the REK unit seems to have... with the driveline bending 90 like it does... all in a 6" space... I think there may be some unwanted friction...

It's important that people make sure their flex can "float" in there, and isn't tightly jammed into the coupler or stub... doesn't need much, but some... And LUBE it every run... the Nitro guys are great sources for special lube mixtures...

[Flyguy55]

I think it might be fairly easy to check the drag with a wattmeter and Tach. for comparison between lower units .
If everyone used a SV 27 motor and the same prop and checked the amp draw at the same RPM I think we compare the drag ie amps

[PatrickM]

I think it might be fairly easy to check the drag with a wattmeter and Tach. for comparison between lower units.

Thats plausible if it's done under load to take cable wrap-up and thrust drag into account. Actual running conditions would be best.

One of the nitro guys claims to have checked a few outdrives on a dyno and says that there is virtually no power loss difference between the Lawless and a stock K&B 3.5 unit. He's one of the regulars on IW.... a search may turn up the posts from a few years back. I seem to recall someone citing this info as the reason that Richard Konnen did not make the REK an angle setup. It would be interesting to have fresh data on all the lower units: OS, K&B, REK, Lawless, Hyperformance (old and new), etc.

[Darin Jordan]

Patrick,

I know that Grim swears by the OS-Max lower ends... I have two REKs and a LawLess 3.5... the Lawless is a work of art and very smooth... but the REK isn't too bad functionally either...

I think that the square-drive leaves a little to be desired... It's not as smooth while rotating under load when moving from flat to flat... and I'm sure that causes a touch of drag... Once they are broken in a bit, however, they seem to free-up quite a bit...

[properchopper]

number of laps for OPC/SV 27

Any decision on race length yet ? I'm testing with a X642 [ runs nice & fast] and
4S 4100's ; after 3 1/2 - 3 3/4 minutes the battery was @ 135 - 140 degrees. Not sure that's good ; would like to see reduced laps to keep reliability reasonable, or prop way down. I may have to try stuffing the 2 X 2S 4800's [I intend to use for LSO] in to get some more battery headroom for a longer race. I hate to have to re-model the battery box to do this

[Darin Jordan]

Any decision on race length yet ? I'm testing with a X642 [ runs nice & fast] and
4S 4100's ; after 3 1/2 - 3 3/4 minutes the battery was @ 135 - 140 degrees. Not sure that's good ; would like to see reduced laps to keep reliability reasonable, or prop way down. I may have to try stuffing the 2 X 2S 4800's [I intend to use for LSO] in to get some more battery headroom for a longer race. I hate to have to re-model the battery box to do this

Tony,

We tried running ours for 10-laps... so about 4-minutes... with the same results... Batteries were draining beyond the 80% mark (4350mah packs...)...

We reduced it to 8-laps and that lowered the temps about 20-degrees... (mine went from 150 down to about 130...)...

I think we've settled on 6-laps for our club races... though we may stretch that to a mile depending on the NAMBA rules vote... A mile is doable with the new 4800 or 5300 mah packs (Elites)... I have three 5300 mah Elite packs and they are quite a bit longer than the 4500 Elites... but interestingly enough each cell is thinner...

4500s => 5.98" long x 1.73" wide x 0.30" thick (per cell)
5300s => 7.40" long x 1.81" wide x 0.27" thick (per cell)

For my TS-2 and my WoodStuff... the 5300s actually fit better than the old PolyRC cells I have, because I had the extra length inside the box... but not the thickness... the Elites are thinner so they fit no problem... Price is right too... Elite 4S 5300mah 30C cells for $200.00... Or the 4500s are $160.00 (cheapbatterypacks.com)...

Of course... it'd be less costly to just par the laps down to say 6-laps...

[properchopper]

re :

If I understand the WW IV rules correctly, there's a 5000 mah limit for Spec/OPC. That being said, I'm thinking that for anything over 6 laps, a batt like the Elite 4800 would be a safe bet, although I'd have to raise the roof of my box a tad to get it to fit. Hopefully the race coming up in AZ prior to WW IV will shed some light.
For 5 or 6 laps I'd use some of my 4100's & save some $$ [& box remodeling] I guess I'll hold back & see what's decided.

[D. Newland]

Tony-I'm not the judge and jury of the OPC class, but I think all involved wanted to run 5 laps on 1/8th course. We'd rather have successful test results over damaged equipment!