Lsh

[Dan Bourgeois]

I see these motors listed on the web page for the
Proposed LIMITED SPORT HYDRO Rules

Graupner 6306
Graupner 6316
Fine Design FD-EM 775
Robbe Power 700 9.6
MPI ACC373 Promax 700
Hopf Viper 700 QC 9.6 Volt Neodym-Race 66mm
Hopf Viper 700 QC 12 Volt Neodym-Race 66mm
Hopf Viper 700 XLG 9.6 Volt 66mm

Will all these motors be legal?? I thought it was only going to be graupner 700 bb motors. Can someone tell me the graupner part number to the exact motor we are allowed to use?

[RvE]

Dan
The Graupner part number for the 8.4 v Speed 700 BB is GR6316. Not sure what the part number for the 9.6 v NEO is. Not sure which motor is better for LSH.

For 12 cell mono hull, there was a lot of debate and comparisions on the 8.4 v BB vs the 9.6 V NEO. A lot of folks preferred the non NEO 8.4 V but it may be totally different for a hydro. I bought a non NEO 8.4 v BB for my Electro Vee based on the comments of others.

Ralph

[Doug Forrester]

Hi Dan
Up until this year, in its 12 cell Spec Mono class, MMM only allowed the Graupner Sp 700BB Turbo 8.4v - #6316.

This year, to bring this class and the new LSH class into alignment with 700 motor class definitions that are being voted on by Namba, MMM decided to allow use of the Sp 700BB Turbo Neo 9.6v - #6306. The other motors listed as legal by Namba are variations in name on the 700 Neo available elsewhere in the world. The only one that we are likely to see here is the Fine Design 775. It is the same motor as the #6306.
There has been considerable difference of opinion as to whether the 8.4v BB or the 9.6v Neo is better despite its higher price. The 8.4v BB has higher RPM but the Neo has greater torque and lower RPM on 12 cells. Personally, in a hydro, I'm not convinced that the more expensive Neo will be better.
The only thing that I'll definitely predict is that we'll know for sure at the end of the season!

[Dan Bourgeois]

that clears things up a lot

thx

[K.R.Joye]

Originally posted by Doug Forrester
The 8.4v BB has higher RPM but the Neo has greater torque and lower RPM on 12 cells.

Sorry DOUG I dont mean to be critical but i think you have the descriptions of these 2 motors backwards.

From all the motor charts i've seen the 700BB 8.4v has greater torque and a lower redline than the slightly higher RPM 9.6v Neo version.

Personally I'm planning on running 700BB8.4v in my LSH, I've found it to be less tempermental and more forgiving to set up.

[Doug Forrester]

Hi Ken
It all depends on which specs you use and how you define the performance. Your comment got me curious and I thought i would consult the PCalc program and see what it said about the two motors.

700BB 9.6v Neo - Kv (rpm/volt) - 1672
Kt (in.oz./amp) - .808612


700BB 8.4v - Kv (rpm/volt) - 1750
- Kt (in.oz./amp) - .772572

Comparative simulations:

1. 700BB 8.4v
12 - RC 2400 cells Load - 7" X 4" (air prop)

17,736 rpm @ 30.332 amps 66.7% efficiency
max. efficiency - 71.9%
current @ max. efficiency - 17.8 amps

2. 700BB 9.6v Neo
12 - RC 2400 cells Load - 7" X 4" (air prop)

18,319 rpm @ 30.54 amps 73.9% efficiency
max. efficiency - 77.3%
current @ max. efficiency - 19.12 amps

The load created by a 7" X 4" airplane prop was arbitrarily chosen to represent a 30 amp load. The LSH class runs 10 laps which should take under 3 minutes. Actually, I think that eventually they could approach 2 1/2 minute heat duration. This means that theoretically it should be possible to draw 35 - 40 amps from RC2400's and finish 10 laps. Whether the motors will stand up to this long term remains to be seen. Frankly I doubt it. It wouldn't surprise me to see 30-35 amps as a prudent limit.

[K.R.Joye]

DOUG thanks for doing the math. I figured it would be something like that. Wow 2.5 min predictions for 10 lap LSH!I think someone may do a sub 3 min this year. It will probably take a very efficient light hull,good driving,in minimal traffic. Will have to keep posting data as we make advances in the class.

DOUG Question are the rr ride pads on your hydro designs parallel or do they have an angled approach to the water?

[Doug Forrester]

Ken
I'm not sure what angle you are referring to exactly. On the majority of my hydro designs, the sponson ride pads have a longitudinal angle of attack (to the direction of travel) of 5 degrees. Generally, I use 3-4 degrees of lateral dihedral on the ride pads as well.
I hope this answers your question, Ken.

[K.R.Joye]

Doug the rear(transom)ride pads profile?

[Doug Forrester]

Ken
Please tell me I'm especially dense this morning. I'm completely baffled by your reference to "rear ride pads (transom). I assume that we are talking about sport hydros and not riggers. The "tunnel roof", at the transom, is 0 degrees. The bottom edges of the rear "non-trips", forming the two tunnel rails or "air dams" are also at 0 degrees in both directions.

Is this what you are referring to?

[Steve Reesor]

I seem to remember the Miss Bud came out with rear ride pads, ~1/2" by 2.5" long mounted either side which helped keep the transom up in corners. Is this what you are referring to Ken?

[K.R.Joye]

Thats correct just wondered if DOUG used them,if so what size and angularity profile of them in his LSH design.I know ANDY K has made reference to them on his hulls also.

[Doug Forrester]

Ken
Sorry for the mis-communication. I guess I didn't get it because I have never used them on any of my sport hydro hulls. The closest that I ever came was on my Mk III design (the 2001 Nats hull was Mk IV) which used 2 small ramps on either side of the tunnel at the transom. They were about 3/4" wide by 3/4" long and just the air dam thick (3/16"). This hull also used a small ride pad on the bottom of the strut. Dan Chase has this hull now.
I did not use these features on the Mk IV hull and it didn't seem to hinder performance any!