Q tunnel props

[rumrunner]

What are good prop choices for Q tunnel?

 

[HTV Boats]

Depends on what motor & KV's your running. With a 1600kv an M445 works well. An M545 is faster but eats up more amperage (needs bigger batteries)and creates heat that may prevent 6 laps. Kind of a balancing act with each individual setup.

Mic

 

[rumrunner]

Would a abc 47 x. 60 be to big 1521 with 1600 kv.

 

[lohring]

Another issue is the boat you are running. Our tests on a Leecraft XT-460 showed that the torque from an electric motor could easily cause the right sponson to bury. We ran the prop much shallower than with a 7.5 mod engine. We ran the same 1450 prop on the electric at a similar rpm. A smaller diameter prop would probably help even though the motor easily turned a larger 1455 that I ran with 11 cc engines. The boat ended up to be faster with the electric setup, even at a heavier weight. It was a handful to drive. I'd pick a larger boat. The same power plant is now in a Sport 40.

Lohring Miller

 

[RonShaw]

Shane,
I would think 45-55mm range, according to what pitch you run. Mic is right, you have to watch the current draw carefully as increased pitch/diameter will have a negative effect. I also think Carl's new 355 THOR may end up being a perfect choice for a Q Tunnel. It is almost 36" long and also has a wider beam that really helps handle the more powerful Nova 46 and should work as a Q as well. I want to try a Q one day. It will be a totally new learning experience I'm sure.

 

[stan simpson iv]

I would ask Kris Flynn what prop he run's on his...it looked real good,and handled well. Im sure he will chime in later

.

 

[HTV Boats]

Diameter is the killer here more than pitch. I am not positive if Lohrings group ran an outrunner which is around 1250kv. We ran a 545 to set two lap record with a 1520/1600 Castle. An 1816 to 1914 for SAW's ate 3000ma in two passes. With the torque I find smaller diameter running deep worked best on the Shaman, Warhead & Vision. The FE motor will turn any prop you put on it. Making 6 laps without a fire is the challenge. Start small and work your way up checking heat and MA's used.

Mic

 

[rumrunner]

Thanks guys .

Kris where you still running the M445 ?

 

[Kris Flynn]

You assumed i would read this...how sad for me haha

Run a 65mm prop mate...REAL fast...just ask Ze Germans about the 1000amp speedo in their 109mph mono ;-)

Seriously, I would love to see a 36" boat tame a real Q setup in heat racing form...but I think you're pushing **** up hill. The 36" THOR is a nice wide boat and could be interesting.

something to note also... the 7.5 shaft assemblies last a LONG time with only 45mm props

Run the Gas THOR mate. ..what could go wrong?

 

[Kris Flynn]

Btw more prop is not always faster ;-)

Spin em up!!!!

 

[lohring]

The power plant details are at We ran Scorpion outrunners, but there are less expensive choices these days. The 1100 KV gives around 20,000 rpm. Despite K&B ads, long ago data logging gives something like this on stock nitro tunnels. We were trying to develop a spec electric replacement for the once popular 7.5 stock tunnels. Maybe there will be a readily available, low cost motor and speed control combo for 6S. That size is a lot more forgiving than the P spec size boats.

Lohring Miller

 

[RonShaw]

Guys,

One question I have that may help Shane as well, what RPM ranges have you found most efficient (taking in account slippage and speed) in relation to P and Q tunnels? With so many KV selections available, this would be helpful information. Im thinking 40-45k in both classes but totally a SWAG. Thanks.

 

[HTV Boats]

The nice thing about Q tunnel is you don't have to buy the biggest powerplant and ESC availiable. The hulls will take care of that as Kris eluded to. Q over P lowers the amps required by 1/3. Voltage does the work now so speedies live longer.

As for RPM the formula is volts X KV's. That gives unloaded speed. Actual RPM's are about 80-85% under load. Take 1600kv X 22.2 volts (6S average under load) and you get 35,520 prop speed unloaded. My data logger will read 28000-30000 actual RPM which is just that 80-85% depending on prop used. Lohring using an 1100kv outrunner would be 24,400 unloaded and 20000 something actual. That's why he can run larger props, This is what you need to figure out for your hull and how it handles. No wrong answer just how efficient can you get.

My thoughts on heat racing is the 25000-30000 range actual prop speed. For SAW you might go up to the 36000-46000 range. Bear in mind an outboard propshaft is not as true as an inboard shaft and as you go up in RPM it will have more resistance. As you increase RPM your prop diameters will load your motor exponentially. SAW props are generally less diameter and more pitch.

In my opinion for heat racing 2200kv is where I start with a "P" and 1600kv for a "Q". Records 2 lap and SAW need more RPM,

Mic

 

[RonShaw]

Mic,

This is great info. Nice to know what actual to expect over no-load RPM. I am starting to change my views now on overall motor KVA and looking at the smaller more reasonable motor choices such as the Leopard's. If the larger motors simply end up trying to torque-roll the boat, or make it uncontrollable on the water, not going to be a smart choice. At the end of the day, solid fast lap times always prevail. One more question, what amp speed controls will be sufficient using these lower KVA setups for the Full P and Q classes? Thanks.

 

[HTV Boats]

As for speedies the T180 (Turnigy-Seaking) will work with up to a 3500 watt (40X82 or 1520/21) motor, In my mind a Neu 1520 1Y costs $280 and will be money well spent over a leopard or TP. I have a box of burnt Leopards and TP's and yet to toast a Neu or Castle. Not that is can't be done. Watch for 1521 1600kv Castles on OSE 4 sale or try WTB there. I have scored 3 from $100-125 so far. On a light boat a Castle 1515 1Y (less than $150) on 6S will spool a 442 into the 60's and go back to 4S for "P" class. 2500-3500 watt motors will let you run 180-220 amp speedies.

Back to ESC's. The Swordfish 200-220-240's are OK but the T180 seems to be more reliable. Castle 1/5 th scale car MambaXL2's can be converted and are basically the old Hydra 200/240's. If you have extra cash ($300-400)Rocketcityracing handles MGM's which are rated very well.

Mic

 

[RonShaw]

Thanks Mic. Great "sparkie" info. I knew you used to run the Leopards so thanks on the update that Neu/Castle is the way to go. I will start looking for a couple T180's and a 240amp ESC's as well. This info will help a lot of FE newcomers.