Setup for Whiplash GV or Backlash

[Brushless55]

Very cool, and so glad to see video of a CC2028 8s Hydro!

[RaceMechaniX]

Electric,

It would help if you zoomed in on the data. Click and drag on the data screen to zoom into an area. 1-1/16" on the strut is still too low. Raise it to 7/8". No where in the video's does the boat look loose so you should have plenty of margin. It would also be helpful to see the graph of RPM. Since you are probably turning more RPM than an average gas boat you probably need to remove more lift from the prop.

TG

[electric]

Thanks Oscar and Tyler, this confirms my suspicion that the strut needs to come up and I need to get some more "lift' under the boat. When I put it on a flat table and just stared at it yesterday I thought the AOA looked way to low and this all makes sense to me now. Oscar your thread shows 3/4" and Tyler is at 7/8" so it is probably somewhere in that range.

Tyler I do have some data from the two runs I made yesterday and will post it here in the next day or two when I get some time in the evening.

[detox]

Yea, hopping is a sure sign of strut being too deep or too much angle causing sponsons to run too flat and wet. You want to run on back edges of sponsons...boat will haul ace and draw less amps afterwards. A setup board and filler gauges will really help dial boat in. I would not add too much weight to that LONG hull.

Raising and adding 1 degree to ride pads will help. Sounds logical to me anyways

[electric]

Here is some DATA from the two runs yesterday. Interesting note, I blew off a water line on the first run. The interesting part to me is the temperture climb is not much different from the second run where we had water flow. We did restrict the water flow a bit on the second run to keep the lines from blowing off.

RPM's seem about right. 780kv motor * 29.6(volts) *.90 (efficiency of motor) = 20,779 rpm’s. You can see some voltage sag and amps up which is an indication of load on the motor, but still the rpm’s are maintained pretty close to what they should be. Really, I am very close to correct when I think about it. If I get the hull aired out some more I may get there.

[electric]

Yea, hopping is a sure sign of strut being too deep or too much angle causing sponsons to run too flat and wet. You want to run on back edges of sponsons...boat will haul ace and draw less amps afterwards. A setup board and filler gauges will really help dial boat in. I would not add too much weight to that LONG hull.

Raising and adding 1 degree to ride pads will help. Sounds logical to me anyways

Ok, dumb question, what is a "filler gauge"? I get what you are saying and I would like a more exact way to measure the AOA, but was wondering how that is done. I figure there must be some math formula where I measure the heal of the sponson foward a set amount of distance and then measure the gap and that gives me the degrees(AOA)? I am not an engineer and am now wishing I had paid a bit more attention in geometry class. chuckle. I would like an exact way to measure this though so I can be more precise in my adjustments.

Just did a google search. http://en.wikipedia.org/wiki/Feeler_gauge This is what you are referring to? I used to use these to gap spark plugs on my old car when I was kid. If I am measuring the gap at a certain point then what is the formula to derive AOA?

Just rambling here at this point, but it would seem to me that rather than discussing strut height we should be discussing the AOA of the sponsons? As and example, if you are looking for 3 degrees of AOA then you would adjust your strut to get that and this takes out any variations in the mount point of the strut and buiding variations? Not sure if that makes any sense?

[RaceMechaniX]

Electric,

Send me the raw data file so I can zoom in for you. email is my handle @gmail.com and I can post these for you.

Detox meant feeler gauge. We use them to add slight changes in strut angle. For example "0.020 under the nose" means with the strut flat on the board, put a .020 feeler gauge under the nose of the strut and tighten down.

We typically leave reference to AOA to sponson angles. For the whips generally you will start with the boat level i.e. the bottom of the hull parallel with the set-up board and set the strut dead flat. Because you are heavier than a typical gas powered whip you will likely need to raise the strut to loosen up the front end. Don't worry if it looks like the tail is dragging in the water.

TG

[RaceMechaniX]

Jim,

Here are some zoomed in views.

Tyler

Jim Stevens Backlash Castle 2028 8S2P Castle ICE 200 run 2 all data.jpgJim Stevens Backlash Castle 2028 8S2P Castle ICE 200 run 2 part 2 all data.jpg

I can only assume the water/air was pretty hot to begin with. I don't see any temps below 100 Deg. So higher temps are normal.

Once at full throttle you are pulling 170-200A consistently. Once you log the data with the new strut setting we'll compare.

TG

[electric]

Jim,

Here are some zoomed in views.

Tyler

[ATTACH=CONFIG]100131[/ATTACH][ATTACH=CONFIG]100132[/ATTACH]

I can only assume the water/air was pretty hot to begin with. I don't see any temps below 100 Deg. So higher temps are normal.

Once at full throttle you are pulling 170-200A consistently. Once you log the data with the new strut setting we'll compare.

TG

Tyler, welcome to TEXAS, yes we started the runs with 95 degree air temps and the water will get there to in a few months. We run HOT here. Tell me again how you Zoom it?

[RaceMechaniX]

Oh I know about the heat. My wife lived in Valley View for 2 years and I remember the sauna conditions.

To zoom just left click and hold, pan across the screen to highlight the data you want to view and release. You want to make sure you select close to the top and bottom of the page so you do not cut off the lower and upper lines.

TG

[electric]

Oh I know about the heat. My wife lived in Valley View for 2 years and I remember the sauna conditions.

To zoom just left click and hold, pan across the screen to highlight the data you want to view and release. You want to make sure you select close to the top and bottom of the page so you do not cut off the lower and upper lines.

TG

Thanks! I was control clicking, shift clicking..etc... will try this trick out tonight.

[detox]

Here is an interesting tread about correcting the Backlah ride pad angle...just in case you built yours wrong. He now includes stepped ride pads in his newer Backlash kits

http://www.jrcbd.com/showthread.php?t=55236

Picture below is my heavy Whip 40

[electric]

Some observation ,The turn fin should be mounted on the inner side of the bracket. The ruddder should measure 3-3/4" from the underside of the deck

This boat will fly on ABC 3016 prop, just make sure you have 0 to 1 postive degree angle on the strut setting

Testing this boat again, since I will be racing it in March this year. I tried this prop today. Excellent prop. Boat ran 74.4mph in 2 inch chop. This prop had considerably less lift than the propworks prop and that seemed to smooth out the boat (no hop). The boat used to dive on the start, but with this prop it just takes off with no diving. Still think I am pulling to many amps so I am going to try some slightly smaller ABC props. to see what I get. I will also be getting another Propworks prop with slightly less pitch and see how that does.

[battlefury]

If the stern of the boat still hops after postive angle applied, try a prop with a less lift
The 6719/3 is suggested by blazer but my backlash hauls the mail wif the 7316/3 prop.

[electric]

Here is some data from the 74mph run. My feeling is I am a bit to loaded up on the ABC 3016 prop and am going to go with a smaller diameter prop with a bit less pitch in it to see how it behaves. Really, if I could feel confident I could keep the boat from blowing the esc or draining the batteries before I get through the race this prop would be great. Be better to get the same speed with bit less amp draw on the motor. Look how the rpm's drop off in the turns. I am not letting my hand off the throttle, just loading the motor up and bogging it down. Seems that way from the data. Just thinking out loud here.

I am running 8s2p with four 4000mah batteries. I think I can squeeze in some 5000 mah batteries possibly.