Blackjack Test Run

[hkusp45]

Good question!!

Ill have to hook up the eagle tree next time out.....

Nothing was ever hot so I did not worry about it!!

[Tunda]

Im going to try a 640 prop tha i just got from OSE.........

[Jeepers]

Im going to try a 640 prop tha i just got from OSE.........

I put my hydro on a m640 with a 8XL and it went slower on that prop then a m440, speeds on the 640 was just over 38 mph the 440 was over 43mph both were on gps. apparently guys are finding that 35mm 36mm props are faster then the 40mm props. you might want to try these as well, I know I am going to.

[ROOSTERTAIL]

GPS may be incorrect. The NHRA has been doing some testing with gps systems and have been finding that not all are as accurate as claimed, they have put up to 6 units in a single car and found 6 different speeds on the same pass with up to 13 MPH differences. I have put 2 in a r/c boat and r/c drag car and have never had the same reading on either of them. I believe a real time data logger with sensors and lap top is a much better choice.

[SJFE]

I think that is the way to go also. Even a stop watch over a measured distance will give you an acurate reading. A little off topic but I lost my faith in my garmin the morning I ran hard aground following the same plotter course I had been using for a week. I blew the entrance to a 15 foot wide creek @ 30 mph by 6 feet. It gets mighty cold in October @ 4am. Had a buddy drag me out of the sod bank 3 hours later.

[hkusp45]

GPS is just for a base reading. I would not call record run with a GPS. As for navagation I trust my Garmin in my car. As for plotting on a boat I have no knowledge on that.....

[Tunda]

to each his own.................

[Fluid]

For anyone who wants actual test data in an FE boat rather than guesses and dubious "reports": I have run a GPS in many of my SAW boats running through official time traps, and I have never seen a difference of more than 2 mph between the GPS and official times. The reason for those few discrepancies was the fact that my boats were still accelerating through the traps so the average trap time was slower than the peak speed that the GPS recorded. As long as the boat is held at a constant speed for at least a second or two the GPS is highly accurate.

Of course any electronic instrument can malfunction - I was at one SAW race where the official speed recorded for a 6-cell mono pass was over 170 mph - but correctly used a quality GPS is a highly accurate way to measure you boat's speeds, especially for tuning purposes. It is more accurate than radar for high speed boats.


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[Jeepers]

GPS may be incorrect. The NHRA has been doing some testing with gps systems and have been finding that not all are as accurate as claimed, they have put up to 6 units in a single car and found 6 different speeds on the same pass with up to 13 MPH differences. I have put 2 in a r/c boat and r/c drag car and have never had the same reading on either of them. I believe a real time data logger with sensors and lap top is a much better choice.

what was the cars tested in, if tested in Top Fuel you have to remember that those cars accelerate 0-100mph in less than a second, it takes that long just for the gps to communicate with the satelites. so your gonna have some different numbers.

[Fluid]

Concerning the previous comments about a smaller prop size giving higher speeds with an 8XL - that is reality. Several P Sport hydros in our club running 8XLs have gone from x640/x642 props down to m440/x442 props and their lap times have been lowered. (The GPS also showed a speed increase of a few mph.)

All electric motors have an optimum range of amp draw and rpm which delivers the best power to the prop. While we often see speed increases as we increase the prop pitch, once we exceed the optimum amp range for the motor the speeds will decrease. Less pitch and more rpm can result in higher speeds and cooler equipment. But choose a prop with too little diameter and its efficiency drops and speed decreases.

With catamarans, raising the strut will usually result in higher speeds until the prop blows out. A club member's 24-cell SuperCat gained almost 10 mph by raising the strut 1/2". The higher strut setting allowed him to run a larger prop with more pitch; because the prop was not deep in the water it let the motor to unload and run in the optimum amp/rpm range.


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[SJFE]

Thats handy information on cat setups. In my case the Jolly Cat has fixed strut. I would need to do some heavy mods to make it ajustable. I will just use the cg for ajustments. I am not hacking this hull up.

[Tunda]

Smart move thats a beautiful hull................

[SJFE]

Thanks man. I don't even care if I run it all that much. It just looks great on the shelf.

[Tunda]

didnt think that this thread would go this long...But really good info...........

[Tunda]

SJFE man i gotta tell you you should of kept your BJ. I love this boat im going to run it this weekend and try to shoot some vid..............