Mike Connor

My Feedback: (5)

Is this going to be another work of art? There is always the option of a quick flat build and use it for a warm up plane. It will still be fast and it won't be as big a deal when the expiration date arrives. My flat fun fly Demon is quick and a blast to fly. I am sure it will be nice looking regardless of how you build it. We still have some time before much good flying weather arrives.

Speedy-Gonzales

My Feedback: (202)

Neither of these two planes are or will be meant to be a "work of art" but built to take advantage of their full capability. I don't believe in doing anything "Half Fast" ( that's a play on words ) I could never date an ugly woman. In retrospect I can not fly an ugly model. Oh yes... they must be clean too!!! This will be a much faster build since I have one build under my belt. Speedy

Speedy-Gonzales

My Feedback: (202)

I have also been giving some thought for a build with a K/B 3.5cc RE. I think with the 3.5cc it would still be quite quick and light. I would not fully sheet this model. I think a modest speed of 125 mph could be possible. I think the 125 mph mark would be the challenge with this setup. The O.S. .32 SX would be another possibility but I really want my next Demon to be rear exhaust. What do you think about the 125 mph goal with a K/B 3.5cc Mike?

Mike Connor

My Feedback: (5)

My experience is that breaking 16,000 rpm static with a 7 pitch will put you there. Doppler did show my winglet version breaking 130 mph in level filght with a 9 x 7 but I want to duplicate that before making any claims. I have not had an opportunity to test many props much under 9" diameter so I am not sure where a lack of thrust will be a problem with speed. So far my speed runs are in level flight and NOT out of a steep dive. I doubt there will be much further testing until the weather warms up some and I know your winters are colder then mine. I must be getting old because I like 60 degrees F or warmer to fly.

Speedy-Gonzales

My Feedback: (202)

My rules for claiming an achieved speed is in Straight Level Flight ( SLF ). You can dive before entering SLF but when in a verticle dive do you measure the speed before or after you make contact with terra firma!!!! There should be an approximate distance of 100 yards after returning to SLF, from a dive, before any timing or doppler measurement reading is taken.

Mike Connor

My Feedback: (5)

I believe the rules used at the German speed cut allowed a steep dive plus the altitude variation allowed through the traps could be used for a slow decent.

gooseF22

The downsides are voltage, size, and weight. This is offset by the positives of C rating and safety and charging. The size on them are about like a long C cell. They are very robust and safe, they can withstand severe heat, and charge at 4C...usually at max amps of any charger. THe other part is that being 3.3 volts nominal it takes one or two additional batteries to equal lipo voltage.

for instance on my bobcat, I ran a 3000 MAH 4S and it achieved pretty good results with the 2500 kv and 6x4 prop. It did about 67 amps in that setup.

Without changing anything, I switched to a 6S A123 battery pack with heavy wiring, 2300 Mah, and the voltage under load was close. 13.9 volts and over 70 amps, and the overall weight was a wash because the lipo pack was heavy kokam. I didn't mind weight for the speed...helps actually. In most apps, it adds about 25% weight if using for main power. But using a UBEC works great because you cannot kill them. I get about 2.3-2.5 volts per cell under 60+ amp load with them.

The cells weigh 2.75 oz per cell. so they are lighter than a 5pack of nickles, but heavier than Lion and lipos

I also use them in a 2S config for Receiver batteries unregulated. they come in 2300 versions (dewalt packs) and 1100 mah (VPX packs) but require a max of 7.5 volt cutoff instead of an 8.4 volt CC/CV charge. I charge them at 6 amps often. Over 1000 cycles.

People are making packs now, and several chargers have LiFe programming now. I do believe its the future in modeling. They hold their voltage great...very flat, but require different checking.

Mike Connor

My Feedback: (5)

Thanks, it sounds like you know your electric stuff pretty good. Please post pics of your setup when you get to it so I can ponder my plunge into electrics.

freakingfast

My Feedback: (3)

I dear say, that the future of RC and speed will be electric. The over reactive environmentalists will soon see that our little two stroke RC engines are the major cause of global warming and ban our nitro fuel, LOL. The first clue that something is up when OS released a "green" 55AX-BE (Bio Ethanol). Here in California our gas powered little weed whackers, chain saws and leaf blowers now have catalytic converters, and run like c**p. [:'(] I’m not kidding!

I like it when I see guys working out the details on electric speed deltas so that those of us that have nitro in our veins can convert to electrons and not create a total dog of a plane. I'll sit on the sidelines a bit longer to see how the prop, motor and battery combinations pan out.

Mike Connor

My Feedback: (5)

Catalytic converters on chain saws may be a sign there are too many people on this planet. Some day it will make its way to Oklahoma. []

I am also watching the electrics making progress. I will probably end up using Li-Po batteries since I am such a weight freak. Seeing an electric delta at 150 + mph with a 5.5" prop will probably push me over the edge. I think it will happen by Spring.

gooseF22

Mike
I posted pics of the little bobcat awhile back, its the identical power plant. Will post the build pics sometime soon I hope, been on the road alot lately.

Speedy-Gonzales

My Feedback: (202)

Do you guys believe the doppler method of calculating actual speed of a model aircraft is accurate? Has anyone ever challenged this notion. I am sceptical but will accept doppler readings if anyone can actually prove they are accurate. Do you have any factual references showing accuracy compared to radar or photo triggered measured timed distances. I am curious if anyone has actually proven the accuracy of the doppler software for giving such readings.

gooseF22

I think mike has hit it pretty close.

Mike Connor

My Feedback: (5)

I-Love-Jets from Germany in the NC speed thread recently claimed extensive comparing of photo triggered timed distances and radar. He claimed the radar was often up to 10% fast.
http://www.rcuniverse.com/forum/m_68...mpage_2/tm.htm
It sounded fairly convincing and may be true but HighPlains came in right behind him and put doubt in my mind.
We usually do not have photo triggered times so we use other methods. The writers of the Doppler program show a 1%-5% margin of error and I feel that is close because of my comparisons.
In the Speedboy video, Doppler and radar were very close.
In the SlipStream video, Doppler and radar were vary close again.
A check against Bob27's Q40 was again very close.... and the list goes on.
My thoughts are that if more then one method of checking speeds are close to each other it will give you a pretty good idea of how fast you are going.

iron eagel

There is a problem with the photo triggered time trials in as much as the rise time of the detectors used are often not included in the calculations. What I mean is for many photo sensitive devices there is a lag time between the event and the time that the device actually changes state. One example of that is how that works is: have you ever seen a night vision system when it gets overloaded by a bright or hot event and it takes time to recover? That same thing happens in almost every optical device I had ever dealt with in electronics, and in the past I did deal with some fairly advanced systems. Rather than say that there is a lack of accuracy in doppler or radar I would say that the optic readings would be suspect.

Speedy-Gonzales

My Feedback: (202)

Mike, Thanks for the reply. Sounds convincing and the doppler method is the safest and cheapest when considering the other two methods. I had a radar gun but decided that the possibility of getting a true dead on reading is almost impossible and find it not a safe practice to stand in the path of a model airplane traveling at these speeds. Kinda like volunteering to see if someone can shoot an apple off the top of your head! Even with the radar mounted to a tripod it is very hard to get a reading with the small target area involved. Doppler it will be! Speedy

Mike Connor

My Feedback: (5)

In a court of law the radar is perfect but comparing different methods is what convinces me.

iron eagel

The math used for the doppler is very good and I would trust that as being about as close as we can get given the instrumentation that is out there. And if I recall you also used time over a measured distance to compare you results with and they were both very close, as a matter of fact I think they were within the margin of error that the doppler program claims.

Speedy-Gonzales

My Feedback: (202)

The Ohio State Highway Patrol claims there is absolutely no deviation in their radar units!

HighPlains

My Feedback: (1)

Police radar is based on Doppler shift.

Mike Connor

My Feedback: (5)

They were close but I trust Doppler over MY timing method. Using video is very accurate as far as timing but a manual adjustment for parallax does leave room for error.

Mike Connor

My Feedback: (5)

I got an email from one of my customers the other day.
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Today I broke my record pass at 172mph straight and level.
Speed checked using a Decatur Prospeed Professional Cordless Sports Radar Gun CR-1K.
Sport Jett 50 - 8.75 x 8.0NN Pylon prop APC - HS 625MG on Elevons (Hitech) - HS 85MG on throttle (Hitech) - 1200 Nimh pack 6V - HD switch with regulator - Coopers 15% High Performance Fuel
SO Macon Ga.
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I am wondering how much speed would be gained by a spinner and the shorter pylon tuned muffler?
No video yet but I will share it when one becomes available.

FYI - Kits are now shipping with the regular laser cut fins PLUS the laser cut winglets.
Free shipping (U.S.) on remaining kit(s) with out winglets.

SpeedBoy

172 mph straight and level [X(]

And I am wondering how much speed would be gained in a dive [X(]

Mike your own design is amazing !!!!!!! [sm=thumbs_up.gif]

bob27s

My Feedback: (19)

Yeah, that looked like a nice project......

Very likely that it could do a bit better with the SS muffler setup, or Q-500 muffler.

But that 170+ seems like pretty fast enough

Mike Connor

My Feedback: (5)

What I posted is what I got. Not sure if there was a dive before checking speed or if there was a tail wind. Regardless, that is fast.