Author Topic: Something interesting about the primary force (Read 5745 times)

Horby · « **on:** August 04, 2015, 10:51:17 PM »

Looks like I have a dr jeckle and mr hyde on my hands.
I was at the Western Canada Championships over the week end, no big deal accept my Primary force was a completely different plane than what I was used to.
Normally I fly at 3500ft at my local field and my PF usually flies ok but would wash out in hard corners when I pushed it. Well, over the week end i was at 100ft for the competition and my plane was amazing, it flew better than any thing I have had in in a long time. I did the same with my Toutor last year but not even close to the same performance increase. The other thing that happend was that my power consumption did not change either, I didnt change a thing on my setup and all I did was lose 2 tenths per lap ther than that nothing else changed. Kind of scratching my head over this.

Warren

Target · « **Reply #1 on:** August 04, 2015, 11:10:20 PM »

Sounds like thicker air slowed down the lap times, but also made the turning more efficient.

Paul Walker · « **Reply #2 on:** August 08, 2015, 01:59:26 PM »

Check the dendity ration for the two sites you flew at. They will be quite different, and that is why it flies "better" in Vancouver.

I normally fly at 2100 feet elevation, and when going to a competition in western Wa or Or I have to add about 2 frams tip weight and slow the motor down.

Target · « **Reply #3 on:** August 08, 2015, 07:05:22 PM »

Who doesn't love posting from a cell phone?
I don't!

Horby · « **Reply #4 on:** August 10, 2015, 08:46:16 PM »

Interesting, I changed nothing and the plane did fly a few thenths faster but a whole lot better. I will be back home this week and we will see what changes I need to make it fly the same. I suspect I will have to add about 200 rpm.

Warren

john e. holliday · « **Reply #5 on:** August 11, 2015, 04:22:48 PM »

Might try a different prop or more nitro if your tank is big enough. Then when it does go faster you may have to go longer lines or shorter lines with set up you already have. Planes for some reason have a speed they are happy with depending on where you are flying in this great land of ours.

Horby · « **Reply #6 on:** August 11, 2015, 08:44:39 PM »

Lol nitro might be a little hard to increase........ I dont have a fuel tank.

;-)

Keith Renecle · « **Reply #7 on:** August 12, 2015, 12:18:33 AM »

Quote from: Chris Behm on August 08, 2015, 07:05:22 PM

Who doesn't love posting from a cell phone?
I don't!

Nice one Chris......it sure ain't easy with fat finger like mine! Anyone have a conversion of frams to oz??

Target · « **Reply #8 on:** August 12, 2015, 08:24:23 AM »

Thanks for playing Keith. I hope that Mr Walker also finds humor in the auto correct function of our beloved smart phones.
R,
Chris

Keith Renecle · « **Reply #9 on:** August 13, 2015, 07:35:15 AM »

Mr Walker has a good sense of humour! He's been around Howard Rush for so long he must have a great sense of humour!

Igor Burger · « **Reply #10 on:** August 13, 2015, 08:09:33 AM »

Quote from: Paul Walker on August 08, 2015, 01:59:26 PM

Check the dendity ration for the two sites you flew at. They will be quite different, and that is why it flies "better" in Vancouver.

I normally fly at 2100 feet elevation, and when going to a competition in western Wa or Or I have to add about 2 frams tip weight and slow the motor down.

that is what I had to do in Pazardzhik when we started to fly early morning and then officials were afternoon, temperature on that very dry place rised so much that I had to keep track of trim changes during day :- )))) ... since then I have table of setting regarding air density

Target · « **Reply #11 on:** August 13, 2015, 12:17:05 PM »

That's some serious preparation, Igor. That's why you are one of the champs!

MikeyPratt · « **Reply #12 on:** August 13, 2015, 01:36:27 PM »

Hi Warren,
it sounds like you were flying the P/F a little slow. I've flown the P/F at different places ranging from Denver to Iowa and always had to set the lap times around 5.1 to 5.2 with slight adjustments. Adding or removing tip weight, increasing or decreasing handle spacing, or changing the prop. That's why we have all the adjustable things so we can dial it in.

Post a few photos of you model see we can all see it.

Later,
Mikey

Horby · « **Reply #13 on:** August 15, 2015, 04:49:01 PM »

Hi Mike, at 3000ft I was flying on 58' lines with a 5 sec lap with 10200rpm and when in Vancouver I changed nothing and went to a 4.8 sec lap. I am also using a reversed rotation prop. When I flew my Tutor last year doing virtually the same thing not much changed. However the thicker has to be the game changer. I also have to say the PF is one tough plane! I have pancaked my plane 4 times and only rebuilt the center wing once, changed motor shafts and props 4 times and no other damage other than having to straighten the landing gear. As for my full set up..... I am using an E Flight E15 with a Turnagy trust 50a esc, KR governor 4s2800mah batteries and an APC 11x5.5 reverse rotation prop. After 5min 30sec I am left with 14% usable power left in the battery. The plane weight is 46oz.
I have tried to attach a pic of the plane, hopemit works.

Cheers,
Warren

Horby · « **Reply #14 on:** August 27, 2015, 06:57:06 PM »

Well I got another weekend in at a higher altitude. First flight with nothing changed ..... same as my home field 5.0 la time. No line tension and stalling. Second flight..... bumped the lap time to 4.8sec and all was happy. Soooo, the PF needs a bit of speed to perform properly. Now I just need to know why my rpm dropped once I got in the air.

Warren

GonzoBonzo · « **Reply #15 on:** August 27, 2015, 11:18:34 PM »

Don't think your RPM changed. You ARE using "set RPM" mode aren't you? At altitude your propeller is losing efficiency, but there is also less drag on the airframe, hence the same lap time. Problem is, you need more "ground" speed, (faster lap time at altitude), to get the same "air" speed for the plane to maneuver the same as it does at lower altitude.

Chris Cox · « **Reply #16 on:** August 28, 2015, 09:20:49 PM »

Hi Warren - looks like you have learned a very valuable lessen regarding Density Altitude and its effect on stunt planes. I once had a Berringer Gee Bee that flew pretty good here in Vancouver, but in Edmonton, it would stall in the third corner of the Hourglass. Not fun.

Did you notice Bruce Perry's wind meter sitting on the tri-pod last weekend. Bruce isn't nearly as interested in the wind speed and direction (he can feel this), but he wants to know what the Density Altitude is. On a warm day, Bruce told me it is not unusual to see a Density Altitude of 5,000 feet or more!

Pancaked 4 times huh? Hmm, what was that nickname they tagged you with last weekend? OK, I remember, but will save you the embarrassment.

Cheers

Horby · « **Reply #17 on:** August 29, 2015, 10:22:36 PM »

Ya Chris.... 4 times lol. I am going to do some more reasearch on density altitude for sure. Dont you just love learning curves?

Cheers,
Warren

David Hoover · « **Reply #18 on:** August 31, 2015, 06:07:20 AM »

Warren, get yourself a Kestrel 4500 Weather Tracker or the equivalent. It calculates the density altitude for you. Amazing how much it changes from 8:00 AM to noon. It's a little pricey and there may be less expensive options out there but I know this one works.

http://kestrelmeters.com/collections/frontpage/products/kestrel-4500-weather-meter

Chris Cox · « **Reply #19 on:** August 31, 2015, 10:00:14 AM »

Warren - the Kestral 4500 is the unit Bruce is using. Top of the line. I am considering the Kestral 2500 as it computes altitude, wind speed, temperature, etc, but not humidity. It is half the price of the 4500.

phil c · « **Reply #20 on:** October 08, 2015, 01:03:15 PM »

There's about 13% more air at 100 ft. compared to 3500ft. That's pretty significant. I've found 5% changes are noticeable.

Lift varies with the square of the velocity, so 5.0/lap to 4.8/lap is about 8% better. That makes up most of the difference. 4.4/lap would get you close to sea level performance but you'd have to practice up on the reflex!