RE: (Something Fast?) Delta Build Thread

RE: (Something Fast?) Delta Build Thread
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RE: (Something Fast?) Delta Build Thread - 9/2/2008 3:17:40 PM

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All these maiden flights are getting me excited. Looking forward to some video.

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(in reply to mk1spitfire)

RE: (Something Fast?) Delta Build Thread - 9/2/2008 3:37:08 PM

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exciting enough for you to make some more kits???????

(in reply to Mike Connor)

RE: (Something Fast?) Delta Build Thread - 9/5/2008 6:09:02 PM

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From: tecumseh, MI, USA
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Hey Mike , and everybody else, I was able to get my electric motor fixed quicker than expected I hope for some good flights on sunday and a friend of does a real nice job on videos. Hoping it will all come together. Heres some pics of the inside and finished trim nothing special just for fun.

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(in reply to mk1spitfire)

RE: (Something Fast?) Delta Build Thread - 9/5/2008 6:21:18 PM

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I never saw an electric version of my design fly. Can't wait for the video.

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(in reply to skyflyer47)

RE: (Something Fast?) Delta Build Thread - 9/7/2008 2:31:08 PM

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From: tecumseh, MI, USA
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Just a question for all you aerodynamic gurus. Does a larger diameter prop cause more drag because of the disk area? Even if said prop provides more thrust.

(in reply to Mike Connor)

RE: (Something Fast?) Delta Build Thread - 9/7/2008 3:16:57 PM

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Yes.

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RE: (Something Fast?) Delta Build Thread - 9/7/2008 4:09:16 PM

Speedy-Gonzales

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YES! Mega dittos.... evan-RCU

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RE: (Something Fast?) Delta Build Thread - 9/8/2008 1:40:46 AM

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From: tecumseh, MI, USA
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ok thanks, but my electric set up seems happy with an 11 " prop 8 or 8.5 pitch. today I tried it with a 10-7 apc e prop. It didn't have enough thrust to take off out of the launchers hand and hit the nose hard then bounced on it again, the gusty wind was also a factor it caught under it and fliped it over. I was happy to see no damage except for a broken prop. Sorry Mike no good video yet, my video guy didn't show up. any way I did get a video of the crash with my camera not sure if I can load it because it's on a dvd from the camera.

(in reply to Speedy-Gonzales)

RE: (Something Fast?) Delta Build Thread - 9/8/2008 1:53:25 AM

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From: tecumseh, MI, USA
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I'm sorry i lied, the guy I had running my video camera turned it off just before the crash then back on after. Oh well theres always tommorrow. It was the first time he ever tried to use it.

(in reply to skyflyer47)

RE: (Something Fast?) Delta Build Thread - 9/8/2008 4:37:29 AM

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quote:

ORIGINAL: skyflyer47

ok thanks, but my electric set up seems happy with an 11 " prop 8 or 8.5 pitch. today I tried it with a 10-7 apc e prop. It didn't have enough thrust to take off ....

Too small of a diameter prop can be as bad as too large of a diameter. The airframe and engine/motor needs to be considered. With a glow engine your delta would not need more then 9". Your setup must have a slow rpm and requires the thrust from a larger prop.

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RE: (Something Fast?) Delta Build Thread - 9/8/2008 5:32:38 AM

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From: Oceanside, CA, USA
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Well today I got some more good flights in!

I also got some decent video of the Demon Tiger which should be uploaded by tomorrow night (sorry to tease). I am still working on getting the motor to run well. My first flight, which is in the video, was a bit too rich and didn't seem to get on the pipe. It tached at about 18,250 RPM with a 7.5X8 Q40 prop. My second flight, no vid, I was able to squeeze a bit more RPM out with 19,500 RPM & same prop. It still feels like the pipe isn't kicking in like it should but I will try a couple more things. I am running 15% and have cut another .75" off the header since the maiden flight(s). I wonder if I need to cut off more!?

Now with a few flights under my belt I am really starting to enjoy how well it flies. It is rock solid and grooves along. I think the winglets out on the end really keep things stable. They also work well with orientation when it gets far out. Launching is a no issue so far but not quite able to self launch yet. Everyone at my field loves it and is amazed I am firing up a glo plane and getting greasy. Although when the motor gives me starting fits I am quick to remind them why I haven't rushed back to glo in a while

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RE: (Something Fast?) Delta Build Thread - 9/8/2008 1:26:44 PM

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Joined: 7/15/2004
From: Indianapolis, IN, USA
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quote:

ok thanks, but my electric set up seems happy with an 11 " prop 8 or 8.5 pitch. today I tried it with a 10-7 apc e prop. It didn't have enough thrust to take off

What RPM aare you getting? it sounds like the motor has to low of a KV for the number of cells and RPM goals you have. lower KV motors need more cells to spin fast with smaller props. what is your setup? (#cells , motor KV , and max amps?)

with 3 cells you are looking fior ~2000 kv minimum (aiming for 20k RPM no load speed) for good speed I'd be closer to 3000kv (30kRPM)
with 4 cells ~1500 Kv minimum (aiming for 20k RPM no load speed) I'd prefer 2000kv or more for 4s speed use.

a good quick and dirty formula is: no load rpm goal/(#cells * 3.5) = good starting KV
then use moto calc to determine the wattage required to spin the diameter prop you want that rpm and fine tune the setup.

(in reply to Troy-RCU)

RE: (Something Fast?) Delta Build Thread - 9/8/2008 2:22:35 PM

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From: tecumseh, MI, USA
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I am running an Axi 2826/08, the KV is 1130, It tacked out at 12,900 with a 11-8 apc, 13.200 with the 10-7. I am using a 3-cell battery 4000 mah.
according to my watt meter it draws about 60 amps with the 11-8, 630 watts. this motor only can handle 3 cells.
I think my crash was more due to gusty wind and poor throw than lack of thrust.
where can i get an out runner with the 2000 kv you speak of?

(in reply to cncswiss1)

RE: (Something Fast?) Delta Build Thread - 9/8/2008 3:00:18 PM

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Joined: 7/15/2004
From: Indianapolis, IN, USA
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Amperage and wattage cooks motors, not voltage. that motor can handle more cells, but you must use a smaller prop to do so.

try 6 cells and a 8-6 for starters. then ease up in pitch as the wattage allows. the hard part is getting 6 cells to not weigh a ton. a simple Y connector and using your existing 3 cell packs will work for testing, but may not be the lightest option.

part of your crash is the torque of that big lumber up front, and the gyroscop problems associated with it.

*edit for typo, it's 8" prop not 9" OOPS

< Message edited by cncswiss1 -- 9/8/2008 8:21:32 PM >

(in reply to skyflyer47)

RE: (Something Fast?) Delta Build Thread - 9/8/2008 7:18:23 PM

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From: tecumseh, MI, USA
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wow never considered that. theres no way to fit both my 4000 mah packs in there. what would happen with 2 1600 packs, besides a very short flight?
Mine was built to just barely fit one pack.

(in reply to cncswiss1)

RE: (Something Fast?) Delta Build Thread - 9/8/2008 8:20:50 PM

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Joined: 7/15/2004
From: Indianapolis, IN, USA
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as long as you have the "C" rating to cover the ampl you intend to pull you will be fine.. @60 amps you will need 40c packs!

I have been playing on moto calc a bit and it helps a lot
http://www.motocalc.com/

what speed control do you have? is it up to 6c? to get about the same wattage ~630 on 6s requires a 7" prop

but you could spin that 7.5 x 8 pylon prop mentioned above at 18K rpm on the ground, but throttle management will be absolutely necessary or you'll cook that motor.. allow for good cooling, and keep full power blasts short.

(in reply to skyflyer47)

RE: (Something Fast?) Delta Build Thread - 9/9/2008 2:40:27 AM