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Cox Engine of The Month
CEF speed contest Design Discussions (2014)
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Re: CEF speed contest Design Discussions (2014)
Hi everybody,
I just re-read the post I put up regarding Jim's plans, rudders and such and I feel I need to apologize.
When I read it this morning, I felt it came across as somewhat snarky and sarcastic, and that was NOT AT ALL what I intended!
Jim, your planes are very clever, well designed and built. When I said I felt that you are a sharp guy and that I can't wait to see what you are up to, I meant it very sincerely, but the way it was written it could be perceived as being sarcastic. That is in NO WAY what I intended, and if it did come across that way to anyone, especially Jim, I sincerely apologize.
Mike
I just re-read the post I put up regarding Jim's plans, rudders and such and I feel I need to apologize.
When I read it this morning, I felt it came across as somewhat snarky and sarcastic, and that was NOT AT ALL what I intended!
Jim, your planes are very clever, well designed and built. When I said I felt that you are a sharp guy and that I can't wait to see what you are up to, I meant it very sincerely, but the way it was written it could be perceived as being sarcastic. That is in NO WAY what I intended, and if it did come across that way to anyone, especially Jim, I sincerely apologize.
Mike
Re: CEF speed contest Design Discussions (2014)
Theo Kleynhans wrote:That plane of yours looks interesting Roddie. You should maybe try and fly it now that you are experienced.
All of this talk regarding the rudder and airfoils is a lot to take in.
I have another question regarding engine position. If you have a look at the picture below of the Nemesis, you will see that the engine/prop is not situated in the middle vertically at the nose. It is actually higher than the centre line of the nose. Can I mount my engine the same way? Higher up like the drawing. Will this make a difference?
Theo
As long as your thrust line stays the same you can mount above or below centerline. It really only poses a problem if you build in up or down thrust .
Cribbs74- Moderator
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Re: CEF speed contest Design Discussions (2014)
For small offsets using a straight thrust line works well. Offsetting the thrust line somewhat significantly is one way of handling prop rotation effects. In order to fully account for engine offset drag of all parts of the plane must be accounted for.
There is reasonable preference to having everything in line.
Hang your engine inverted and run with it for the scale look.
Phil
There is reasonable preference to having everything in line.
Hang your engine inverted and run with it for the scale look.
Phil
pkrankow- Top Poster
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Re: CEF speed contest Design Discussions (2014)
pkrankow wrote:
Hang your engine inverted and run with it for the scale look.
Phil
I agree with Phil.. and utilizing the scale "air-scoop" would help when you cowl-in an inverted cylinder. You could put louvers.. or some other venting rearward in your cowl, to scavenge the exhaust-wastes out.. and insure good airflow/cooling of the engine. A side-hole in the cowl for an exhaust-prime might be a good idea to help start the engine. Leave just enough of the glow-head exposed out the bottom to attach your battery clip.
Re: CEF speed contest Design Discussions (2014)
roddie wrote:pkrankow wrote:
Hang your engine inverted and run with it for the scale look.
Phil
I agree with Phil.. and utilizing the scale "air-scoop" would help when you cowl-in an inverted cylinder. You could put louvers.. or some other venting rearward in your cowl, to scavenge the exhaust-wastes out.. and insure good airflow/cooling of the engine. A side-hole in the cowl for an exhaust-prime might be a good idea to help start the engine. Leave just enough of the glow-head exposed out the bottom to attach your battery clip.
The thumb says minimum 2x the exit area as the intake area for the vents.
Phil
pkrankow- Top Poster
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Re: CEF speed contest Design Discussions (2014)
Hi Guys. Thank you for all the tips and suggestions.
I agree that putting the engine upside down will look the best, but then I need to build a whole cowl and nose for it and I am not that confident in building yet. I would not even know where to start.
I was thinking of mounting it normally and just adding a plastic cowl like some of the ones in the first round.
I will have to sit and think a bit before starting this phase.
Theo
I agree that putting the engine upside down will look the best, but then I need to build a whole cowl and nose for it and I am not that confident in building yet. I would not even know where to start.
I was thinking of mounting it normally and just adding a plastic cowl like some of the ones in the first round.
I will have to sit and think a bit before starting this phase.
Theo
Theo Kleynhans- Gold Member
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Re: CEF speed contest Design Discussions (2014)
Mike,Mike Mulligan wrote:Hi everybody,
I just re-read the post I put up regarding Jim's plans, rudders and such and I feel I need to apologize.
When I read it this morning, I felt it came across as somewhat snarky and sarcastic, and that was NOT AT ALL what I intended!
Jim, your planes are very clever, well designed and built. When I said I felt that you are a sharp guy and that I can't wait to see what you are up to, I meant it very sincerely, but the way it was written it could be perceived as being sarcastic. That is in NO WAY what I intended, and if it did come across that way to anyone, especially Jim, I sincerely apologize.
Mike
No need for an apology, no offense taken. Thank you.
Jim
JPvelo- Diamond Member
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Re: CEF speed contest Design Discussions (2014)
Here she is, 5.5oz of glory:
Test ran the engine with the sealed intake, numbers are the same as when it was mounted on Miss Ashley. The 35% nitro is attacking the rustoleum in places. The cowl also split from trying to tuck the filter into it, I can glass it on the inside.
Jim
Test ran the engine with the sealed intake, numbers are the same as when it was mounted on Miss Ashley. The 35% nitro is attacking the rustoleum in places. The cowl also split from trying to tuck the filter into it, I can glass it on the inside.
Jim
JPvelo- Diamond Member
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Re: CEF speed contest Design Discussions (2014)
Boy that is pretty.
Phil
Phil
pkrankow- Top Poster
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Re: CEF speed contest Design Discussions (2014)
Nice Build There Jim if it goes as fast as it looks were in for another speedy adventure Getback
getback- Top Poster
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Re: CEF speed contest Design Discussions (2014)
Hahaha! When you just kind of sit there staring at it with glazed eyes and your mouth slightly ajar. JIm does that to me now and then. Roddie's Bearcat did too. We really have some artful builders, Theo is one of our newer ones too. He's really good and a fast learner. My planes look nice, but in a utilitarian sort of way. Maybe the dirty fingernail crowd lusts over mine .Mike Mulligan wrote:To quote Rusty, that's just stupefyingly cool!
Rusty
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Re: CEF speed contest Design Discussions (2014)
Thanks guys,
We will find out if it flys next Friday.
Jim
We will find out if it flys next Friday.
Jim
JPvelo- Diamond Member
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Re: CEF speed contest Design Discussions (2014)
That's a very nice built model Jim. What would be the advantage of fixing the belcranck to the upper wing? more stable flight?
Hey, where are the first 30 or so pages of this thread?
Hey, where are the first 30 or so pages of this thread?
OVERLORD- Diamond Member
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Re: CEF speed contest Design Discussions (2014)
Thanks,OVERLORD wrote:That's a very nice built model Jim. What would be the advantage of fixing the belcranck to the upper wing? more stable flight?
Hey, where are the first 30 or so pages of this thread?
I have my theory about having the bellcrank above the vertical center of gravity increasing speed but mostly it was "ease of assembly".
I noticed yesterday the topic had been split, the rest is on page two of "cox discussions".
https://www.coxengineforum.com/t5910-cef-speed-contest-design-discussions
JPvelo- Diamond Member
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Re: CEF speed contest Design Discussions (2014)
I started cutting out my second entry, to be powered by a Hot Rod Space Hopper. It's a Airtractor 802 gunship:
With a 12" fuselage the wing scales out to 20"x2.25" for a dead on 45 squares. The long thin wing is theoretically more aerodynamic. I wonder at what point does frontal area of the model outweigh the advantage of a low aspect (long thin) wing?
Jim
With a 12" fuselage the wing scales out to 20"x2.25" for a dead on 45 squares. The long thin wing is theoretically more aerodynamic. I wonder at what point does frontal area of the model outweigh the advantage of a low aspect (long thin) wing?
Jim
JPvelo- Diamond Member
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Re: CEF speed contest Design Discussions (2014)
That reminds me I need to the motor on my duster down and see if I can get it to run this weekend since I expect my big brother here to help launch and stuff.
Phil
Phil
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Re: CEF speed contest Design Discussions (2014)
One of our club guys, David Smith flew his speed plane at Triple Tree yesterday. It's a 21 proto speed. I e-mailed him to find out the line length and engine, so I'll post that when I find out. This mother was Loud! Listen to it slice the air on the close passes. 26 laps and he's leaning back against the pull.
_________________
Don't Panic!
...and never Ever think about how good you are at something...
while you're doing it!
My Hot Rock & Blues Playlist
...and never Ever think about how good you are at something...
while you're doing it!
My Hot Rock & Blues Playlist
RknRusty- Rest In Peace
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Re: CEF speed contest Design Discussions (2014)
RknRusty wrote:One of our club guys, David Smith flew his speed plane at Triple Tree yesterday. It's a 21 proto speed. I e-mailed him to find out the line length and engine, so I'll post that when I find out. This mother was Loud! Listen to it slice the air on the close passes. 26 laps and he's leaning back against the pull.
NICE!!! I'll guess 52' lines. What a SCREAMER!! Nelson engine?
Re: CEF speed contest Design Discussions (2014)
That's my guess too. I'll let you know when he returns my e-mail.roddie wrote:NICE!!! I'll guess 52' lines. What a SCREAMER!! Nelson engine?
_________________
Don't Panic!
...and never Ever think about how good you are at something...
while you're doing it!
My Hot Rock & Blues Playlist
...and never Ever think about how good you are at something...
while you're doing it!
My Hot Rock & Blues Playlist
RknRusty- Rest In Peace
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Re: CEF speed contest Design Discussions (2014)
Yeah, that was pretty quick..
Cribbs74- Moderator
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Re: CEF speed contest Design Discussions (2014)
This engine runs very well...
You can find NovaRossi, R&B, or Rex engines, good choice for speed models...
You can find NovaRossi, R&B, or Rex engines, good choice for speed models...
navion34- Gold Member
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Re: CEF speed contest Design Discussions (2014)
Hi Guys
Can someone please also paste the video link, I cannot watch the video as it is shown at the moment.
Theo
Can someone please also paste the video link, I cannot watch the video as it is shown at the moment.
Theo
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