RE: CD ScaleDesigns Sopwith Snipe build  
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RE: CD ScaleDesigns Sopwith Snip... - 6/3/2008 2:54:57 AM   
abufletcher



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From: Zentsuji, JAPAN
Status: offline 		The hub area on the APC 13/6 prop is actually a bit smaller than the the prop washer. But then the hub on the APC prop is much smaller than the hub are on the scale (display) prop which would be closer to 1 1/4 inches. But since we're talking about a flying situation here I would think that 7/8" - 1" would be fine.

I hate to impose too much on your here. I'm curious what sort of weight this would come out to be. I'm guessing something like 3 oz.

(in reply to geezeraviation)
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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 10:44:30 AM   
abufletcher



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Joined: 2/13/2004
From: Zentsuji, JAPAN
Status: offline 		QUICK QUESTION:

In doing the balancing is the top of the stab the key line? That is to say, should the model be balanced so that the stab is at 0 degrees (even though there is some minimal tail incidence)? Or should the balance be relative to a line running straight through the engine shaft ("thrust line" )?

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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 11:29:16 AM   
Schnap-Roll


 

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Joined: 5/9/2008
From: Park Rapids, MN, USA
Status: offline 		I think your asking fore and aft balance, in which case I go with the thrust-line close to level or slightly nose down. However, don't forget port and starboard balance. Generally the difference between the thrust line and incidence of the stab is only a couple degrees and is negligible. I have never been able to keep the longitudinal and lateral axis straight in my head.

(in reply to abufletcher)
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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 11:49:39 AM   
Frank Sopwith



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From: Westervoort, NETHERLANDS
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quote:

ORIGINAL: Schnap-Roll
slightly nose down.


thats right, a few degrees nose down is needed when balancing !

Frank


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(in reply to Schnap-Roll)
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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 12:09:23 PM   
abufletcher



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From: Zentsuji, JAPAN
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quote:

ORIGINAL: Frank Sopwith
thats right, a few degrees nose down is needed when balancing !


You mean the engine shaft is pointing down a few degrees? I guess if the stab is perfectly level that would mean that the engine shaft would be pointing down the amount of the stab incidence (relative to the engine shaft).

(in reply to Frank Sopwith)
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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 12:45:03 PM   
CTDavies



Posts: 262
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From: Weeze, GERMANY
Status: offline 		The thrust line (engine shaft) needs to point down a bit, between 1 and 2 degrees only. It has nothing to do with the stab, it's to ensure that the plane is slightly nose heavy, so to be more on the safe side. You might need to shift around the CoG slightly afterwards anyway.

correction: it's not the engine's thrust line that points down (some planes are built with the engine having downthrust) it's the longitudinal axis of the fuse.

< Message edited by CTDavies -- 6/3/2008 12:48:54 PM >

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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 1:24:47 PM   
abufletcher



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Joined: 2/13/2004
From: Zentsuji, JAPAN
Status: offline 		To continue my never-ending series of "dumb RC questions" How do you guys tell if there's 1-2 degrees of down? Do you just eye-ball it? I'm not sure my eye-ball is calibrated to 1 degree measurements!

I understand measuring down-thrust (and have one of those nifty laser thingies) but this is longitudinal axis of the fuse.

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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 3:49:07 PM   
BobH


 

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From: Springfield, VA,
Status: offline 		If you have an inclinometer you can tell pretty easy. If your firewall is set at Zero Degrees you can use a protractor set on it and measure the prop shaft to see where it lies. That should give you and idea what the down thrust is.

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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 4:13:18 PM   
abufletcher



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quote:

ORIGINAL: BobH

If you have an inclinometer you can tell pretty easy. If your firewall is set at Zero Degrees you can use a protractor set on it and measure the prop shaft to see where it lies. That should give you and idea what the down thrust is.


As I said, I know how to measure down-thrust. What I can't figure out is how to check whether the fuse centerline is level or a couple of degrees inclined towards the nose. All this would have to be done with the cowl and prop on in "final flying state" to get the balance right.

Despite the "real (office) work" that still needs to be finished, I finished up the dummy plate and mounting brackets. It looks pretty good but my oh my but that firewall is busy! Looks like a REAL airplane! The weight at this point, nose slightly down (to my eye) is 4.3kg.


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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 4:49:06 PM   
TFF


 

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From: Memphis, TN, USA
Status: offline 		The centerline of the fuse will really end up where the incidences and down thrust equal out, but if it looks like the plane will make a shallow decent across the field, that is what I call nose down. Why dont you get your Legionair up and flying for flight pratice?

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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 5:05:41 PM   
abufletcher



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quote:

ORIGINAL: TFF
Why dont you get your Legionair up and flying for flight pratice?


Now that I've gotten the new batch of Nelson's Clear needed to "finish the finish" I think I'll do just that. It shouldn't take more than a week or so no more work that assembling an ARF. Between that and the Cub it should get my thumbs in shape and let me know if I'm ready to fly the Snipe. The annoying thing about maiden flights is that you only get one!

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RE: CD ScaleDesigns Sopwith Sni... - 6/3/2008 9:55:48 PM   
Schnap-Roll


 

Posts: 16
Joined: 5/9/2008
From: Park Rapids, MN, USA
Status: offline 		Your really thinking to much about this. It's really just as simple as the fuselage level or slightly nose down. For the first flight, slightly nose down is a safe bet.

(in reply to abufletcher)
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RE: CD ScaleDesigns Sopwith Sni... - 6/4/2008 1:02:26 AM   
geezeraviation


 

Posts: 109
Joined: 11/4/2007
From: Houston, TX, USA
Status: offline 		Thank you Schnap-roll, were not talking about down thrust we're not talking about stab incidence what we're talking about is does it look slightly nose down. I dont know why this is the way it's supposed to be done, it makes me crazy. Why not move the balance point foreward an 1/8 of an inch and do it level. After all if it's slightly nose down then its not balanced, its a bit nose heavy, isnt it??? Nose heavy is ok, a nose heavy airplane will be particularly un aerobatic but it lives to be readjusted to fly again. A tail heavy airplane can be a very unpleasant experience and often tail heavy airplanes fly only once. Start at about 25% a little nose down and when youve become comfortable enough to spin the model (a few flights down the road) if it just spirals move the CG back 1/8 of an inch at a time and keep working till it enters cleanly and spins about its own axis and that should make all the aerobatics you will want to do with a scale model doable with pizzaz. Oh Don I have the Tap. I have no idea what it will weigh, Ill make one and weigh it, and let you know ASAP. Later Doc.
Hey I went over a hundred posts and no one told me!!

< Message edited by geezeraviation -- 6/4/2008 1:03:29 AM >

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RE: CD ScaleDesigns Sopwith Sni... - 6/4/2008 1:20:31 AM   
abufletcher



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quote:

ORIGINAL: geezeraviation
I dont know why this is the way it's supposed to be done, it makes me crazy. Why not move the balance point foreward an 1/8 of an inch and do it level. After all if it's slightly nose down then its not balanced, its a bit nose heavy, isnt it???


I've been thinking the same thing. But I suppose this is just "the way it's always been done." And maybe a visual reminder.

quote:


comfortable enough to spin the model (a few flights down the road)


Hmmm...I don't think I'll be doing too much spinning with the Snipe at least until bo