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Author Topic: Scale beginner needs some geometry help  (Read 11563 times)

Offline Danny Fenton

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Scale beginner needs some geometry help
« on: November 03, 2014, 11:33:49 AM »
Hi I am new to this forum so please go easy  ;) I am building a Chipmunk to fly control line scale. I have heard varying opinions on where the bellcrank should be, fore and aft and up and down. Where should the bellcranks position be relative to the c of g, thrustline etc? And also what about the leadouts?
Sorry if it has been covered before. I tried a search and didn't really come up with anything helpful.

Any help will be gratefully appreciated

Cheers
Danny


Offline Tim Wescott

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Re: Scale beginner needs some geometry help
« Reply #1 on: November 03, 2014, 11:43:31 AM »
It doesn't matter where the bellcrank is with respect to the CG or thrustline.

It does matter where the bellcrank is with respect to the leadout guides, and where the leadout guides are with respect to the CG matters a LOT.

The leadout guides need to be behind the CG -- probably about 3/4" for a normal sized airplane.  See if you can scare up a link to Line III on Google.  Download it, install it, and use it to figure out your leadout position.

Up and down, the leadout guides need to be pretty close to on the CG.  This probably doesn't matter as much in scale as in stunt, but you're modeling an airobatic plane; if you're going to do any negative-G maneuvers as part of your scale flights then you want the vertical position of the leadout guides on the CG (if you don't, the plane will be rolled in, either upright or inverted, depending on whether your leadout guides are too low or too high).

Once you've got your leadout guides figured out, you want the bellcrank positioned to minimize the amount of bend at the leadout guides, without making your construction impossible.  Mostly you're trying to minimize friction at the leadout guide.  On that plane, placing the bellcrank so it never gets closer than about 1/2 or 3/4 inch (assuming a 4 or 5 foot wingspan) to the leading edge is probably good enough, although if you feel like being fanatical you can try to get it further forward.
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Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #2 on: November 03, 2014, 02:19:51 PM »
Thanks Tim, I appreciate you responding. Sounds quite promising that I can move it. With the Chipmunk If I position the bellcrank hi up on the thrustline then I am going to fill the front cockpit with detail but not the sort of detail I was aiming for, it will be the bellcrank! If I can mount it so that the bellcrank pivot is behind the the c of g, but closer to the floor of the cockpit it can be more easily hidden. ie below thrustline. I am mounting the battery pack low in the fus so the c of g may actually be lower in the fus anyway, and not high up on the thrustline. Which will help with the roll you are talking about.
No joy with Line III, well nothing control line related :(
Cheers
Danny

Offline Tim Wescott

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Re: Scale beginner needs some geometry help
« Reply #3 on: November 03, 2014, 02:32:01 PM »
Get on the open forum and ask for a link.  It's out there, somewhere.

I assume it's a DHC Chipmunk.  If so, then bringing the lines out of the (vertical) center of the wingtip should get you fairly close, particularly if you get the vertical location of the CG down.

I'd love to say just how close you need to be, but I fly stunt -- figure that you'll be pretty darned close for round maneuvers, and hope that one of the real Scale guys gets on and tells you how important it is that your loops be perfect, compared to a good static score!
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #4 on: November 03, 2014, 02:42:05 PM »
Thanks Tim, I appreciate your help, I thought I would post a quick pic because it does sound like where I am going should work. Although the Chippy is aerobatic, I doubt I will dare do more than a wingover  ;)

If the pic has uploaded, I have used a couple of lengths of piano wire as indicators of the guide route. And funnily enough its come out right near the centre of the tip as you suggested. But I did this before i saw your reply :)


Cheers
Danny




Offline Tim Wescott

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Re: Scale beginner needs some geometry help
« Reply #5 on: November 03, 2014, 02:55:34 PM »
I hadn't realized you'd already built the plane!

To check the vertical location of the CG, hang the airplane by the leadouts and verify that the wing is hanging straight up and down (I just eyeball the wings with respect to a doorframe or other known-vertical reference).  It's more challenging with dihedral, but if you can hold it out far enough, just check that the wing tips are one atop the other.

For just a wingover, you don't have to worry much.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #6 on: November 03, 2014, 03:06:13 PM »
Hi Tim That's brilliant thanks. Yep at the point where i need to position internal stuff. The piano wire in the wing may be confusing but this will have removable tips, guides and weight. To allow it to fly rc too ;) so it has ailerons.
Well that's the plan :)
Cheers
Danny

Offline Fred Cronenwett

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Re: Scale beginner needs some geometry help
« Reply #7 on: November 03, 2014, 03:32:02 PM »
Danny,

Tim is correct the bellcrank location really does not matter. I put the bolt about 1" behind the CG but even that is not important.

I put the line guide at a location on the wingtip so that there is about 3 degrees of line rake. If the model is big enough put an adjustable line guide so that you can move it fwd and aft. Move the line guide fwd if there is too much line tension, move it aft if the line tension is too light.

your lines will form a straight line from the CG thru the line guide to the handle, and you want the nose of the model pointing outwards from the circle during flight. 3 degrees is a good starting point and can be adjusted after the first test flight.

This is our club website here in St Louis, and the scale page might give you some more insight into other topics

http://lafayetteesquadrillecl.wordpress.com/lafayette-esquadrille-cl/cl-models/scale/

where do you fly?


Land Softly,
Fred Cronenwett
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Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #8 on: November 03, 2014, 04:18:16 PM »
Hi Fred, and thank you for the information. I think between you and Tim you have answered my questions. Thanks too for the link to the web site, some great information on there  :) The Large bomber you feature, the "Apache princess" I saw at a local event in the uk during the summer. It is an awesome sight and a wonderful sound with two 400cc Mokis.

I fly RC in the UK at a couple of clubs, control line I am still looking for a venue, I hope to do a few competitions next year with it.

Thanks again guys looks like I will be able to hide at least most of the bellcrank  ~>

Cheers
Danny

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #9 on: November 03, 2014, 04:52:40 PM »
Just going through the 133 page pdf on your site Fred and it is excellent! Answers lots of questions. Perhaps that doc should be a sticky post on the C/L scale forum. This is where you tell me it is  :-[

Thanks again, I really appreciate all your help.

Cheers
Danny

Offline Fred Cronenwett

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Re: Scale beginner needs some geometry help
« Reply #10 on: November 03, 2014, 05:43:52 PM »
I hope the UK allows CL scale models to use 2.4 Ghz controls soon, we have been flying with 2.4 Ghz for throttle and everything else except the elevator since 2013. When RC guys see me flying a CL scale model with a 2.4 Ghz transmitter they are really confused at first, then I explain what we are doing. You might not be able to fly in competition with 2.4 Ghz but for sport flying should be ok....

Enjoy!

Fred
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Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #11 on: November 04, 2014, 01:02:03 AM »
Hi Fred, you are well versed with UK (BMFA) rules. As you say 2.4 is not yet allowed in scale but is in other disciplines. I know this is under discussion and seems to make sense that it will be allowed.
A friend and I have designed our own multi channel encoder/decoder system, it works great on the bench, just need to flight test it. The decoder/Encoder uses parts from a UK electronics supplier Micron, and they do two version of the small boards one with 2.4 RF and one without. It will be very simple to swap in the RF version if the rules change, and leave the lines out of the equation.
I am currently studying handles to see how best to make something nice and ergonomic.

I read through your 133 page doc, it is excellent, a great introduction for newbies like me :)
Cheers
Danny

Online John Rist

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Re: Scale beginner needs some geometry help
« Reply #12 on: November 05, 2014, 09:43:20 AM »
Back before we were allowed to use 2.4 GH I also did my own down the wire encoder / decoder.  I mounted the encoder in a mini box on the handle.
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Online chuck snyder

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Re: Scale beginner needs some geometry help
« Reply #13 on: November 05, 2014, 10:47:10 AM »
Danny,
Lots of good advice you have gotten so far. I would like to add a little. I have an Aichi Val that is arranged very much like your Chipmunk. Looks like you are doing a removable wing; my Val has that. My bellcrank is in the fuselage and the leadout guide (which is adjustable) is attached to the top of the wing. The lines connect right outside the fuselage. The leadout guide screws into hardwood blocks that were let into the wingtip. It remains with the lines. Note that the bellcrank screw is supported both top and bottom. I think this is important with heavy scale models to keep the screw from tipping under load if there is only a single mount. The black line in the leadout photo is insulated, the other is bare. I use JR direct servo control down the lines. I fly way more R/C than control line and use a neck strap to hold my transmitter. Throttle, flaps, retracts (on other models), and bomb drop (other models) can all be done with my left hand while I fly the elevator with my usual handle in my right hand.
Chuck

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #14 on: November 05, 2014, 10:56:51 AM »
Thanks John, yes I am doing something similar. That's a very tidy unit you have there :)
Thanks Chuck, good advice on the bellcrank. I have not been able to do that as the fuselage has a fairly visible cockpit :( This is what I have done, shout if you think it may not be strong enough. I hope to get the model down to around 5lbs max, it is 1/6th scale and 68" span.
Cheers
Danny

Offline eric david conley

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Re: Scale beginner needs some geometry help
« Reply #15 on: November 05, 2014, 12:26:03 PM »
     Danny, I was looking at your attached picture of your elevator bellcrank and noticed there is a servo connected directly to the bellcrank. I'm wondering how this works with lines and handle connected to the bellcrank along with a servo? Eric
Eric

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #16 on: November 05, 2014, 01:55:00 PM »
Hi Eric, thought i had replied but my message isn't showing so maybe i didn't press post :(
Anyway the model will probably fly rc most of the time. Pop the balljoint to the servo and connect the lines. I am thinking of two sets of removable tips. One set with a weight and guides the other plain for rc
Cheers
Danny

Offline eric david conley

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Re: Scale beginner needs some geometry help
« Reply #17 on: November 05, 2014, 02:45:11 PM »
     That's really cool Danny. I hope some of your RC followers do the same. Thanks, Eric
Eric

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #18 on: November 05, 2014, 03:26:22 PM »
The reason i am doing this is two fold. I started like many with control line as a kid in high school. So C/L hold great memorys, so trying to recapture that. Also I spent a few sessions taking photographs with the C/L scale guys at the British Nationals over the last few years. And they are a really great group of guys, incredibly helpful and so layed back they were nearly horizontal. I want to join them next year, not interested in winning but don't want to look an idiot either ;)
One thing that was said in the document that Fred posted, he said the horizontal stab should be set to zero incidence, thats obviously going to be different for RC so that may be an issue......

Cheers
Danny

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #19 on: November 05, 2014, 03:35:12 PM »
This was Mike Chapman's Winning Zero, just coming round for the bomb drop. The zero is from the old Marutaka kit. I know totally off topic  mw~

Cheers
Danny

Online chuck snyder

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Re: Scale beginner needs some geometry help
« Reply #20 on: November 05, 2014, 05:08:01 PM »
Danny, I have had 4 C/L scale models that were from R/C kits. All flew fine with the "R/C" incidence and CG locations. I don't think you need to worry about your planned setup. My Top Flite Gold Edition P-40 actually flew as an R/C model for a time.
Chuck

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #21 on: November 05, 2014, 05:27:58 PM »
Thanks Chuck that's good to know, I will see how it goes as the tailplane and incidence is set know and would need remedial work to correct. But at least if something is odd I know where to look first :)

Cheers
Danny

Offline Fred Cronenwett

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Re: Scale beginner needs some geometry help
« Reply #22 on: November 06, 2014, 04:56:17 AM »
We discovered the horizontal tail incidence when a friend built a F4F wildcat using the 3-view that had a lot of positive incidence on the horizontal tail. Regardless of where the CG was located the model did not fly very well at all.

When the horizontal tail was set to zero on the wildcat it flew great and trimmed out perfectly

Another model was the hanger nine 81" piper cub, another club member flew his and it flew tail high during level flight, when I assembled mine from the same kit I pushed the horizontal tail incidence back to zero and then it flew level like it should

Some RC kits might be ok as is, but in these two cases listed above we had to change the horizontal tail incidence to get the models to trim out correctly

Fred
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Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #23 on: November 06, 2014, 05:00:46 AM »
Hi Fred yes that's what I remember reading in your document.
Can I ask what you are using as the reference angle, wing incidence, thrust line?

Cheers
Danny

Offline Fred Cronenwett

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Re: Scale beginner needs some geometry help
« Reply #24 on: November 06, 2014, 05:05:16 AM »
We were using the thrust line thru the fuselage, the engine might have some down thrust but the centerline thru the fuselage in relation to the wing was the datum were using to establish the horizontal tail incidence

Fred
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Online John Rist

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Re: Scale beginner needs some geometry help
« Reply #25 on: November 06, 2014, 07:18:48 AM »
Danny,
Lots of good advice you have gotten so far. I would like to add a little. I have an Aichi Val that is arranged very much like your Chipmunk. Looks like you are doing a removable wing; my Val has that. My bellcrank is in the fuselage and the leadout guide (which is adjustable) is attached to the top of the wing. The lines connect right outside the fuselage. The leadout guide screws into hardwood blocks that were let into the wingtip. It remains with the lines. Note that the bellcrank screw is supported both top and bottom. I think this is important with heavy scale models to keep the screw from tipping under load if there is only a single mount. The black line in the leadout photo is insulated, the other is bare. I use JR direct servo control down the lines. I fly way more R/C than control line and use a neck strap to hold my transmitter. Throttle, flaps, retracts (on other models), and bomb drop (other models) can all be done with my left hand while I fly the elevator with my usual handle in my right hand.
Chuck

Be careful of using only one insulated line.  If you have two different diameter lines you will have more drag on one line then the other.  At low throttle and low line tension the extra pull on the larger line can cause uncontrollable up or down elevator causing a crash.  I had this happen to me.  The Eindecker pictured in my thumbnail is no more because of this.  Part of the problem is that in scale we tend to fly with no twist in the lines allowing them to bow out different amounts.
John Rist
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Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #26 on: October 09, 2015, 07:10:33 AM »
I want to thank you all for the advise posted on this thread. I have nearly finished the model, and though I didn't have it ready for the british Nationals this year, it will hopefully be there for next year!
There are still a few bits to do but here it is out on the cricket pitch near me....

Cheers
Danny

Offline Jim Fruit

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Re: Scale beginner needs some geometry help
« Reply #27 on: October 09, 2015, 08:14:24 AM »
Great looking model, Danny. I can see that you are adept at the use of the camera also. Using the low sun as a backlight is quite striking.

Jim Fruit

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #28 on: October 09, 2015, 09:14:09 AM »
Thanks Jim, luck on the piccy front, like most of my photography ;)

Cheers
Danny

Offline Tim Wescott

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Re: Scale beginner needs some geometry help
« Reply #29 on: October 09, 2015, 11:08:55 AM »
Very nice work Danny.  If you could have found some scale grass the airplane would look real.
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Offline Clancy Arnold

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Re: Scale beginner needs some geometry help
« Reply #30 on: October 16, 2015, 07:38:53 PM »
Danny
Email sent.
Clancy
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Offline Avaiojet

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Re: Scale beginner needs some geometry help
« Reply #31 on: October 17, 2015, 10:42:21 AM »
I'm glad I didn't give Danny any advice, because it looks to me like he doesn't need any.  LL~

Nice work Danny, great looking model!  H^^

Charles
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Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #32 on: October 20, 2015, 08:52:15 AM »
Thanks Clancy, I will enjoy reading those articles that you kindly sent across.
Charles thanks for the praise, I am quite pleased with how it has come out. I am pretty confident the model will go okay RC but control line is something of an unknown.

I flew a Hangar 9 PT19 profile fus model yesterday, first time on the lines for nearly 40 years. I still was able to revolve without getting dizzy, but the model was very sensitive in pitch especially when flown at full throttle. Things were more manageable when i throttled back. Maybe it just takes time to get dialled in again?

I am unable to alter the bellcrank throws as I am as far "in" to the pivot with the pushrod as I can, and on the elevator horn I am as far "out" from the hingeline as I can. I am thinking of making a new handle akin to a Reyco  item, to allow me to move the lines closer together to de-sensitise the pitch. The c of g is about 1/4" rearward of stated on instructions, adding yet more lead may also help matters, but as it gets better when I slow down I feel it is not the c of g, just too much control movement?



Anyway well chuffed that i could still fly control line after all these years :)

Cheers
Danny


Offline Avaiojet

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Re: Scale beginner needs some geometry help
« Reply #33 on: October 20, 2015, 10:28:26 AM »
Danny,

Nice job! Is that your yard?

Charles
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Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #34 on: October 20, 2015, 10:35:41 AM »
Thx Charles, no unfortunately.... It's a football (okay Soccer...) pitch about two minutes walk from home. No good for RC as it is surrounded by trees, and then houses, but great for electric control line just need a spotter to avoid decapitating dog walkers ;)
Any thoughts on the pitchiness?

Cheers
Danny

Offline Avaiojet

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Re: Scale beginner needs some geometry help
« Reply #35 on: October 20, 2015, 10:52:44 AM »
Thx Charles, no unfortunately.... It's a football (okay Soccer...) pitch about two minutes walk from home. No good for RC as it is surrounded by trees, and then houses, but great for electric control line just need a spotter to avoid decapitating dog walkers ;)
Any thoughts on the pitchiness?

Cheers
Danny

Danny,

Correct balance and no play in everything that moves. How's that?  LL~

Are you a Brit?

I'm glad I can't do videos.  n~

Charles

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Offline Fred Cronenwett

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Re: Scale beginner needs some geometry help
« Reply #36 on: October 22, 2015, 10:30:26 AM »
The elevator control sensitivity will decrease if you move the CG forward, in general as the CG shifts aft the airplane will get more and more pitch sensitive.

Also decreasing the spacing at the handle will also help, I have a spitfire that I fly and it was really pitch sensitive so I had to move the CG forward and fly with a handle with short spacing between the lines. Now it's calmed down

if possible you can install a longer control horn that will decrease the amount of throw on elevator

Fred
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Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #37 on: October 22, 2015, 10:44:00 AM »
Hi Fred, that is great information. I have made a hard point handle with a variety of spacing, much closer than the original handle.

I have also added yet more lead to the nose, I hate adding useless weight  HB~> But I need it to fly right :)

 

Just waiting for some calmer weather to have another go

Cheers
Danny

Offline Tim Wescott

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Re: Scale beginner needs some geometry help
« Reply #38 on: October 22, 2015, 10:52:03 AM »
Hey Danny:

Correct CG is more important than a super-light plane.  If it needs lead -- add lead.  Half of my planes have those "heavy hubs" or other bits of balanced brass bolted to the crankshaft -- it's probably wearing out my engines faster, but it's also correcting their flying characteristics.

As far as the plane getting easier to fly when it's slow -- that's not unheard of with CL.  On CL stunt one of the things you look for is how it behaves just as the engine cuts -- if it's fast enough with the engine running but tends to balloon and float when the engine cuts, then the CG is probably too far aft (I say "probably" because some people like it back there).  Conversely, if the plane doesn't slow down at all when the engine cuts and you can easily whip it around the circle with a dead engine then the CG is probably too far forward.

It's probably not as necessary for scale as it is for stunt, but don't be afraid to put as many holes in your hard-point handle as you need for adjustment.  The picture is of one of my carbon fiber handles, which has fewer holes than I'd like because CF needs to be bushed lest it or the line connectors wear prematurely.
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Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #39 on: October 22, 2015, 11:24:55 AM »
Thank Tim, that all makes sense.
I am struggling to come to terms with why the C of G should be different between RC and C/L but I guess that is going to mean two settings and that I will have to add nose weight when the model flies in C/L mode as opposed to R/C.

Cheers
Danny

Offline Tim Wescott

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Re: Scale beginner needs some geometry help
« Reply #40 on: October 22, 2015, 11:51:20 AM »
Thank Tim, that all makes sense.
I am struggling to come to terms with why the C of G should be different between RC and C/L but I guess that is going to mean two settings and that I will have to add nose weight when the model flies in C/L mode as opposed to R/C.

I don't know the why of it, but I certainly know the effect is there -- I'm a retread who resumed RC flights about ten years before I resumed CL flying, and the whole CG thing tripped me up for a while.  With time, the brain cells that were objecting died from exhaustion, and now I'm smarter.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Mark Scarborough

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Re: Scale beginner needs some geometry help
« Reply #41 on: October 22, 2015, 02:05:11 PM »
I don't know the why of it, but I certainly know the effect is there -- I'm a retread who resumed RC flights about ten years before I resumed CL flying, and the whole CG thing tripped me up for a while.  With time, the brain cells that were objecting died from exhaustion, and now I'm smarter.

WELL....THATS YOUR STORY ANYWAY  ;D LL~
For years the rat race had me going around in circles, Now I do it for fun!
EXILED IN PULLMAN WA
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Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #42 on: October 22, 2015, 04:32:23 PM »
Well I think I know what Tim means Mark, I am an R/C retread of about 8 years, and just touching control line again. I guess you can remove the balsa from the modeller, but not the modeller from the balsa, it's a virus that I guess you  never shake LOL

Cheers
Danny

Offline Tim Wescott

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Re: Scale beginner needs some geometry help
« Reply #43 on: October 22, 2015, 04:40:04 PM »
Well I think I know what Tim means Mark ...

Mark was commenting about my comment about brain cells.

As the friend of mine in college used to say when people criticized him for his level of recreational drug use: it's pruning, Mark, just pruning.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #44 on: January 04, 2016, 01:58:25 PM »
Hi Chaps, the project is nearing completion now and I have a couple of questions for you wise sages out there, if I may?



First one is how much tip weight do you reckon I will need? The model is roughly 70" span and weighs bang on 6lb ready to fly, and I was thinking of 60' lines, if that helps?

My other question is regarding the pull test. This model is built light with contest grade balsa throughout with a ply doubler to spread the bellcrank load, but isn't that strong. The model will not be flying fast however I believe that makes no difference, and the pull test for the UK BMFA states 5G. Am I allowed to hold the fuselage such that I am not stressing the front and rear of the model??

Cheers
Danny

Online chuck snyder

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Re: Scale beginner needs some geometry help
« Reply #45 on: January 04, 2016, 05:34:19 PM »
Danny,
I'll probably be odd  man out with this response, but I don't bother with tip weight in scale models. I figure that the dihedral and CG location relative to the readout guide are way more important in determining whether the model flies level.

My Typhoon and HS-129 weigh right at 15# and have to withstand a serious pull-test. I make every effort to put one hand right in front of the bell crank mount. The other hand supports the model.

Chuck


Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #46 on: January 05, 2016, 01:42:49 AM »
Hi Chuck, and thanks for the info. I will try without a tip weight first, there is a fair amount of dihedral with the Chipmunk, and I can add weight easily enough if it should be needed.

I guess I had better do the pull test myself, in the manner you have described and to see/listen what happens.......

I have set the C of G around 1/2 more nose heavy than the R/C suggested position, that seemed to be the concensus of oppinion, would you suggest this needs changing to be in line with the R/C position?

Thanks again to everybody for all your help, it is much appreciated :)

Cheers
Danny

Offline bob whitney

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Re: Scale beginner needs some geometry help
« Reply #47 on: January 05, 2016, 09:36:32 AM »


  i would not put all that time into a scale ship and do first flight with NO tip weight .one of the top scale builders built a profile scale ship with dihedral, and everytime it came into the wind, the wind got under the outboard wing and tried to roll it in .at least put some clay on it for the first flight ,how many stunt ships do u see with NO tip weight
rad racer

Offline Danny Fenton

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Re: Scale beginner needs some geometry help
« Reply #48 on: January 05, 2016, 09:46:03 AM »
Hi Bob, I take your point. I do have the ability to add weight I made the wing tips hollow and the tip rib has a weight box so it is easy to add some weight. I do also have a throttle so if it gets hairy I can set her back down.

How much weight would you suggest as a starting point 1/2 oz (14g)? That was the tip weight in my PT-19, but it has a larger inboard wingspan.

Cheers
Danny

Online chuck snyder

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Re: Scale beginner needs some geometry help
« Reply #49 on: January 05, 2016, 10:44:41 AM »
"I have set the C of G around 1/2 more nose heavy than the R/C suggested position, that seemed to be the concensus of oppinion, would you suggest this needs changing to be in line with the R/C position?"
Again I am marching to my own drummer and balance my C/L models the same as my R/c ships. Actually the HS-129 is balanced a bit aft of the "R/C" spot. It is an FAI
model and nose weight was limited by the max weight restriction.
Chuck


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