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Pusher AP plane build thread

Old 12-11-2005, 04:16 PM
  #51  
Fieldrut
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Default RE: Pusher AP plane build thread

I Have a passion to build a platform such as you are doing / have done... after many loooong hours of researching what seems best in an AP/AV platform I have come to the conclusion this design basically suits all my needs.

Love the idea of using flat bottom trainer wings (about $99 to buy made up) and I do like the idea of the three piece fitting of the wing., it makes it easier to get 90" wingspan out of a 80" wing kit set.

No I have not built up my own wings, though I am looking to do so if I can find some place to cut out the parts as I wish them to be...size profile etc. If anyone knows of a cutting place ty in advance.

Another question, this time on props... current trainer has the 3 leg prop and seems to be well matched to the alpha 60 evolution .60 nitro motor. Can I just reverse the prop on the shaft and keep it in one piece being reversed ??... another question would be using this config.(tri leg) as a pusher, would it be a workable solution for slow stable flight, or will I have to go to a std pusher prop.

Finally, I agree with light weight strutting for the body, but feel it would have to be cut and reinforced a few times while getting things "set up" and installed. I have seen some that have been sheet boxed, also some that have been molded etc. weight being an issue, but stability of installed components have me heading towards just sheeting the body.

Oh, that really means if I cannot carry a sheet box with the gear, and the extended wing width, then I got a whole heap of other issues like getting it off the ground anyway..;-)


TY for letting Me drop in and look over your shoulders, I plan to be making my platform this winter and recording the efforts and results for discussion here, if you do not show ppl, then the knowledge you gain is lost to the future efforts by others. I appreciate your efforts to teach and impart your knowledge.

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Old 12-11-2005, 08:16 PM
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Default RE: Pusher AP plane build thread

Flipping the prop around won't help. I sure wish it did. You have to buy a pusher prop to do the job. Also make sure the label is facing forward on your prop. Or that prop Leading edge meets the air. You can probably use an 11x7 or a 12x6 for that engine. Tower hobbies sells various pusher props in the size you'll need.

http://www2.towerhobbies.com/cgi-bin...=++&search3=Go

Dan
Old 12-11-2005, 08:29 PM
  #53  
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Default RE: Pusher AP plane build thread

TY Dan, as I have not done pusher before, your answer has led Me to more research...


and another question...

Placing the motor, we have the fuse, and the motor behind it.. therefore a blocking of the airflow to the prop... well we will not put in direct line behind the fuse, but is there a formula or a basic height that the centerline of the motor gets based at so to minimize the "blocking" effect?

I have seen the posts on elevated pods to place the motor behind, My other thought was to run twins off the wings... yes I know jumping out the pan into the fire...

Questions none the less... replys accepted with thanks...;-)

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Old 12-11-2005, 09:40 PM
  #54  
Tall Paul
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Default RE: Pusher AP plane build thread

Twins and pushers let you have the camera face forward..
Here's two versons of my latest.
The electric twin was a miserable failure... too heavy to take off.
Installed the pusher motor pod with an OS 15 FP from a previous plane.. (planned for in advance), and it is a winner...
The weight change due to removing the 8x2600 Nimh battery dropped AUW from 68 oz to 54 oz.
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Old 12-11-2005, 10:25 PM
  #55  
kd7ost
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Default RE: Pusher AP plane build thread

ORIGINAL: Fieldrut
Placing the motor, we have the fuse, and the motor behind it.. therefore a blocking of the airflow to the prop... well we will not put in direct line behind the fuse, but is there a formula or a basic height that the centerline of the motor gets based at so to minimize the "blocking" effect? Questions none the less... replys accepted with thanks...;-)
Fieldrut,

If care is taken when sizing the fuselage it won't be an issue. You also have the engine facing backwards, on the firewall, on a mount of some sort so the prop is set back 5 to 6 inches or so. There is no real formula for basic height. The closer you are to having everything lined up, the more efficient your setup becomes. By that I mean your thrust lined up with your lines of drag and lift. Putting the engine up on a pod is always an option but to me needs quite a good reason to do it. If you're building from scratch and not trying to modify an existing tractor style plane, I would avoid pylons. (Thats just me) They do work though and plenty of guys use them effectively. They are not typically efficient. By pylon I mean engine way up above wing and fuselage.

I don't want to hijack Skycam41's thread getting into design aspects but if you want to talk about that, start a thread and you'll likely get more help than you want or need.

Here's my pusher design.

Dan
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Old 12-11-2005, 10:42 PM
  #56  
Skycam41
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Default RE: Pusher AP plane build thread

I'm not worried about hijacking...this is all great information...keep it coming.

Update: For some reason the camera mount has been thrashing around in my mind for the past few days and I just could not come up with a good solution till this afternoon. I really like Mike's drawer concept and used that idea to build upon. I don't have a picture yet but I will try to describe the completed idea. Instead of a drawer I used a panel that is hinged at the bottom, exposing the camera area of the fuse. I small tray will slide in and out of that compartment for easy access to the camera and its settings. The camera itself will sit in a custom made half box with 1/4 foam for a snug but not overly tight fit. The camera box will be mounted to a variable tilting shelf which in turn is mounted to the sliding tray...sounds much more complicated that it will be. I can vary the angle by using something quite unique...some of the rubbery foam wedges found in a womans make up kit that they stuff between their toes then applying nail polish, well at least thats what I think they do with them. To stop the tilting shelf from tipping all over I will use a piece of Velcro to keep it snug against the foam wedges. This way the camera will be surrounded with foam and the tilting shelf will be isolated from the sliding tray with foam so hopefully all that foam combined with optical image stabilization in the camera will provide sharp pictures.....phew that was long and drawn out! Oh, the hinged side panel will obviously have a hole in it for the lens to poke through and will be held closed with 2 flat plastic landing gear straps that will clip onto a screw.
Old 12-11-2005, 10:53 PM
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Default RE: Pusher AP plane build thread

Sounds intersting. I think I have it pictured but will be waiting to see the actual pictures to make sure.

Dan
Old 12-11-2005, 11:48 PM
  #58  
Fieldrut
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Default RE: Pusher AP plane build thread

Skycam41, thank you for your acceptance of my "barging in" so to speak...
Kd7ost, thank you for the reply and info as well.

Both of your planes show me the variations and what your points were in description.

I will email you both and let you know when the project is etc, and what I have been planning and researching on thus far.

Old 12-12-2005, 01:27 AM
  #59  
Skycam41
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Default RE: Pusher AP plane build thread

Thats what is great about this hobby is the willingness to share and help others. I would not be where I am now if it were not for many, many folks helping me out and I hope I can give something in return. I am sure I could have spent hours of frustration trying to eliminate vibration but Dan and Mike have shared their great insight to this topic...keep up the good work lads
Old 12-12-2005, 02:28 AM
  #60  
randall1959
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Default RE: Pusher AP plane build thread

Just when you think you've learned it all someone comes along on here with something that blows everything else out the window.
Old 12-12-2005, 06:19 AM
  #61  
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Default RE: Pusher AP plane build thread

ORIGINAL: Skycam41

Thats what is great about this hobby is the willingness to share and help others. I would not be where I am now if it were not for many, many folks helping me out and I hope I can give something in return. I am sure I could have spent hours of frustration trying to eliminate vibration but Dan and Mike have shared their great insight to this topic...keep up the good work lads
Its all been trial and error, trial and error, repeat!
I like the hinged door and slide out idea, that will be interesting to see, I think itll work fine.

Mike R.
Old 12-12-2005, 08:30 AM
  #62  
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Default RE: Pusher AP plane build thread

Vibration....

I have found a great deal on vibration, the harmonics of it all it boiled down to.

Dragging out my links notes so I can find it again for you all, the end result was harmonics come in various freq. (our old friend) from high through to low.

If my memory is correct the low freq. ones are what we are trying to dampen/eliminate. Now I dont know what these would be 2cycle v's 4cycle but they are there in both.

I do know there is a post and pics on this RCU site, or the other one.. something done with rubber bands in a cross pattern from the fuse bulk heads and connected to the corners of the camera to dampen the effects and allow for higher quality result from pics. I will hunt the pics and posts.

Something I found on cameras was the specs on the Lumix models, and their image stability system. I have not seen the new results from this in post, but feel that if the specs are what they are, our efforts to dampen freq. will not have to be as intense.


Old 12-12-2005, 11:03 AM
  #63  
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Default RE: Pusher AP plane build thread

Richard Shelton has an excellent article on vibration here. http://www.hicam.com.au/art_vib.htm It helped me a lot.

Dan
Old 12-12-2005, 10:18 PM
  #64  
Skycam41
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Default RE: Pusher AP plane build thread

Pictures say a lot more than words so here is my tilting camera shelf. The tray slides in and out of the camera bay and will be able to be used from either side of the plane. The tilting shelf is not mounted yet but you get the idea. I have still to make the camera box/holder and to line it with foam (on order). You can also see the little "toe" wedges that the tilting shelf sits onto. I will use velcro to stop the shelf from moving while in flight. Obviously the fuse side panel will have a hole cut in it
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Old 12-12-2005, 10:28 PM
  #65  
kd7ost
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Default RE: Pusher AP plane build thread

Nice work Skycam41. How did you cut those slots for the tray to slide into? Must have a nice saw for that?

Where did you order your wing kit from? Was it Sig?

Dan
Old 12-12-2005, 11:42 PM
  #66  
Skycam41
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Default RE: Pusher AP plane build thread

ORIGINAL: kd7ost

Nice work Skycam41. How did you cut those slots for the tray to slide into? Must have a nice saw for that?

Where did you order your wing kit from? Was it Sig?

Dan
Hehe, I wish I had a nice saw...it's just 2 peices of hardwood glued to the former with a gap between it

I ordered thw wing kit from Great Hobbies in Edmonton, Alberta. I phoned them today and it was sent to me today...guess they had to order it in. The closest hobby shop for to me is 100 miles away...it sucks as you always forget someting and then have to pay shipping over and over [&o]
Old 12-13-2005, 07:17 AM
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Default RE: Pusher AP plane build thread

Very nice work skycam looking goood, keep it up..
Old 12-17-2005, 12:22 PM
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Default RE: Pusher AP plane build thread

Thanks for the encouragement all The wing kit arrived yesturday so I will be starting on it this weekend....
Old 12-17-2005, 01:12 PM
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Default RE: Pusher AP plane build thread

For the life of me I cannot see where you told us what wing kit you were using... or had just got
Old 12-17-2005, 01:31 PM
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Default RE: Pusher AP plane build thread

It's a Sig LT40 wing kit Fieldrut...70" span and 13" chord.
Old 12-17-2005, 08:09 PM
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Default RE: Pusher AP plane build thread

OK, things moving along now. Seeing as I will never get a 70" wing in my car with twin booms and tail feathers permanently hooked together I am having to modify so the booms and tail will come off from the wing. After thinking hard on several techniques I went with mounting using 3-1/4" ply rails to fit between two wing ribs. I will then drill a hole through the boom and through the rails at those three points. Blind nuts will be used on the rails and a small 1/16" ply plate fitted to the boom where the bolt head/washer will fit to stop it from crushing the boom wood. I have used doublers on the wing ribs as you can see from the picture. Nothing is glued at this point. Just thought I would share my thoughts before hitting the glue bottle. I fell pretty confident that this will provide a secure way of attaching the boom to the wing.....any comments?
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Old 12-17-2005, 08:17 PM
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Default RE: Pusher AP plane build thread

IMHO to limit "tension crush" I thought of glueing cut out pieces of plastic icecream container sides to each side of the doubled ribs...

If you never built one (as I have not) you come up with dumb stuff like that

head bowed

Ken

Old 12-17-2005, 09:37 PM
  #73  
Tall Paul
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Default RE: Pusher AP plane build thread

I've used a couple of methods attaching booms to wings.
One had the boom going into a socket at the front of the near the spar, a plate glued to the boom at the trailing edge, with a screw coming thru the trailing edge from the top.
Another used a clip glued to the boom at the trailing edge fitted over the trailing edge, with a clip slipping over the front of the boom and over the top of the wing at the leading edge..
And another with the clip at the leading edge glued to the boom, with a plate on the boom on the bottom of the wing, a screw thru a plate on top of the wing into the lower plate.
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Old 12-18-2005, 12:52 AM
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Default RE: Pusher AP plane build thread

ORIGINAL: Skycam41 OK, things moving along now. Seeing as I will never get a 70" wing in my car with twin booms and tail feathers permanently hooked together I am having to modify so the booms and tail will come off from the wing. After thinking hard on several techniques I went with mounting using 3-1/4" ply rails to fit between two wing ribs. I will then drill a hole through the boom and through the rails at those three points. Blind nuts will be used on the rails and a small 1/16" ply plate fitted to the boom where the bolt head/washer will fit to stop it from crushing the boom wood. I have used doublers on the wing ribs as you can see from the picture.
Sounds sound Skycam41. It looks like a good method to me. Nice mod on the rails and rib doublers. Sounde like you got a handle on it. I might go out a bay or two on each side of that mount and add in light triangle stock or something like that in critical area's to help disperse the boom loads across several ribs and bays.

Nice work sir

Dan
Old 12-18-2005, 10:30 PM
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Default RE: Pusher AP plane build thread

I might go out a bay or two on each side of that mount and add in light triangle stock or something like that in critical area's to help disperse the boom loads across several ribs and bays.
Dan
Dan, I was planning to use triangle stock on the ply rails up against the ribs and spar but I am not too sure where else you mean to add some reinforcement to help disperse the load. You will see on the plans from the last picture that I originally intended to run the boom up to the leading edge of the wing but have decided against that as the wing profile starts to turn up towards the leading edge which in turn would create a gap to the boom. The boom will end just slightly forward of the main spar.

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