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Old Apr 14, 2012, 02:43 PM
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joyalflyer's Avatar
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Help!
Dihedral of rubber powered plane

hi guys I am currently working on Messerschmitt rubber powered plane from Guillows and a Grumman F6F Hellcat. Both of these need a dihedral, but I am not quite sure how to do it. i have searched the internet but there isn't that much of any information or resources. So if you guys can help me that would be great?
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Old Apr 14, 2012, 04:57 PM
F1B is ok.
Monheim am Rhein Germany
Joined Jul 2008
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I'm not sure if that helps here. http://www.youtube.com/watch?feature...JNmh_n44U&NR=1

http://www.hippocketaeronautics.com/...p?topic=9354.0

Heinz
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Old Apr 14, 2012, 05:52 PM
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Thanks for the reply but I need more detailed information
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Old Apr 14, 2012, 08:38 PM
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Rio Rancho NM
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Conventional wisdom is 1" per ft of span. But both are low wingers (could almost call the Hellcat a mid wing). So conventional wisdom there is wing tips a little higher than the thrustline.

Bruce will probably chime in with more info. Or maybe Yak52.
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Old Apr 14, 2012, 09:47 PM
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Oh... OK... Since you mentioned me....

Joyalflyer, just to set the stage by starting with low wing scale models you're biting off a rather large hunk for one mouthful. Low wingers bring a lot of odd stability issues and greatly reduce the odds of success for those fairly new to rubber power. On top of this you're trying to also toss in the scale aspect. A double whammy against the chance of success.

To have a fighting chance of success you want to use enough dihedral that the wing tips come up to around half way up the canopy in each case. I know that is a lot and will make the model look funny. But it's going to give you, who is apparently a relative rubber power beginner, a fighting chance of flying decently.

If what you are asking is how to glue in the dihedral then I suggest you study the plan more. Typically the Guillow kits were good at showing a diagram of how to block up the wings to do the center joint with dihedral.
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Old Apr 15, 2012, 04:14 AM
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UK
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Could you be more specific in your question? Then a more detailed answer will be possible...

Are you asking a question about the design, ie what angles are neccesary?
Or are you struggling with the actual construction of the dihedral break of the wing?

As Bruce has said if you are just starting out, more dihedral will make trimming easier. You might have to compromise the scale looks a bit but at least you'll get it flying...
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Old Apr 15, 2012, 09:36 AM
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What I really want to ask is the actual break of the wing. I actually don't know how to do it?
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Old Apr 15, 2012, 11:15 AM
B for Bruce
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The 'Wack, BC, Canada
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There should be a sketch on the plans. But I agree that they are not allways that clear.

The classic way to do it is to make the two sides separately. Then with one still pinned to the building board to bring the other into place and raise the tip by twice the amount of dihedral you want and pack it there with a block of some sort. Pin the raised wing with pins near the center line to hold it and trim the spars as needed to achieve a good match. Then glue the ends together to hold things steady while you then glue the dihedral braces across the face of the butt joint. You definelty want some sort of wood to span the joint as the end to end butt joint has very little strength. Gluing a brace across the long grain faces is far stronger.

THe root rib has to be fitted in there at some point. It also has to be cut out to allow for the braces. When to add it is the question and it depends on how many upper spars you have. It's simply a question of when is the most convenient time to stick it in there without it getting in the way.

That help?
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Old Apr 15, 2012, 01:22 PM
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It helps a lot, but like video would be much better
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Old Apr 16, 2012, 08:45 PM
Balsa Flies Better!
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Another way to do it is pretty simple- just build in the dihedral like Bruce says- fit in the root rib- and add some gussets to the corners. Make sure that the grain runs along the long axis of the gusset.

However, while the Hellcat has a great planform for FF, Guillows designs generally suck- too much wood and too heavy. Try starting with a Golden Age Reproductions kit- the P-51 isn't too tough a build, and mine has everybody in WWII mass launch events indoors scared. (not of collisions, its the slowest plane up there.)

Sam
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Old Apr 18, 2012, 09:34 PM
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I seriously doubt there's anything along the lines of a video on this sort of thing. Also there's so many options for what needs to be dealt with.

Sometimes you just need to walk the tightrope without the safety net.

Many of us here trying to help you did it ourselves with nothing more than a little planning and though before the internet, videos and You Tube were even something written about in Science Fiction. So just wade on in, the water is fine...
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Old Apr 18, 2012, 11:21 PM
Culper Junior
eastern pa
Joined Feb 2007
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Here's something from Mike's Flying Scale Model Planes site. Proceed to chapter 6 on building wings and you will see some pictures on the dihedral subject. I'm cutting and pasting so I hope you see the right pages.

http://www.ffscale.co.uk/comp6.htm



And here's a place with lots of color pictures of models and a section with building tips (in the 'selection' box)
http://www.easybuiltmodels.com/
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