trying2fly
After a catastrophic launching of my first biplane, I am finishing up a rebuild and if anyone has any pointers please feel free to ck these pictures out and to tell me what I am doing wrong thus far! ha!  Thank you all for any critique ! BiPlane Rebuilt 005.jpg  BiPlane Rebuilt 011.jpg 
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quorneng
trying2fly
An interesting design. I can see no obvious reason why it should not fly.
You need to be a bit more specific describing in detail what actually happened on its first disastrous flight.
What is the span? How much does it weigh? What is the motor, prop and the battery? Where is the balance point?
I doubt you really need all those ailerons. It could make the plane very twitchy to fly.
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trying2fly
The weight is 23 oz.  I am using a 2200 mah battery with a 2212 13t 1000Kvp motor and a 9x6 prop.  The proposed balance point is to be 25% in from the leading edge of top wing. The top wing is about 1/2 in. forward of the lower wing.  The first plane looked similar but my wings weren't set right.  I have almost no perceptible angle of incidence with either wing(kind of like the original Wright Bros).  Hopefully I have them parallel although I am aware that some angle is probably best...I am just trying to get it up.  The first launch went almost straight up and over to the left and crashed big time  I am running no tail wheel or landing gear as the terrain out here is prohibitive!!  Rocks, cacti, more rocks, more cacti.
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DualDesertEagle
Sounds a little nose heavy to me. As I've described in another post I would say the CG would need to be somewhere near the first third of the combined wing chord length.

U say ur upper wing is half an inch ahead of the lower wing? Then I'd try 1/3 the chord of the wing, minus 1/4 inch (forward) on the lower wing and plus 1/4 inch (backward) on the upper wing.

From there do short glide tests onto ur bed or sofa to see how it behaves, and then modify it accordingly.
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Wildthing
Those wings look much better 🙂 This one will fly. On the AN-2 I am about 28% back on the top wing for cg
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trying2fly
Sounds a little nose heavy to me. As I've described in another post I would say the CG would need to be somewhere near the first third of the combined wing chord length.

U say ur upper wing is half an inch ahead of the lower wing? Then I'd try 1/3 the chord of the wing, minus 1/4 inch (forward) on the lower wing and plus 1/4 inch (backward) on the upper wing.

From there do short glide tests onto ur bed or sofa to see how it behaves, and then modify it accordingly.
  Yes, I read your former post and I guess after  going straight up with my first one on launch that I was a little queasy about CG being too far aft.  I have understood that if it is too far to the back..fly once.....if it is too far forward....maybe fly again.  LOL.  Your suggestion is super and very very close to Wildthing's  proposal.  Thanx to both of you
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trying2fly
Wildthing wrote:
Those wings look much better 🙂 This one will fly. On the AN-2 I am about 28% back on the top wing for cg


I was going to balance it by putting a pencil under it and rolling it back and forth and adjusting the battery....is there a better way?  Chas
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trying2fly
Wildthing wrote:
Those wings look much better 🙂 This one will fly. On the AN-2 I am about 28% back on the top wing for cg


It was more difficult than I thought to set those wings!!!!  I will do as DDEagle suggests also and try a glide test in some tall grass(if I can find some).  Quorneng made a good point.  I may reduce my throws  on those large ailerons.
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solentlife
trying2fly wrote:


I was going to balance it by putting a pencil under it and rolling it back and forth and adjusting the battery....is there a better way?  Chas


Finger tips under top wing !! 

You cannot balance a biplane by using bottom wing .... you must have more weight below pivot than above ... 

Example :

Cessna high wing - you test CoG upright by using that high wing.

Spitfire and other low wing models - you INVERT and then treat it in same way as a high winger.

Shoulder wing models - usually upright because the undercarriage adds lower weight but can be either way. 
I'll fly anything if I can launch it ! Youtube : solentlifeuk
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trying2fly
I was not aware of the pivot pt. in balancing. Thank you so much.  I learn more everyday from experts like you.  You probably saved me once again! lol! !Chas
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quorneng
tryingtofly
"Going straight up on the first launch" suggests one (or more!) of three possible things.
1 The CofG is too far back. If it really was at 25% of the top wing chord that is unlikely.
2 The elevator was set with too much 'up' and you did not have the skill to apply the correct amount of down elevator in the split second before things got out of hand.
3 The launch technique was poor. Thrown too hard and upward rather than a gentle toss level with the ground. Unless the wing span is very small, say 24" (but I hope it is more like 36"!) as a biplane at 23 oz it should not fly that fast at all.

The first flight of a home design really requires quite a high level of skill to control successfully, particularly in those first few seconds. Any chance that an experienced RC pilot could do the 'maiden' and get it trimmed for you?
Then you know it flies and any difficulty is down to you not the design of the plane.😉

I also fly from a rough field so every plane I have is hand launched even the few that actually have undercarriage.
My only biplane uses a slightly more powerful motor, a 9x5 4 blade prop and a 2200mAh 3s. It weighs a bit more at 26 oz but with a 50" span it still flies very slowly!



    
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Wildthing
trying2fly wrote:


I was going to balance it by putting a pencil under it and rolling it back and forth and adjusting the battery....is there a better way?  Chas


All those extra prop adapters you have that's what I use. I glue them on the cg mark , easier to balance by the finger tip or  my now fail safe one is I still use the washers but I also made some tripods . The tripods are positioned/centered onto the washers, now just move everything around until the plane is balanced. Here I used two old wifi antennas , built a base, shrink wrapped the shaft so they don't bend  and away you go.  2019_0609_185558_001.jpg  2019_0609_185607_002.jpg  2019_0609_185635_001.jpg 

Here is one sitting on the tripods. 

2019_0820_154129_004.jpg 
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solentlife
I have the Hobby King CoG machine ... fine for small to medium stuff with modification ... 

But at end of day - two fingers do the job OK.

I nice setup avoiding dents in foam etc ..... large block of wood and two pencils with eraser ends .... drill block with series of holes in a line across the block ... so you can set pencils apart to suit ... or two separate blocks with pencils set in. The eraser ends of course are the ones that touch the model.

With biplanes though - that simple approach cannot work as you have the bottom wing in the way. So you need to have an inverted L shaped upright so that it goes between wings to have top wing sitting on them.
I'll fly anything if I can launch it ! Youtube : solentlifeuk
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