It's all in the balance

[Keith Evans 3]

After having a major clear out and tidy up I came across an old two piece wing of about 700 sq.ins.

My thoughts are to make a cartoon biplane from it .

I've sketched a few ideas and I have a few balance questions .

I know the wings will need balancing because each root portion has Ali tubes buried in them for when I was using a joiner . ( I can't get them out .)

So do I balance each wing individually ?.This will mean adding approx. 2 oz . to each tip or do I complete the plane and see if any balancing is required and compensate for the lighter wing tip only .?

I believe statically balanced it should be O.K. but I'm not sure if dynamically it would be acceptable as there will be the vertical distance between the wings to consider .The gap will be in the order of 5".

The other issue is to get the C.G.in the right position I'm either going to use a pile of church roof ,a bigger engine ,lengthen the nose ,build the tail light or a combination of all these .

My least preferred option is to lengthen the nose ,a thing I've done many times in the past ,as it will detract from the styling .

Your suggestions are very welcome

Keith

[Frank Skilbeck]

Keith you don't need to laterally balance both wings, if the upper wing is port heavy and the lower starboard heavy but the model balances laterally when assembled that would be fine.

As regards the centre of gravity, it's always best to lighten the tail if you can, 1 oz saved their is often 4 off the nose, so a 1 oz saving at the tail can equate to a 5oz overall. A 5" gap between the wings shouldn't cause any dynamic balance issues, note might be worth reading up on Bipes a bit, it's often better to put one wing at a slightly raised angle of attack then that one stalls first, if the wings were staggered then you'd want the most forward wing to stall first so the model noses down.

[Simon Chaddock]

Keith

I suppose the issue about dynamic balance on biplane wings is just how fast do you expect the plane to roll?

A far bigger issue with "old" wings is how aerodynamically balanced they are. In other words have warps developed over the years? Such things can make for odd handling close to the stall.

[Zflyer]

No advice but a long nose is surely an aid for any cartoon. Lol

[John Wagg]

With having a wing that joined in the middle then the tubes will be in opposite ends if the wings are built into a biplane.

Yes the top wing will be heavier on the opposite side than the bottom but overall there shouldn't be that much difference in balance..

[Engine Doctor]

Just balance the model laterally when assembled as with any model.

[Keith Evans 3]

HI everybody thanks for the input .

Frank --I have a lot of modelling books regarding the aerodynamics of flight but they are all a bit sparse when it comes to biplanes . I've searched the web but have found nothing suitable .

Any suggestions would be appreciated .

Stay well .

Keith