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Secondhand Flair Pup

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Mark a18/06/2017 09:37:26
321 forum posts
3 photos

Morning all

I picked up a secondhand Flair pup at Weston yesterday and have a question regarding the c of g. The model has an ASP 61 fs up front which maybe over kill for this model but it has good compression so it will be staying. I have read various c of g recommendations but I'm after a good starting point to balance the model.

Cheers

Mark.

Peter Miller18/06/2017 09:43:46
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10060 forum posts
1189 photos
10 articles

The way that I do biplanes is this.

Mark the 25% point on the top wing and the bottom wing. The CG should be in the middle between these two points.

Always worked for me.

Tom Sharp 218/06/2017 17:56:41
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3456 forum posts
17 photos

Only works if the wings are staggered.

Mr.B.18/06/2017 18:01:36
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412 forum posts
26 photos

My one is 130mm back from the top wing LE as per the flair instructions.

**LINK**

Mark a18/06/2017 19:25:21
321 forum posts
3 photos

Thanks for the help guys. I'll balance it at 130mm and see how it fly's.

Mark.

onetenor18/06/2017 20:16:49
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1900 forum posts

The midway between the two 25% positions is fine but what about backstaggered wings.Does it still apply

i12fly18/06/2017 22:05:01
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544 forum posts
21 photos

Beware Mark! The instructions say use 130mm with a slightly nose down attitude.

In error I balanced mine at 130 with it level at flying attitude and it was tail heavy -a real handful!

I finished up adding several ounces more lead to get it correct (8oz in total with a 70FS too)

David Davis19/06/2017 04:44:42
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3368 forum posts
591 photos

I agree entirely with il2fly. I have had two of these and both were difficult to fly with the cg in the recommended position. I would recommend a cg of 110mm with the model level.

Bob Cotsford19/06/2017 09:11:31
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7923 forum posts
436 photos
Posted by Tom Sharp 2 on 18/06/2017 17:56:41:

Only works if the wings are staggered.

Can you explain why that should be please Tom? It sounds to be a workable option for anything without sweep.

pete taylor19/06/2017 09:47:10
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348 forum posts
162 photos
Posted by Tom Sharp 2 on 18/06/2017 17:56:41:

Only works if the wings are staggered.

It'll work the same, staggered or not Tom.

With 100mm stagger the mid-point will be 50mm behind the top mark. With 50mm stagger it'll be 25mm behind and at zero stagger the mid-point will also be zero.

The idea works for reverse stagger too.

Mark a19/06/2017 14:50:35
321 forum posts
3 photos
Posted by David Davis on 19/06/2017 04:44:42:

I agree entirely with il2fly. I have had two of these and both were difficult to fly with the cg in the recommended position. I would recommend a cg of 110mm with the model level.

Thanks Dave 110mm it is.

Cheers

Mark.

Tom Sharp 219/06/2017 16:46:10
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3456 forum posts
17 photos

Not all biplanes have staggered wings. Some have the same leading edge position for both upper and lower wing, therefore the same balance point on each wing. Swept or not swept.

Kevin Fairgrieve19/06/2017 19:17:33
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1588 forum posts
2844 photos

As per the plan on mine.

Kev

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