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Mark P

Pressed Foam Wings

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Mark P

I am currently making some aerobatic models.

Greg Dakin kindly supplied me with a French aerobatic model called a Sonic. The fuselage is excellent but unfortunately the wings leave a little to be desired so I decided to make my own wings and tailplanes using a different wing section. As the original plane is the Sonic I thought I would call the updated version the Hedgehog.

Things are progressing well so I thought I would share a few build pictures to show how we used to make planes in the good old days before mouldies.

 

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Mark P

Did the tailplanes earlier in the week.

They came out at 14g each

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Mark P

Templates are home made from good old fashioned 1/16 birch ply.

Supergluing the edges means they can be polished up to a hard smooth finish

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Mark P

First wing out of the press.

Good torsional rigidity. Weight is 145g.

 

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wookman

Nice work Mark. Hopefully your HQA section is not too far from SV96. Sonic was all about light, low and slow. Your work is impressively light. Is that where you are going with this one or are you planning a more sky eating kind of performance from your Hedgehog variant? One thing for sure you are guaranteed a great looking plane. Keep us posted as you progress with the build.

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Mark P

Looking to build a model that will fly aerobatics in light air but not with  as much emphasis on low and slow as the VTPR models. Not looking for sky eating performance with this one.  Airfoil is slightly lower camber and thinner than the SB96 so should have slightly better inverted performance and be a bit more slippery at the expense of some lift in positive flight. Keeping the plane as light as possible to compensate.

 

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Mark P

2nd wing out of the press - this one weighs 146g. Pretty damn close to the firs one.

Also made a foam balsa/rudder/

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wookman

1 gram in 145/6 is impressive!

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CTR

Hi Mark,

Did you use epoxy to get the stiffness? What type of foam and what is the thickness of the balsa?

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Andy_B

OK if I drop Gregs Le Mande  fuz off to you at the English open ..?  assuming hes ok with tHAT 

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Mark P
15 hours ago, Andy_B said:

OK if I drop Gregs Le Mande  fuz off to you at the English open ..?  assuming hes ok with tHAT 

No problem. 

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Mark P
15 hours ago, CTR said:

Hi Mark,

Did you use epoxy to get the stiffness? What type of foam and what is the thickness of the balsa?

Epoxy Laminating Resin from Bucks Composites.

Balsa is 0.8mm thick with 49g glass cloth at  45 degree bias and an extra layer at the root,

Foam is the type that Builders Merchants sell for flooring - under screeds etc. Got mine from my local Jewson.

As the balsa is only 0.8mm I will also be skinning the wings with 49g cloth. 

 

 

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Mark P

Steady progress to date.

Tailplanes are nearing completion. Joiner boxes  made for the wings together with some shaped wingtips.

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Mark P

Tailplane shaping finished. Quite pleased although I say so myself.

Wings trimmed and ready to be joined.

Didn't get as much done as I had hoped - been out setting up my new Freestyler ready for the English Open next weekend.

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Gromit

Following with interest Mark, nice work .

 

  Stu. 

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Mark P

No flying today so back in the workshop for some more work on the Sonic before Greg's Redshifts arrive for fitting out.

Time to get the wing joiners in starting with the main carbon joiner.

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oipigface

Can you give a few more details of the construction of your joiner boxes, please, Mark? Looks like the joiner itself is 10mm CF rod, but what else is in the box?

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Mark P

Joiners are 9mm CF rod.

Box is 1.5mm birch ply sides with 10mm square spruce either side of K&S 10mm brass tube,

CF rod from Hyperflight, brass tube from Ebay

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Mark P

Front and rear boxes installed.

5mm CF joiners. ply boxes with 6mm pine strip from B&Q.

 

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Mark P

 

Aileron wires fitted and leading edges glued.

Fresh blade in the razor plane and then some serious carving next time

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