Just popped my canopy out of the mold (my first attempt using a proper vacuum contraption). Also popped out the spinner and exhaust manifolds while I was at it. This vacuum forming thing is as addictive as...... building from correx ...now that I have found a way to simplify the mold making (carved foam covered with...paper mache)

ES!
Your vac forming is flippen awesome!!

Where are close up pics of Baron's Impala ?

Originally Posted by Extreme Sports

BTW, what are the variables Cm and Xtr1?

Cm is the amount of pitching moment the airfoil produces, ie how hard it tries to 'tuck under'. I've no idea what Xtr1 is all about though.

Thanks for posting those shots of your wing, it looks a lot more conventional. But be honest, it was really just to show off that you're putting retracts in a correx plane wasn't it

Originally Posted by nebbian

But be honest, it was really just to show off that you're putting retracts in a correx plane wasn't it

Was it that obvious?

What software are you using? I'm quite keen to get some simple software and analyse the different airfoils that can be easily built in correx and see if I can modify them to improve park flying characteristics (since this is my normal mode of flying)

Originally Posted by Extreme Sports

Was it that obvious?

What software are you using? I'm quite keen to get some simple software and analyse the different airfoils that can be easily built in correx and see if I can modify them to improve park flying characteristics (since this is my normal mode of flying)

I'm using xflr5 (http://www.xflr5.com/xflr5.htm) which is available for mac and windows.

Attached is a zipfile with the data files I've used. I'm glad someone else is interested in this, it really gets my propellor head going

The nicest corro wing design I have seen is the CorroBat. Has a nice leading edge with a routered chase and carbon tube.

That's perfect RN! I had actually thought about doing something similar, but routing the flutes looks like a great idea.

http://www.rcsoaringdigest.com/pdfs/...SD-2008-03.pdf

Originally Posted by Rusty Nail

The nicest corro wing design I have seen is the CorroBat. Has a nice leading edge with a routered chase and carbon tube.

Thanks - the corrobat method is on my to-do list. Its quite an easy modification for a constant chord wing, but a bit more difficult if you want to taper the LE as one would ideally do for a MIG or similar corroscale warbird (I know the corrobat does have a tapered wing..). But I agree it gives a really nice profile...just would like to use the software to test the resulting airfoil vs the std one to see if its worth the extra effort of making a tapered LE vs the normal folded correx one.

Thanks Nebbian - will download XFLR5 and give it a try when I have a bit more time on my hands

Originally Posted by Extreme Sports

Just popped my canopy out of the mold (my first attempt using a proper vacuum contraption). Also popped out the spinner and exhaust manifolds while I was at it. This vacuum forming thing is as addictive as...... building from correx ...now that I have found a way to simplify the mold making (carved foam covered with...paper mache)

Hey ES!,

That Stang of yours is going to be a beauty. Can't wait to see pics of her when she's finished

Originally Posted by Extreme Sports

Just popped my canopy out of the mold (my first attempt using a proper vacuum contraption). Also popped out the spinner and exhaust manifolds while I was at it. This vacuum forming thing is as addictive as...... building from correx ...now that I have found a way to simplify the mold making (carved foam covered with...paper mache)

I love that vac former - any chance you could pop up some more detail? Are those aluminium grill surrounds you have used? Is the Plastic held between the two frames and then I assume there is a box underneath where the vacuum is formed using a vacuum cleaner by the looks?

There are a couple of old a/c duct frames lying in the corner at work - I think they will be joining my stock of "bits for Future Use"

Alan

Extreme, carbon tubes are available tapered from kite stores and as blanks from fishing rod or golf club repairers (free when broken).
I have used wooden dowels tapered in a drill chuck.

Originally Posted by Rusty Nail

Extreme, carbon tubes are available tapered from kite stores and as blanks from fishing rod or golf club repairers (free when broken).

Ha! now that is something I never thought of.....and the final piece of the LE puzzle falls into place. Clearly its time to develop a sudden interest in fishing!! Hope the local fishing stores have such blanks. Never seen a kite store in SA, but plenty of fishing suppliers.

Thanks for the pointer.

Also, what was your sense of the performance of the more rounded edge? Did the stall improve?

BTW, we should probably continue this discussion on airfoil performance and construction techniques in the SPAD forum and not hijack FB's thread any more than we have already. [EDIT: made a post here: https://www.rcgroups.com/forums/show...5#post26374941)]

GerryAttrick

Search RCG for vacuum former and you will get lots if info.

Mine is even simpler than the simplest ones I found:

1) The base is cut from ~20mm ply shutterboard and has a hole cut in the middle into which I forced a 40mm PVC elbow (std size for kitchen sink drains)

2) I used a combination of correx and duct tape to taper the 40mm elbow to the right diameter to fit my vacuum cleaner - its a snug push fit (just tape all the holes in the flutes closed or the air just gets sucked in through these holes). The base then stands on 2 old Pb-acid batteries/ telephone books or whatever is at hand.

3) The frame is in 2 parts. The lower one is ~20mm aluminium U tube and the upper part is made from aluminium angle (exact sizes are unimportant as long as they are not too big, but wide enough for the clips to get a decent grip). The plastic sheet is held between these two frames.

4) I used foam weatherstrip stuck to the wood base to create a seal between the aluminium and the base - got this idea off RCG

5) You usually need a perforated plate to mount your plug on - the air is then sucked through the holes on either side of the plug. The best idea I saw was using fine wire mesh; others used electronics pc boards or drilled holes themselves in hardboard/ply. I could not find any mesh, and by this stage was eager to get cracking, so just stabbed multiple holes through some corrugated cardboard with a screwdriver. I then glued some sosatie (kebab) sticks to the base to make sure that the air could still flow under the corrugated cardboard.

There is a bit of practice required to know when the plastic is ready to be molded (too soon and it does not form; a few seconds too late and it melts in the oven) - see the RCG posts.

Attached is a document I cut and pasted from the internet with quite detailed instructions - excuse the lack of formatting.

I'll get some pictures later today.

EDIT: Pictures added

Spitfire wing is coming along: