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edgraydallas
Joined: 13 Jun 2008
Posts: 74
Location: Dallas, Tx
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 Posted: Wed Oct 08, 2008 11:28 am Post subject: Leading edge |
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Needing advice or input about leading edge.
Now building KF II and about to cover wings. I have installed the new plastic leading edge cuff and intend to cover the upper leading wing surface with aluminum over the upper false ribs. The alum. Is 12 inches wide and will butt against the leading edge cuff, epoxied and riveted to the ribs and spar, and covered with ceconite. My concern is the potential of oil-canning or ripples due to wing flexing. The purpose is to smooth the leading edge. The weight penalty is six pounds (maybe less since less finish will be needed). I plan on segmenting the aluminum material at alternate ribs to avoid oil-canning. Either cut the material completely or slit it from 2 inches behind leading edge through the trailing edge with a saw kerf.
So, all you engineers (pro or otherwise), please think this over and post your input or advice. Also, my fuel system plan is each six gallon wing tank routed to the alum. 1.1 gallon header tank mounted behind the right seat, which feeds into a facet pump under right seat then to the supplied cutoff valve below the throttle cable, then to the gascolater on the lower right front side of firewall, then up to the impulse pump on the firewall and out to the bing carbs on the 582. Vapor return line from the alum header back to the right wing tank. The left tank will have a fuel valve on the headrack, so I can isolate the two tanks and only fuel the right side for short flights. Plan to use the Facet on takeoff and steep climb, per Lynn Mattesen. Anyone see problems with my plan? Thanks for advice. Do not archive.
Ed Gray, Dallas, KFII No. 705, 582 grayhead, GSC 3 blade
PS I have a backpack emergency chute to wear while I test the plane. I have jumped before, but does anybody know someone who has bailed out of a Kitfox, ie. Any problem getting the door open or clearing the lift strut? egraylaw(at)swbell.net
[quote][b]
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paul(at)eucleides.com
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| Posted: Wed Oct 08, 2008 2:01 pm Post subject: Leading edge |
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On Wed, October 8, 2008 12:25 pm, Ed Gray wrote:
| Quote: | Needing advice or input about leading edge.
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| Quote: | Now building KF II and about to cover wings. I have installed the new
plastic leading edge cuff and intend to cover the upper leading wing surface
with aluminum over the upper false ribs. The alum. Is 12 inches wide and
will butt against the leading edge cuff, epoxied and riveted to the ribs and
spar, and covered with ceconite.
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Ceconite? Really? Not using Poly-Fiber? It's been a while since I compared them but
what's recorded in my head is not more than my conclusion and that was that Poly-Fiber
a better choice.
<http://www.polyfiber.com/stits/index.htm>
It's lighter, won't support combustion and is more easily repairable.
As to the Aluminum idea, customizations can look very nice but every ounce you can
save in weight is one that you'll wish you had more of when you get to flying. It's
extra work, extra cost, extra weight and doing so is bound to extend the time before
you start flying. Even with your ideas for preventing "oil canning", you can't be
certain of that without some pretty complex modeling or field trials. Also you're
bound to introduce bending stress concentrations at the relief joints where the design
was intended for a uniformly distrubuted load.
| Quote: | PS I have a backpack emergency chute to wear while I test the plane. I have
jumped before, but does anybody know someone who has bailed out of a Kitfox,
ie. Any problem getting the door open or clearing the lift strut?
egraylaw(at)swbell.net
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If you're able to escape and you're high enough above ground, then that would work.
But you'd surely lose your aircraft. Using a BRS ballistic parachute, achieves nearly
instantaneous deployment and would likely save you and the plane.
Some history
<http://www.brsparachutes.com/About+BRS/BRS+History/default.aspx>
contact them to find the current cost and the weight.
<http://www.brsparachutes.com/Contact+Us/default.aspx>
Then tell us what you have decided. I'm going to put one in my Merlin GT because I'm
just not at all certain about what will happen when being pulled by a Rotax 914.
That's more engine than has been used on any I know, although using a 912 is common.
--
Paul A. Franz, P.E.
PAF Consulting Engineers
Office 425.440.9505
Cell 425.241.1618
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Guy Buchanan
Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA
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| Posted: Wed Oct 08, 2008 4:11 pm Post subject: Leading edge |
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At 12:25 PM 10/8/2008, you wrote:
| Quote: | | I have installed the new plastic leading edge cuff and intend to cover the upper leading wing surface with aluminum over the upper false ribs. |
Do you mean you have installed the PVC leading edge from a IV onto a II? Or is there some other leading edge treatment for a II I am not aware of? (I thought they used the aluminum tube as the leading edge.)
| Quote: | | The alum. Is 12 inches wide and will butt against the leading edge cuff, epoxied and riveted to the ribs and spar, and covered with ceconite. My concern is the potential of oil-canning or ripples due to wing flexing. |
A reasonable concern, considering how much flex I see when I fly. If I were you I would definitely hang the plane by the tips before covering and jump up and down on the fuselage while observing the top skin. It should be pretty obvious if there's going to be a problem.
| Quote: | | then to the gascolater on the lower right front side of firewall, |
Well the gascolator won't do much, and certainly won't pick up any water, since the height of the valve precludes any water reaching it from the tanks. You also didn't mention filters, which are a good idea and a topic of much previous discussion, (hint, hint,) here. I have been flying a similar configuration 300 hours without any aux pump, and with a race car filter. I do, however, rebuild the fuel pump every year.
Guy Buchanan
San Diego, CA
K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar. [quote][b]
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_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
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lcfitt(at)sbcglobal.net
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| Posted: Wed Oct 08, 2008 4:48 pm Post subject: Leading edge |
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Hi Ed
I am currently doing just as you propose. First, regarding the leading
edge, I had someone come into my hangar as I was working on the first wing,
and mentioned that he had spoken to Harry Riblet about the Kitfox wing. I
can't recall who it was, unfortunately. Mr. Riblet said that the biggest
problem with the Kitfox design was that the most critical portion of the
airfoil was the initial 10% of chord on the upper surface. That is the
first five inches on our wing. That is where the fabric on the typical
Kitfox wing dips down behind the forward spar between the ribs and false
ribs. In talking to others, I suppose the major performance benefit, if
there is in fact such a thing, would be near stall where flow separation
starts - maybe reducing stall speed. Cruise, don't know, but laminar flow
should be improved.
I have done one wing and there are some tricks. Some I solved and others I
guessed at with proof after flight. Regarding oil canning, a possibility, I
suppose, but there are lots of airplanes out there with aluminum leading
edge - Rans for example.
Lowell
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MichaelGibbs(at)cox.net
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| Posted: Wed Oct 08, 2008 5:32 pm Post subject: Leading edge |
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On Oct 8, 2008, at 12:25 PM, "Ed Gray" <egraylaw(at)swbell.net (egraylaw(at)swbell.net)> wrote:
| Quote: | st1\:*{behavior:url(#default#ieooui) } <![endif]-->
Needing advice or input about leading edge.
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I'm really intrigued by this new composite leading edge John McBean announced the other day. I'd be inclined to wait and see how that works out and what they end up charging for it.
Mike G.
N728KF, Kitfox IV-1200 Speedster
Phoenix, AZ
[quote][b]
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henrysfork1(at)msn.com
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| Posted: Wed Oct 08, 2008 6:12 pm Post subject: Leading edge |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> John showed the new leading edge material on my visit yesterday, It looks like it should work just fine. If I were in the build process I would opt for the new product rather than metal.
Dee Young
Model II
N345DY
Do not archive
[quote] ---
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