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RV-8 ALUMINUM LEGS---HULA GIRL GETS SEXY---NEW VENDER!

BruceEicher

Well Known Member
Aeronautical Engineer/Aircraft Designer Ken Krueger is installing his new legs on my plane as I write this today. Made of aluminum, airfoil shaped to match profile of fiberglass fairing. Gun drilled for elimination of brake lines, made to bolt on existing holes, but come with new “U” brackets and longer bolts to accommodate the slightly thicker and wider gear.

One side is done and going quite well. As we work thru the minute details I will update the install as I see it. Ken is developing complete instructions with many good pictures for explanation of the slight differences between these and the stock steel legs.

Speaking of stock; why spend the money for these? Well for one, it’s like putting new polished wheels on your truck or sports car to replace the plastic wheel covers over cheap steel wheels. And then weight savings; Ken strung up my old leg, hardware, leg fairing and brake lines on a scale and then did the same for the new components. BTW, the new inner U bracket is made of aluminum rather than steel, an added savings. Total weight reduction confirmed with two scales and then doubled for both legs and hardware came to right at 15lbs total diet results. Hula’s happy with her new lines.

Ken’s website here. FWIW, I have no investment in this product and have purchased the gear outright but have received free labor of the install. Thanks Ken and Klaus!
Click to Ken’s page then click or tap photo for more info and prices:
https://www.skydesigns.aero/products

And as this writing, three more pairs of legs are produced but unspoken for. Ken may bring some to Oshkosh.

Hula Girl did elect for the polished finish upgrade, being a dancer and all.

I will add more detailed pics and a flight report as time allows.

Klaus-Peter Morhard, German RV-7 builder/pilot removes the old steel gear leg. I think Ken is in the cockpit napping.
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One steel leg off, looking like a cold stork:
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We primed the inner ends of the aluminum.
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The U brackets fit tight with a few taps of the mallet.
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Ken and Klaus trial fit. We trimmed a little non-structural belly skin for the larger hardware and thought out the brake hook-up.
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Ken is trying not to get too many of his finger prints on Hula’s leg.
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We did choose to upgrade our outer U bracket nuts as per AE Steve Smith’s recommendation. Thanks Steve! This helped inside the gear boxes fitting the smaller 12 point socket too.
Steve’s VAF thread: http://www.vansairforce.com/community/showthread.php?t=42630
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One leg done. Once we have both done we will check and re-align toe-in/out to neutral.
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Both legs installed
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To follow will be new brake fluid and an adjustment to the lower and upper intersection fairings.
 
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Details of the gear mount; plenty of room for the fuel vent line and brake line installed as per factory plans. We elected to eliminate the brake line bulkhead fitting and simply threading the line thu the now installed snap bushing and connecting an uninterrupted line to the fitting under the panel. This reduced the line connections by two and made easy work of bending line to the gear’s 90 degree fitting.
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We had plenty of aluminum line in the hangar so we made our own at the wheel brake end. Ken measured also for the option of a professional made steel braided line. A relief cut was made in the top center of the wheel pant attach racket to clear the shape of the new gear leg. Ken made a template for this that I believe will become part of the install instructions.
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I trimmed the outboard edge of the inspection plate to fit inside the outboard U bracket. The U bracket will be covered by the intersection fairing.
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Here’s a pic of the old gear. While in this photo they look shinny, it’s only a facade made of heavy steel, fiberglass and plastic chrome film.
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Final Test flights

After a test flight without, I installed the wheel pants (with some slight trimming to fit the wider airfoil gear.) And then flew again last night. Several wheel and 3 point landings all felt just like the stock steel legs. One notable difference (even though I started these flights with full tanks) it felt less heavy flying solo than before. 3 pointers are no problem solo without running out of elevator, now even better. I do have a fixed aluminum prop, IO-360 180 hp and Earth-X battery all helping to lighten the nose more than some other -8s.

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Now to get to work on the english wheel and make a real polished aluminum canopy skirt rather than the current facade. :)
 
Is the total delta weight savings ~ 15 lbs per gear leg or ~ 15 lbs total with the new gear?
 
After a test flight without, I installed the wheel pants (with some slight trimming to fit the wider airfoil gear.) And then flew again last night. Several wheel and 3 point landings all felt just like the stock steel legs. One notable difference (even though I started these flights with full tanks) it felt less heavy flying solo than before. 3 pointers are no problem solo without running out of elevator, now even better. I do have a fixed aluminum prop, IO-360 180 hp and Earth-X battery all helping to lighten the nose more than some other -8s.

hs5atz.jpg


Now to get to work on the english wheel and make a real polished aluminum canopy skirt rather than the current facade. :)

Sexy Beast!

Were you able to use your original intersection fairings with just some modification, or did you start over and make new ones from scratch?
 
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How are these different from the Grove?

To the eye, they look like a more completely contoured airfoil shape. I seem to recall the Grove ones had a leading edge area, a trailing edge area, and a flat intermediate area? I could be wrong, just how I remember.
 
Sexy Beast!

Were you able to use your original intersection fairings with just some modification, or did you start over and make new ones from scratch?

Lower intersection will need a slight change in airfoil shape, thinner and slightly longer than the fiberglass leg fairing. The upper intersection is currently cut to fit and chrome duct taped. I will remake this fairing. If you are doing these legs in an original build, no extra work. As you know, Van?s stock lower fairing is thin and flexible to fit, then you add a couple cloth layers to make a ridged fit. The upper is made from scratch per factory instructions anyway.
 
These are a true airfoil. Not a round leading edge with a straight taper on the back. It was all done with 3D milling. It even has a bit of pressure relief on them!! I have a short video showing part of it, but dont know how to upload it.
 
These are a true airfoil. Not a round leading edge with a straight taper on the back. It was all done with 3D milling. It even has a bit of pressure relief on them!! I have a short video showing part of it, but don't know how to upload it.

Hi Richard,
The video would be interesting. If you can post it on Youtube then copy the link to the VAF post. Thanks again for the work on the legs!

And, chatting with Ken and Steve about the airfoil; Ken chose for the Sky Designs legs (given that aluminum airfoil legs are all about sexiness) a slightly modified NACA 66(4)XXX section...he always thought that section had a nice pretty shape :)

And Ken said, "Given the low reynolds number, there can't be much of a drag reduction benefit to using such a section but it certainly won't be producing more drag than the stock fairing! It would be fun to dribble some oil on the aluminum legs and see if there aren't any clues as to whether there is any separation aft of the max thickness point. FWIW: The thickness at the top of the leg is 21% and at the bottom it is 19%."

Here is a pic of the bottom of the leg, showing the thinner shape compared to the old transition fairing that fit the stock gear leg fairing. A gain of 10 kts don't you think? :rolleyes:
You can also see the slight mounting hole correction needed to fit the fairing on the slightly wider leg.
I will be forming new transition fairings, from Van's for the lowers and from scratch for the uppers when the flying season slows down. For now this gap will have to be overlooked.
Cheers!

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I wish you guys in the states would stop tormenting me! Now I will have to try to come up with $3900 AUD :)
 
Its about 30% less if you polish it yourself!!!

https://youtu.be/H077CoYKMVc

Here is a really poor quality video. I have never done youtube, so I asked a friend after I texted the video. I think something went wrong in the transition... I will try again and update if it works better.
 
Love the wheel pants too!!

Bruce, Hula Girl is gorgeous! I'm still at the QB Fuse stage and starting to get going on it, but have been trying to keep the " polish" option an option. My hangarmate swapped his stock legs for the polished Grove ones and gave me the stock legs. I will probably just use the stock ones for now trying to save a little money here and there just to get my -8 in the air!

I'm really interested in your wheel pants! How did you achive that look? Are those custom aluminum pants or Van's stock ones with some aluminum added?
 
Bruce, Hula Girl is gorgeous! I'm still at the QB Fuse stage and starting to get going on it, but have been trying to keep the " polish" option an option. My hangarmate swapped his stock legs for the polished Grove ones and gave me the stock legs. I will probably just use the stock ones for now trying to save a little money here and there just to get my -8 in the air!

I'm really interested in your wheel pants! How did you achive that look? Are those custom aluminum pants or Van's stock ones with some aluminum added?

Hi Jeff,
Thanks!
Actually it?s only chrome and blue vinyl over the stock pants. Did the same on all fairings and canopy skirt including the old leg fairings now eliminated.
You can see my wrapping thread here. http://www.vansairforce.com/community/showthread.php?t=98932

So you had Van?s eliminate the stock gear legs and fairings from the fuselage kit? How much did that save? I ask because I have a set to sell, cheap.

Cheers!
 
I saved $600 from the fuse order by eliminating the stock legs. My hangarmate gave me his for a few periodic BBQ lunches!

That wrap is very cool! I love the look!
 
Bruce,
Nice to meet you yesterday, thank you for taking the time and talking with me. Or rather me talking your ear off!

Kent
 
To the eye, they look like a more completely contoured airfoil shape. I seem to recall the Grove ones had a leading edge area, a trailing edge area, and a flat intermediate area? I could be wrong, just how I remember.

Steve, that's correct on the Grove legs. You can see the flat area in the reflection in this photo:

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How are the ends formed Richard? Bent Milled then treated?

We mill them flat, have them heat treated to soft state, we bend them while soft with our press, and then send them back to the heat treater's to get aged to the hard condition. The brake line hole is of course drilled while it is flat before heat treating.
 
Transition Fairings

I had a free weekend to layup new transition fairings to fit the airfoil of my new gear legs. I did use Van’s stock lower leg to wheelpant starter fairing, but if you are making your own upper, not much more work to make the lower from scratch too.

One evening taping with box tape, plastic wrapping and forming clay.
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Layup on Sunday
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Monday, Layups removed, showing is one of the old chrome vinyl covered fairings. Also I added small bumps on the sides of each wheelpant for additional brake clearance from shimming them out to clear the larger tires added last year.
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Monday continues, Trimming, rough shaping, mounting for flights these next few weeks. Will final fill, shape (reduce size some) and chrome vinyl soon, but flight ready
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If you are at Oshkosh, lookup Ken with his new airplane debuting there, and he should have a pair of sexy legs to show you too, RV-8 aluminum airfoil landing gear legs to be more specific.
 
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Have any calculations or structural tests been made before production?
Compared to the originals, what resistance do they have?
 
Have any calculations or structural tests been made before production?
Compared to the originals, what resistance do they have?


Yes, by the same designer and machine shop as the original factory legs all the way to fail. And the aluminum took more abuse/weight than the steel before failure.
 
Yes, by the same designer and machine shop as the original factory legs all the way to fail. And the aluminum took more abuse/weight than the steel before failure.

I like the idea and not that I'm qualified to say, but its not one-time load failure that I wonder about, its cyclical fatigue. Aluminum is poor at it and steel is very good at it. I'm assuming that small planes fly so little that you'd never get to the cyclic fatigue limit?
 
Done...

Back to indoor activities here in Oregon; so I finally took the time to finish the wheel pants from the larger tire upgrade and the transition fairings for Hula?s new Aluminum Airfoil Gear Legs.

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...because I was inverted

Bruce, your intersection fairings look great! All the more impressive considering that it required infusion of resin while inverted indoors.

Susan and I have three sets of aluminum legs ?in-stock??two sets un-polished and one set polished.
 
Bruce, your intersection fairings look great! All the more impressive considering that it required infusion of resin while inverted indoors.

Susan and I have three sets of aluminum legs ?in-stock??two sets un-polished and one set polished.

Thanks Ken for both your help and compliments. We saw Harmon and all the gang last night at our party, sorry you weren?t there. I did not think, maybe you don?t get the chapter emails?
And, my iPhone thinks I?m right-side-up, but computers (MS?) like to invert my pics posted here. :confused:

I?ll demo your tie downs next. :)

Merry Christmas to You, Susan, Amy and...
 
We did choose to upgrade our outer U bracket nuts as per AE Steve Smith’s recommendation. Thanks Steve! This helped inside the gear boxes fitting the smaller 12 point socket too.
Steve’s VAF thread: http://www.vansairforce.com/community/showthread.php?t=42630

Just ordered a set of the polished gear legs and am about to place an order for 4 of the upgraded NAS1804-6 outboard nuts.

I'm assuming that the NAS6606-36 outboard bolts supplied with the new gear legs were long enough to accommodate the taller NAS1804-6 nuts based on the OP, but was wondering if this can be confirmed. Understanding the longer bolts supplied with the legs are likely primarily for the thicker gear legs themselves, I was wondering if even longer bolts might be needed for a taller nut than stock.
 
The "dash 36" length bolts supplied with the Sky Designs installation kit are indeed long enough for the taller NAS1804-6 nuts...no need to order longer bolts.
 
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