JAVRON Dihedral
- Thread starter HelioJoe
- Start date
Here's a good thread to read.
http://www.supercub.org/forum/showthread.php?36711-Wing-Washout-from-where
http://www.supercub.org/forum/showthread.php?36711-Wing-Washout-from-where
Bill Rusk
BENEFACTOR
Sandpoint, Idaho
Joe
Welcome to SC.org
The Javron Cub is a replica of a stock Supercub so all values found in the Type Certificate Data Sheet (TCDS) will be applicable. I don't remember the exact value but the number is out there, and can be found by searching through this site. Also, some folks choose to change the dihedral, washout and other values to change the performance characteristics to suit their particular mission. Jay does build in the washout; however, there is considerable flex in the wing and as a result you can change that to your preference as well by adjusting the rear strut length. But by building in the washout it means the wing has no internal stress created by adding that twist after the fact. In fact, if you were to decide that you wanted no washout in your wings (and adjusted the strut length to make that happen) you would be twisting the wing and creating resting state stress.
I hope this helps
Bill
Welcome to SC.org
The Javron Cub is a replica of a stock Supercub so all values found in the Type Certificate Data Sheet (TCDS) will be applicable. I don't remember the exact value but the number is out there, and can be found by searching through this site. Also, some folks choose to change the dihedral, washout and other values to change the performance characteristics to suit their particular mission. Jay does build in the washout; however, there is considerable flex in the wing and as a result you can change that to your preference as well by adjusting the rear strut length. But by building in the washout it means the wing has no internal stress created by adding that twist after the fact. In fact, if you were to decide that you wanted no washout in your wings (and adjusted the strut length to make that happen) you would be twisting the wing and creating resting state stress.
I hope this helps
Bill
There have been lots of discussions about washout here through the years. Cubflier and AkPA-18 educated most of us about the correct interpretation of the certificated airplane setup when using Gordon Mandell's instructions (read the thread I linked above), but you're experimental so you can deviate from that. Many of us have used a 1-3/8" block at the outboard rib when the wing is on level sawhorses but for years guys used 3/8" and those planes fly fine. In fact you'll find guys who say less washout improves performance. If your wings were rigged for 1-3/8" twist when the leading edges were installed it'll be hard to twist them back to 3/8" and vice versa. The easiest path is to go with what was built in.
Hey Bill...................many thanks for the message and the welcome but I did join in 2007. Just did not have to much to say. I've built about 15 different Super Cubs from stock to experimentals but could not find anything for Javron yesterday. Fortunately Jay did call me this morning and we got it all worked out.
Saw your end quote of being Blessed..............yes Sir, me also, very, very Blessed since I was shot down 9 times in Viet-Nam, 1965 & 1966 and still flying and building today.
In HIS service............Joe.
Saw your end quote of being Blessed..............yes Sir, me also, very, very Blessed since I was shot down 9 times in Viet-Nam, 1965 & 1966 and still flying and building today.
In HIS service............Joe.
Hi Jim,
I do remember and as a coincidence I was just looking at photos of it when I took my grandson for a ride. She still looks good and was a sweet flying airplane. Yes Sir, after you left we moved into a larger hangar and building 5 airplanes at a time.
Since you were here, we built about 10 of the Van's airplanes, mostly the 4 seat RV10. Super Cubs built were 3 Backcountry PA-18s (Wyoming), 2 SQ2s, just shipped an Alaska Airframes with Dakota Slotted wings to Africa yesterday, finishing in a few days the Backcountry REV2 (big airplane) and the Javron in another month or so.
Time to get to work at the hangar....X50 Massey in Edgewater, FL now. Stay in touch...............Joe.
I do remember and as a coincidence I was just looking at photos of it when I took my grandson for a ride. She still looks good and was a sweet flying airplane. Yes Sir, after you left we moved into a larger hangar and building 5 airplanes at a time.
Since you were here, we built about 10 of the Van's airplanes, mostly the 4 seat RV10. Super Cubs built were 3 Backcountry PA-18s (Wyoming), 2 SQ2s, just shipped an Alaska Airframes with Dakota Slotted wings to Africa yesterday, finishing in a few days the Backcountry REV2 (big airplane) and the Javron in another month or so.
Time to get to work at the hangar....X50 Massey in Edgewater, FL now. Stay in touch...............Joe.
Scott A
FOUNDER
Park City, UT
Yes, I also spoke with Jay in the past week about rigging. This thread is older and I am not sure when Javron changed but Bill mentions above that the Javron is the same as a stock Super cub - currently, as you pointed out that is not the case. Javron's (as of now - guess it would always be good to double check with Jay) have the front main spar fittings higher (about ¼ inch) which gives us the ⅛ inch block for the washout at the 15th rib instead of the 3/8 inch on the 'stock' cub.
If you zero the digital level at the root rib and use the ⅛ spacer block at the 15th the level should read 1.8 degrees when washout is set.
If you want to skip using the ⅛ spacer block with the digital level - zero the level at the root rib (spanning from front spar to rear with the same 30-inch level (or longer just stick the excess out the front, have the back end on the rear spar). Then at the 15th rib, the reading should be about 2 degrees (Sam did the math in his Javron for dummies thread = 2.04 degrees to be exact and I concur).
I have to do some more tweaking, my right side struts ended up turned in (shortened) about 4 or five more turns than my left side. You can go down a rabbit hole with the digital level. With my fuselage level both longitudinal and lateral the dihedral measures out to .80 of a degree on both sides, yet my string is ⅛ inch off (right side showing higher) 3 inches and 3 ⅛
skywagon8a
MEMBER
SE Mass MA6
...have the front main spar fittings higher (about ¼ inch) which gives us the ⅛ inch block for the washout at the 15th rib instead of the 3/8 inch on the 'stock' cub.
It should make no difference how much twist is used with the front main fittings raised or not. The twist amount should be the same. The whole purpose of the twist (wash out) is to ensure the root stalls before the tip in order to maintain positive aileron control.
Sum Ting Wong. The strut forks should have come out close to matching on both sides as long as you don't have a twisted fuselage and/or different length struts.
It should make no difference how much twist is used with the front main fittings raised or not. The twist amount should be the same. The whole purpose of the twist (wash out) is to ensure the root stalls before the tip in order to maintain positive aileron control.
Scott A
FOUNDER
Park City, UT
Yes, bothers me too so I will do a double check and measure more. I may toss the digital level as far as dihedral and just go with the string.
Also yes, washout would be the same regardless of incidence - Javron washout is about 2.04 of twist, slightly less than the stock (2.5?).
skywagon8a
MEMBER
SE Mass MA6
Remember, Javron is just a kit copy with modifications of a PA-18. Built by many, flown by many but not with any particular flight test analysis. Use the Piper rigging instructions.
cubflier
Registered User
Palmer, AK
The stock/factory washout of a PA18 is also 2 degrees as measured between the but rib and the outer aileron bay.
Jerry
Jerry makes a good point. The 2.5 degree number is called out a lot but it is 2 degree from butt rib to outer aileron bay. I know some that run a flatter wing with very good results and mild stall tendencies. Being experimental I would start at 2 degrees max and adjust for best all around performance stall speed vs stall manners.
DENNY
DENNY
BC12D-4-85
SPONSOR
Fairbanks, AK.
If mine I'd test dihedral/washout flaps up first, then bring them into the flight after I was happy. Watch the ailerons for equal deflection ball centered and wings level. Do some stalls level and in turns while coordinated. Kick a rudder when level and note how it recovers. Add flaps to see if anything changes, as they can affect the CL and drag, and then AOA at stall (lower than outboard) of that wing section.
I prefer rudder over aileron when real slow to pick up a wing.
Gary
I prefer rudder over aileron when real slow to pick up a wing.
Gary
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