Warp in fuselage causing several issues...

[Geowitz]

Hi. Glad you guys are here. Lots of good info. Thanks!

I picked up a IV speedster kit and am up to the step of rigging the wings. Please bear with me as I try to explain this.

My fues is a little warped. I used string lines to find this out when my dihedral wasn't making any sense. The strut carry through tube is shifted about 5/8 inch to the right side of the plane. In other words, the top spar tubes and bottom strut tube are both parallel, but the bottom strut tube is racked to the right side of the plane 5/8 inch. Like a rhombus shape if you are looking at the front of the airplane. Therefore, to get the dihedral the same on each wing I had to move the left set of strut brackets 5/16 inch in and the right set 5/16 inch out making up for the 5/8 inch shift(5/16 + 5/16= 5/8). Dihedral came out at exactly 0.6 degrees on each wing. No problem really for flight, but due to the change in geometry when I fold the wings back the tips are not aligned. I know why this is happening, but I'm not sure if the flaperons will clear the top of the horizontal stab with the wings folded. The trailing edge of the left wing is about 6 inches above the stab and the trailing edge of the right wing is about 4 inches above the stab.

I need to figure this all out before I drill any holes.

How much clearance do I need for the flaperons over the horizontal stab? What are the suggested dihedral settings?

Other thoughts?

Thanks

[SkyPirate]

first ..is the plane covered?

[Geowitz]

No, not covered. I am literally up to the step in the instructions for the wing rigging.

I basically just need to know how much clearance I need at the trailing edge over the horizontal stab for the flaperon to clear. I may need to add more dihedral to get that clearance so I also need to find out typical dihedral.

[SkyPirate]

are you sure you don't want to fix the "tweak" first? then go from there?
it might not take too much to straighten the fuse first,.if it's 5/8" (.625) out ..that's only .3125 or 5/16" you need to tweak it to loose the 2 inch diference when folded,..that little bit you might be able to do without heat

[SkyPirate]

pick a spot in the center of the tail where you can attach a string and have a clear shot to the front lower cross section in line with the front door/ wing posts on the bottom,..mark center on that cross section and draw the string tight,.measure your strut mounts from the string ..each side,.then measure from strut mount to rear wing attach points each side,..if this is equal measurement then the rear wing mount and strut mounts positions are square,..this is a good thing,..means you just have to tweek the section between the wing connect points forward ..top or bottom,..depending on measurement.

[Geowitz]

I'd have to tweak it 5/8 inch by pulling on the bottom of the fuse in one direction and pulling on the top in the opposite direction. All while maintaining lateral stability. Pretty complicated rigging for my resources. I don't think that is a feasable option at this point if my horizontal stab clearance is fine or it can made to be fine with a little more dihedral.

[SkyPirate]

then your out 1.25" ? ..you take the ammount it's out and divide it,..that how much you tweak it,..too bad your not closer ..I'd give you a hand ..it's really not that hard to do ,..a couple heavy duty ratchet straps about 20 minutes of tweaking and your golden ,..

Chase
call me 573 435 6023

[t j]

Geowitz, My Classic 4 fuselage has one strut fitting 1/4 inch ahead of the other. I chased the rigging for several weeks trying to get the wing tips even when folded. I finally used a plumb bob to find the source of the problem.

I trust you have found this Service Letter. http://www.kitfoxaircraft.com/suppor...ters/sl25b.htm When I called Skystar about my wing rigging problem he pointed me to it.

Now to answer your question. When the wing is folded the leading edge of the flaperon hangs down 4 and 7/8ths inches below the trailing edge of the wing. Looks like you need more dihedral.

You also need to check two other places for wing folding clearance. The point where your mass balance weights will be installed. They need to clear the fuselage. Remember they will be hanging straight down as the flaperon will be vertical at this location. Also check the clearance at the flaperon control tube bushing attach tabs on the fuselage. The flaperon will remain horizontal as it swings over this location.

For what its worth. The skew in my fuselage results in 1/2 inch difference in the wing tips when folded. I have standard dihedral that is built into the rigging instructions (not a speedster) and that gives about seven inches from wing trailing edge to trailing edge of horizontal stab.

I spent a lot of time getting the rigging to a nat's eyebrow and it was well worth it. She flys hands off after first flight with just a slight tweek of the horizontal stab leading edge.

[SkyPirate]

not to blow my own horn ,,but I've built 14 planes working on 15th now ( my own design)..loads of race cars ,..worked in the sheet metal and fabrication field for 20 plus years,..was the R&D engineer/welder /fabricator for Jone & Lamson for 3 years,..repaired/rebuilt 100's of wreck cars too ..
certified AWS in every phase of welding

I wouldn't steer you wrong

Chase

[t j]

Geowitz, one more thing I just thought of to put a note in your manual about. Your jury strut installation may need to be tweeked. On one side the front top attach hole ended up more than half way up into the wing fabric. They can be made to fit below the fabric with a longer attach tab and the jury struts slightly off the vertical. That was my solution anyhow and no one has ever noticed the flaw.