XL-79 progress

[Kamcoman77]

Brock, I put a 1/2" wide bead of VE/flox mix along the inside edge of the top. I made a slightly more liquid mix and put a generous bead along the top edges of the box, and a bead on the inside of the box touching this. I taped the top to the box and turned it upside down. I carefully banged the whole assembly on my workbench letting gravity force the beads together. Then scraped most of the excess off the outside except for what was under the tape (2nd pic). I don't have any photos of the VE/flox beads before assembly but in the 2nd pic you can see how much VE/flox squeezed out. The excess that was under the green tape had to be ground off with a sanding disc.

[Jeff XL79]

Finally got the seat built. Used webbing and large headed rivits.  Each webbing can hold 1500 lbs. Ends where rivit goes through are double and triple layers at the rivit. It's very comfortable and I don't think it'll give me the dreaded waffle butt. 

Jeff

[Jeff XL79]

I'm working on the control stick. My aluminum piece is 1" .058 wall. My steel 1" 1/8 .035 is very sloppy over the aluminum.  I'd really like to shim it up so I'm not just hanging on by rivits only. A nice snug fit would be stronger and safer. What's your thoughts eaglers?
I'm trying to avoid paying Aircraft spruce shipping for another piece of 4130 that would fit better. I've got some nice shim material but wanted to find out if anyone else has this concern. 

Thanks 

Jeff

[Brock]

I don't have the plans in front of me nor have I yet looked into this but.  Is the 4130 tube the control stick that goes over the aluminum at the pivot?  If so, can you split the tube a few inches lengthwise with a relief hole in the end then bolt through so as to make it clamp the aluminum.

[Chuck in Indiana]

(scratching head)There's no steel tubing on the control stick?

[pappyadkins]

I'm assuming you're talking about the tube that makes up the pivot on both ends... If so, the front one you'l take a slice out of it anyways for the pulley... the rear one, you'll be welding on the control horn as well - after you weld the arm on, see how it slides on... you could always split it and re-weled it if you had to... I welded a sleeve on top for a guide (you can check it out in the video @ about 4:25); but it slid on just right with no issues...

[Jeff XL79]

Thanks Pappyadkins, that was what I was asking about. I should have called out the specific part of the assembly. I'm going to call it the aileron torque tube assembly.  I like the idea to split and weld the steel sleeves.  I'll just use some scrap 1" 4130 to slip inside the 1 1/8" to ensure diameter and also to heat sink it. It should TIG up nice.


Jeff

[Jeff XL79]

I've been trying to come up with a solution for a center mount fuel tank.  So far everything that has made it to mock up looks like crap. With the tank humped up to give  enough volume the resulting look is really bad. I think it would be a drag inducing shape with a case of the uglies. The only other option that would make it possible would be to add width to the wing mounts. That in turn adds weight and requires adding width to the struts,  cables, center cover plus mount supports.
I really don't want to widen the wing mount. It stretches the mount out in a way I don't like.  This mod is abandoned. 
I'll be figuring out the next steps for a wing tank. I don't like it and may still opt for the cowl but the center tank is out.

The wing location will require some additional structural additions also in order to carry 30 odd pounds.  I'm leaning toward beefing up the second rib in to be like the root. Adding .8mm ply around the bay and thin aluminum angle around the base for support. I can stiffen the divinycell sides and bottom with thin carbon sheet. 

I gotta say, the fuel tank has been a challenge to get from the plan to reality in a good way. Plenty of people have done it well but it's going to be custom regardless.

[Brock]

I saw, a while back, a picture of an ultralight with small pontoon looking tanks mounted one on each strut sets.

[Jeff XL79]

Rudder pedals are done. Just used a strap of .090 4130 for some extra contact area. Home Depot aviation springs also seen on screen doors. Cable guides and turnbuckles to the rudder also complete.

[Jeff XL79]

Control stick done. Just need castle nuts for the pivots.

[pappyadkins]

looking good...

[kalazzerx]

I thought about the center mount fuel tank myself but in the end I did not do it and glad I did not try.  The main issue for me not doing a center mount fuel tank is access to the wing pins!  I have a trailer setup and I mount and dismount the wings every time I go flying (no hanger near me).  I have issue getting the pins in when I have 4 or 5 inches of room between the wings - I would hate to deal with something that had less and no access but from the bottom or something like that.  I think the best approach is just to build the CE that has room for tank.  I actually find the weight in one tank in the wing is just not an issue, I cannot feel the wait on the tank side when I am flying and I find it is easy enough to drain the tank after a flight.  I use a quick connect fuel connector between the tank and the fuselage line going down to the engine.  The quick connect I use seals the lines when disconnected, I then connect a drain hose that drops down to one of my fuel cans. By the time I take off the non-tank wing the fuel has all drained and I can then take that wing off.  BTW, my trailer is all rigged up to move the wings in and out so easy one man operation - something like what Les does.

Awesome job on the fuel tank!!

[Jon Miller]

Nice work Jeff!  I have to ask though, am I the only one stressed out at not having dimensions on what would seem to be important stuff like control stick bolt hole locations?  I'm ok with "close enough" on kitchen cabinets, etc, but for something that will fly I find this less than ideal.   Maybe I should seek counseling or something......

[pappyadkins]

Jon, I split the distance from the seat front to the pulley... 4" each way & I have plenty of movement for the elevator...