Legal Eagle XL in Pennsylvania

[Pilotarix]

Hi,

Thank you for your answer.
That is quite a variation.
And yes, I thought that the dimension would not be very critical, but there is a lot I don't know, so I'd rather ask.

Now I can continue with what I have already started.

[Kamcoman77]

I like your bending forms. Don't know if you bent aluminum tubing before, but you will probably have to move your forms toward each other after your first bends because of springback. I moved my forms a couple of times until the final bends looked OK. Here is a little video of bending tailfeathers.    Also look on YouTube for flyguyeddy. He has several videos about the tail.

[Pilotarix]

Thanks for the link to the video. All good information.

I have not bent aluminum tubing before but a lot of wood. Certainly, that is not the same, but there is spring back as well. I never accounted for it since the wood could be bent to the desired shape during the final installation without introducing too much stress.
It sounds that this is different here. We don't want to introduce stress into the piece by just forcing the tubing ends into the correct location during the final installation.
I have changed my bending blocks a little, so far only on paper. This new shape would allow me to bent the tubing further than necessary to account for spring back.
Not sure if that would work, but I will give it a try.  The lower bending block has to be installed first, and after making that bend is made, the upper bending block can be installed.

I have made some progress with the ribs. Unfortunately, the last one got stuck in the jig and was damaged. Some have used wax or the like to avoid these problems, is there anything specific suited well without interfering with gluing?

[914pete]

Costco sells a Parchment paper that I've been using and have yet to find anything that sticks to it. Even when epoxying the ribs to the spars rather then cover my whole work table I just cut 5"x5" squares and slid them under each joint I was gluing to catch any runs avoiding gluing the ribs/spars to the work table. After drying the glue drips just fall off the paper so it can be re-used over and over. Its transparent enough that I used it to cover my rib jig right over the rib drawing. Like $9 for two huge rolls.

[Pilotarix]

My plan is laminated and this stuff seemed to be pretty slick. Epoxy is not really sticking to it. I have no wooden positioning blocks in glue areas as well, but some small plastic blocks to keep the gussets in place. In hindsight, that was not the smartest idea and I removed almost all of them. It works fine without them. I only kept the Delrin blocks, one is the spacer for the rear spar. Nothing sticks to them. Now it works much better. Just got #6 out of the jig this morning.

No need to speed up the rib production too much because I don't have the wood for the spars.
First, I am undecided in what lengths I should order. The long spar caps are 154" and 12 foot is the maximum length that can be ordered, so I will have at least one scarf joint per spar cap.

Now the question becomes if I should order in 6 foot - 3 pieces per spar cap and two scarf joints oder in 8 foot and 6 foot - 2 pieces per spar cap and one scarf joint.
The advantage of the 6 foot pieces is that they might be easier to get.
The advantage of the 8 and 6 foot pieces is that there is only one scarf joint towards the end.
Thoughts?

Second, I am considering using Okumee plywood. Marine grade, Lloyds certified 1088. It's light and strong but not as rot resistant as Birch plywood. I has been used extensively in aircraft production. It's expensive but I can get this locally and there is not transport cost. Transport cost are astronomic for plywood sheets.
I am considering building a main spar with Doug Fir (quater or rift sawn and clear straight grain) and slightly reduced thickness of the spar caps and 6 mm Okumee plywood. And break it... meaning, test how much load it can withstand.

Not sure yet.   

I have been on the phone with aircraft spruce, they told me that they don't get the amount of wood that they normaly getting and delivery time is dependend on what I order. Long pieces (6 and longer) take longer to source. Up to 4 months, maybe longer.
I could finish the rib production make them nice and shiny and then work on the tail. If that is done and the wood has not arrived I could start on the fuselage. But that opens a whole nother can of worms due to my (none exsisting) welding capabilities. 

[Kamcoman77]

If you go with spruce for the spar caps, I suggest the 3-piece spar cap with two splices (one nearer the tip). A proper splice is as strong as one piece when you put a small ply web over the splice side opposite the main web. Just remember the splices will take almost a foot from each piece you order (overlap), so don't order too short.

[Pilotarix]

… Just remember the splices will take almost a foot from each piece you order (overlap), so don't order too short.

Thanks! I was aware that a scarf joint needs some “space” but I was not really calculating with almost a foot, not sure why…  I will go with 6’. That gives me 18’ with a good amount of room for the scarf joints and screw ups.

[Pilotarix]

Hi all,

Here is the progress since my last post.

Yesterday I made, what is called in the IronDesign plans the K-Block Cover Gusset. Twenty of those are needed, and there is enough information in the plans to transition them quickly into a CAD system. So I did that and then let the laser do the work.



I did 12 wing ribs so far. One a day and on weekend days 2 a day. I thought that I could do 2 every day, but that did not work out.

I am making each wing rib for its dedicated position in the wing. I made the first compression rib for the right-wing and cut the gussets accordingly.


I added some clothespins to the end of the jig to hold down the gussets while the glue dries like described by Kamcoman77. For the very small gussets, they work better than the toggle clamps, and their clamping pressure is enough if T88 glue is used.

We currently see heavy rain that is likely given to us by "Henri" and as bad as it might be it's also a perfect excuse to spend a big part of the day in the shop.

BTW... is there a way to put pictures into the text instead of having them all at the end?

[Pilotarix]

Thanks!

My plan was not to cut the K-Blocks with the laser. For the thin plywood, the laser is OK, but for the 1/4" plywood, it becomes a pain in the behind and a lot of smoke. This is only a toy laser with 15 or so watts. Anyhow, since I could not start bending tubes for an embarrassing reason:  ... I cannot get the sand in the 5/8 tubing ... I made the CAD drawing for the K-Block. That was a little challenging since there were only two measurements, and the rest has almost an organic shape. Then I made a test cut on the laser, 1/4" Birch plywood, not too bad.  I assume that I will make the actual parts on the CNC router.
For the picture, I put the K-block gusset and the K-block on a finished rib just to see if and how it fits.

Also, I may have found another source for aircraft plywood and spruce, but I have to confirm that tomorrow.

[Kamcoman77]

Very nice looking K-block. I cut mine on a bandsaw and they are not nearly as true to shape as yours. I did not put sand in my tubing. I used those cheap, spring type tube protectors to keep the tubing from flattening in the curves. Worked great.

[Pilotarix]

... I did not put sand in my tubing. I used those cheap, spring type tube protectors to keep the tubing from flattening in the curves. ...

I am not sure what exactly brought me to the "sand in the tube" method. I think I did this before with thin stainless steel tubing. Even though I used very dry and fine aquarium sand, the tube clogged up immediately. Anyhow, I have already abandoned this method and ordered the doohickeys you and others have used.

Meanwhile, I continue with my wing rib business. I have made eight "normal" and three "right side compression ribs" so far.  One more than I have to change the setup for the "left side" compression ribs. Four compression ribs on either side if I interpret the plans correctly.

Today I had some spare time and put more of the pieces from the plans into the CAD. This time the nose rib.
With the nose rib, I cut a K-Block on the CNC. The plus of the laser is that you don't have to do any fixation for the pieces to cut. The big downside is you have to sand all the glue faces; otherwise, you may get into severe trouble later.

One big question, I see that you have used - like others - 4130 steel tubing for the leading edge of the vertical stabilizer. The plans don't call for that. At least I have not seen that. Is there a specific reason other than more stability?

[Kamcoman77]

Very nice work! The 4130 leading v-stab edge was recommended by several experienced LE builders/flyers. They said the 6061-T6 LE showed some fluttering/vibrating, but the 4130 is rock solid.

[Pilotarix]

Very nice work! The 4130 leading v-stab edge was recommended by several experienced LE builders/flyers. ...

Thanks, fluttering is definitely not what you want. So I will go with 4130 for the leading edge of the vertical stabilizer as well.

So far, I could manage to make at least one wing rib a day. We will see if I can continue at this pace.
Today I made the first compression wing rib for the left-wing. According to the plan, the 1/4x3/4 wood strips are only glued to one side, the side facing the wing root. That seems to be not so clear in the Iron Design drawings. There it appears that they are on both sides. Anyhow, I will follow the original plans.


I also made the Aileron Stiffener. It took me a while to figure out the shape, only because I didn't realize that one side is not a straight line; it's following the wing profile. 
The "test piece" is done, and the shape is confirmed on the wing rib and the plan. I still don't have the aircraft-grade birch plywood, so I can't make all the pieces, only test pieces.   

Finally, a picture of my glue cup collection. Always when I work with Epoxy, I keep the residual glue at least until the next day to see if it hardens correctly. I realized that if I try to break off the stir stick, the hardened glue puddle breaks before the stir stick. That never happened with thickened WestSystem Epoxy. There, always the stir stick breaks. I checked my mixing ratio, but that is correct, and it is the same in two different batches of glue. Maybe that is just the way it is and today for the first time the stir stick broke before the glue puddle.

[Pilotarix]

Yes, that is exactly what I am using. 10 and 8.3 and there is always a little bit leftover in the cup. It hardens as expected  and I made another test where I broke a joint with cap strips and gussets, the wood seperates but not the glue joint so I think it should be OK.

Tonight the bending doohickey showed up on the front porch and if I don’t have to work all night I may do some tube bending tomorrow.

[Pilotarix]

Nothing new today. Had to work the entire night so wasn't even able to make a wing rib today.

I am still in limbo with ordering the rest of the wood. I thought about other wood types, like Okumee for the spar web and Doug Fir for the spars but that would really involve testing and will take too much time. My goal is still not to monkey around too much, get it done and in the air. Hence I am going with Sitka Spruce and Birch plywood.  The latter, aircraft grade Birch Plywood is not easy to get. All my local suppliers failed on that one and currently it seems that I have to order from Aircraft Spruce and pay the crazy transport cost. However, the transport cost are not the only caveat. I realized that Aircraft spruce only offers 4x4' Birch-Plywood which means that I have to do 2 scarf joints to make the entire length of the spar web.

Is that what most of you have done?
Or ... were you able to get plywood in 4X8' sheets? Is there Birch in 4X8' ? I have not seen that, only 5X5' at best.

I think I have seen pictures where the spar web did not look like it was Birch Plywood and they seem to have only two scarf joints. Could that have been Mahogany Plywood Mil-P-6070?  That is available in 4X8'.