Eagler's Nest
General Category => Builders logs => Brock's bits - LEXLV3 => Topic started by: Brock on August 05, 2024, 02:12:05 PM
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Build Table - check!
Mount Theo's fuselage bottom and level. - check!
Decide on firewall - whoa, stop and scratch head for a bit then ask other's opinions.
What do you think.... here are some things I've read on the firewall.
-shorten a few inches to allow W&B for the Verner 3V(LA).
-instead of mounting 13.5"W x 11.5"T (landscape) consider 11.5"W x 13.5"T (portrait).
-mount the Verner 3" high of center for prop clearance.
With all this and measuring my feet/shoes my thoughts are to just make the firewall 13.5" x 13.5". This would help in raising the engine mount point and not cramp (horizontally) my feet. Your thoughts?
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I don't see why not if you are going to build a different station 1 anyway.
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It's been years since I dusted off my TIG welder and struck a bead. A few days ago I came to the conclusion that I couldn't put it off any longer and eventually I'd have to melt some filler. So I did just that on some scrap material. The result was appauling and discouraging. You can see the initial results below. Not to be beaten I sent a few txt messages to a local pro welder (recently retired) and he invited me over to run a few beads with his supervision. WOW, I am so greatful for those 45 minutes. By the time I left my welds were looking awsome. I'll weld up the other side of this picture after I change out some hardware and practice some on my equipement.
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Uh, yeah. That tungsten is seriously contaminated. :grin: I like the clear cup.
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This is an update to the picture posted above. I've been practicing and taking advice from a welding mentor. Today I finally stopped practicing and decided to melt metal on the airframe. Finished up station-1 firewall frame. Not the prettiest welds but not ugly either. Baby steps. This was done with a setting of 35 amps using 1/16 filler on the inside of the bend and .035 filler on the outside.
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It won't come apart. :) In the future, a little more filler on the outside where the base metal goes away and/or a little less heat would be just the ticket. Nice job. As you have already found out, "it ain't easy." :)
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Station 2 is finally tacked in. Only took two tries. You know the addage "mesure twice cut once" well after welding the to sides to the the top (on the welding table) I went about to cut the sides to their proper length. I measued each side about three times then cut them off nice and equal - uh so I thought. I measured after and not only were they different by a 1/2" but they were both short. Called it quits for the day and returned the next and did it correctly with little effort.
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Progress has been slow but steady. Spent the day puzzling over the top tube which gets suspended in outer space. As you can see I did finally get it in place but not without some questions.
The plans call for that tube to be 29". But it isn't clear if that 29" is from end to end or if I really should make it 29" from the center of the welded tubes comming from the instrument panel. In that case the tubes should be cut long (I did add 1/4" on each end but that might not be enough. Can someone fill in some lack in my understanding of this?
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I'm away from my plans & plane right now, but I believe the 29" is the center to center if I remember correctly everything on that page should be center to center (the width of your wing mounts/spars is approx 29"; therefore, NOT the length of the upper tube (It extends forward if I remember correctly or maybe that was something I added for folding the wings) - but point to point is the answer for the measurements for sure... I hope this makes sense... You'll have the square crosstube (wing mounting tube) with flat metal plates coming down to the frame members that should be the same distance as your wing mounts (i've attached a screenshot from my video)... Anyways I believe this measurement, 29 inches needs to be the same as your wing spar; so if your spars are 28.75 then these need to be the same... Hope this helps - I just realized I didn't cover that in my video (note to self, may need to add this to future video)....
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I see you have changed the lower dimension to the firewall. You'll need to change the upper dimension the same amount or you will be moving the wing aft. This will negate the CG change you are aiming for. Moving the wing has considerably more effect than moving the engine on CG. Yes, from memory ::) the dimensions shown are from center to center. I built the wings first so knew the exact distance between the spars and made that happen. You will just have to make sure that when you build the rib jig the spar distance is the same as your fuselage fittings.
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Edit: Chuck, I just reread your msg. I kept the firewall vertical and so didn't (need to) give a thought as to shortening the upper distance location. Pay no attention to markings on the diagram above as they are not all representative scribbles.
The firewall was made taller (13.5 X 13.5 instead of 13.5 X 11.5). Then it was moved Aft by 2" but the angle of the floor remained the same. Thus the firewall moved down slightly as well as up.
CG: I've been making all dimensions referencing station #2 at the floor. Thus, no, the wing did not move. At least I don't know how it could.
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Today I tacked the cluster where the top seat tube and wing rear tubes meet. Took some thinking to decide how I was going to do it but seems I should have thought about it much more. Now I have an open tube that needs to be finished off. Any suggestions how to finish this. There still are two more tubes that go here (seat back and reaward brace).
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In Solidworks the open ends of tubes are covered up with a thing called an end cap. Make a disk about the same diameter as the tube, out of whatever thin stock you want to use and weld it over the end of the tube.
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Thanks Ifly. Yes, end caps were how I had planned on dealing with these. No doubt some folks here have come up with more elegant ways of dealing with these particular clusters.
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Here is a photo of a nicely made XL fuselage.
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These bits and pieces of tubing are all starting to look like something organized. Looking forward to cleaning off the bench and unclamping to set this bird free.
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Tacking up the first flat-cluster made me feel good, like hey I can do this. But then there was what I call the 3D-clusters. The first one was a dismal failure (though I claim part of it was due to another project already started). Nice thing about failures, we learn more from them than we do from the easy successes. I've some ideas already to see if this cluster can be salvaged. Well finally, after all the clusters have been done, I know how to make them come out the way they need to be.
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Nice work..(looking for that thumbs up emoji again..) :)
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Today I declared this frame fully tacked. Just after this pic was taken I had the joy of unbolting it from the table. Now to get serious about welding.
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(https://img.freepik.com/premium-psd/thumbs-up-emoticon-face-isolated-transparent-background_220739-157785.jpg?w=740)
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Attaboy. :)
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Welding every little cluster (big ones too) is taking longer than I had figured. Clusters can be tricky like this one with eight tubes! One important lesson, it takes less time to carefully cut and cope the tubes to fit tight than it does to weld up large gaps that should not be there. I'm not proud about this welded cluster as far as quality and beauty of weld but I am quite satisfied that it is done and looks like it's not going to fail. Might touch it up a bit.
So, the progress has been, cut-cope-tack-weldsome-weldSomeMore-weldAgain(to fix missed spots). I've not yet done the last 'weldAgain' part. Skill keep growing.
Question: almost every day I have a puddle "JUMP" up to the tig electrode. At first I thought i was just dipping in the puddle but now I'm certain the puddle is jumping to the electrode. Whats up with that and how do I stop it?
Trial fit. Like a new pair of jeans that need to be checked for fit, today I decided to try-on this airframe. Looks like I'll need a shorter stool.
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Prolly something causing an unstable arc...
May have a plugged gas lens or leak in shielding gas hose. May have contaminated tungsten. May have bad ground. May have regulator turned up too high...
Is the tungsten tight in the collet?
Might try the ground clamp closer to the joint you are welding...
Could always sell the tig rig and get oxy-acet. :emoji_u1f635:
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Yeah, that is the toughest cluster on the airplane. I'm guessing, and only guessing is that you are adding filler too close to the electrode. It should be in the first third of the puddle, but I'll bet you have figured that out. :) I *may* have mentioned before that learning TIG is a steep hill to climb. ;) Welding clusters adds a degree of difficulty.
Nice job.. that's not coming apart.
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Yes Chuck that's the big one. The underside of that cluster is pictured about 6 posts earlier (left side). So you can see with the gaps it was a real challange and I had to go over the weld several times. The good news is that I'm getting good at fixing blow holes and gaps. My welds are big as I'm using 3/32 filler. Haven't yet felt comfortable with the smaller filler. Everything is a compromose, especally when learning.
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My welds are big as I'm using 3/32 filler.
"Maybe" that large filler rod increases the size of the puddle as you dip it to cause a Q tip. (?) The largest I've ever used is 1/16".
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Today I picked up a Harbor-Freight "tube roller" and installed a set of 5/8" roller dies from "swagoffroad.com". Not sure how much use this will get in the future but it's always fun to have a new tool to work with and increase possibilities.
So next was to figure out what diameter to use for the seat tube bend. Thanks to Chuck's post (https://www.eaglersnest.com/forum/index.php?topic=2197.msg13491#msg13491) I've a starting radius of 34.75". But, at 21" my XL is a bit narrower than plans 24". I'm thinking it might be more comfortable to use a slightly tighter bend.
Does anyone have comments on changing the bend for the seat back based on the narrower airframe?
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Probably the most ergonomical way to shape the seatback tube is to stretch a heavy cord across the seatback area. Lean back against the cord and have a helper pull it to varying degrees of tautness. When the curve feels just right, take a photo or measure the amount of curve. Bend your tube to match. At least, that's the way Forest Gump would have done it.
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Man.. I wish I had that tube roller. I gave up trying to make a round engine mount for the Verner. Now, I have to make a bigger heavier one for the 90 Lambert I'm going to use on the Pietenpol project.
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Chuck you are welcome to come over (from IN to WA) and use this bender. It's much simpler to use than I expected. Bending the seatback 5/8" tube took about 5 minutes. I wiped the roller dies and tube with WD40 slid it in and ran it back and forth. Not even a scratch on the tubing just a nice smooth bend.
So Today I installed the last major tube and hope to start on the landing-gear/strut brackets.
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There must be some technical term for the short pieces of filler rod that become shorter than a welder cares to use/hold. I'm call'n them Filler Nubs. Anyone have a better term? The reason I'm thinking of Nubs is that I've got a small collection of them which means I've been be getting some welding done ;-)
Today I finished off the landing gear brackets. These brackets were a learning opportunity. They get mounted on each side of a 5/8ths inch tube but are specked to be 3/4" appart. The solution is to statigically bend them which takes expirence which takes practice. So now that I've practiced I'll be ready for the next build, no going back on this one.
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When you build your next one :) you can keep from bending by making a bracket that doubles as a seat belt mount.
(https://static.imgzeit.com/large/2726b6340d2dce95/IMG_20210417_161348836.jpg)
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Can anyone tell me why these 3/8 bushingings are welded to the side, of the 4" Stabilizer Connectors, and not through the center like their counter parts on the fuslage?
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I just figured it was because the horizontal stab connector tube thru-bolts had no need to be centered on the axis of the tubes, and welding them to the side was easier than drilling and welding in the center. Although, truth be told, for the application I doubt that either really must be centered. The distance the attaching bolts would be off center if the bushings were welded to the side of the fuselage tube is likely negligible. (I compare the rigid attachment set up to the trim jack screw assembly used by the Piper rag wings. In that case it was way easier to offset the jack screw assembly reference the connector tube) But that's just me......
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Just a little heads up for anyone who hasn't made the connectors. Use 7/8" x 0.058" for the H. Stab TE and 3/4" x 0.058" for the LE instead of 0.062". Your 3/4" H.stab TE & 5/8" LE will slide right in (no reaming). Also use 0.058" wall for your elevator horn tubing unless you are making a folding tail.
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A little progress. Today I finished the stabilizer connecting tubes as well as the mount point on the fuselage. Learnt a few things along the way. First ah-ha was don't drill the connecting tubes through the stabs until they are mounted on the airframe. Reason is that mounting them on the airframe first makes sure the bolts will just slide right in. I was close enough but had to drill through to releave a bit of alignment. Second, the length of the airframe 3/8x1/4 bushings is shown as 1.5" but it does not show how much to leave on top or bottom. After some figuring it looks like having the minimum (or less) so that elevator travel will not contact the frame. Making the bushings short will allow them to be adjusted with aluminum washers (lighter than 4130) and ensure the shortest possible bolt (again weight).
All in all I'm quite happy with the results. Sighting down from the firewall to the tail reveals a very straight verticle and level horizontal (off maybee 0.4 deg Measured with a calibrated eyeball). It could have turned out much worse. You can see in the first pic that I drilled the connector tube through for the bushing, then after welding I milled them down to the weld. Just now, I can see why one would want to weld the bushing on the side. It makes for a lower profile mount as the weld is on the side of the bushing and not on the end. Oh-well, I'll likely cut down the bushings in the fuse anyway for minimum stand off from the frame.
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You can easily square up the tail with the brace wires, FWIW, I made the tabs out of 4130. Nice shop, and nice job. Attaboy.. :)
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Today was spent cutting and drilling elevator hinges. Most of the time spent went into thinking and head scratching.
Question: Does the Aluminum need to be treated before mounting the 4130 hinges? Along the same lines, does the Aluminum need treating before fabric?
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Aluminum tubes need cleaning with alcohol or acetone before hinges or fabric. I guess you could give them a light scuffing with red Scotchbrite pad if they look extra dirty. I used JB-weld under my hinges for a little extra security, even though I used full circle hinges installed during empennage build.
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Yesterday I managed to mount the last hinge. Welded a 3/8 x 3/16" x 1/2" tube to station 5. A bit tricky to weld as it needed a bit of space from the rudder tube. Needs some clean up but seems it will be solid enough. The excess JB-weld covers old rivet holes as the tail feathers I received had the gussests extended to meet each other not leaving room for the hinges.
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Aluminum tubes need cleaning with alcohol... full circle hinges installed during empennage build.
I see you used 3 sets of hinges instead of the plans two on your vertical fin. So then you would use four sets on your rudder eh? Would you do it that way again?
Flu-Flu has just two sets of half-hinges on the vertical and one tripple on the rudder/station-5
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I used three sets of hinges on all my empennage, except the rudder. I did use four on the rudder.
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Seems I've been away from this project for months. Today I finally got back to work. Actually part of the delay was analysis paralysis. Since I used such a large axle (20mm) I started with a 7/8ths inch tube with the center drilled out to 5/8ths inch. I was looking for cleaner solution, though possibly heavier. The axle is all one peice and strong enought to never need replacing. You can see a slightly different manner of welding on the tabs, just seems slightly cleaner. The tabs are .090" which I had extra of.