Jury struts

Wow much progress.

The new bi-metal, 14tpi band-saw blade arrived.  Makes a huge difference.  Why didn't I invest in a band-saw before?  Cuts straight, fast, and the teeth marks less ragged than the old blade.  It probably also helps that I spent twenty minutes aligning the blade and making sure the line guides weren't too loose.  Now the saw doesn't make tick-tick-tick noises.

So I cut a whole bunch of flat parts one weeknight.

Ten 3/16" quick pins in one evening, oh my.  That was more 3/16" long bolts than I had for the pins, so I had to stop at eight.  I think there are just four more pins to go after these eight.  Really knocking them out.

This weekend has been a jury strut weekend.  First, I put in the sleeves to the forward and aft struts.  Boy are those ever fun.  I measured a dozen times where exactly the sleeve should go (a little different since I added a few inches to the span), and made a circumferential mark around the strut.  Then, I used a straight-edge to find what level is for between the fwd and aft struts.  From here, I drilled one of the two 3/16" holes and made a point to deburr inside of the hole.  Now we're set up. 

Taking the sleeve, I drew a center-line on it.  This piece I slid into the tip-end of the strut and pushed it down slowly with a measured push-stick.  Push until the sleeve centerline arrives at the pre-drilled strut hole. 

Center-punch and drill the sleeve through the strut hole.  Drop in a bolt to maintain alignment, and drill the opposite side of the strut through bolt the strut and the sleeve.  Push the bolt all the way through and call it done.

Now that the jury strut eye-bolts are in-place, I can start the jury struts. 

And I did!

First was to put the plate that spans the fwd and aft tubes.  This should make handling my strut assemblies so much easier!  Feels better too.  Weird to start crimping tubes again after doing all the cable work recently.  And I did a bit of work too on the forward and aft jury struts.  Here they are on the left wing with Clecos holding one end in place.

The string you see will hold the alignment for drilling the diagonal member.  I didn't happen to make the forward jury strut quite long enough for the diagonal-member to attach to it, so I'll have to look at options for that later. 

That's it for this update.  Busy for the next few weekends, so may not be a whole lot of progress for a bit.  Have a whole bunch of wing secondary structure brackets and ribs to make eventually, so might start on that in the evenings.  We'll see.

Bandsaw

Few good steps forward this weekend.

Bought a used bandsaw ... finally.  It is a reasonably new Craftsman 10" with a rusted deck.  After some steel wool and fluid, it's looking pretty good.  Ordered a bi-metal blade more appropriate for cutting the aluminum brackets, and I'm up & running.  Thanks Duane!

First part cut was a set of new 3/16" quick-pins.  I was already done with the 1/4" pins, now I'm up to four 3/16" pins.  Think there are 6 more to go total.  Now with the saw, I should knock those all out in an hour.

Final swaging on four internal wing cables ... Trent (who helped with the FEA) came over and we did some measuring to try resolving my uneven wing twist.  We realized the wing internal truss bracing was slipping during the setup and allowing the wing to both parallelogram and twist (explaining the extreme washout last time I assembled it).  So we took everything back apart and carefully jigged & measured the squareness of the left wing alone.  Finally, we very carefully final swaged the first and second truss cables and remeasured everything again.  Perfect under a 1/16th inch.  This sets up the rest of the alignment process.

I also jigged up the right wing to do final swaging before realizing that I am out of thimbles.  Darn.  I borrowed enough from the aft sweep cables to start the left wing, but will have to order more.  Bummer considering I just put in and received an order from Spruce.  Should really go through again and find what more stuff I need.

Reassembly with the newly final-swaged wing cables makes the alignment much more positive.  While there is still some jiggling needed for pinning the struts right now, it's so much more solid once assembled that my confidence level is soaring.  This is going to work great!

Cables and tensioning connectors

Columbus Day was mid 70's and super sunny.  And my wife had work, so I was home alone and took the chance to work on Goat all day :-)

I set Goat up outside the front of the garage rather than the back yard so I had better access to my tools.  The tire was leaky (around the stem, no way to patch that one), so removing this also let Goat sit level rather than roll back & sit on a wing tip.  Convenient!  And Aircraft Spruce got another $11 from me, doh.

The main idea for today was to replace all the string with cables, working through them one at a time.  I started with the sweep cables, which first meant adjusting all the internal wing bracing to get the leading edge straight.  Then, cut cables and swage one end.  I also needed the non-tensioning connectors for the leading edge tube ... found something pretty close in my leftover parts bin for a temporary part (shown in picture).

I now realize I need to make a whole bunch of 3/16" quick pins, which means cutting a whole bunch of 1/2" wide brackets.  Need additional tools...

Next I decided to tackle the strut, cabane, and nose section attachment point.  This has been a sticking point since I decided to switch from cable-braced to strut-braced configuration.  The old temporary cabane attachment with the single tongue kept falling off the back of the quick-pin, even with the rubber loops.  I did previously put in the AN-42B eye bolt into the strut attachment as per G3 drawings, so switching to that was the logical choice I guess.  I tried to match things up as best I could, cutting off the lower hole from the cabane, and effectively lengthened the cabane about 1/4" in the end.  The new attachment, being in double-shear and capturing an eye bolt, feels way more solid.  I still need to shorten the aft cabane strut.


Here is a shot of mid-way through the modification process.  The lower hole shown was the previous upper hole, resulting from cutting 1" off the tube.  The forward attachment bracket is inside the cabane.  I need to match drill the second bracket, and match drill these for a new upper cabane hole.  Then I'll have to shorten the rear cabane strut.  The other end will be easier to shorten since it is round.



So here's the cabane to strut to nose section carry-through as I left it tonight.  Muuuch better. 

I realized the plans call for a castle nut and cotter pin for the cabane to strut attach, but this is better assembled using a 3/16" quick pin.

I have seen some modifications to the quick-pins by others on the internet.  I'm going to reserve judgement until I finish more.  Perhaps a reusable cotter pin.

Now I'm just going to post some random photos without descriptions, just because I think you might like pictures.

Mid 70's in August?

The weather this weekend is too nice for me not to put some time working on Goat.  And it's only Saturday!

I was working earlier this week on making some brackets for the jury struts the other night, but then I realized I drilled them at 3/16" instead of for rivets, so that was frustrating and I quit for several days.  Throwing away parts sucks.

But today is another day.  Doing some swaging, the left wing now has four steel internal bracing wires.  They're still temporary on one end, but it's nice to feel it getting stiffer already.  These lengths set the wing as a rectangle rather than a parallelogram.  Working on the right wing is the current task.

A little rearranging in the shop & garage helped also.  Now the drill press and belt sander are in the garage for much easier access.  I'm seriously considering buying a Grizzly brand band saw (now that I'm well over half-way) for making the aluminum bracket work go faster.

Speaking of bracket work, here is a before and after shot of the trailing edge strut upper attach bracket.  The completed one just needs final 3/16" holes drilled, but will be used to help match-drill the new one, which is still just a sharpie outline on a piece of flat stock.  A dozen minutes with a hacksaw to cut the rectangle, belt sander to round the corners, file to chamfer the edges, two clamps to hold the new part to the existing one, Dremel with a 1/16" bit to make the match drilled holes, cordless drill with a 3/16" bit to make the thru holes, and a deburring tool for these new holes to complete the part.  Simple, eh?

As a point perhaps of interest, here's a picture of all the bolts remaining to go into Goat.  It's several pounds of fasteners.  Some are AN42B eye bolts, lots of general AN bolts, both drilled and undrilled, nuts, washers, and the stainless cable hardware.  Boltalicious :-)

I did do a test assembly in the back yard today, but forgot to take pictures.  Really feels good to see it coming together again.  Visible progress is awesome.

Some more strut work

On an extremely rainy morning, I cleaned up the shop and did a little work on Goat, for a change.  The as-drawn trailing-edge strut upper attach brackets I found were too short to allow an interference-free fit of the TE tube and the strut.  An easy remedy was to remake these brackets with the same length spacing as the LE brackets.  Easy enough, but I guess I lost momentum when I found this a month or more ago.  A little hack-saw work this morning and cleanup on the belt sander, and out popped three (still one to go) shiny new parts.  Working on the most accessible wing turned out to be the left panel and that one is now installed.  I do think in all the hole marking with regards to strut length, there is a wee twist in how the bolt holes and double-shear brackets line up.  Not sure if it's anything to be concerned about, but that's why I'll have a local A&P over before getting too much further.

Finally, I started looking harder at cables.  I put in a single cable and have paused to think about it.  I should really take this end into work and get a thumbs up or down just to feel better about the work.  There is a lot riding on each of the Swagelock crimps and I'm just not familiar enough with them yet to have full confidence.  Once confidence is up though, there are a solid dozen cables to make up that will really make a huge difference in the feel of the setup of this Goat.  Obviously the photo to the right is of the temporary setup with a cable clamp.

(this post is for you Walt)

Struts delight!

A big day for Goat, getting through cutting the aft struts to length.  It took several hours for me to sort out why my measurements were still coming out with about 2" of asymmetry.  Everything seemed to check out and yet the right strut measurement kept coming out as 2" longer than the left strut needed.  I was aiming for no washout, given that this is a rectangular wing and will stall kindly anyway.  Adjusting every which string tension didn't seem to do it.

Then it hit me: the wing was a parallelogram.  A quick measurement confirmed that, two inches out of square. Loosen all the internal drag bracing, pick one to tighten, and viola now the struts matched up.  Took off 6.5" exactly from each aft strut and that was about as close to no washout as I could set it.

Only took five hours to make two cuts and drill two holes.  And that doesn't include last weekend's setup.

While I had everything out and assembled, I finally match-drilled several of the 3/16" holes out to their full 1/4" hole size.  The LE and TE center wing joints and the strut attach to the nose section.

Now I'll make motions toward cleanup of the assemblies and also make steps toward jury struts!  Solid progress.

Aft struts

Here's the pictures...

Forward struts with their attachment brackets. I cleaned everything up and put the second bolt through the strut today, which I didn't have ready to go last night.  Even still, it felt so much more solid than using string to tie everything together.

Note that normal AN42B bolts do not fit a 3/4" diameter bracket like are drawn in G3W13.  Instead, you have to file down to a smaller radius to get it to fit.

It might be a little boring unless you really like aircraft construction, but here's an evening's timelapse on what it took to cut the tubes to length and drill two holes (since I drilled the other pair tonight):

Fwd struts cut to length

Sorry no pictures, but the front struts are now cut to length.  After several hours of setup in the back yard, I was pretty sure everything was as aligned as I could get it and so I cut 6" off each of the forward struts.  Aligning to get a good set of through holes, drilled just the outer of the pair.  Now I can put the front struts on without needing the kingpost.  Honestly, there may be a little forward sweep built in and I'm not immediately sure how to get rid of that.  I aimed for 1.5deg of dihedral angle; Goat 4 lists 1deg, but that didn't look like any; Goat 3 lists 3deg, which looked like a lot, so I picked 1.5deg.  Yeah real scientific.  Pretty sure everything is going to shift as these strut attach points firm up.

May get to the aft struts tomorrow.  Excited to get rid of the kingpost and most of the cables.

Outer strut attach

A bit more Goat work on a muggy Sunday instead of fixing a hand-launch glider recovered from the trees on Saturday.  Word to the wise: your battery will always die on a 1000 point round.  Boo.  But everyone was quite encouraging having recently seen pics of Goat!

There is a pair of brackets for each of the four strut attach points, and each of these pairs gets a quick-pin and captures an AN42B eye-bolt to transfer load to the wing tubes.  Not sure if this was really the intent of the eye-bolt... the load test should prove this system out.

Maybe this week I'll have the chance to jig up the wing, trim the struts to length, and mount those new brackets to make it a whole lot less wobbly.

Aft strut attach

A little effort on the aft strut attachments...

Drilled the attach points in the forward strut (I'm out of AN3-16's now, so had to put in a bolt order).  Also I put the sleeve into the aft strut and put in six rivets per the drawings.  Then with some filing, the aft strut can bolt in the correct location with just enough clearance to not rub.

I also did the other side, but again with the running out of bolts, it's not put together.

Here is the strut attach point on the fuselage.  I do have the AN42B-16A installed per Goat-3 here.  Still looking at options for the cabane attachment, so this counts.

Yup.  Every bolt/hole/fitting is one step closer.

Forward strut attachments

Today was very productive!  I started with the right forward strut attachments, completing the bend and the through-hole on the aft plate.  Then I slid everything half-outside the garage and worked on the left to get it up to the same spot.

As with all the 1/4" attach points, I keep them as 3/16" holes until everything is held in place together and can be match-drilled to the full 1/4" diameter.  This might be overkill since it needs to be a sloppy 1/4" for a slip-fit pin insertion, but it feels better to do it this way.  The final match-drill is so much more satisfying knowing there is no slop.

The Goat 1, 2, and 3 all use an AN42b eye-bolt for the cabane attachment to the strut.  Since my cabanes were already built, they were too long to do this without remaking the aft cabane tube.  Instead, I'm trying to redesign the junction.

This is the right strut attach point with a first look at the new cabane attachment.  It's not exactly done yet.  For starters, the connection is just a tab that the strut pin goes through, which could slip off the end of the quick-pin if the bungees broke.  Much better to have two tabs so the pin has to fall out all on its own.  I'm still thinking...

Here is the tab on the cabane.  Like I said, I'm not totally sold on this alone.  I'm thinking about a bent tab similar to the Goat-1 compression ribs (G1W13) using the two obvious bolts.  Then again, I might space apart the two tabs on the struts and slide this next to the fuselage carry-through tube to be inside the strut tabs and therefore captured.  We'll see.

I did shorten the main cabane tube by about a half-inch.  That was a definite committal moment.  But you know, reworking this joint is maybe a good way to show how forgiving the "boltalicious" Goat construction is.  Need to make a change after it's all built?  Just unbolt, make a new whatever, and bolt it back in.  Pretty awesome.  No welding or re-riveting needed.

One consequence of attaching the cabanes along with the strut quick-pin is they are pinched in closer to the center-line than on the original Goat designs.  This means the cabanes pinch and interfere with the seat-back, which is now too wide.  I could lean the seat forward a bit (which is what I did for now), or narrow the upper seat tube.

Finally, here is how I spent most of the day, with Goat hanging half-way in the garage and half-way out.  The forward struts are simply taped on the leading edge as a mock-up, but it was enough to make some measurements and sort out the lengths needed for setting the dihedral angle.

Oh also, the forward sweep cables really do make a big difference in holding the leading edge in place ... right at head-height in this orientation :-)

Starting the struts

Had to make a few additional brackets for attaching the wing struts.  Break out the measuring tools, hacksaw, file, and clamps plus some elbow-grease for good measure.

I wanted to start with the forward strut at the fuselage first so I could jig the whole thing outside and measure the exact correct length for the strut.  And I also wanted to cut two of everything to take care of both left and right at the same time. 

But first, I need to sort out converting the Goat-4 carry-though to a Goat-3 style.  For the strut attach points themselves, I'm planning to follow the Goat-3 drawings.  It's a change to the cabanes too... that's the fun one. I'm not sure what I'm going to do for that one yet.

Beautiful spring day for a Goat

I'm sitting outside on the porch looking over an amazing sight: the first time Dan's Goat has been assembled with the wings on.

Now I started down the path of a cable-braced wing and will be switching to using wing struts, so use your imagination to remove many of the temporary lines.  However, this is the first time I have the big-picture view of sitting in the pilot's seat and looking down the length of the wings above me.  Such a cool sight.

During assembly, there were a few lessons learned already.  Handling the wings is a challenge at this stage, with a lot of flexing and wobbling to move them into position.  I know with covering on they'll get more torsionally rigid, so there's no cause for concern, just noting an 18ft by 4ft panel is big to move around.  The LE and TE pins aren't too tough to align and install.

Next is the fuselage attachment.  This involves awkwardly standing the fuselage on the tail, pinning the LE tube, then moving the fuse into place for pinning the cabanes.  Now on the strutted version this will be different, but no doubt it's going to be a magic step.  I also definitely need a piece of carpet or something to toss on the ground and keep the tip of the fuselage from poking into the dirt.

Rotating the fuselage and wings up is going to be a lot easier with rigid struts.  Using some 150lb test cord I had laying around, I rigged up the kingpost and flying wires.  It definitely took pulling a lot more tension in the upper lines than I initially thought to keep the wing with positive dihedral.  There is a lot of stretch in my thin lines.  But once the wing and fuselage are triangulated together, they rotate up as a unit just fine by pulling on the nose to rotate everything up onto the wheel.

Since it's so nice outside, I had to attach the tail as well.  This too is a little awkward as the fuselage attach point is leaned a little so the vertical tail assembly needs to be rotated as well.  Attach the lower pin first, then the upper pin, not too tough.  The horizontal stabilizer is a piece of cake from there.  Then connecting all the control cables is quick and painless.  Viola, Goat!

What else can I say?  It's coming together.  This feels like I've crossed the half-way point.  Structurally, I have the struts, their respective attach points, and the jury struts remaining.  Then it's all secondary structure for the wing: lots of ribs, wing tips, control surfaces, hinging, control rigging, and d-tube sheeting.

Oh I also weighed the current structure while assembled: 62.8 + 6.8 + 17.2 = 86.8lb  This doesn't represent any particular reference state, but does give me a warm-fuzzy that there is 60-something pounds to stay in the Part 104 glider class.  The struts aren't light and there is a lot of aluminum in the ribs and control surfaces to go.  Then covering / paint.  Fingers crossed guys.

Getting back into it?

So I finally finished off the kitchen renovation project, which entailed dismantling the old kitchen down to the studs, removing a wall, and moving all the appliances, not to mention new tile floors, new cabinets, new countertop, and new backsplash.  It's been a busy year.  And that only compliments the other house projects that have been keeping me busy. 

Yeah...

The funny thing about putting this project down for months is that I don't remember where I stopped.  Even with all the photos and descriptions here, it's a bit of a mystery what my next few moves were supposed to be.  The left wing panel was further along, so I finished match-drilling holes for the two ribs and riveted in the two compression ribs.  While in the area, I also bolted in several tangs and used rope tied with a bailing knot to pull taught the internal bracing.  This did add some triangulation for support, but it's still pretty flopp
y and will be so until the struts hold the spars in place.

This reminds me where I stopped.  Getting the right wing up to this same point should be routine now that I have the left wing assembled.  But the next big question is how to attach the struts and, importantly, how to align the spars & fuselage to cut the struts to length.  I started making a GOAT-4, but liked the looks and improved aerodynamics of the strutted GOAT-3.  This leaves the strut attach point half-way between the two currently.  The cabanes attach to the fuselage carry-through and there is nowhere to tab through for the struts.  Yet.  This will be my pondering point for the time it takes to get the right wing up to par.

The garage isn't long enough for both wings, any my driveway slopes down.  May be fun aligning the wings for measuring the required strut length.