Sunday, September 21, 2014

Back doing something, anything.

How long has it been since I worked on Goat?  Almost a year.  Woof.

Last weekend I cleaned out the garage so I had some space to work.  First thing Saturday morning I reassembled on the driveway and assessed that I stopped work on the Jury Struts long ago.  The front one was about 1/4" short and I had a give-up moment upon that realization.  For this weekend, I prepped the end of three 3/8" tubes and started making the new connections.  Left wing first, on Saturday.  Then I left Goat outside overnight and finished off the right wing on Sunday.  It was beautiful weather for it.

I'm not entirely convinced of the upper rear connection, but it's a thing now.

The one major item is the incredible new stiffness feel the structure has to it.  Yes, more triangles, but also boxing in the torsion mode so the twist is held in rather firmly also.  The only place that seems flexible is how the nose can float a little left to right, but I think that'll go away once the wings load up under lifting loads.  Overall, I'm very impressed with the improved stiffness and it's clearly an airplane now.

I will be building a rig and load testing the primary structure to +3.5 G's.  Just lifting up this structure by the outer strut connection (my wife helped me move it out of the garage for Saturday night), it feels like it'll hold some weight.  I'm thinking 1190 lb of water for the 3.5 G's (which, when added to the wing's own weight, should be close to 4 G's).  But that's coming later.  Maybe this winter if I keep actually working on it.

Oh, current structure weight is 97.6 lb as measured on the bathroom scale.  Flaps, ailerons, ribs, and covering remain.

Sunday, October 27, 2013

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.

Sunday, October 20, 2013


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!

Monday, October 14, 2013

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.

Saturday, August 24, 2013

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.

Sunday, August 18, 2013

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)

Saturday, June 15, 2013

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.

Locations of visitors to this page