Decked. But now too stiff in bending.

A beautiful fall weekend was an excellent time to install some decking.  The three plywood boards were all bolted down with stainless steel hardware.

I did manage a couple drives around the neighborhood with the deck bolted down.  The anti-rattle hitch makes a huge difference.  But, the trailer is now fairly stiff in bending, to the point going over bumps is harsh, and the trailer once literally jumped when going over a pothole.  This is not good for the relatively fragile structure of the Goat wings.

After some deliberation and talking with some friends, a Flexiride 935lb torsion half-axle set is now on order to replace the leaf springs from the good ol' Harbor Freight donor trailer.  I struggled with putting yet another $500 into the trailer.  But, thinking about the decade of time into this project Goat, it makes more sense to protect that investment.

The trailer weights are:

• 180lb aluminum (160lb estimated, 180lb attempted measurement)
• 175lb plywood (estimated at 70lb each 4x8ft, including a seal-coat)
• 150lb Goat (the nose section rides in the back, but additional trailer structure for strapping down)
• 15lb miscellaneous (hitch, chains, hardware, lights, wiring)
• 520lb total

Flexiride has a 550lb option and an 925lb option... that was a tough decision, selected because trailers never get lighter, and I need some margin for bad bumps.  We'll find out if this was the right call.

Speaking of the wings, I tried the second real loading of the wings into the trailer bed with a deck installed.  The first wing half fit nicely, which is great to see.  However, it rested directly on the plywood, and it will be a harsh ride without any padding.  Laying the second wing directly on top of the first is a bad idea, so I clamped temporary cross-support members into place.  With some foam pool noodles and a couple more cross-members, I think this might work out okay.  I now really wish I'd made the ailerons and flaps fold all the way against the wing upper surface.

The wings fit comfortably with the 20ft overall inside length.  This pic was with setting the wing on 2x4's and starting to look at how to run straps.  But ignore that.

That's all for this weekend's edition.  Hopefully I can keep up some momentum next weekend!

Reflection on the trailer

After taking the trailer for a test drive in the dark last weekend, I realized it needed some help with visibility...

This new reflective tape on the rear beam should really help with visibility from the back.  I also cut one-foot strips ready for the sides (after finish welding is completed, since the tape might melt).

The new trailer lights are now installed.  The broken one was thrown away.  LED lights are brighter.

I also tidied up the wiring by installing several more TC105 zip-tie mounts to hold up the wires.  A couple colleagues and I are having an argument about the relative merits of ETFE Ty-Rap zip ties (which are on three Mars rovers!) versus using wax lacing cord.  It might be fun to try both on the trailer to figure out which lasts longer.  FAA 43.13 Chapter 11 prefers lacing cord, of course.  Trying something new can be hard.

Also notable, I installed an anti-rattle clamp thing to hold the hitch tighter into the receiver.  It was previously quite loose and made lots of noise while driving around.  I'm sure this will be significantly quieter.

My target for the next few days this weekend is to bolt down the decking, figure out how to tie down the wing panels, and then go for a drive to a friend's house.

Trailer to do's are now:

• remove the diagonal truss bar elements
• grind and sand the surface flat again
• buy new diagonal truss material
• cut and bevel new diagonal trusses (12x for the sides, 2x for the ends)
• tack weld the diagonal trusses
• buy replacement lights (I broke one this weekend)
• install replacement lights
• install additional TC105s and zip-ties
  
• buy reflective tape (DOT-C2) for higher visibility
• add reflective tape on the back
  
• trim decking plywood
  
• put more air in the tires
• add an anti-rattle hitch stiffener of some variety
• bolt the ply decking to the floor
• figure out how Goat parts sit in the trailer
  
• take all of Goat for its first trip around the neighborhood
• finish weld the vertical elements
• add reflective tape on the sides
• install and wire running lights on the sides
• epoxy-coat seal the ply decking
  
• create a rear door that can be quick-pinned in place
• figure out front/side/back walls
  
• dream up a top lid

For the first-flight:

• backyard final assembly and thorough pre-flight check, including weight & balance
• re-weld the tow hitch release (I'm now doubtful it had good penetration) 
  
• replace the nose tube (done)
• buy tow rope, weak-links, and end rings
  
• buy/borrow radios (1x airborne, 1x car)
  
• find a place to fly
• travel
• fly

After the first-flight:

• add leather patch to wing tips where will rub the ground
• install leather patch guides for elevator control lines
• paint trim color
• install wing root kiss seal
• build a wing tip dolly
• build a wing wheel
• jury strut fairings
  
• main strut fairings (after flying to figure out the right angles)
• emergency parachute
  
• real variometer (LXNav with a TEK probe is my intention, if it is sensitive at low speed...)
• dogue chute

Much better with trusses

The trailer structure stiffened up tremendously when switching from 1/8" x 1.5" bar stock to 1"x1"x1/8" angle, and running diagonals in every open rectangular panel.  Go figure, static mechanics from freshman year was right...

I removed the five bar diagonals using an angle grinder.  It is really amazing just how little metal is attached in a weld.  The rosette welds themselves were well-melted, but the perimeter of the bar stock is just not very much surface area.  Welding along a long edge is much better.  Even that, though, is only a small length of structure, as compared to composite structures where bonding surface area in king.  These are very different construction.

To add the angle diagonals, I measured the bevel and cut one piece, adding a rounded edge to fit neatly into the inside of the railing.

The lower side is just a right-angle cut, with the lower corner aligned to the bottom of the main beam.  This leaves two very long edges to weld along the main beam, and the clamp holds everything square during welding.

After fitting one diagonal beam nicely, it was rinse-repeat for others.  The "A" piece was used to trace out the symmetric "B" piece, transferred using a fine-tipped Sharpie line.

Cutting the bevel was a simple affair on the bandsaw with a wood-cutting blade (which is getting quite dull after cutting all this aluminum).

Rinse-repeat a dozen times...

Then after two more days of cutting, clamping, welding, and cleaning up, a trailer appears!  It's still very long, but is now stiff enough to drive a couple of laps around the neighborhood and on a rural road at 45mph.  It definitely needs a half-mile of finish welding, decking, and a lot of additional running lights on the side.  However, it is behaving properly and is not scary to tow.

To-do's include:

• running lights / reflective tape on the sides
• a "door" for the back
• decking (the 3/4" plywood fits this bill for now, but will need a coat of epoxy and then something to protect the epoxy from UV)
• bolts to hold down the decking
  
• more air in the tires
• an anti-rattle hitch stiffener of some variety
• complete welds everywhere

This upcoming weekend, my target is to install the plywood floor and the anti-rattle hitch, then try to carry the wings to a friend's house.  This would be the first real trip any part of Goat has made since moving into the garage some 13 years ago.