Trailer floor plywood epoxying (part 1)

Day 1 of sealing the trailer floor with epoxy started sketchy.  It was below freezing to start the morning.  Even with the epoxy warm from being inside all night, it immediately turned to gel goo when poured onto the cold plywood.  That would have been a disaster.  A heat gun directly on the plywood surface and epoxy started to lower the viscosity enough to let the brush spread the epoxy around.  I'm sure the plywood could have absorbed the epoxy better if it were warmer.  We'll see how it turns out.  One side each of the 4x4ft and 4x8ft plywood are sealed and have to cure overnight (or a couple of days).

West Systems 105 resin and fast hardener.  I always write down the opened date on the jug and usually write out the mix ratio for myself while mixing.  100g is a HUGE amount for me, relative to smaller RC airplane parts.  The 4x4ft piece took 130g of resin (before hardener) and the 4x8ft piece tool 250g of resin (before hardener).  That was roughly a half-quart of resin for a third through the sealing.  I have another quart in the basement, but will have to pick up more hardener.

First 4x4ft plywood floor (the bottom) is coated.  Only after doing this did I realize this one doesn't have holes.  The "real" part is a different 4x4ft piece.  Fortunately, I can just transfer over the holes and trim to the same dimensions.  Crisis averted.

Mid process of coating the 4x8ft piece shows the change in color.  Using furniture grade plywood for a trailer floor is wayyyy overkill.  If these pieces hadn't been sitting on my basement floor for about a decade, I would have used something less expensive.  With lumber prices still quite high after the pandemic, the price for this furniture grade piece was the same as I'd pay for crappy plywood today.

One related note is the epoxy is not UV stabilized, so the top of the floor will need another coat of something on top to stay protected from the sunlight.  I'm looking at Total Boat Wet Edge 1-part polyurethane (because they sponsor so many home-built boat channels) and a friend recommended Awlgrip 2-part polyester urethane.  Both of these are marine grade and meant for constant UV exposure.  It seems plausible either would survive plenty for a first flight this summer.  

I may be able to paint the floor after the floor is bolted in place.  I do have more welding on the inside of the frame, so bolting now would be premature anyway.

Floor:

• 4x4 epoxy bottom
• 4x4 epoxy top
• 4x8 epoxy #1 bottom
• 4x8 epoxy #1 top
• 4x8 epoxy #2 bottom
• 4x8 epoxy #2 top
• 4x4 UV paint 
• 4x8 UV paint #1
• 4x8 UV paint #2
• 4x4 bolted
• 4x8 bolted #1
• 4x8 bolted #2

 Trailer to do's are now:

• build three lid trusses
• weld in six backer blocks for the lid trusses
• seal the ply decking
• finish weld the upper rail to the vertical supports
• figure out how Goat parts sit in the trailer
  
• take all of Goat for its first trip around the neighborhood 

Optional trailer to-do's:

• install and wire running lights on the sides
• add reflective tape on the sides
• figure out front/side/back walls 
• create a rear door that can be quick-pinned in place
  

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) 
  
• 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

Put a lid on it!

The new tabs that hold the hitch pin bolt in double shear worked as expected, and they are done (enough).  My welding started off poorly, but got better working through the six tabs.  It is ready for a trip around the neighborhood to see if stiffer is better.  I suspect stiffer will be a firmer ride, especially without 200lb of plywood.

The tabs were cut from some scrap 1/4in aluminum.

Each tab was located using the existing hole and aligned with a transfer punch.  Clamped in place, the tack welds were done on the ends.

It was tough welding upside down.  But it was stuck together well enough to finish match-drilling the tabs and to mount the hitch pin clips.

If it gets warmer, I may take it for a lap around the neighborhood this afternoon.  We'll see.

Trailer to do's are now:

• build three lid trusses
• weld in six backer blocks for the lid trusses
• finish weld the upper rail to the vertical supports
• epoxy-coat seal the ply decking
• figure out how Goat parts sit in the trailer
  
• take all of Goat for its first trip around the neighborhood 

Optional trailer to-do's:

• install and wire running lights on the sides
• add reflective tape on the sides
• figure out front/side/back walls 
• create a rear door that can be quick-pinned in place
  

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) 
  
• 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

Lid trusses

Getting closer.

Three trusses (all identical length and construction) are now fabricated and pinned in.  It's wonderfully stiff.  They all need a corresponding pin block support welded into the upper rail before I can drive (it would rattle like crazy currently), but the stiffness is noticeable.  It also only takes a few seconds to de-pin and remove / pin and install.  I like it.

 

Creating the lid trusses started with a 1in bar, which was hand-milled down to 0.9in to fit inside the 1/20in wall thickness.  I started with the band-saw and then tried to use an end mill on the drill-press.  It was functional, but scary, and I don't recommend doing this.

After getting 0.9in thickness, I lopped off 1in long sections that become a welding plug.

It did not take much work to weld the plug into the end and match-drill a through-hole.  A few minutes with the sanding and filing tools cleaned up the welds.

The first plug was easy enough.  I have three trusses (and three wing support cross-members) that all need both ends plugged.

After a while, the trusses were ready for fitting.  I put just one end first and figured out my spacing so that each of the three lid trusses was identical length, and thus are all interchangeable.  It was 90-5/8in between holes, if anyone cares.

After drilling both ends of the truss and making sure the holes in the rails were all set for the same spacing, the trusses are all installed.  I still need to weld in a 1in cube backer block.  The hitch-pin keepers will bump against the backer block nicely so they do not rattle.  

Trailer to do's are now:

• build three lid trusses
• weld in six backer blocks for the lid trusses
• finish weld the upper rail to the vertical supports
• epoxy-coat seal the ply decking
• figure out how Goat parts sit in the trailer
  
• take all of Goat for its first trip around the neighborhood 

Optional trailer to-do's:

• install and wire running lights on the sides
• add reflective tape on the sides
• figure out front/side/back walls 
• create a rear door that can be quick-pinned in place
  

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) 
  
• 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

First hitch pins

I finally took a weekend off of work and got a little done on the trailer.  It isn't much, but the trailer finally now has removable pins for the rear spreader bar.  I welded in a small gusset plate and then match-drilled holes to install a removable hitch pin.  Only very gross tack welds are in place so far.  All finish welding is going to be for another day.

I narrowed down how to finish off the structure.  The "lid" will be three 8 foot trusses of 1/16th inch wall, 1 inch square tube.  The ends will have solid aluminum inserts for supporting the hitch pin, and the trailer rails will have a 1 inch block welded in and drilled for the hitch pin also.  With these three trusses c-clamped onto the frame, it's finally stiff enough in torsion.  Once these truss pieces are in place (and several broken welds are repaired), I'll take another test drive around the neighborhood and hopefully make a small road trip.

Sealing the plywood floor with epoxy is waiting for warmer weather to arrive.  Once the sealing is completed, those pieces will be bolted to the frame for good.

Last, I also figured out how to create cross supports to hold up the second wing.  Pictures of this will come out later.  Getting the two wing panels tied down into the trailer and out for a drive will be a momentous occasion.

My goal is to fly this summer.

Trailer to do's are now:

• paint axle assembly with some enamel paint
• repair left tail-light wiring
  
• buy more Argon gas
  
• finish weld the vertical elements
• finish weld the upper rail
  
• epoxy-coat seal the ply decking
• quick-pin the rear "door"
  
• dream up a top lid
• build lid trusses
  
• figure out how Goat parts sit in the trailer
  
• take all of Goat for its first trip around the neighborhood 

Optional trailer to-do's:

• install and wire running lights on the sides
• add reflective tape on the sides
• figure out front/side/back walls 
• create a rear door that can be quick-pinned in place
  

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) 
  
• 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