Weak links

I've been trying to figure out the attachments for both ends of the tow rope.  Based on today's research, it appears common for sailplanes to have a weak link on both ends, including a 25% higher load rating on the tow-plane side.  It appears common for hang gliders to have two releases for redundancy.  Lots of learning.

Here is what I've come up with for the car side.  I have a fid on order to do an eye splice in the rope (yellow).  The eye can accept a pre-made weak link loop (neon yellow) with a double lark's head knot.  The welded ring can be put onto the loop with a single lark's head.  This setup mates the release to the rope.

On the airborne end, I'm working toward the as-designed release mechanism.  A parachute release pin is in the mail, and after "borrowing" a hair loop from my better half, all the components will be in play.  We'll see how it all looks together next weekend.

To-do's before the first flight are now:

• figure out how all of Goat parts transport together
  
• take all of Goat for its first trip around the neighborhood 
• finish weld the upper rail to the vertical supports -- need Argon
• finish weld the frame joints -- need Argon
• UV paint on the plywood decking -- paint arrived
• buy weak-links and end rings
• put eye splices in tow rope ends
• sort out car-side weak link and ring
• sort out plane-side weak link and release
• do a very thorough pre-flight check
• do a weight & balance
• get radios -- need 1x airborne, 1x in car

Deferred until after the first-flight:

• leather patch to wing tips where will rub the ground
• leather patch guides for elevator control lines
• trim color paint
• wing root kiss seal
• main strut fairings
• jury strut fairings
  
• emergency parachute
  
• drogue chute
• variometer

Curing hangar rash

There is no cure for hangar rash. There is only maintenance...

I patched seven holes in the covering.  Several of these holes came from trying to keep the struts on the wing panels - the eye-bolt heads poked through the covering.  Other holes were from things like bolt-heads in the jury struts and a general tear from I-don't-recall-why.

Patching is an easy affair with the Stewart Systems process and using the 30NF Fastbond from 3M.  I cut out doilies with pinking shears, lightly traced the shape on the covering, put a layer of 30NF and wiped off all the excess.  After it dried, I ironed the patch in place at 110C, then saturated the patch with more 30NF before wiping off all the excess.  After it dried again, ironing at 120C, putting on two layers of Glidden Gripper paint cut with 30% water by weight (15g paint + 5g water), and the repairs were completed.

 

Et voila, gone! 

 Trailer to-do's are now:

• figure out how all of Goat parts transport together
  
• take all of Goat for its first trip around the neighborhood 
• finish weld the upper rail to the vertical supports -- need Argon
• finish weld the frame joints -- need Argon
• UV paint on the plywood decking -- paint arrived

For the first-flight:

• covering repairs
• backyard final assembly and very thorough pre-flight check, including weight & balance
• buy weak-links and end rings
  
• get radios -- need 1x airborne, 1x in car

After the first-flight:

• leather patch to wing tips where will rub the ground
• leather patch guides for elevator control lines
• paint trim color
• wing root kiss seal
• main strut fairings
• jury strut fairings
  
• emergency parachute
  
• drogue chute
• variometer

Tow hitch welding (with the last 20psi of Argon)

The tank had only 20psi amount of Argon left, which was just enough for finishing on one of the first welding projects: the tow hitch release mechanism.  The vertical tab needed fillets.  I originally tried and did not have enough heat (you can see remnants of the failed weld puddle), so today I fix this.

During the previous weld attempt, I was only on a 110VAC circuit, which limits to 120A of current.  Hooking into the 220VAC mains lets me run up to 200A of current, which is more than plenty.

 

 

I welded the vertical tab in place with a new bead all the way around it, including on the bottom, ends, and sides.  The weld bead isn't the prettiest, but it is structural and way better than before.

I also added a tack to the sides of the plates that hold the release mechanism itself.  These vertical plates have tabs that go into slots in the base, and those tabs are welded to the base from the bottom, so this additional tack was mostly for cheap insurance.

After a cooldown period and quick reassembly, the release hitch is ready for duty.  

I also now have 1000ft of yellow polyethylene 1/4in rope for the maiden flight.  Last minor items will be the weak links at either end, tying off, and ensuring the airplane-side release mechanism works reliably.

Trailer to-do's are now:

• figure out how all of Goat parts transport together
  
• take all of Goat for its first trip around the neighborhood 
• finish weld the upper rail to the vertical supports 
• finish weld the frame joints
• UV paint on the plywood decking

For the first-flight:

• covering repairs
• backyard final assembly and very thorough pre-flight check, including weight & balance
• re-weld the tow hitch release (I'm now doubtful it had good penetration) 
  
• buy weak-links and end rings
  
• get radios (1x airborne, 1x car)

After the first-flight:

• leather patch to wing tips where will rub the ground
• leather patch guides for elevator control lines
• paint trim color
• wing root kiss seal
• main strut fairings
• jury strut fairings
  
• emergency parachute
  
• drogue chute
• variometer

Hooked myself

The Goat drawings show a small hook tool that one person can carry a wing panel.  My better half was traveling and I decided to make the tool.  A more typical sailplane assembly aid is a wing cart.  I once bought a small toy from a yard-sale and tried making a wing cart.  It didn't work at all.  So now the hook tool:

 

The hook tool worked to take a wing panel to the back yard to stage for putting into the trailer.  I didn't get a picture of carrying a wing panel because it was just me.  I also couldn't figure out how to get the panel into the trailer myself, so the lower wing mounting will wait for another day.

 

Trailer to-do's are now:

• figure out how all of Goat parts transport together
  
• take all of Goat for its first trip around the neighborhood 
• finish weld the upper rail to the vertical supports 
• finish weld the frame joints
• UV paint on the ply decking

For the first-flight:

• covering repairs
• backyard final assembly and very thorough pre-flight check, including weight & balance
• re-weld the tow hitch release (I'm now doubtful it had good penetration) 
  
• buy weak-links and end rings
  
• get radios (1x airborne, 1x car)
  
• 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
• 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...)
• drogue chute

First time a wing went 55mph

The right wing has officially gone 55mph on the trailer. The trailer is certainly heavier with the addition of 200lb of plywood, but it rides better and the little Prius is able to get momentum okay.  The thought of a 3 hour drive is terrifying.

The wing was held in place using a single ratchet strap and a Velcro strap.  I really, really wish the aileron folded down more and that both control surfaces folded all the way flat against the upper surface of the wing.  The drawings show this, but my tweaks to the design broke that feature.  If you're reading this considering a Goat build, do yourself the favor and make sure the surfaces fold down cleanly.

 

 

I think the lower wing will be easy with some foam noodles and strapping all the way around beneath the trailer frame.  The wing sits much nicer flat without the struts mounted.  The struts should be easy to strap to the trailer's upper trusses, and the tail and elevator sections will need to strap with them.  Hm.  The nose should fit inside the back of the Prius.

 

The plywood will be removed to get a good coat of urethane top-coat.  That'll be a good opportunity to do all the finish welding on the frame (fourth tank of Argon).

 

1000ft of 1/4in yellow polyethylene rope is in the mail for a tow line.  It'll be a little work to set up the ends and sort out the quick-releases and weak-link.  I might tie several streamers to the line instead of finding or buying a tow parachute this early.

 

Trailer must-do's are now:

• take another drive around the neighborhood
  
• figure out how Goat wings sit in the trailer
• figure out how all of Goat parts transport together
  
• take all of Goat for its first trip around the neighborhood 
• finish weld the upper rail to the vertical supports 
• finish weld the frame joints
• covering repairs
  

Non-critical / Optional?

• UV paint on the ply decking
• index the axles to 12deg at 1G (if needed)
• create a rear door that can be quick-pinned in place

For the first-flight:

• backyard final assembly and very 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
  
• get radios (1x airborne, 1x car)
  
• 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

 

 

 

To-do list to get to first flight

It's a small thing, drilling several holes in the wing shelf beams and supports, getting them all installed with quick-pins, but makes a small positive step forward. 

 

 

You can see the epoxy coating in the cold wasn't terrific, and the plywood is already weathering-in.  I'm leaving putting a UV paint on the decking as a to-do.  Next big step will be to test if the wings can be strapped to the shelf and supported well enough to travel.  I expect that I'll need to add multiple more of the cross-beams for more support.  I also expect that strapping down the wing panels will be awkward, since my ailerons and flaps don't fold cleanly against the wing's upper surface.  We'll see.

Trailer to do's are now:

Must-dos:

• finish mounting wing shelf cross-beams
  
• take another drive around the neighborhood
  
• figure out how Goat wings sit in the trailer
• figure out how all of Goat parts transport together
  
• take all of Goat for its first trip around the neighborhood 
• finish weld the upper rail to the vertical supports 
• finish weld the frame joints

Non-critical / Optional?

• UV paint on the ply decking
• index the axles to 12deg at 1G (if needed)
• 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
  
• get radios (1x airborne, 1x car)
  
• 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

Actual canoe float

It floats for real. On to the next project!