Neil’s Blog

I’ve wanted to build an Ultralight aircraft for years… This January, I got my chance to start construction on one. During an evening of drinking beers and bullshitting with my neighber Hal, we decided to go in 50% each and build one. Cost would be the #1 issue on this project (besides safety of course ;). Ultralights can get VERY expensive if you’re not careful. An average kit can cost $15,000 for just the metal and fabric covering.. The engine can run another $5,000+.

The requirements for the project would be as follows:

1. Safety - Any sort of recreational aviation can be dangerous. From an engineering standpoint, material selection, load/balance calculations, and other factors must be made in the design phase. More importantly, these factors must be adhered to in the construction phase.
2. Cost - Build it as cheap as possible, while still meeting requirement #1. This rules out 99% of all “kit” planes, since these packages average $5,000 - $15,000. The only thing we had a chance of affording was a scratch-built design, based off a set of plans purchased on the internet. Luckily, there are tons of designs to choose from.
3. Portability - Most ultralights are stored in aircraft hangars, at a local airport. At my local airport, these run ~$300 per month, or $3600 per year. Fortunately a few Ultralights have been designed to be trailered, with folding wings and removable/foldable horizontal stabilizer. The Kolb Firefly has foldable wings, but the basic kit starts at $8,500 (and therefore doesn’t meet requirement #2). Another design, the Weedhopper, has foldable wings, and also met requirements #1 and #2… hmmm……
4. Ease of construction - “Simplicity” would also make a good bullet point. The easiest design I was able to find was the Weedhopper.
5. FAR-103 legal - For non-aircraft types out there, there is this requirement set by the FAA, that requires Ultralight aircraft to meet the following:
   • Weigh less than 254 pounds
   • Have only 1 seat
   • Have less than 5-gallon capacity fuel tank
   • Not capable of more than 55 knots
   • Stall speed less than 24 knots
   • Used for recreational purposes only

   There are several designs out there which meet the cost, safety, portability, and ease of construction requirements, but unfortunately do not meet FAR-103. The Affordaplane was designed to meet all of these, but they’re really hard to get under 254 pounds. Back to the Weedhopper, they almost always fall under 254 pounds, so no problem there.

So after months of research, it was decided that the Weedhopper best fit our needs. The only downpoint was the quality of the plans. The set I picked up on Ebay were originally drawn in 1970, and full of errors. I decided early on to redo the drawings myself, in CAD. Every piece would become a 3-dimensional model on my computer, added to the main assembly, and any errors in the plans would show up immediately. In a few months when the drawings are complete, I’ll post them on this site for free.

A few pictures of completed Weedhoppers:

Blade Doyle’s Weedhopper:

[zoomer]40|400|0|Blade Doyle’s Weedhopper|0|0[/zoomer]

Dean Scott’s Weedhopper:

[zoomer]41|400|0|Dean Scott’s Weedhopper|0|0[/zoomer]

[zoomer]42|400|0|Dean Scott’s Weedhopper|0|0[/zoomer]

[zoomer]43|400|0|Dean Scott’s Weedhopper|0|0[/zoomer]

Keith Murchison’s Weedhopper:

[zoomer]44|400|0|Keith Murchison’s Weedhopper|0|0[/zoomer]

Below is the progress we’ve made on the plane up until today. The entries are listed in reverse-chronological order, since Wordpress lists the rest of my posts that way. So start at the bottom and work your way up.

2/03/2008: Fuselage mock-up

Today we did a mock-up of the fuselage. Surprisingly, everything just bolted together without any real problems… I was almost certain we would have to re-bend or re-drill something.

[zoomer]7|400|0|Fuselage mockup|0|0[/zoomer]

[zoomer]8|400|0|Fuselage mockup|0|0[/zoomer]

Unhappy mom:

[zoomer]9|400|0|Unhappy mom|0|0[/zoomer]

She doesn’t like the idea of her son flying a deathtrap :)

1/30/2008: Fuselage construction

Fuselage construction begins!

My custom CAD plans:

[zoomer]10|400|0|My custom CAD plans|0|0[/zoomer]

Fullsize template:

[zoomer]11|400|0|Fullsize template|0|0[/zoomer]

bending jig:

[zoomer]12|400|0|Bending jig|0|0[/zoomer]

Vee-block jig:

[zoomer]13|400|0|Vee-block jig|0|0[/zoomer]

Me, making some measurements:

[zoomer]14|400|0|measurements|0|0[/zoomer]

Whoops - misaligned boom holes. Don’t expect the drill bit to exit the bottom where it needs to be. Learn from our mistakes, and drill the top/bottom separately. Wrap a piece of paper around the tube, then fold it in half to get the opposite hole. Drill the top, flip it, then drill the bottom.

[zoomer]15|400|0|whoops|0|0[/zoomer]

1/21/2008: metal arrives

The metal showed up today after being back-ordered for almost 2 months… This is probably the last time we buy metal from Aircraft Spruce :(

[zoomer]6|400|0|Metal arrives|0|0[/zoomer]

1/12/2008: Picked up a used set of sails

We picked up a used main-wing sail from Rick on the Weedhopper group. The final cost with shipping was $323. To contrast, a new main-wing sail costs around $1200. We will have to make a few patches here and there, but overall it seems to be in great shape.

[zoomer]21|400|0|Weedhopper sail|0|0[/zoomer]

Not my first choice of colors :) We’ll probably use these for a year or so, and eventually sew one from scratch or order a new one at full-price. We’re still not sure on the color scheme, but I would like to the Red Baron scheme, like in this picture.

12/18/2007: Plastic pieces arrive

Since the Weedhopper factory has been out of business for quite some time, getting replacement parts wasn’t easy until Scott McClure started making them. We pretty much bought a few of every piece he offered:

• Saddle Washer kit - $17.95
• Contoured rib tip - $2.00/ea
• Raised rib clip - $3.00/ea
• Wing tip block - $7.00/ea
• 2-1/2″ tube end - $5.00/ea

[zoomer]22|400|0|Weedhopper plastic pieces|0|0[/zoomer]

Aviation, Weedhopper ultralight Weedhopper ultralight