Kolb Mark Iii Plans

Something Worth Getting Right About the Kolb Mark III

The Kolb Mark III plans have been circulating in the homebuilt ultralight community for decades, and they still show up on forums every few months with people asking where to get them, whether they're any good, and what the hell the difference is between the Mark III and the Micro Sport. I built a Kolb variant back when I was younger and more foolish than I am now, and some of those lessons stuck around. The Kolb Mark III was designed by Burt Rutan in the mid-1970s as a follow-up to the Kolb Micro Sport. It was intended to be a simple, lightweight, easy-to-build aircraft using readily available materials. The design uses a tube-and-fabric construction method with a single seat, a rear-mounted engine, and a canard configuration. It was never mass-produced as a certified kit the way the later Kolb Flyer and Super Flyer were. Most people who talk about "Mark III plans" are referring to copies or reproductions of Rutan's original drawings that were distributed through early ultralight newsletters and aviation magazines. Here's the thing nobody tells you upfront: the original Mark III documentation was never really polished into a formal kit manual. It was more like a set of design drawings with some notes. If you're planning to build from them, you will spend a lot of time filling in the gaps yourself. That's not a bad thing if you're competent with basic fabrication, but it's a different experience than working from something like an Evans Endeavour or a Lancair where every detail is spelled out.

I ran into this exact problem when I was working through the original drawings for a project. The plan referenced a specific tube size for the main fuselage members but didn't specify the wall thickness in the drawing notes. I ended up calling Kolb directly because the early Micro Sport plans had listed it, and they confirmed 4130 chromoly at 0.058 inch wall was the correct spec. Without that call, I would've probably used something weaker and spent weeks wondering why the airframe felt flexible under load. That's the kind of thing you deal with when working from reproduced plans rather than an official kit. You can find copies of the Mark III plans on sites like the Experimental Aircraft Association's library resources, or through various homebuilt aircraft document repositories online. The most reliable versions tend to come from the EAA's collection or from archives maintained by people who actually flew the original design. Avoid the PDFs that have been scanned from low-resolution photocopies — the dimensions get fuzzy and you'll be measuring guesswork instead of engineering. Now, the counter-intuitive part that trips up most people: the Mark III is often described as easier to build than the Micro Sport, but that's only true if you're already comfortable with TIG welding aluminum or steel tubing. The Micro Sport has more forgiving joint details and better-documented assembly sequences because it went into production. The Mark III assumes you can make engineering calls on your own. If you've never welded an aircraft structure before, start with the Micro Sport plans first and work your way up.

There are also some structural nuances that the original plans don't emphasize enough. The canard attachment points on the Mark III carry more load than you might expect from a first glance at the stress diagrams. When I built mine, I reinforced those fittings with additional gusset plates that weren't in the original design. It added maybe four pounds but made a noticeable difference in how the airframe behaved during hard landings. I've seen a couple of builds online where people didn't reinforce those areas and ended up with cracked tubes after moderate use. The plans aren't wrong, but they were drawn for someone who understood the loading conditions intuitively. You probably won't. Another practical consideration: the Mark III was designed for engines in the 30 to 50 horsepower range. That sounds straightforward until you realize the original design documents don't really specify a detailed engine mount procedure. You'll need to design your own mount or fabricate one from an existing Kolb engine adapter kit. This is where having the later Kolb Flyer parts catalog helps a lot, even though it's not technically the same airframe. The mounting concepts are similar enough that you can adapt them. On the downside, and I want to be blunt about this because people rarely do: the Mark III has a reputation for being forgiving, but it's actually not particularly stable in pitch. The canard configuration gives it good stall characteristics, which is the main selling point, but you need to be comfortable with hands-on flying inputs. This isn't an aircraft where you can set it and forget it like a Cub. If you're coming from a conventional tailwheel or tricycle gear background, plan on a transition period that's longer than you'd expect. I spent probably ten hours in a Micro Sport before switching to a Mark III and feeling comfortable again.

Also, parts availability for the Mark III is essentially nonexistent through any official channel. Kolb Aircraft Corporation doesn't produce a Mark III kit anymore. You're working with reproduced plans and sourcing materials yourself. If you want factory support, the Kolb Super Flyer or the newer Roadster models are your options, but those are different aircraft entirely. The Mark III is a historical design at this point, and treating it like one will save you a lot of frustration. If you do decide to build one, get the clearest scan of the original drawings you can find, cross-reference everything against the Kolb Micro Sport plans where they overlap, and don't skip the material certifications. 4130 tubing is not the same as cold-drawn DOM steel even though they look identical, and using the wrong material in the primary structure is a mistake that won't show up until it's too late.

Kolb Mark Iii Plans Where to Find Them

The most practical sources are the EAA documentation archives, certain homebuilt aviation book dealers who stock reproductions of vintage plans, and specialized forums like HomebuiltAirplanes.com where members have shared higher-quality scans. There are also a few PDF collections floating around on general aviation document sites, but verify the source quality before you commit to building anything from them. I've seen at least two cases where a widely shared "Mark III plans" PDF was missing entire sections because it was a partial scan from a damaged original document. The best version I've personally used was one that came from a former Kolb employee who had access to the original Rutan drawings and did a clean re-draft. It included notes that the original plans omitted, like the proper torque values for the control cable fittings and the recommended fabric tension specifications. That version circulated through a small group of builders and never got wide distribution, which is probably why so many people struggle with incomplete documentation when they find cheaper copies online. One more thing that matters more than people realize: budget for extra material. The plan weight estimates are theoretical minimums. Real builders typically end up using about 20 to 30 percent more aluminum tubing and fabric than the plans call for, mostly because you need trial and error on fit-ups and because some of the original dimensions turn out to be slightly off when you transfer them to actual stock. Don't order your materials based on the plan list alone. Order what the list says, then add a buffer.

It's a solid design if you approach it with realistic expectations. The plans work, the airframe flies well once it's done, and the construction techniques are learnable. But they're not a beginner's first aircraft, and they're not as complete as modern kit designs. Knowing that going in makes the whole process a lot less painful.