Add a Flight Deck. And a Hangar.

The Surly Big Fat Dummy has a great big deck in the back. Using a 40″ kicktail longboard and some hardware, Lets make it bigger. And a double decker to boot.

The Surly BFD Project Menu
Prologue
Episode 1: 138L (each) Panniers… Seriously?!
Episode 2: Big Fat Dumb Wideloaders
Episode 3: Kickstand Kaos
Episode 4: Add a Flight Deck. And a Hangar (You Are Here)

In the Beginning…

Back when I put together the Mongoose Envoy Project, I used a skateboard deck to cover over the long, but only marginally-useful-on-its-own rear framework to create what ended up being an aircraft carrier landing deck.

I started out with a 33″x10″ double kicktail which I mounted on top of eight 25mm tall by 13mm dia. spacer posts. The idea behind the spacers was to give me some working room to attach a net to the top of the deck, and have room to easily mount its hooks to those posts. It worked well, but I left money on the table with only a 33″ deck. I could go longer. So I did. I found a 40″ longboard with a single kick and mounted it on 10 posts, this time.

It was great, but of course, I thought I could go one better. So I scored a 44″ double-kick longboard, and – since the 25mm posts were a bit fiddly trying to get my fingers in that small space – swapped out for taller 40mm replacements. I also made some other improvements, and that deck remains on that bike as you see it here to this day.

Fast Forward To The Present…

Now I have a Surly Big Fat Dummy, and I want to do the deck idea one better (AGAIN!). I still have the 40″ deck left over from the Mongoose build. Since the BFD is already like 8 feet long I don’t need something that makes it longer, so this ‘shorter’ deck will do just fine. I drilled some new holes, repainted it and took the spacers a step further.

The Next Level (literally)

Unlike the Mongoose, which had nothing but a framework, the Surly Big Fat Dummy already has a pretty good deck as it is. On the Mongoose Envoy I was trying to cover over the bare framework and make something useful. This time I am trying to make something already useful more so.

To preserve the utility of the existing deck, I went with much larger spacers. That created a ‘hangar’ under the deck of this aircraft carrier of a bike. This new hangar’s purpose is to house things that need to be carried along, but generally kept out of sight. Stuff where I can benefit from it being reasonably handy, but kept out of the way.

Great Idea. But first I had to assemble the parts and make the thing.

To give plenty of room between decks, I went to McMaster-Carr and acquired ten 3″ long alloy spacers, 5/8″ outside diameter, sized for 1/4″ bolts. Then I went to Pegasus Auto Racing and, after measuring the exact stack height I would need, grabbed ten AN4 1/4″ hardened airframe bolts of the proper length, along with ten AN970 hardened large-area washers for 1/4″ bolts (for the top deck side) and a bag of AN960 1/4″ x 0.32″ flat washers, where I would need 30 for the deck underside, plus the top and bottom sides of the alloy dummy deck. I wrapped up the party with ten AN365 nylock hex nuts.

Airframe bolts have a specific thread length designed to fit a single bolt and a single double-thick washer. This project uses 4 washers of two different varying thicknesses. Measure carefully.

Wow thats a lot of hardware

Like my previous decks, I wanted to use enough spacers and bolt anchor points to make the deck an integral, structural part of the frame. No wiggling possible. Part of what it takes to do that is to use the widest spacers I can find (the 5/8″ OD are it, and dictated why I couldn’t stay metric). To further solidify the connection laterally, I needed washers everywhere clamping everything.

You can still see the holes from when the deck was bolted to the Mongoose, as well as the holes for the trucks that aren’t there anymore.

And excepting the spacers themselves, its all Grade 8 hardened steel. Its. Not. Moving.

Notice also I used hex bolts and did not bother to work with countersunk heads, matching washers etc. as with the previous decks. This thing is spray painted in truck bedliner to help keep things from sliding around, and the hex bolt edges do the same job.

Airframe bolts exist in a wide variety of very finely diced sizes. I am not giving the size I used because the ones you may need will vary according to the thickness of your top deck.

Here’s what the finished assembly looks like up close:

Now that the aircraft carrier has a landing deck, we find out what we stuff down underneath in the hanger.

Up front, fitting just barely between the front posts, is a 3-amp weatherproof adjustable charger that is a permanent companion to this ebike. In the middle is the toolkit for this bike, containing a pump and all sorts of other goodies. It fits just between the two sets of spacers so it can be dragged out the side. And in the back we see a big thick plastic ziploc freezer bag wedged in between the rear 4 stanchions. Thats the in-case-of-disaster emergency inner tube.

Since then I have added another little jewel:

Thats right. A folding chair. Held rattle free thanks to the net. Stuck in line at curbside pickup? Have a seat and relax.

Take the crap off the top of the deck and you have yourself a work table. Or a coffee table. Or a picnic table. Its 40″ long so use your imagination.

See that net? Its 30″ long before it gets stretched out, and since I ordinarily have the Great Big Bags on the bike, I generally do not need to use the top deck for storage of items up so high. But when I do, that nice long cargo net does a great job.

Here is one of the rare times the bags are full and I need to stack something up on the deck other than a rolled up jacket

Now What?

Got a Big Fat Dummy? And a drill? And a skateboard? Make yourself one of these. Next time you have to sign a peace treaty, host a banquet or make off with an emergency supply of toilet paper… you got this!

Author: m@Robertson

I'm responsible for the day-to-day operations at my place of business: Leland-West Insurance Brokers, Inc. We do classic and exotic car insurance all across these United States. I'm also an avid auto enthusiast, a born again cyclist (i.e. an ebiker) and participate in medium and long range CMP and NRA sanctioned rifle competitions.

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