Chapter 24 - Section 11

Main Gear Fairings

 

Without much specifications in the Plan for the main gear fairings, you'll find many different designs and configurations on the flight line of Cozys. One of the key considerations for the fairing design is that our main gear flexes relative to the fuselage between landings and in the air. Some builders have their fairing attached to the fuselage, some to the gear legs, while others have it half and half. I went to one of our local canard fly-ins (Corona, CA) and took a bunch of fairing pictures from all the canards. Later on that evening, I picked through them based on looks and ease of building them. I opted for the fairings attached to the gear legs with a thin slot cut between the fairing and the fuselage. The only concern I have, at this point, is the clearance needed for removing the main gear cover at the bottom of the fuselage. I decided to deal with it when the time comes.

 

Establishing the Shape

I took the carpenter widget and traced out the surface profile of the gear leg next to the fuselage. I transferred the profile to a cardboard and added 2" all around the outline. With the cutout template, I fitted it to the gear leg / fuselage intersection and traced the outline onto the fuselage. Based on that outline, I used a 2" dowel and projected an opposing outline back onto the gear leg (starting point of the fairing).

 

 

 

 

 

 

 

Shaping the Fairing

You can find many different ways to make the fairings. My main concern was making the right similar to the left. Cutting foam and shaping it would be easy, but a bit permanent. In other words, there is a point of no return if you sand it down too much. I decided to follow Jon Dembs approach - using Play-Doh as the shaping material. K-Mart sells a Play-Doh set that comes in 4 colors - each in a small can. with the help of a paper tube and a long socket (with an extension), I was able to shape (roll) the play dough to a relatively pleasing shape. I used 2 1/2 cans of Play-Doh per fairing. You can see my two tone fairing (left). It was getting late by the time I completed the shaping of both legs, I decided to quit for the night.

 

 

 

 

I was surprised that the Play-Doh dried up overnight and developed voids and cracks throughout. I wasn't thrilled about re-doing both fairings again. I decided to tape it up with electric/packing tape to smooth out the dried up bumps and cracks.

 

Here's a picture of the 'taped' fairing on the opposite side. The pencil mark at the leg is 1" from the transition line. I will be using it as a guide to lay down my 3 BID glass layer.

 

 

 

 

 

Removing the Play-Doh

After the glass cured, I removed the peel-ply and, as expected, I was not able to pop the gear cover off - the fairings were in the way. Fortunately, my wings were off the plane at this time. So I took the opportunity to turn the plane over and do some extra work on the bottom of the plane. After the plane was turned over, I removed the main gear together with the gear cover.

 

Here, you can see the play dough that fills out the fairing cavity with the gear cover stuck in the midst. I trimmed off the sharp edges along the fairing and started to remove the white electrical tape and Play-Doh. Surprisingly, that was quite a chore - especially right at the seam where the fairings start. The electrical tape and 'dried' Play-Doh did not want to come loose and I do not have any really thin tool that is rigid enough to scrape it out. All in all, it took me several hours to clear them out (at least as much as I could).

 

Trim To Fit

After I got all the Play-Doh out of the cavity, I trimmed the edges of the fairing to fit. I had to trim the inner fairing a bit more - to give room for removing the gear cover. By doing so, I ended up with a 3/8" gap. I decided to cover it up...

 

 

 

 

 

 

 

 

 

Overlapping Gear Fairing

Using Play-Doh again, I formed a transition between the gear fairing and the gear cover (picture left).

 

 

 

 

 

 

 

 

 

 

I applied packing tape over the play dough and gear leg. Then I laid 4 plies of BID onto the gear cover, overlapping the gear leg. After cure, I removed the Play-Doh, & packing tape and trimmed to shape. Here's the final result.

 

 

 

 

 

 

 

 

 

Things to Do:

Fill the fairing cavity with foam for added fairing support.