Mar11

15 Mar 2011

I'm in the scramble mode trying to get mods done in time for SnF, but a nagging cold is slowing me down. The days have been warm so I've gotten some work done. I'm making the main gear air dams and initially began making them using balsa. I spent several hours on it and then decided I didn't like the way it was looking. So I switched to using Great Stuff foam as I have with other projects. I didn't really like the way it was shaping up either and the decision was made (after hours of work) to abandon the foam idea when it caused some fiberglass to pull loose from the mold. So, then I needed something that I could shape and that would hold the fiberglass in place. I had used modeling clay in the past but wasn't fond of it's limited workability and the difficulty with removing it after the resin cures. I got out my boxes of clay to find they had hardened too much to use. I guess 5 years of sitting around didn't help. So, off to the local craft store aviation department to get fresh clay. It turns out Crayola makes a nice white modeling clay that is moist and easy to shape. So home I came with about 14 pounds of it. Tomorrow morning I'll get to work on it.

	As with the nose dam, I laid glass flat on particle board and squeezed the resin out between two tape covered boards which left me with a flat surface to cut out the tire openings
	On right, the critical spot on making the main air dams is just aft of the tires. In the landing attitude, and especially if dropped in slightly or if the tire pressure is low, the wheel pant behind the tire can contact the runway. So I must have a tight fit here.
	I used some scrap .040 sheet to make a vertical piece to lay the fin on. Also, by making it this way I can pull the cured piece apart from the rear in order to remove it.
	I tried the Great Stuff foam as I'd used on earlier projects, but it didn't work well in this application
	I had to devise some of my own tools to shape the foam. Using spray-on 3M adhesive allows me to apply sandpaper to various shapes. I put various grits on aluminum tubes and pvc pipe. As seen on the right, the foam did not shape up well. This was after several hours of careful work

I'm also looking at adding to the nose air dam. I'm making a foam shape that will fit underneath the air dam and in front of the tire to guide the air around the nose tire. It will be very close to the ground so I'm going to make it the weak link by making it with foam covered with only one layer of fiberglass. If a rock gets jammed under the air dam, it will damage the new lower fairing rather than break up the wheel pant. At least that's my theory. The new fairing will provide a more streamlined transition to go around the nose tire. I also made changes to the air dam just aft of the nose tire. Video showed turbulent flow at that point so I'm working on making a smoother transition there. I'll have to tuft test again to be sure of an improvement.

Marching on toward 200KIAS.

16 Mar 11

Got to work today with the Crayola modeling clay to shape the air dams. Had to remove all of the previously applied foam and start over with the clay. It is slow, tedious work, but eventually I got them done. I'll let them dry overnight and do some sanding before applying glass.

The modeling clay works reasonably well. The only hassle is removing it after the glass cures. This is the first time I've used white clay and it seems to be the better clay to use.

I laid glass on the (what I'm calling) tread fairing. It will fit directly in front of the tire tread to deflect air around what is left exposed of the tire. It fits very close to the ground and will only be used during racing. It is made with a single layer of glass so anything contacting it should break through rather than stress the rest of the wheel pant.

	The tread fairing will fit forward of the tire under the nose air dam. I don't know yet if it will work well, but it is an experiment.
	Two layers of glass on the bottom and one layer on the streamlined portion. Left is before trimming and to right is after initial trimming.

Tomorrow I lay glass on the main air dams.

17 Mar 11

Got the tread fairing attached to the nose air dam and filled scratches on the dam. I'll sand it and prime it tomorrow.

The tread fairing attaches using three nutplates.

After some cleanup work, I attached the nose dam to the nose pant and pulled the airplane out of the hangar. Opps, the tread fairing scrapped along the ground. Obviously too close to the surface. I'll reengineer it later.

Got the fiberglass laid for the main air dams. Hard to say how they're going to turn out. Getting the cloth to round the corners was tough and I got some wrinkles - which will cause lots of cleanup work.

Trimmed the upper gear leg fairings and I'll finish drilling for fasteners and start filling and sanding tomorrow.

Next update Mar 18