UH-18SP Thrust Duct Construction - Page 4

The next step was to make the wedges to fill in the gap between the foam and the plywood on the duct. Pretty much all the plans said to do was cut wedges to fit in gap. I didn't just want to star cutting a whole bunch of wedges and fitting each one so I found out what are they need to be cut at to make the bend around correctly. The two measurements I used for the radiuses were 150" and 157 7/8" they came out just a little to long in the front so you could probably use 157 5/8" or 157 1/2" insead of 157 7/8". Then we just made a template for the size they needed to be made and we sanded them that shape.

Here is one sanded.

Here are two of the wedges in the duct.

Here are all the wedges in place.

Here is a close up.

Here we have it most of the way sanded and almost ready to glass. Right click this link and click on "save targes as" or "save link as" to download a video of how we finish sanded the inlet lip of the duct.

If you didn't watch the video it is of us spining our thrust duct to finish sand the inlet lip. This worked very well and made the lip simular all the way around. We didn't use any bearings it just spins on the doll rod going through the center.

THe next thing we needed to do was to glass the leading edge that we just got done shaping. We also glassed the trailing edge to the plywood disk.

Here is a close up of the leading edge. You can see some white stuff under the glass, it is light weight spackle and we used it to fill in the slits and some low spots.

Here is the Light weigh spackle. we buy ours from Menards. If you go to buy some and it feels like the bucket is empty it isn't, it is really filled up to the top this stuff is just super light.

Here is the thrust duct completly finished. It turned out much better than the duct on our 10f.

Here is the inlet lip, you can see the spackle in there that we used to smooth it out.

Here we are holding the duct up to see what it will look like.