Building Test to Destruction (part 9)

Back again again. I sanded down the fin edges. Finally I can move on.

Next thing I did was to build the baffle. This was from a Sunward baffle kit. Their instructions say to inset the baffles in the coupler by about 1/8″ so I used a small scrap of balsa with some wax paper on top as a spacer.IMG_1900I put the bottom plate on the spacer, spread yellow glue inside the coupler, and pushed the coupler over the bottom plate.IMG_1901

Same with the top plate.IMG_1902

Finally I added some glue fillets.IMG_1906

While the baffle glue was drying I worked on the motor mount. I used the mount from an Estes Patriot kit I’m using for parts, except for the thrust ring, which I used already, so I took that from a Rocketarium motor mount kit, which I guess I’m using for parts. I won’t bore you with the details; I built it as directed by Estes, using yellow glue.IMG_1918

And while that glue was drying, I cut a piece of 100# Kevlar braid, about 11″ long, and tied a loop in one end.IMG_1917

(Later on I realized I wanted an overhand knot in the other end, so I did that.)

I cut out the fin marking guide. Why doesn’t OR give you the launch lug line too? I added that, wrapped the guide around the body tube, and marked the fin and launch lug positions.IMG_1920Then extended the lines with my aluminum angle. You know the drill.IMG_1921

That body tube, by the way, is BT-60, 6 5/8″ long. I’m using two such pieces, also taken from the Patriot kit. I could have used a single longer piece of BT-60 but decided I’d rather have a long piece in my parts box than two short pieces, and since I’m using a baffle here, it’s not like I’m adding weight with a coupler. It’ll be more work to finish, that’s all.

With the baffle ready, I taped the Kevlar to the aft end of the forward body tube. The position is such that the looped end of the Kevlar is just aft of the forward end.IMG_1924

Then I applied 5-minute epoxy inside the body tube and pushed the baffle halfway in. The Kevlar is sandwiched between the baffle and body tube, but the coupler still fits in easily enough.IMG_1926

I painted more epoxy on the face of the lower baffle plateIMG_1930and stuck the Kevlar end (with the overhand knot) into the epoxy at the edge of the disk.IMG_1932

I made a mistake next. I should have let this dry before proceeding. Instead I put epoxy in the forward end of the aft body tube, and pushed that on. The end of the Kevlar got displaced a little and had to be pushed back down with a stick. I think it’ll be all right, though.IMG_1933For a small rocket like this, I think between being epoxied between the baffle and the body tube and having the knotted end epoxied down, the Kevlar will stay put without having to be tied around anything. In retrospect maybe a better solution would have been to tie around the motor mount tube between the centering rings, then run from there up between the baffle and body tube. But I expect this to work.

Finally I used more epoxy to install the motor mount flush with the body tube end.IMG_1937

That’s that. Fins go on next, and launch lug. Don’t let me forget the launch lug, OK?


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