Ye Olde Rocket Forum - View Single Post - Dr. Zooch Mark II build...

Okay, when we last left Batman, he was... oh wait a minute... the Mark II, yeah...

So, next I did the fins. I like papered fins, for the added strength. Since the fins on this kit are 1/16 balsa, it's probably not a bad idea. Cut the fin template from the wrap sheet, and align it with the grain as marked, and outline the fins on the balsa. Cut them out with your hobby knife and stack them, sand them to final shape, and using a sheet of typing paper cut in strips, paper the fin. Coat one side with glue (I used Titebond II dark), note which is the leading edge (has the small rounded corner from the leading edge with the grain parallel) and put it face down on the paper with the remainder of the strip ahead of the leading edge of the fin. Squirm it around a little to make sure the glue is spread, and press it down firmly, then coat the backside with glue. Fold the fin over onto the paper, keeping the paper tight against the leading edge as it's folded over the leading edge. Press firmly and work any bubbles or excess glue under the paper out by pressing from the center toward the edges. By the time you've done this, any glue squeezed out around the fin should have softened the paper a bit; take a rounded smooth object (Sharpie cap/opposite end, rounded hemostat end, whatever) and run it around the outside tip edge of the fin that will be out in the airstream. Gently burnish the paper down over the fin edge, especially around the curve at the fin tip/leading edge junction. Set them aside to dry. Once they're dry, I lop off the excess paper with scissors, and then carefully cut them out with the hobby knife, and then trim the edges with the hobby knife of all excess glue and paper until it's all flush with the edge of the wood. Be especially diligent trimming the root edge so you get a good glue joint. After trimming and light sanding of the edges, flat to true everything up, then lean the fin over at a 45 degree angle and very lightly draw it toward you to shave off any paper 'fuzz' on the fin edge, flip and do the other side. I then wicked a small amount of CA along the outside tip edge of the fin and the curved part of the leading edge to make sure the paper is set for good at the edges, and to harden the balsa and paper. I started the double-glue joint by applying a small amount of Titebond II dark along the root edge of the fin and standing them up aside to dry.

Next, and the instructions don't really elaborate here, but mark the tube for the four fins. I don't have a tube marking "bullseye" so I wrapped a spare strip of printer paper around the tube overlapping itself, marked the end, took it off, measured it in millimeters, then divided by four and put three extra marks on the strip at 19.5 millimeters apart to properly space the four fins. Wrap the strip back around and tape the ends together, turn to align the end with the wrap seam mark along the length of the tube from before, and then mark the location of the other three fins. Remove the strip, and with your doorjamb or handy-dandy aluminum angle/tube marking jig, extend the lines from the mark square to the tube. Since the launch lugs will be located on the seam line, put the fins just to one side. I gently sand off a strip about 1/8 inch wide behind the line (to the right) to get rid of the glassine to get a strong glue joint. Rotate the rocket in your hand so all the fins are mounted to the right of the line as you work your way around the tube sanding the glassine. Then apply a light smear of Titebond II dark and set it aside to dry. Within 5 minutes the Titebond should be plenty dry to glue the fins on. That is one thing I notice about the Titebond II; it seems to dry pretty darn quick! I do the fins on opposite sides of the tube so I can attach a "U" shaped piece of balsa to the fins with spring clothespins to hold the fins square as they dry, since I don't have a fin jig. Apply a light bead of Titebond II to the root edge, and press it to the tube over the dried glue on the tube and align with the pencil line. Hold for 20-30 seconds and it will be pretty well set. Be sure to do any alignment pretty quick, because the glue will 'grab' within ten to fifteen seconds. I like this method because it has a lot of the 'almost instant' benefits of CA without some of the drawbacks. I set the rocket aside with the balsa alignment jig clothespinned to the fins, and came back 30 minutes later and did the other pair of fins. Fillet with the Titebond "Molding and Trim Wood" glue. I read about this stuff on a forum and found it in the store, so I picked up a bottle to try it out. This is the first time I've used it, and I must say, "I'm sold"! It's thicker than wood glue, which helps it make and hold nice fillet shapes as it dries, so you can do the layups on ALL the fillets at one time, because as you work your way around, they will be 'set up' before you turn the tube over to do the other side. One word of warning though-- I tried to just smooth the fillet with my finger, and the glue seemed to want to come right off the rocket with my finger. A quick wipe off, reapply, and wet the fingertip before smoothing with water (I just licked my finger to be honest) and a quick swipe and the fillet is made! VERY slick! After the fins had dried and the fillets dried, I then went over the fins with a thin wicking of CA just to harden the balsa. I also wicked some CA into the paper rocket nozzle, just because I'm anal...

Do a light sanding just to take any 'grit' or hardened paper fuzz off the fins and smooth the CA down pretty, and you're ready to paint. I brushed on some Testor's "1180 Steel" per the instructions on the fins, tube bottom below the wrap, and I went ahead and painted the nozzle too. I could've done a better job painting, so I took a bit of 800 paper and lightly sanded the fins; actually broke through the paint in a couple spots, so I repainted after I took the pics and it looks MUCH better now. I just didn't see breaking out the airbrush for about 12 square inches of painting...

Here's the pics! Enjoy... to be continued... OL JR