TLP Indigo Build

I prefer to plan enough ahead of time that mistakes don't happen. I knew this would be tricky for me though, and have learned a lot for next time. It's not like I'm unhappy about a mistake though, I'm back on track, problem solved. If I didn't solve that problem now, it will be a bigger problem later. I'm too damn lazy to allow that to happen.

Since I'm waiting for a Bradycros-inspired sanding tool to dry, I figured I'd post. It was time to cut the slots. I used a BT-80 coupler I got in a Red Arrow Hobbies' Scratch Builder's Assortment to back-up my cuts. It's longer and more heavy-duty than the included coupler.

The slots are cut. I did it freehand with a good 'ol #11 blade. Anybody else notice how cheap the X-acto handles are nowadays? I'm almost afraid to use my razor saw it's so rickety. And I work with knives for a living.

Things look like they match up pretty well with the engine assembly, I'll post a picture after sanding but I doubt you will be able to see much.

I lined up the slots with the braces on the exhaust tube all the way around, best I could, and found the best one. A 57mm long piece of 1/8" balsa fit in pretty well, so in it went. It locked everything in place so I could sand the slots and braces with a popsicle stick cut off square at the end, with 220 grit glued on with glue.

I also marked a point on the body tube and centering ring with a #11 so I can line everything up again if need be. Sorry for the blurry picture, I was going to take another but batteries need charging again. You get the idea though, I bet. Next step is to make a modified rear fin template, but that will probably come tomorrow.

After zooming in on these two pictures and taking a long hard look at them, with some holding up a fin template at different angles to my monitor thrown in,
View attachment 80030
I came up with this drawing.

I'm convinced the rear of the fins are at an angle, not straight across. I figure a little extra fin area won't hurt. The 1/4" dowels on the ends of the fins will be 1/4" shorter, with an ogive shape. That should save me about .8 grams after weighing the dowel. So in the future I will include my home-made ring, it cancels out. It will make finishing the rocket much easier I think with a little extra backing for the tail cone. One last thing, I added a little to the fin to conform to the shape of the pointed dowel. On the template I left a little extra in this area, and will sand the balsa to shape. So with fin tabs, here's the completed template.

I'm almost convinced also by looking at the zoomed-in photos on my hard drive, that the leading edge of the fin has a sharp taper (pretty obvious), and it is a more rounded one at the rear. Any opinions on this?

I need to get an outfit like that guy in the picture. Those are some cool threads.

Before I cut out any fins I need to do some experimentation involving wax paper. I don't have any. Therefore, I decided to work on the dowels on the ends of the fins. I marked the center of an end of the 18" dowel best I could. I stuck the end of it in a pencil sharpener I have in this strange trianglular closet I have. I don't know why it's in there, but it's old. It did a crappy job of sharpening the dowel, but good enough. I cut it off at 4 1/8" from the semi-sharpened tip using my rickety saw. I then semi-sharpened the tip of the less long dowel, cut it off, etc. until I had four of them.

I then squared and slightly rounded the rear end of the dowels. I compared those with my fin template, and wrapped masking tape around where I thought the tapering of the front of the dowels should start.

I sanded down with 220 grit on a block to almost the right shape of one of the dowels using that center point and the masking tape for guides. I then switched to just a piece of sandpaper formed into a cone shape, backed by my fingertips, to smooth it out by spinning it around in there. Here's a comparison to a rough cut dowel I need to shape yet.

I still need to do the other three to this point, get them all to the correct length, and fine sand them, but that will be for another night.

I couldn't resist putting everything together. It almost sort of looks like part of a rocket. I took off .2 grams sanding the tip of the dowel, more than I estimated. If I drill out the dowels I might get close to neutral weight in the rear, which would make me jump for joy.

It's another night. I shaped the front ends of the other dowels, and then taped all the dowels together so I could sand them all to the correct length. I don't know why I rounded the rear ends last night. I found some 150 grit in my stash so I used that instead of 220. It was quite a bit of work, in retrospect I would have cut closer to the 4" required length. Or used my Ryobi Dremel-like tool, which I didn't think of until I was almost done, and thought, "Man, this is a lot of sanding."

This is almost the final dowels. I will probably mess with them a little yet, but they are close. It's always hard for me to know when to stop. It's easy to go too far.

I bought some wax paper, now for some experiments.

The kit recommends painting thin CA over the fins for strength. On my Lance build, which I still haven't finished because of multiple problems, the fins warped when applying the CA. I thought I would apply the CA first before sanding to see what would happen. I clamped the balsa (not what was included in the kit but 1/8" thick) between two pieces of wax paper, applied some CA, and spread it out with a piece of thin cardboard about one inch in from the edge.

I flipped the balsa over, applied clamps and repeated process, but this time went in two inches. Flipped again etc. and ended up with an about three inch square piece of saturated balsa. It was unwarped, so far so good. I cut an untreated balsa section the same size and weighed them, a 1.1 gram difference.

It is even smaller than the fin, so a fin coated would be more. It adds a lot of strength against the grain, but hard to tell short of breaking them with the grain. With that dowel on the end, I'm not sure the fins need that extra strength with the TTW construction. However, if it forms a more defined taper to the airfoil when I sand, it might be worth it. Well, except for one fact, I used about .3-.4 ounces of CA to coat just that one piece of balsa, very expensive real estate if it were laying on the ground. It's time to go to Michael's, and pick up some basswood. I will do some comparison measurements and tests, and then try to decide what works best.

A trip to Michael's might take a couple days, so I think the next step will be the tip of the nose cone. I'm going to give Bradycros'es JB Weld method a shot, even though I've never used the stuff before. The rocket built stock requires an ounce of nose weight, so a nice strong tip will be a plus, and will still need plenty of weight. Here's his Logo rocket thread with the how-to.
https://www.rocketryforum.com/showthread.php?t=10709&page=2 It starts on post #54.

I started on the nose cone. I first washed it with dishwashing detergent inside and out. It was impossible to get all the water out of the inside until I drilled a hole in the tip, which is needed for the JB Weld anyway. I let it dry for a while, and used 400 grit sandpaper to give the cone a good sanding, especially the seams. I used 150 grit on the tip where the JB Weld will go. I then wiped it off with a paper towel dampened in rubbing alcohol.

I mixed up some JB Weld before sanding, and it sat around for a half hour before I started to stuff it in the tip hole with a toothpick. It was still pretty soft, and slightly runny, but I thought that would be a good thing since at this point I want it mostly inside the cone. I got quite a bit inside, and a pile on the outside too which I feathered with a rubbing alcohol-dampened Q-tip. I left the cone point up for a while so the Weld could firm up a little more, and also get further into the cone.

I've been poking at the pile of excess Weld periodically to see how it is firming up, it's still workable after an hour and 20 minutes. Tomorrow I'll wait at least this long before applying more to get closer to a pointy tip. I turned the cone point down after 1.5 hours, supported by the other body tube in the kit. I'll check it in a little while, looking for the point where I can form the rivet of Weld with a 3/16" launch rod inside the cone. I think this is going to be way easier than I thought it would be, it's just going to take three days. I have the time.

I couldn't wait any longer as I'm tired. I tamped the inside of the nose cone tip with the launch rod. It's probably too soon as the Weld came back out a bit, but I don't think it will matter. I'll leave it point side up until tomorrow.

After sitting for 19 hours, it is hard as rock and it settled into the same place as the picture two posts above. I mixed up another batch of Weld and I'll check it in an hour to see if it's thick enough to continue with step two. Anyone know how sandable JB Weld is?

Round two of the JB Weld application. I'm being cautious, I probably could have added more. I'm in no hurry. I'll wait until tomorrow night to add the next round.

I have decided to make the fins out of balsa. I'm gonna cut out at least one tonight.

I cut out the fins using the provided balsa in the kit. It had hard and soft on the sheets, I made sure the fin tabs were on the hard part. I used a cork-backed steel rule to guide the cuts, which I made with a popsicle stick. Wait, a #11.

Here they are stacked up on each other.

I sanded the tabs just enough to make them fit into the body tube slots. I placed everything together and took a couple of pictures.

I am not going to add CA to the fins. I just plain don't like that method. I can't see the rocket coming down anywhere but on the dowels under 'chute, which will distribute the shock and compress the balsa along the grain, and into the strength of the exhaust tube/engine mount assembly. At least that's the plan. I will save more than enough weight to come up neutral in the rear over a stock build according to the directions if I'm figuring right. A good amount of the rocket's weight will be in the nose cone so that's a lot that won't be stressing those fins on landing. And just think of the drag of that airframe with all those fins coming down. I keep thinking that anyway, and won't know a damn thing until she launches.

Hmm, just as I was getting the hang of it, it is different. First picture, final sanding of the dowels. But I may just make them a little pointier yet. I did this while the JB Weld was firming up for the third application to the nose cone. I didn't wait as long last night, about a half hour. It gets a little sticky and stubborn if left too long. I left it upside-down in the other body tube as level as I could. The results are picture two. One more day, and I think it will be ready for the filler.

I'm getting deja-vu, working on the same components. Final sand (really this time) of the dowels. I made them a little pointier, and made a more slender curve to the tapered part. I mostly used that popsicle stick with 220 glued to it, that I used to sand the fin slots, to make a sharper point. After that a final spin in a sandpaper cone to finish them. I got to that point were the limits of my eyesight and skills meet, and I'll probably make things worse if I continue.

One more layer of JB Weld. I applied it like the previous post. I'm not sure how many days this will take now, because if I add more at a time it becomes uncontrollable. It's not hard, but you need patience. I have quite a bit of that. Once it gets pretty hard, I may try adding another layer tonight without this one being fully cured. I've been using a popsicle stick to scrape the Weld to keep it in-line with the taper of the cone, and when the Weld is a little firmer I use the alcohol-dampened Q-tip to feather and smooth any bad spots. I flip the cone periodically for the first couple hours, or it starts to form a drip or a flattened blob. An afterthought, after a couple hours of curing you can mold it a little like clay. This is proving to be useful.

I arbitrarily numbered the fins and dowels 1,2,3,4 to match them up. I then sanded the fin surfaces where the dowels will glue to for a tight fit conforming to their shape. I mostly used 400 grit wrapped around that D-12 case for the curved part, I need to dig out a smaller case for tighter curves. Otherwise I used my finger for a block, and my popsicle stick a little. On the straight part, I used my block with 220. Here they are matched up.

I then stacked up the fins and sanded them all together to the same size. I used my 220 block. Here's the picture after sanding.

I applied one more coat of Weld, it's getting there.

Tomorrow I'm going to go to a local piano restoration shop, and see if I can get some .0625 diameter wire. I also need to find a nice flat board about 6" wide and a foot long. Jig Mk II will be needed soon. Here's a link to Jig Mk I, for those that are interested. It will save me a lot of time explaining what I'm doing coming up, if you glance over it.
https://www.rocketryforum.com/showthread.php?11070-Easy-to-make-fin-sanding-jig

I drove all over town on my quest for 1/16" steel wire at a reasonable price. A piano uses .044 gauge at the biggest, I found out. The bass strings have a copper coil around the steel. I went to Menard's and they had a hook for 50 feet of 14 gauge steel wire, but they were out. I wasn't even sure that would be the right size, but maybe I could improvise. Michael's is out that way, and nothing. I drove to the other Menard's on the other side of town, they were out of 14 gauge as well. Finally I went to V&S Variety store, this crazy store with hardware, and all sorts of things. They even have a 500 gallon aquarium for display which is empty now, but they do sell fish. There I found my grail, three rods of 1/16" piano wire three feet long for $3.49. I am set for life. I couldn't even cut it with a pliers, so I held it with the pliers and bent it back and forth until it broke. I CA'ed it to a shelf out of my entertainment center. I found the particle board seems to have plenty of friction on the balsa, so I don't need to mess around with rubber cement.

I drew a line on both sides of the fins 21mm from the leading edge. This will be the start of the taper. I just picked what looked right, as I couldn't get an accurate measurement from my pictures with what I have available.

Here's the aluminum shield cut out of a can. It had a straight line all the way around on the label, which made things easy. I used the scissors on my trusty Swiss Army knife to rough cut apart the can, and the more heavy-duty X-acto up from a #11, a nice old handle, for the rest of the cuts.

The board is a little wide for my clamps, so I put a couple balsa strips in for more support for the jaws of the clamps.

Everything in place, the edge of the aluminum is along the line I drew earlier.

I now need a shim to fit in this space after flipping the fin over.

I cut some sketch pad paper into little rectangles, I needed 8. I then carefully slid them under the fin clamped to the board, with wax paper underneath it all.

I then carefully removed the clamps and fin while holding the rectangles down with some fingers. I applied CA to the rectangles, glued my finger to the rectangles, pried it off, and waited for cure. Then I flipped the shim over and applied more CA. I then slid it under the fin, and marked where I should cut the excess off. The finished shim.

I sanded the other side. The actual sanding only takes a few minutes, and now that the shim is done I can whip right through them. A picture from the side, a knife edge. I applied some Titebond to the edge to toughen it up. A small amount of balsa came off the edge, I'll have to fix that, and I think I'll add some Titebond to the leading edge first to prevent that from happening to the other fins.

Another layer of Weld on the cone, I'll apply one more tonight, and that may be it.

There's a couple pictures of a new coat of Weld. It's proving hard to form a point, another night yet at least.

If you want to hit your mark on the fin, you have to set the aluminum shield back a bit to make up for the thickness of it. The aluminum must be fooling the light sensor on the camera so the picture is dark, but hopefully you get the idea.

All four fins rough sanded. The glue on the leading edge seemed to do the trick, even though it all peels off after the sanding is done. No more pieces coming off the fin. I re-straightened the aluminum by cutting off about 1/8" after two fins. It took me about an hour for all the sanding, once the shim was made. Before I do the front fins I'll probably remove the piano wire and turn it 90 degrees, as it does get worn down. I think for final sanding, I'll use rubber cement. Things are moving around a little too much.

One more Weld coat on the cone. Soooo close.

I felt it was time to install the engine assembly. I had enough of sanding for one day. I need to put glue about 4mm past the slots.

I also made bigger marks to find the precise #11 marks I made earlier on the mount and MBT easier.

I used Elmer's Glue-All, and a stiff-bristled paint brush about 3mm wide out of that pack to apply it. The assembly went in easily, Glue-All gives you all the time you need. I then left the MBT to dry tail-down. Some might think, "That's not enough to hold that!" There will be a bunch of stuff added shortly so that not even an F engine will budge it. After all, it's not like a big hand is holding the rocket down, applying force to all the joints back there. She will want to go up.

I added (I hope) the last of the Weld. I'm just waiting for it to cure a little more for the last of the sculpting. I waited about an hour and a half before applying this time, so it was nice and firm.

I'll decide tomorrow if this was the final application of JB Weld. Before final sculpting next to a stock cone.

After sculpting. I used a popsicle stick, and then a paper copy of the cone included in the kit taped together. I spun it around on the tip after the Weld was almost set.

I applied Titebond inside the slots between the body tube and the balsa on the engine assembly using an old #11 blade. I didn't go crazy, just enough to glue them together. I used that same blade to scrape any excess glue that was in the slots. I held them tight until set with both hands. I then applied glue to the rear centering ring and body tube,

and glued my home-made ring in place. I used that coupler I used to cut the slots to hold the ring in place until the glue set.

You have far more patience than I - looking good!

Thanks, man. It's easy to do the JB Weld thing, I just work on other things after the three minute or so application thing, and check on it from time to time. It cures so slowly that it is really hard to mess it up. I've learned a lot, and next time will be quicker I think.

Before shot of the last JB Weld application on the nose cone. I went this far, might as well do it right, eh?

Final sanding of the ring I made. The better job I do now the easier it will be later.

I used that paint brush I used a couple posts ago to apply glue (Titebond) to the MBT (Main Body Tube) and my ring.

I put the cone on, lining up the seam beneath a fin slot. The seam might be a trouble spot in the future, might as well hide it underneath a fin.

I applied thin CA to the tail, and smoothed it out with a piece of paper moving fast so it wouldn't get stuck. Lumps will be avoided that way, and save on sanding later.

plus the ca will harden the tail cone to the point that spot putty can be applied/sanded . looking good!
rex

After pictures of the final nose cone shape, next to the stock cone, and by itself. I waited until the Weld was almost hard, and spun the paper cone tool on it to finish it. I'm happy, it shouldn't need much filler. I thought about drilling a hole in the tip, and having a place to hold an easily replaceable balsa dowel to replicate the rod on the tip of the missile. I don't want to poke anybody's eye out though.

I applied thin CA to the tail cone, using a thin piece of cardboard to smooth it out. The directions say to do this, so I'm not worried about excess weight on this step. I'm still confident I'll come up neutral on tail weight so I'll jump for joy tomorrow, I'm too tired to do that tonight.

Thanks Rex. I'm trying really hard. I have been winging it on some of these techniques, or have been refining old techniques that didn't work in the past as well as I would have liked. Tons of fun.

I mixed up a batch of Elmer's Carpenter's Wood Filler mixed with water, to about the thickness of latex paint. My tub is getting dried out, I should probably keep it in a zip-lock bag. It still works though, it just took a lot of mixing. I painted the lower body tube, tail cone, and nose cone on the seams and the JB weld tip with a sponge brush. It worked way better than a bristle brush I've used in the past. I made a point to poke filler under the seam of the tail cone. I was going to do the front of the rear fins also, but need to mix up another batch. I have to take care to not erase my fin lines when I sand, but I'll put a mark inside the fin slots just in case.

I now need to wait for it to dry. I weighed the nose cones, the JB weld comes in at 2.2 grams, much lighter than I thought it would. Almost 26 grams of weight to go in the nose still.