Level 3 Build - Rocketry Warehouse Terminator

EeebeeE said:

Pretty cool, but I am on a budget. I already have a flanged retainer, which is why I decided to cut the tailcone by 1". This is what mine should look like. Not as streamlined as yours, but close.

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They all look great from 500'

DizWolf said:

They all look great from 500'

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Exactly how I think about all my paint jobs.....

Adrian

Did the first set of fillets. I'm going to need a lot more RocketPoxy. When all is said and done, I will probably use 18 oz. of this stuff instead of 6-8 oz. Ordering more tonight.

jd2cylman said:

Exactly how I think about all my paint jobs.....

Adrian

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What is this "paint" of which you speak?

EeebeeE said:

Did the first set of fillets. I'm going to need a lot more RocketPoxy. When all is said and done, I will probably use 18 oz. of this stuff instead of 6-8 oz. Ordering more tonight.

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I'd imagine about .77oz per fillet (i mix in 22 gram batches typically don't ask why) so yea... lots more.

If you're really in a rush to go I've got some rocketpoxy here if you wanna drive here and get it

Thanks, Dave, but I'm not in a rush. I put in an order this evening.

cherokeej said:

Y
Edit: Ever consider attaching the main harness to the forward closure of your motor? A cast eye-bolt, jam-nutted to the forward closure, will be the strongest point in the entire bird, and eliminate the need to reach inside to attach the harness. Just drop the end thru the mmt, attach, and slide in the motor. Bingo.

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^+1. This.

jderimig said:

^+1. This.

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I'm thinking about this.

First set of fillets is done. 2 more sets to go. This first round I did not heat the epoxy before applying it. I may do so next time for the internal fillets because it heating it makes it temporarily more runny and would allow me to pour it in instead of spread it.

TTW fillets are the most important for stability/strength so I always migrate to doing those first, but I guess it will work in the sequence you are doing it also...

dixontj93060 said:

TTW fillets are the most important for stability/strength so I always migrate to doing those first, but I guess it will work in the sequence you are doing it also...

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The internals stiffened the fins up a lot, and that was without the externals in place.

Bases for rail buttons. The longer one is for the forward button. It extends 5.5" to the forward CR from the button and the forward end is angled so recovery materials will not get caught. The small one is for the rear button It will be glued to the motor tube, rear CR, and the airframe. so even though it is small, it should lock in place pretty well. The wood is ash. there are 1/4-20 brass threaded inserts in the holes. The rail buttons are aerodynamic, so I will add another nut on the outside of the airframe, screw the buttons in place, then slip a wrench around the outer nut and tighten it down there. That way the rail buttons will be able to pivot. Aerodynamic rail buttons are not supposed to be screwed all the way down because they can hang up on the rail if they are. The lower base is off-center because it has to fit around a threaded rod. I suppose I could glue it to the rod as well.

I rethought this. The lower rail button base was a little too small and I didn't like the off-center hole for the insert. At the same time I could take advantage of the threaded rod to better hold it in place. So I cut a larger block, drilled the hole in the center for the insert, then drilled out an area to the side where the threaded rod interferes. Now I have a bigger base, it is glued on three sides plus the threaded rod. This should stay in place a lot better.

For a fiberglass rocket I never back the rail buttons, I just drill the FG, tap the hole and screw the buttons in.

jderimig said:

For a fiberglass rocket I never back the rail buttons, I just drill the FG, tap the hole and screw the buttons in.

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+1!

jderimig said:

For a fiberglass rocket I never back the rail buttons, I just drill the FG, tap the hole and screw the buttons in.

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I normally do as well, but I am working with an out-of-town CC, so I figured I would overbuild rather than underbuild. I can tell you, these rail buttons aren't going anywhere.

Fillets are finished.

EeebeeE said:

I normally do as well, but I am working with an out-of-town CC, so I figured I would overbuild rather than underbuild. I can tell you, these rail buttons aren't going anywhere.

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Hah, I never use buttons without backing. It is funny how much we think about various design and build decisions, and grow strong feelings about our habits, when so many ways work perfectly well.

That plus since this is a cert flight, the last thing I want to have to deal with is a rail button coming off.

I am digging that fin can work, by the way. I was struggling to visualize when you only had words, but now that I see pictures I think it is great!

watermelonman said:

I am digging that fin can work, by the way. I was struggling to visualize when you only had words, but now that I see pictures I think it is great!

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Thanks, I saw a thread of someone building a rocket in Europe who did this. Makes both a lot of sense to do it and also makes strong internal fillets. The other thing it allows you to do is to see the glue application of the fin roots to the motor tube. All through the build you can ensure good beads and good contact of the glue with all parts being connected.

Now it's starting to look like a rocket. Forgot to photograph this, but the way the motor tube was mounted was to draw lines where the finroots would meet the tube. then glue the forward area that would come in contact with the CR and glue along the lines. The tube was then inserted into the fincan at a 45-degree angle away from the glue, then twisted into position so that a maximum amount of glue came in contact with the finroots. For this application, I heated the Rocketpoxy to kickstart the hardening process. That initially makes it very runny and easy to use, but it tacks up very quickly that way so you only have about 15 minutes to work with it, and even though It hasn't set yet, it locks in place and is not movable.

The base for the rail button was inserted and held in place with a screw. I had to drill out the aft CR holes for the threaded rods a little to get them to fit, but other than that, it went into place well. Glued the threads with Rocketpoxy, tightened down the nuts.



The boattail was glued into place using heated Rocketpoxy. I was going to use the same method of twisting it into place and over the glue, but the epoxy had started tacking up so I quickly twisted it roughly in place, whacked it with a hammer (hitting a board, laying on top of the boat tail. then using c-clamps to do the final twisting into place. I will keep the clamps in place until the epoxy sets.

Here you can see the glue application.





This thing isn't coming apart anytime soon. Using G-Flex epoxy and strips of fiberglass, plus an old Kevlar shock cord, I will fill the gap around the motor tube, creating a 1" bond. That will effectively make the boattail a thrustplate.

IN the process of building the lower fincan, I must have knocked a couple fins slightly out of alignment. So while still clapmed together, I took a hairdryer to the lower fincan on the boattail. It softened up the epoxy just enough that everything lined up. Cool.

This is what it looks like with the booster completely assembled.

Filling the gap between the motor tube and the inner boat tail wall. I used G-Flex epoxy and FG cloth first, then wrapped a piece of of Kevlar shock cord around the top. I will sand when finished. This will create a solid bond and also enable me to use sheet metal screws to hold the flange motor retainer in place.

You'll sand the epoxy.

But if you soaked that Kevlar with epoxy and let it cure, you're not going to be sanding it.

You don't sand Kevlar. You use Kevlar to destroy unwanted sandpaper.

cherokeej said:

You'll sand the epoxy.

But if you soaked that Kevlar with epoxy and let it cure, you're not going to be sanding it.

You don't sand Kevlar. You use Kevlar to destroy unwanted sandpaper.

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True.

Well actually Kevlar is susceptible to abrasion. It will turn to fuzz if you sand through the epoxy to the Kevlar. For that reason try not to do that. Shape it as best you can without getting down to the Kevlar.

Got into it a little, so I will recoat with Epoxy, lay a sheet of plastic over it and cover with a piece of steel until it hardens. The other thing this does is essentially form a 1" thick centering ring. The flange covers both the epoxy ring plus the back of the tailcone, so I have a makeshift thrust ring.

Well, The surfacehas been smoothed. Holes are drilled for screws, but I am going to need Torx head sheet metal screws. The Kevlar grips the threads so tight you can's screw them in very far. I have 1" screws now. Stripped the Phillips heads out of three of them. I am probably going to get 3/4" screws.

Retainer is almost mounted. Stripped the heads of some stainless steel sheetmetal screws even though I drilled the holes out a little more. Not too bad, and it is on there solidly. Now it is on to the altimeter bay.