"College Funds" Yet another scratch build.- Up in flames at Hellfire 18

I'm having a little problem. The primer comes off the tube without much effort. I can scrape the primer off with my fingernail. It doesn't come off as readily as it does on a plastic NC, but isn't sticking like on a paper tube or a fiberglass one. It's been at room temperature for a few days now so I don't think it's a curing problem.

Alex

Did you scuff up the tube a little bit? I have always found that to help.

I googled 'sanding sealer' and here was the first non-shopping result:

https://www.rockler.com/blog/index.cfm/2007/3/23/When-to-Use-Sanding-Sealer

A word of warning is in order. The stearates make sanding sealer rather soft. If you put a hard, brittle finish, like lacquer, over a thick, soft one, like sanding sealer, it is much more likely to chip and crack. For that reason, if you use sanding sealer, stick to one or two coats at the most, and plan to sand most of it back off. For the same reason, and because it tends to shrink as it cures, it is not advisable to use sanding sealer instead of pore filler.

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This is in the context of woodworking, but it sounds valid here.

CarVac said:

I googled 'sanding sealer' and here was the first non-shopping result:

This is in the context of woodworking, but it sounds valid here.

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Thanks CarVac, I saw that page but somehow read over the part you quoted.

I might not use sanding sealer for the lower portion of the rocket. Just primer and paint.

Alex

Really, the best way to prevent any dimensional instability of Blue Tube is to fiberglass it, even one wrap with really light glass.

CarVac said:

Really, the best way to prevent any dimensional instability of Blue Tube is to fiberglass it, even one wrap with really light glass.

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I know. I was considering it when I first started the build. It would be so much easier to finish too. No spirals to fill, no warping, no peeling primer. I didn't because I dont have unlimited FG cloth and because I needed a little break from composites.
I don't think I'm going to use blue tube any more after this build, or at least not in diameters of 2in or larger. It just gets too hard to work with. It's hard to paint and the spirals are a major PITA to fill.

I'm going to stick with FG, Paper, or glassed airframes for now on.

Alex

Aksrockets said:

unlimited FG cloth

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I'm so going to miss being at school with our gigantic rolls of fiberglass left over from a senior design project a few years back...

I gave it a few more days and the primer seems to be sticking much nicer now. It still scrapes off, but it takes some work.
I smeared some bondo filler onto the small parts where I missed filling the spirals and sanded them down with 220 grit.

I want this finish to look immaculate. I fully intend to spend more time filling little pinholes and sanding then I have with any other rocket.

The one thing I do like about Blue tube is I can be rough with it. When I'm sanding off filler from tube spirals I go straight to 100 grit- too rough to use on paper rockets. The blue tube doesnt "fuzz up" like paper tubes do when you really dig into them. It just makes filling the spirals a little bit easier.


Alex

I spent most of this evening just filling and sanding.
I switched to CWF for the spirals on the fincan. It's a little nicer to use.


I filled the holes in the back of the fin by hot gluing strips of basswood through the slot and onto the motor mount tube. Over this went wood filler.


The gap between the fins was filled with wood filler as well.


I gave it a good, heavy coat of Deft Sanding sealer and left it outside for the fumes to clear off. About 5 minutes later I took it into my heated workshop to dry.


Hopefully I can do final sanding and prime tonight!

Alex

Aksrockets said:

About 5 minutes later I took it into my heated workshop to dry.

Alex

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Lucky...

blackbrandt said:

Lucky...

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Sometimes.
Its a greenhouse and in the summer, it acts like a greenhouse.

Alex

STOP.

PRIMER TIME.

Im going to do lots of work on this rocket this week and hopefully finish it by next saturday so it can fly at the UROC Febuary Research launch.

I cut all the bulkheads out today using a harbor freight circle cutter and a drill. Some days, I would give anything for a drill press.
The drill is hard to use, but it does the job okay.


I made 2 bulkheads that matched the ID of the body tube and 2 Bulkheads that matched in inside of the coupler. These will be glued togeather and sit inside the coupler. It's a pretty basic AV bay setup.
I took a picture of all the bulkheads layed out but my phone decited to delete it.

I glued both togeather with wood glue and left them to dry.


Here they are! Not bad for only using a drill. They are a little loose but that should not matter too much.


I am using 1/8 all thread to connect them and for the sled to sit on.


I'm liking how this is looking!


Alex

Aksrockets said:

STOP.
View attachment 117149
PRIMER TIME.

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In the name of paint?

This bad boy needs a K160 long burn. In fact, t is begging for one. I had better bring one to the launch next week, just in case you NEED one!

lawndartman said:

This bad boy needs a K160 long burn. In fact, t is begging for one. I had better bring one to the launch next week, just in case you NEED one!

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It DOES need some long burns but going to save the 54mm motors for Hellfire. Hopefully this will fly on Saturday on an AT I357T. It should be a good boost to about 2000 feet. Perfect for a Dual deploy test.

Alex

I did some work on the AV bay yesterday.

I cut a 2.5"x6.5" sled to mount my Adept 22 altimeter on. It's made from the same 1/4in plywood as the fins.
I mounted my Adept 22 with 3 micro screws I found at ace hardware. They seem to be the perfect size.
I also layed out the wiring.


On the Bottom of the sled I epoxied 4 aluminum spacers that slip nicely over my 1/8 in all thread. One was crooked so it had to be removed. Easy fix.


At ace Hardware I found these lamp nipples that will work perfectly for ejection canisters. I drilled shallow holes in the bulkheads and epoxied them in.


Theres quite a bit of space left in the AV bay


Stay tuned!

Alex

qquake2k said:

It's looking good, Alex! I'm curious, why did you mount the altimeter with only three screws, and why did you use only three mounting tubes on the sled?

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I'm lazy. It'll be attached with 4 for the actual flight.

Alex

Aksrockets said:

I'm lazy. It'll be attached with 4 for the actual flight.

Alex

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I'm with ya, bro. Only I'm not lazy, I'm efficient. :tongue:

I got a the base layer of grey on the tube, It tured out quite smooth, despite the cold weather. I'll put on another coat tomorrow morning and do masking tomorrow.


Upper tube:


AARGGG! Apparently the wood filler didn't do it's job well enough. Some spirals are still visible near the fins.


Alex

Why did it not show in the primer?

MasonH said:

Why did it not show in the primer?

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The primer was white and slightly transparent. It made it hard to see imperfections.

Alex

Also, it really takes a long while for the paint & filler to completely cure. You might think it's "dry", but it still could have some curing, and subsequent shrinking, to do. So oftentimes you might have a perfectly smooth surface and then a day or two later (or longer), those spirals show up. What happened was that the paint shrunk a bit, and pulled into the spirals. This is fairly common. And fairly frustrating too I might add.

Still, looking good Alex. I want to see this one fly.

s6

Nice build thread, Alex! I assume that first flight is this Saturday.

stealth6 said:

Also, it really takes a long while for the paint & filler to completely cure. You might think it's "dry", but it still could have some curing, and subsequent shrinking, to do. So oftentimes you might have a perfectly smooth surface and then a day or two later (or longer), those spirals show up. What happened was that the paint shrunk a bit, and pulled into the spirals. This is fairly common. And fairly frustrating too I might add.

Still, looking good Alex. I want to see this one fly.

s6

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Never would have thought of that! It is fairly frustrating but I'm not going to worry about it too much. It's a decent finish but not flawless, mine (unlike yours) are rarely flawless.

Aerostadt said:

Nice build thread, Alex! I assume that first flight is this Saturday.

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Hopefully, yes. But it will take a lot of work, It might fly not fully painted or single deploy if I don't have the time to finish it.

Alex

I finished wiring the AV bay tonight.
The red wires go to the main chute, the gold wires go to the drouge chute and the yellow ones are the switch.

Yes, I'm using duct tape to attach the battery and yes, it will be used for the actual flight. I'm very confident that it will hold the battery on there, nice and tight. Don't believe me? Tape one the way I did to a clean plywood board. It's quite sturdy and simple.

You might notice the electrical tape over my 9v connector - switch wire connections. Both wires were stripped about 1in, tightly wound togeather and folded. The electrical tape is just to prevent shorts. With previous tests, my wires usually would break before my connections failed.

Here is my Forward bulkhead with 2 loops of kevlar instead of an I bolt. I needed to save weight and space so this seemed like an attractive option.



Alex

Well, the paint is just about done.

I'll post all the paint details tomorrow (studying all night tonight) about masking and such, but here is a teaser.




Alex

Lets just say ejection charge testing DID NOT go well.


Alex