Starting Build on Unnamed Spare Parts Monstrosity

[brockrwood]

I am trying to make something out of the rear end of a previous experimental cluster rocket I created many years ago.

The top part of the experiment was stolen for a different, newer scratch built rocket.

Now I just have the cluster tail section to work with.

I added an Apogee BT-20 size tube for the main body tube. On top of that I added a payload bay and nose cone from an Estes X-Ray.

Pretty tail heavy with three engines installed. I will need to put some clay in the nose cone.

Yes, I kind of overdid it with the huge fins. Still, as this bird is tail heavy, maybe the big fins are a good thing.

 

[neil_w]

Those are some big old fins. What does the sim say about stability?

 

[brockrwood]

Those are some big old fins. What does the sim say about stability?

Haven’t entered the data into OpenRocket yet. Need to do that.

 

[brockrwood]

Shock cord attached. Screw eye screwed in and bonded with super pegamento

 

[brockrwood]

I am trying to make something out of the rear end of a previous experimental cluster rocket I created many years ago.

The top part of the experiment was stolen for a different, newer scratch built rocket.

Now I just have the cluster tail section to work with.

I added an Apogee BT-20 size tube for the main body tube. On top of that I added a payload bay and nose cone from an Estes X-Ray.

Pretty tail heavy with three engines installed. I will need to put some clay in the nose cone.

Yes, I kind of overdid it with the huge fins. Still, as this bird is tail heavy, maybe the big fins are a good thing.

View attachment 524319

Oh yeah. Now, how to wire these up without without interfering with the launch rod…

 

[waltr]

Bus bars using two pieces of 14-12gauge copper wire (house AC wire).

Insert igniters so one lead is up (in your photo) and the other down. Then lay the bus wire across all three and twist the top igniter leads around the bus wire. Do same with second bus wire on the bottom leads.

 

[tsmith1315]

Where do you

Shock cord attached. Screw eye screwed in and bonded with super pegamento

View attachment 524458

Hey Brock, where do you get your kevlar cord?

 

[jmasterj]

Where do you

Hey Brock, where do you get your kevlar cord?

For LPR/MPR, I get Emma Kites braided kevlar from Amazon. Just restocked 150lb.

 

[brockrwood]

Where do you

Hey Brock, where do you get your kevlar cord?

Amazon. The stuff in the main tube is 100 pound kite line. This stuff:

emma kites Kevlar Kite Line 500Ft 100Lb Braided Kite String Abrasion Resistant Low Stretch Utility Cord for Outdoor Tactical Survival Hiking Camping https://a.co/d/49byWFI

The lightweight stuff in the two booster tubes hmm. Not sure where. Maybe Uncle Mike’s rocket shack? Sadly, Uncle Mike is out of the rocket businesz. :-(

 

[tsmith1315]

Amazon. The stuff in the main tube is 100 pound kite line. This stuff:

Thanks!

 

[brockrwood]

Well, the Monstrosity came back in one piece at the local park launch today! All three engines lit!

It had three parachutes (one in main tube and one in each booster tube). One booster parachute did not come back. A little scorching on the main tube from the ejection charges in the boosters.

Hmm. Maybe I just omit the parachutes in the boosters and use A8-0’s or B6-0’s in the boosters. I suppose I can cut holes in the booster tubes to let the gases from the -0 engines out.

An engine with no ejection charge should not produce a lot of “ejection” type gases, right?

 

[milehigh]

Hi, Brock,
Try this on for the name of this rocket:
S.P.A.M.-1
It not only works with Spare PArts Monstrosity, but it kinda goes along with real Spam - Spare PArts Meat!

Anyway, great flight yesterday.

 

[brockrwood]

She survived her first launch! She has earned her paint!

Thanks to @milehigh for the photo!

 

[brockrwood]

I am now putting some fillets on to stregthen things a bit. Then we apply the wood filler, primer, and paint and do what comes naturally.



(Wow, that Elmer’s wood glue I used years ago dries really ORANGE.)

 

[brockrwood]

Dang. The Titebond Original Wood Glue left big air bubble holes in my fillets. Should have used Quick & Thick. Live and learn.

It should be plenty strong, just not as purty…



I guess I could fill those holes with Quick and Thick. Or maybe the wood filler will fill them up.

 

[neil_w]

Dang. The Titebond Original Wood Glue left big air bubble holes in my fillets. Should have used Quick & Thick. Live and learn.

Yes.

My standard operating procedure: thin fillets with regular TB (or TBII or whatever) and then cover with larger Q&T fillets.

For the thin fillets: apply small bead and then run finger over it to push it into the joint, not leaving very much glue but enough to see that the joint is filled (if not, add more glue and repeat.) This very thin fillet should dry very quickly, and then you can do the Q&T.

For the Q&T: follow my tutorial.

 

[brockrwood]

Man, it takes a long time for the Titebond Original Wood Glue to dry. It’s been 12 hours.

 

[neil_w]

Another reason for not doing heavy fillets with regular TB. The top layer skins over, sealing in the moisture for the inner glue. It can indeed take a *long* time to dry fully.

I do not know why Q&T doesn't suffer from this problem, but it sure doesn't seem to.

(semi-unrelated): Did you run a finger over those fillets, or are they straight out of the bottle?

 

[brockrwood]

Another reason for not doing heavy fillets with regular TB. The top layer skins over, sealing in the moisture for the inner glue. It can indeed take a *long* time to dry fully.

I do not know why Q&T doesn't suffer from this problem, but it sure doesn't seem to.

(semi-unrelated): Did you run a finger over those fillets, or are they straight out of the bottle?

Finger was used but I slathered it on pretty heavily.

 

[neil_w]

Finger was used but I slathered it on pretty heavily.

Did your finger actually touch the glue? (just pokin' ya)

In addition to my prescription given above (*thin* TB fillet followed by Q&T), I have a few more fillet suggestions:

1. If the fillet is not smooth when it is wet, it will not be smooth when it is dry. When you run your finger over it (best if it is damp, *especially* with Q&T... see my tutorial) you should apply enough pressure to create a smooth, consistent bead, but not so much that mass quantities of glue build up on your finger and up the sides of the joint. If that's true you either are pressing too hard, or put too much glue in.
2. Unlike epoxy, wood glue shrinks (a lot) as it dries. So, creating massive beautiful fillets in one pass works great with epoxy, and usually lousy with wood glue. If you want really large fillets (which are rarely needed, unless you want them for cosmetic effects), you're best off doing them in smaller layers and building up.
3. The deep crevices in tube-tube joints require special treatment, because air is going to get trapped in there under the glue (this applies to launch lug fillets as well). After applying your thin fillet and pushing it into the joint by running a finger over it, let it settle for just a short bit (bubbles will form) and then run a pin through the fillet. This will greatly reduce the bubbles. Any that remain will be covered over by the Q&T.

Sorry I seem to be in a very suggestion-y mood right now.

 

[brockrwood]

Did your finger actually touch the glue? (just pokin' ya)

In addition to my prescription given above (*thin* TB fillet followed by Q&T), I have a few more fillet suggestions:

1. If the fillet is not smooth when it is wet, it will not be smooth when it is dry. When you run your finger over it (best if it is damp, *especially* with Q&T... see my tutorial) you should apply enough pressure to create a smooth, consistent bead, but not so much that mass quantities of glue build up on your finger and up the sides of the joint. If that's true you either are pressing too hard, or put too much glue in.
2. Unlike epoxy, wood glue shrinks (a lot) as it dries. So, creating massive beautiful fillets in one pass works great with epoxy, and usually lousy with wood glue. If you want really large fillets (which are rarely needed, unless you want them for cosmetic effects), you're best off doing them in smaller layers and building up.
3. The deep crevices in tube-tube joints require special treatment, because air is going to get trapped in there under the glue (this applies to launch lug fillets as well). After applying your thin fillet and pushing it into the joint by running a finger over it, let it settle for just a short bit (bubbles will form) and then run a pin through the fillet. This will greatly reduce the bubbles. Any that remain will be covered over by the Q&T.

Sorry I seem to be in a very suggestion-y mood right now.

Love suggestions!

See? No matter how hard we try, every thread eventually becomes a glue thread.

 

[Daddyisabar]

Oh the pain of going back and filling in the gaps and bubbles with even more Titebond II. It takes the patience of a Jedi.

 

[Daddyisabar]

Well, the Monstrosity came back in one piece at the local park launch today! All three engines lit!

It had three parachutes (one in main tube and one in each booster tube). One booster parachute did not come back. A little scorching on the main tube from the ejection charges in the boosters.

Hmm. Maybe I just omit the parachutes in the boosters and use A8-0’s or B6-0’s in the boosters. I suppose I can cut holes in the booster tubes to let the gases from the -0 engines out.

An engine with no ejection charge should not produce a lot of “ejection” type gases, right?

View attachment 524637

View attachment 524638

You can plug the red lable 0 boosters with a nice dollop of 5 minute epoxy. Take it to the park. The old dudes there are like Vader, they are very forgiving of the dark side.

 

[brockrwood]

You can plug the red lable 0 boosters with a nice dollop of 5 minute epoxy. Take it to the park. The old dudes there are like Vader, they are very forgiving of the dark side.

I am thinking of cutting vent holes in sides of the booster tubes. Make it look like an old Buick.

 

[brockrwood]

Fillets still drying 20 hours later.

These things had better be super duper strong.

 

[brockrwood]

I am going to use “Good Stuff” polyurethane foam for my fillets next time. No shrinkage. Dries fast! ;-)

 

[brockrwood]

Glue fillets now drying for 36 straight hours. That’s enough, right? Most of the glue is clear (or yellowish-clear). I still see a small amount of light yellow.

 

[Doug Holverson]

I'm digging the old school scratch built look of this thing.

 

[brockrwood]

You know, you can spend hours making sure measurements are accurate to within hair’s breadth. Sometimes you have to. Other times, the “ocular estimation technique” (eyeballin’ it) is good enough. This is one of those times.

 

[brockrwood]

Where is my pin vise! I need my pin vise!