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Multi-Roc 36 hour build

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Alan R

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Get an email from my friend on Tuesday afternoon saying "hey... the weekend looks good, lets go launch Saturday." Our field isn't huge, but plenty big enough for a D-motor.
I start digging around my stuff. Still packed in the box after the last launch. I shoot an email back, "sounds good. I've got 2 broken fins and 1 missing fin... I'll start gluing"

What I'm looking at in my box though is ... I don't want to launch the Redstone again. Had a great flight (finally, after about 5 bad ones). Spudnik lost a fork, again. Way too much trouble to fix that one. Time to retire those two. Most of my fleet has now moved up to 29mm, so I don't have a lot left.

Wednesday morning then just doing a couple of minor fin re-glues. Replaced the lost fin on the Redstone while I was at it. After lunch I head over to Hobby Lobby to pick up some motors. And while I'm there I'm thinking, you know, I should just pick up an 18mm flyer, and pop it together for the weekend.

Now of course, if I was smart, I would have just grabbed one of those generic plastic-fin-can kiddie rockets and I could just CA it together an hour before launch if I wanted... but NOOOOoooo. Who ever said rocketeers were smart?

Hm, Multi-Roc... with a glider ... how about a real challenge??

When I get back from the store about 4pm, I got a new email from my friend... "Hey, Friday looks great! Let's do this" ... Friday it is then. Ack. A bit less time than I planned on.
Right now it's almost 9 am Thursday. Let's get going on progress so far. I'm only sad I didn't think about documenting this along the way, but let's catch up.

Here it is: (and yes that IS a Spudnik fin in the background!!!)

IMG_0444.jpg
 

BABAR

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Cool.

You can lose three parts with only two motors! ;)
 

Alan R

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Because of the time crunch I decide to skip the booster, but I will attempt to build the glider while the glue dries on the main stage.

Wednesday evening: quick sanding of the parts before popping them out of the balsa sheet (who else really appreciates laser-cut parts? Does anybody remember those die-cut sheets?)

The main fins on one sheet, the glider is all on the next sheet. Booster fins went back in the bag. Had to look closely. Booster fins are larger than main body fins. Glider is much smaller than i expected. Wing span is only about 6".

Just a heads up: look closely at your parts. Dry fit everything. There are a couple of things that can get confusing.

Main fins with miscellaneous parts, the glider sheet:
IMG_0445.jpg IMG_0446.jpg
 

Alan R

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Why do I have time to post? Because I'm currently waiting for fillets to dry a bit so I can rotate to the next set, and the glider wings have been glued to the body.

I have this weird looking fin jig I made ages ago .. actually somebody else printed it for me - and made me realize it was going to be cheaper to buy my own printer than continue down that path. But that's a story for a different thread. Anyway, it came in handy allowing me to attach multiple fins at once.

So.. back to Wednesday evening. Sand sheets, remove fins. Round edges. Attach to main body tube.
I did 2 fins, let them set up a couple of hours, then did the next 2. All four attached so they could dry overnight.

While the fins were setting up I started working on the nose cone. Nose cone for this is a hollow nose with no attachment point. The attachment is a plug that goes in to the base of a short section of BT50. The instructions just say to stick the nose cone in the top so it's snug. Like a payload bay setup. Easy way to lose an NC.
But also confusing because one of the configurations of this rocket as shown on the front and in the instructions is to ditch the payload bay and just put the NC directly on the main body tube. With no way to attach it to the shock cord.

I drilled a hole in the NC shoulder and attached it to the plug with a short run of kevlar thread. I love that stuff. One of the best investments I ever made in this hobby.

Next heads up: I had a LOT of trouble with the nose cone insert and spacer (J and K on the instruction sheet). Mainly... that spacer was too tight and I couldn't get it all the way in after I had applied the glue inside the tube. It went mostly in and stopped. Then I cut off the 1/8" or so that was hanging out. I had actually glued the insert to the spacer, but the glue came loose when I was attempting to insert it into the body tube. Lucky break. Re-glued it after I cut the spacer.

Nose cone insert attached to spacer with model cement. Thread attaches insert to NC.

Pics: weird fin jig, insert, and nose cone
IMG_0440.jpg IMG_0441.jpg IMG_0442.jpg
 

Alan R

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Still Wednesday evening. I've got fins on, I've got the nose cone built. Time to move on to the glider.

Pop out the glider parts. Wings and horizontal stab get a nice round sanding.
(I just had a deja vu. Don't know if that's good or bad. Hope I didn't mess this up completely... )
The body is a 3-part sandwich. It's not exactly clear where things should align. I finally figured out the parts align along the top edges. Reason is the dowel attachment point needs to hang below the body.
Look carefully at the parts.
Align front and back, align along the top. Glue together with some wood clamps on my bench.
While that is setting up I go to work on the wings. The root or center point where the wings attach gets a 30ish degree sanding so they have some surface area to attach when the glue gets applied.
The kit also comes with 2 small balsa stubs to use as a dihedral jig. Nice. Except they don't stand up.
Spend a bit of time screwing around trying to make them stand up. I think this is the point where pins on the construction board help. Stand those jigs up straight, put down some wax paper or work on a plastic mat and glue the wings.

By the time I get the wings aligned and glued, the body has had time to set up so I sandwich in the other side. Attach the rudder at this point. It needs to be glued to both sides.

Let all that dry over night.
 
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Alan R

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Thursday morning.
Start on the motor mount. Standard thing. Except I add a q-tip tube and kevlar thread attachment. Bowline knot on the top end for shock cord attachment. CR's cut for the tube after the glue set up. Tube attached with model cement.

Glue that in to the body, 1/4" overhang. The overhang is for staging. This is basically the point where I start documenting things.

Start the fillets. For scale, you can see the horizontal stab and the dihedral pieces on the table below the rocket. The rocket has been moved to the back of the bench while I work on the glider.

IMG_0439.jpg IMG_0447.jpg
 

neil_w

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Why do I have time to post? Because I'm currently waiting for fillets to dry a bit so I can rotate to the next set, and the glider wings have been glued to the body.
Using TB Quick-and-Thick for fillets will allow you to do all of them in one sitting, since they don't run (at all). Just a thought for the future, *especially* if you're building, shall we say, "in a hurry". :)
 

Alan R

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Using TB Quick-and-Thick for fillets will allow you to do all of them in one sitting
Just using TB2. I can rotate it after 30ish mins and do 2 at a time. In this case I can go back and forth between the glider and the rocket, so not a problem.
I'm doing a quick build, but don't want to rush anything. Right now trying to decide if the glider glue has set up enough to flip it. It's been a couple of hours now.
 

Alan R

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This little glider is tricky. The body got sandwiched together last night.
Spent a bit of time this morning trying to make a jig to keep the wings straight so I could glue them.

Ended up putting it in a vice with some cardboard on each side to hold the wings in the right position. then I put down the glue and dropped a motor on top for weight.

Lots of careful futzing with this, and trimming the cardboard so the wings are (hopefully) on pretty straight. Applied glue and lined up the back of the wing and body with carpenter square:

IMG_0437.jpg IMG_0438.jpg IMG_0443.jpg
 

Alan R

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11 am Thursday.
Glued the stab and pin. Put some plastic under the pin so it stays off the body.
Fillets on the wings.

Rocket mostly done, about 22" tall.

I'll add the launch lugs and glider lug after lunch. Then I have most of the afternoon to think of a paint job. I don't like the idea of a white glider.

IMG_0450.jpg IMG_0451.jpg
 

Alan R

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Applied paint at 4:30. Rustoleum Red (awesome!) and Krylon Yellow (meh.)
Yellow will need another coat. But not today, nor tomorrow.

IMG_0452.jpg IMG_0453.jpg
 

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Turned out good for a rush job.
Hope your first flight today with it goes well.
 

Alan R

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Needed a last bit of time this morning to trim the glider.
The clay that Estes gives you is pretty soft. Tried it, pulled it out and replaced it with the stuff I had here. It's a little thicker/less pliable. But BONUS... Mine comes in colors. A nice red for example.
Did the balance on my finger to the mostly-correct CG and a few test flights inside. I'll final trim on site in an hour or so, but this looks pretty close.
I'm also sure that I'm not a perfect builder. That means there's going to be plenty enough slop in the build to make it lean one way or the other.

IMG_0454.jpg
 

Alan R

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Turned out good for a rush job.
Hope your first flight today with it goes well.
Thank you. Flight pics soon. Good except for that yellow paint job. HA

One of the reasons I did this thread is because I searched the forum and there wasn't any build thread on the Multi-Roc. I hope I passed along a couple of bits of useful information for someone else putting this together.
 

Alan R

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Flight configuration. Borrowed some artsy sparkle duct-tape from the wife to distract your eye from the crappy paint job.
IMG_0455.jpg
 

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Good luck with the flight and glider. I couldn't trim mine to glide well to save my life.
 

Alan R

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Good luck with the flight and glider. I couldn't trim mine to glide well to save my life.
It flew well. Final trimmed the glider on site. The glider flew almost too well. All I can say is .. keep trying.
Launched once with the glider, it arced over because of glider drag. Nice separation, but lost track of the glider when it turned into the sun. Searched the last known vector with no luck, and then found it when zig-zagging back to the launch site. It either took a quick dive from last known position or it did a tight circle in that last 50'.
Video'd the launch but you can't see anything after launch because that glider is too small on the movie.
Altitude was probably +/-700ish feet on a B6-4 with glider attached.
Did a second launch B6-4, no glider. Flew well, maybe a couple hundred feet higher.

multi.jpg
 

BABAR

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Colored Mylar tape on the glider may help visibility.
 

Alan R

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Colored Mylar tape on the glider may help visibility.
I'll probably do that, but even mylar tape is not going to help when it circles round right between me and the sun
 

Alan R

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Built bigger glider - wings, stab, length. I just took the dimensions from the original kit pieces and increased 50%. 3/32 instead of 1/16 also. Single spar for the body with short reinforced sandwich under the wings and rudder for better glue joint.
The pin is now under the wings in the same distance from the tail (175mm) as original. It will hang on the same spot of the booster without dropping the tail below the fins.
CP will be a little more forward. Not sure the weight but would guess only a few grams heavier. There will be lots more drag on the booster. Have to wait til next spring to see how it goes.

IMG_0471.jpg
 

Alan R

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Weird problem. I started work on the booster yesterday. Did the mmt, fins, and now I come to the coupler.
The coupler fits fine, a bit loose even, into the booster. But it won't fit into the main bt.

Has anyone else experienced this?
Even sanding off almost a whole layer its still too tight to fly. I also sanded the interior of the main bt.
Would the paint shrink a tube that much? I think this is caused by fin glue. The couple fits better into the top of the BT. So... glue shrinking tubes this much? Could you dry fit the coupler in while gluing fins to ameliorate that problem?

IMG_0476.jpg
 
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GlenP

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yellow glue can shrink after all the moisture in the glue has dried out.

You can just cut a slot along the coupler and let it curl inside itself, then put a little glue to repair the slot, so it would have a slightly smaller dia. You don't have to cut the part that fits in the booster, just the exposed portion that goes into the sustainer.
 
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