Fliskits Doubles Build thread

[smstachwick]

My package has arrived!

My girlfriend was home with me when I brought the thing in, so she took it upon herself to open it and look through both the instructions and the parts. Nothing appears to be missing or broken, everything is good. The design is unique for this scale, I'm impressed with the love and passion that clearly went into it. Not a half-assed job anywhere. The instructions are informative, yet simple.

I didn't accomplish any building tonight, but I did tick off some important pre-build tasks: measuring the fin templates and building the basic exterior portions of the airframe in OpenRocket, since I did not see a file anywhere on the internet. I don't really have the equipment to measure more precisely than the nearest millimeter or nearest conversion from 1/64th of an inch, so there is no telling how well the sim will reflect reality. But it should at least act as a starting point. Just a screenshot and supplies photo for now.

 

[smstachwick]

The OpenRocket file is as complete as I think I can get it for now. I'm still missing a mass object to represent the shock cord retaining pin that goes in the nose, but that pin is also missing in real life. Next time that little sucker is going in the nose as soon as I open the bag! I also don't have a gram scale to measure actual component masses.

Apogee is about 250ft with my launching defaults, which sounds about right.



Any suggestions on the default density for the Kevlar thread that comes with it? It's very thin, almost like a thick sewing thread, so I just used the Thread (Heavy duty) default at 0.3g/m

 

[smstachwick]

My progress from yesterday. The thrust ring is installed, although I’m not convinced that it’s perfectly straight or strong enough to take the hit. Just as a precaution I’ll be taping the rear of the motor to create an aft thrust ring. I’ll have to anyway, since this is just plain ‘ol butt staging.






My motor that I used as a spacer, marking clearly visible and wood glue starting to dry over the end.



Centering rings installed on the sustainer mount. That blade was on its last legs so I figured that repurposing it as a glue applicator was a worthy sacrifice.

The glue dries quickly enough that the rings want to stick almost immediately. Thankfully this is very soft balsa, it bends enough for me to scoot it to the right place without breaking.



I located the shock cord mount, it was in my bag all along. It’s actually a teeny tiny little cotter pin. Here it is installed.



Assembling the booster’s motor mount completed my day’s work.

 

[BEC]

I was going to suggest a bit of round toothpick (and a bit of glue) to retain the kevlar in the nose cone (which is what I do in scratch builds rather than use the little brass brad)...but it's too late...

 

[smstachwick]

I was going to suggest a bit of round toothpick (and a bit of glue) to retain the kevlar in the nose cone (which is what I do in scratch builds rather than use the little brass brad)...but it's too late...

I’ll file that away for my next micro or mini build, that sounds like a thing to try.

 

[smstachwick]

I’ll file that away for my next micro or mini build, that sounds like a thing to try.

More progress today.



I started by cutting a notch in the forward centering ring for the sustainer’s motor mount, followed by tying the shock cord around the mount and threading it through the notch.

My Scout knowledge has failed me for the second time today, it turns out that there is one artificial thread that will not fuse together under heat: Kevlar. I blackened it in the flame of my lighter, but the fraying was still present. I cut it and tied two half-hitches before it could unravel further.

I was going to glue the mount assembly in, but my continuous opening of the glue bottle to dip in my applicators ruined the glue. I also strongly suspect that storing it outside for the sun to pound on played a part: the dried skin on top of the remaining glue, and also on my knife blade I was using, had turned black instead of its normal light brown. The rest was extremely thin, being more like milk than its normal nacho cheese texture.

After a trip to The Home Depot for a new bottle that I will keep firmly closed except to squeeze it onto a sheet of paper, I got it installed.



During my later project to move the build elsewhere, I cut my leg and bled pretty good when I inadvertently left the knife swinging on its leash secured to my toolbox instead of being locked inside. My girlfriend was kind enough to patch me up, it actually surprised me how small the cut was for leaving blood spots on the ground. But next time I’m checking my box more carefully.

Continuing with the build:



The fins are attached. As with most of my eyeballed installations, they’re close enough that I can’t tell which way they need to go to be aligned, so that’s good enough for me.



Once the fins were strong enough, I glued the cotter pin into the nose for extra reinforcement and put the thing together. I think the sustainer turned out pretty nice.



I’m also pretty satisfied with the result of the full stack. The launch lug completed the glue work.

The last task is to attach the streamer. I’m going to need a stickier tape that will hold it to the shock cord better than the Scotch Magic tape I’ve got that allows it to slip and get stuck in the tube. Currently I’m considering Scotch Super-Hold.

I may start the finishing work soon. I’m undecided at this point what I want it to look like, but I do like the stock look. If only the supplied image were clearer.

 

[tjkopena]

My Scout knowledge has failed me for the second time today, it turns out that there is one artificial thread that will not fuse together under heat: Kevlar. I blackened it in the flame of my lighter, but the fraying was still present. I cut it and tied two half-hitches before it could unravel further.

Nomex also, and other aramid fibers. Some Kevlar thread is "bonded," coated so it won't fray like that. If the thread's not bonded I usually just put some glue around the cut or the knot to stop the fraying. You could also put tape or heat shrink tubing on the thread and then cut it in that section.

 

[smstachwick]

I ended up driving 30 miles for this stuff, I can’t believe it. Every store closer than that was fresh out.



But here it is all taped up.




Previous tape jobs had the streamer fail to deploy because the tape didn’t bind it to the shock cord, the cord just slid through and the streamer got left behind. I tested the strength of the tape joint by holding the nose and flicking the rocket like a wand.

Flick! The booster flew away, but that’s OK. It landed undamaged. I loosened the nose a bit.

Flick! Deployment! ….aaaaand detached nose. The cotter pin pulled out. That appears to be the weak point. But I think I overdid it a little bit, I doubt that a MicroMaxxII ejection charge will separate it as forcefully as I did.

There’s only one way to find out, I suppose: paint it up and test-fly the sustainer by itself, see if I get the nose back. I’ll likely grab a bit of gel cyanoacrylate first and glue the pin it first.

That’ll all be for another day though, rolling a micro streamer into a BT-3 is probably my least favorite way to get a rocket ready. Compared to this, my Alpha III’s BT-50 is like the Taj Mahal.

 

[smstachwick]

Long overdue update: finishing.

I tried my hand at using sanding sealer for the first time. (EDIT: Oops! It appears that that’s wood putty of some kind, no wonder )I don’t know if my can had somehow developed the wrong consistency or I just wasn’t applying it correctly, but I can’t say I’m overly happy with the result. A few grains got filled in at the expense of a few more popping out at the fin edges. I’m also considering whether 220 grit sandpaper is too coarse.



Note the fin being glued back on. I fixed the angle prior to the glue setting completely.

It was at that point that I decided to start on the black fins and nose. I’m actually OK with that color, I won’t put on another coat there.





I’m using my girlfriend’s acrylic paints, cheap Craft Smart stuff. Not fancy but it gets the job done without me having to go outside and deal with this heat.

I’ve been putting on a few yellow coats too. It’s a bit messy but at least I’ll be able to touch up the black areas pretty easily,



I’ve been recruited for a special project so I’m heading to ROC this Saturday. Hopefully I’ll get the decals and rod adapter finished before then so I can fly it.

Always as a single-stager first, then with the booster if I get it back. Currently I’m leaning towards putting an NE motor in the booster to start with, as recommended. I’ve got a couple ideas for what to do if the staging doesn’t go, starting with just using a standard MMX in the booster.

 

[neil_w]

I’m also considering whether 220 grit sandpaper is too coarse.

Generally I don't use 220 to sand balsa. I will use it, gently, to remove the heavy layer of filler or primer on balsa, but once I get close to the wood I switch to 400. On tiny little fins like that I'd probably start with 400, because one errant stroke with 220 can remove half a fin.

 

[Pappy]

regarding sealer, i really like elmers wood filler mixed with water. makes a nice, smooth puddin' for brushing on, and sands wonderfully. easy clean up, too. i keep a little tupperware sauce thing with a mixture in it, and it keeps really well. also, agree that 400 grit is the way to go. 220 okay for some basswood, at least preliminary sanding.

 

[smstachwick]

The Doubles fell by the wayside when I took on another project. Unfortunately I snapped two of the fins when I accidentally set some heavy groceries down on it, and elected to put this other project first.

In the meantime I created a safe place for the rocket in my cabinet and let it be. I also went out and bought some 1/16th inch balsa stock.

Now that other project is as good as I feel like getting it. Over the last week I cut out the fins and glued them on, with the first paint coat going on today. I opted not to sand or putty these fins, even though the balsa is harder and stronger.

 

[smstachwick]

The new fin has been cut and attached, after a minor delay with my printer and network. I like plotting it on graph paper to get a template.

 

[smstachwick]

As an update: I've managed to the get the rocket in the air a few times, at least once with successful staging. The trick was that I put a standard MMX motor in the booster, the delay was short enough that it didn't have an adverse effect on the rocket's trajectory between burnout and staging. It also wasn't super difficult to recover. I'm still trying to get successful staging with the recommended -NE motor in the booster.

The problem with it is that it's very easy for it to be crushed, I don't have much room at the range to set things down. Further work will likely involve replacing the balsa fins with cardstock, possibly with through-the-wall construction. Either that or getting some more folding tables to take to launch days.