Long term project: K&S Super Flash

[Tarasdad]

Boredom is dangerous. While sitting here twiddling my thumbs I decided to go ahead and mount the first rail button. I very carefully triple checked my measurements and markings for the upper CR. Once I was satisfied they were accurate I took a deep breath and applied my sharpest and smallest brad point bit to make a pilot hole. Drilled slow, making sure the bit was perpendicular to the tube at all times. I don't have access to a drill press and my rechargeable drill is dead so I did it the old fashioned way, with a hand drill! Patience and practice paid off as the hole was perfectly centered and straight. So on to the next size and...I forgot to mark the depth and drilled all the way through the CR and into the motor tube! Drat!

So my question is will this cause a problem? I can't figure out a way to get in there to repair the hole. The cardboard bulges in where the hole came out and there's just no way I can put enough pressure to push it back. I can probably work some epoxy into it from the inside but won't do that until I'm ready to permanently mount the rail buttons. Will having it there cause any problems (other than making it difficult to insert long 38mm cases, that is)? Should I seal it or leave it alone?

Darned impatience!

 

[maxvelocity]

I dont see that causing any problem at all other than, like you said may make it hard to push long motors in. Other than thst I would leave it alone. If you try to fill it with epoxy you risk creating a mess in there and making it to where you can't get long motors in, and like you noted you can't get in there to work very easily.

 

[kandsrockets]

Boredom is dangerous. While sitting here twiddling my thumbs I decided to go ahead and mount the first rail button. I very carefully triple checked my measurements and markings for the upper CR. Once I was satisfied they were accurate I took a deep breath and applied my sharpest and smallest brad point bit to make a pilot hole. Drilled slow, making sure the bit was perpendicular to the tube at all times. I don't have access to a drill press and my rechargeable drill is dead so I did it the old fashioned way, with a hand drill! Patience and practice paid off as the hole was perfectly centered and straight. So on to the next size and...I forgot to mark the depth and drilled all the way through the CR and into the motor tube! Drat!

So my question is will this cause a problem? I can't figure out a way to get in there to repair the hole. The cardboard bulges in where the hole came out and there's just no way I can put enough pressure to push it back. I can probably work some epoxy into it from the inside but won't do that until I'm ready to permanently mount the rail buttons. Will having it there cause any problems (other than making it difficult to insert long 38mm cases, that is)? Should I seal it or leave it alone?

Darned impatience!

This is not a problem. I do this all the time on my 38mm with a 29mm motor mount. Just wrap some sand paper around a dowel rod and sand down the inside where you drilled through so your motor casing does not bind up.

 

[Worsaer]

+1, exactly what Scott said. I have done the same thing, and though the perfectionist in me hates knowing that the 'flaw' is there, there's no adverse effect. Simply sand it down to keep motors from binding. It will work just fine.

 

[Tarasdad]

Phew! That's a relief! When I did it I was thinking "aw, crap, now what did I do?" nice to know it's a shared condition! :lol:

 

[Tarasdad]

Got the parts from K&S so all is ready to continue once I have the spirals filled and fins installed. Unfortunately it's going to be a couple more weeks before I have the money to get the stuff I need - IF I can do it then. We'll see.

 

[Tarasdad]

Okay, another question. I've been trying to decide what the best way to put internal fillets on the fins is. As you can see from the photos below there's only 1/4" or so between the motor mount and the body tube. Putting fillets on the conventional way (epoxy applied via the removed rear CR) will be tough as I'm looking at over 8" of depth here. I can still do it but it'll be messy and my hands aren't as steady as I'd wish - getting a tool full of epoxy to the very end of those fins is going to be tough. The alternatives would be injected fillets or two-part foam. I'm open to either although it may have been best to drill the holes for injecting before installing the motor mount.

Suggestions, hints, alternatives? :confused2:

 

[jus_rockets]

I cant see any pictures.

 

[JRL303]

Two part foam...

 

[Tarasdad]

I cant see any pictures.

Well...it would help if I actually posted them, wouldn't it? Updated with pics. D'oh! :blush:

 

[CarVac]

My suggestion: get a good structural epoxy like Aeropoxy ES6209 (the key property is it should be inherently thick, with little running), squeeze it into the slot so it falls onto the motor mount tube right where the fin will go, and insert the fin. Put a fillet on the outside, and you should be set.

You can use an oral syringe to meter it out neatly into the slot, too.

 

[jus_rockets]

You can also double dip the fin. Put epoxy on the fin and fit in the slot, then take it out and smear more epoxy and slide it back on. This should give you a nice fillet between the fin and motor mount.

 

[grouch]

Alternative: mix up some carbon fiber chop and use a skewer to poke the carbon goop down through the fin slots. When you press your fins into it, they will displace the carbon muck enough to make really strong fillets on each side of the fin. I did this on my Nuke and it worked quite well.

 

[Tarasdad]

Aeropoxy would be lovely but is a bit out of my budget. Any epoxy work I'll have to be done with my BSI hobby epoxy. One of the hobby shops in the area carries West Systems and I thinking recall seeing fillers. I'll have to check when I can. I hasn't thought of applying thickened epoxy through the fin slots. That actually sounds like my best bet as I already have the dispensers on hand - lots of 10cc syringes from a home IV session a couple of years back.

 

[CarVac]

Aeropoxy would be lovely but is a bit out of my budget. Any epoxy work I'll have to be done with my BSI hobby epoxy. One of the hobby shops in the area carries West Systems and I thinking recall seeing fillers. I'll have to check when I can. I hasn't thought of applying thickened epoxy through the fin slots. That actually sounds like my best bet as I already have the dispensers on hand - lots of 10cc syringes from a home IV session a couple of years back.

If you are not laminating, get the epoxy that's made as an adhesive; fillers are a giant pain in the butt when you don't need a very large fillet, and a structural epoxy doesn't need them especially if you are injecting (which does weird things to fiber orientations in fillers). Also, I've had chopped carbon fiber somehow catalyze BSI 15-minute epoxy; once we added the CF it suddenly heated up and hardened in a matter of 15 seconds. Just be forewarned.

Regarding cost: Giant Leap carries Aeropoxy ES6209 as "Structural Aeropoxy" in pint sizes (actually, a pint of resin and a pint of hardener), half the typical quantity, for only 25 dollars. I don't know what West Systems costs at your local store, but I doubt you will ever make a better purchase than Aeropoxy ES6209. It's that good. It'll last you for dozens upon dozens of rockets, and it's simply a joy to work with.

 

[CCotner]

I second that-by volume, the aeropoxy (both laminating and adhesive) is cheaper than BSI epoxy, but it's only available in large quantities-the pint-kits Giant Leap sells are a lifesaver in terms of cost. It is extremely strong, you can be very stingy with it, and it will last for probably a dozen rockets. It's 1:1 mix like the BSI stuff, it's less annoying and as strong as fillers and laminating epoxy.

My concern with the BSI stuff has always been safety. BSI has a very unprofessional attitude toward chemical safety in my opinion, given how difficult it was for us to get copies of their MSDS's, and how brief and vague they are. The stuff smells downright deathly, and while neither contain MDA (known strong carcinogen), the BSI brand epoxies all contain (and as a major constituent) Bisphenol A (BPA)-known to cause hormonal problems and being investigated for numerous medical problems. I'd go for the Aeropoxy.

 

[Worsaer]

I personally use West Systems, using their 404 filler to get the consistency I want. In a build similar to yours, with very little room to work, and forgetting to omit the rear CR, I decided to drill small holes in the rear CR, injected epoxy from the aft end one section at a time, tilting back and forth to get coverage, then leveling out while it cured. I then finished by filling the small holes in the CR. I know it wasn't optimal, but I didn't want to mess up the airframe. The down side - I likely used much more adhesive than was needed. If I had to do it again, I would double dip the fin and call it good.

 

[kandsrockets]

You can also double dip the fin. Put epoxy on the fin and fit in the slot, then take it out and smear more epoxy and slide it back on. This should give you a nice fillet between the fin and motor mount.

This is how I do mine and have not had a fin come off. I have broken fins off but the root was still glued to the motor tube.

 

[Tarasdad]

This is how I do mine and have not had a fin come off. I have broken fins off but the root was still glued to the motor tube.

Well, that settles it. This is how I'll do my fins when the time comes. Right now they're coated in CWF waiting for me to feel like sanding them down. Also filled the deeper spiral on one of the body tubes. Still need to do the other spiral on it and do the upper tube entirely. The switch band got filled with Squadron White Putty as an experiment. It works, but the odor is a bit too strong for that much use.

 

[Kehoes23]

The K and S kits are top notch and the e-bay are as nice as it can be and easy to put together, I have the Arctic Wolf duel deploy rocket, I have yet to launch it, the only thing I did replace was the shock cords with Kevlar, I was afraid that the shock cord would get stuck in the body tube and not deploy the parachute and eliminate the need for a cord protecter.
I'll post some pics when I get a chance

 

[gdjsky01]

Just found this thread (why'd you not ping me? :lol - It looks like that rocket is made from nice thick MMT. So I would think a 36 inch at North Edwards would be fine. Maybe even less. Especially of the fin planform is not very wide. Probably be fine at Lucerne as well (if you are thinking of launching there). Lucerne is harder packed desert than Cal City.

Looks like a fine ship. BTW: You can borrow anything you need from me as long as I am showing up. Of course there are plenty of lenders there at MDARS. I have chutes, protectors, motor casings, etc. Just ask.

Unfortunately the MDARS launch was winded out. Nice view of the mountains, clouds hugging the tops, and Windmills turning, but not good for rocketry. I should have tried to get a hold of you can ask the weather! That was 60 bucks of gas down the drain. But I paid my 2013 dues. If we were closer I could just give you some System III and thickener. Oh well.

You got quite a back log of rockets to launch. Don't hesitate to ask me for a motor or two on the cheap. Stuff happens. I have plenty. Especially BP. You can always pay me back by letting me know the weather! :lol: Not charity. Just Rocket nuts helping other nuts.

More pictures!!
Jeff

 

[Tarasdad]

Were you there Saturday? The Sat launch was scrubbed due to a conflict with Edwards flight ops. They were trying to reschedule for Sunday but I don't know if they did or not. Moot point, i can't launch on Sundays anyway.

 

[gdjsky01]

Were you there Saturday? The Sat launch was scrubbed due to a conflict with Edwards flight ops. They were trying to reschedule for Sunday but I don't know if they did or not. Moot point, i can't launch on Sundays anyway.

Working. and

It was rescheduled for Sunday. But was too windy.

 

[Tarasdad]

Tube spirals have been filled and sanding is in progress - lower tube is done, upper is waiting. Have I ever mentioned that I hate sanding? Well I do. Lots. Anyhoo, I finally got the rear centering ring epoxied in place. Once hat cured I mixed up another small (but still too big) batch of epoxy and set the first fin in place usine the "double dip" technique. It's sitting on my workbench curing now.

I'll post more pics later. No point in taking photos of the drudge work.

Couple of quick questions while I'm thinking about it. Should I use a 3/16" or 1/4" quick link for the parachute? Also, what is the best way to connect the shock cord from the motor to the main cord? How about to the nose cone?

 

[Kehoes23]

Ill post some photos on how I conected the shock cord form the mm and to the nose cone, I used a swivle for the parachute attachment

 

[Tarasdad]

Second fin is mounted.

 

[Kehoes23]

here is the Arctic Wolf from K and S, I tied a loop on the motor tube shock cord and a loop on the kevlar cord and attached them as you would two rubber bands, the hole at the bottom of the nose cone is big enough for a 1/4" eye bolt and epoxyed in place, and a swivle to attach a parachute. I hope this helps.

 

[Tarasdad]

Got all three fins epoxied on last night.

The secret to perpendicular fins

Visited Payloadbay.com and created a fin mounting guide. Glued it to a piece of foam core, cut it out, and it made getting the fins mounted far, far easier.

Fin-ished (heh) product

The lower BT with fins installed. Very happy with the results, I must say! Now I just need to figure out how I want to make the fillets. I wanted to do epoxy but I'm not sure my skills are up to the task. I'm also not convinced that Titebond M&T will have the strength I want. Decisions, decisions, decisions...

I also need to sand the upper tube but I'm just not in the mood to deal with the dust! :lol:

 

[Tarasdad]

I've decided to go with a round 30" Top Flight chute for the main. Looking at their chart it should be more than enough for this rocket. Only choice now is whether I go with standard fabric or thin mil to make it pack a bit smaller.

I haven't actually done any work on it recently. I still need to finish sanding the upper tube (been sitting there for a couple weeks in candy cane mode) and do fin fillets. I came close to ordering some Aeropoxy from Giant Leap but just hesitate to spend the money right now. Before I can even attempt a L1 flight I need to join Tripoli. Seems to me I need to do that before I do anything else. Besides, I have plenty of decent epoxy that will work if I just get some sort of filler to thicken it.

 

[gdjsky01]

Most peeps say fillets are aerodynamic not structural. So use whatever is easiest. Assumption being that the fins are well mounted. What i do is seal the fin to tube line with wood glue. The make little dams on each end of the fin with modeling clay. The clay is easy to sand away when done. The I pour the fillet and keep the rocket level while it hardens. The clay keeps the epoxy from dipping around the ends.