Blackhawk 38 Scratch build

Several months ago I decided a Blackhawk 38 was needed to keep my Blackhawk 24 company. However for reasons unknown to me, I've decided to build the beast from scratch. The biggest issue in my building is getting started on a project and then ordering parts, waiting, building, procuring more parts, waiting.... Kind of drags on and I loose the spirit of the build. No more! Employing the principle of "mise en place" which I regularly do with cooking but heretofore have failed to do in rocket construction, I now have everything in place and am ready to begin! Near as I can tell. I've been accumulating needed supplies for about two months now. The following picture is the various materials that the rocket will be derived from, excepting random sundry items commonly found out in the garage.

So the way I see this project, there are several sub-projects involved.

1. Fin construction
2. Body tube construction
3. Electronics bay construction
4. Final assembly

Fins will be the first part of the project. I've already printed out Rocsim fin templates that will be used to cut the 3/16" nomex honeycomb (from Giant Leap) to the correct size. The fins will be edged with round wood dowel (except the root edge) and finally laminated with carbon fiber (Soller Composites) and 4:1 laminating epoxy (US Composites). After carbon is applied, they will be vacuum bagged with my splendid new Seal-A-Meal device, or whatever brand it is. I'll post pics of the process once it is partially complete.

Here are the beginnings of the fins. The "finished" fin was a test using carbon/kevlar just to test and see if my method was feasible.

Here are some more fin shots. The whole setup (each fin) was covered in carbon fiber, placed in a cheap gallon storage bag, poked with numerous holes, wrapped in kleenex and finally placed in the seal-a-meal. Oh yeah, I used the US composites 4:1 laminating resin system.

Fins are done! Just a bit of sanding and smoothing the surface. They're exactly what I am looking for. Not the most aerodynamic but I'm not going for altitude or speed, just acceleration.


While working on the fins, I started on the e-bay using some of that nomex honeycomb and a G10 fiberglass coupler tube. The 9 volt battery is wedged in quite tight and will rest on the aft bulkhead.

Dang! Those fins look awesome! How stiff are they? And what did the weight end up being? Honeycomb looks neat too.

Fins look great! I'll have to check this out at hellfire or whenever you bring it to a launch.

Do you plan on using a tracker or Gps? An I1299 will push that thing pretty high.

When I get a job I might invest in a tracker system (or if I have enough, a gps)

best of luck
Alex

Tominator 2 said:

Dang! Those fins look awesome! How stiff are they?

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Well... the pictures don't do them justice, up close and personal they don't look so great but hopefully they are what I need in terms of performance and integrity. As for stiffness, I'm no engineer although I understand some basic principles (I'm a soil scientist at school, a meat manager at work...) I tried to take a picture of 2 fins in the vise side by side with a 336g mass attached to one of them. Picture sucked. With the fins horizontal, at a point 165mm from the vise to the tip with a 336g mass hanging down, the fin deflected less than 1mm. I have no idea how to quantify that. using my test fin, a 3 pound weight moved it noticeably. For comparison, 3/32" G10 of similar length deflected quite noticeably with the 336g mass. So, they are "QUITE" stiff. Each fin weighs about 14.2g and is about 5.2mm thick. Other fin dimensions are the same as a stock Blackhawk 38. I'll use the Fin Guide Tool at PayloadBay.com to ensure I get the fins on right. I'll be using the black Proline epoxy to attach them.

Here are some more e-bay pics. I think it's almost done. No tracker or GPS, I'll save the 1299 for Hellfire so at least I have a chance of finding it. I will probably put a sonic locator in the nose cone to assist me though. I'm thinking main chute deploy at 600'? I've tested the altimeter in a bottle with little lights. I can suck the pressure to about 7000'. I'm tickled pink with the simplicity of the Adept22 as a first timer so far without flying it yet. I've got a missileworks on order from wildman but would really like a raven. It speaks volumes about customer service when the manufacture posts regularly here. Same for all the others who do kits etc.

I'm loving this thread. Your post regarding vacuum bagging gave my goose bumps

edwinshap1 said:

I'm loving this thread. Your post regarding vacuum bagging gave my goose bumps

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I think the ebay is finished. More finished than in a previous post but nothing photo worthy. Had to drill some holes for the ejection charge ignitors. Anyway, time to start on the upper airframe. I am using sleeves from Soller Composites. First sleeve is fiberglass (hey I'm not made of money), second sleeve is carbon/kevlar, outer sleeve is carbon/red fiberglass if for nothing other than aesthetic purposes. For the mandrel, I found a 1.5" brass tube for $.50 at the thrift store-

New in package! It's designed for hand rail and commercial type railing applications. To provide release from the epoxy and to get the appropriate internal diameter of the tube, I wrapped 2 layers of parchment paper around the mandrel. This brought the diameter up to 38.61mm which will accommodate the coupler tube/ebay. I applied the sleeves in order and taped them at each end. Whole thing was covered in saran wrap just for storage lest little fingers wanted to touch.

I figure the epoxy will penetrate adequately. We'll see. I will then cover with the gooped up tube with heat shrink tubing and zap it with the shrink-ray to remove excess resin as per Soller Composites instructions on their web site. Now it's wait 'till cure and we shall see later today how things went.

I am SO paying attention! Good stuff!

What is everyone's take on the "wrap everything first, then wet" approach? I've been wondering how you are supposed to do all your layups in the 20 minute handling time of the laminating epoxies. I'd think it would work if you didn't have too heavy a weave, or too many layers, but where you draw that line, I don't know. I'd also think this way would work better for making a tube from scratch than it would for strengthening a tube, as it won't grab on to the inner tube as well as if you applied the epoxy straight to the tube.

Lentamental said:

What is everyone's take on the "wrap everything first, then wet" approach? I've been wondering how you are supposed to do all your layups in the 20 minute handling time of the laminating epoxies. I'd think it would work if you didn't have too heavy a weave, or too many layers, but where you draw that line, I don't know. I'd also think this way would work better for making a tube from scratch than it would for strengthening a tube, as it won't grab on to the inner tube as well as if you applied the epoxy straight to the tube.

Click to expand...

Because you can't put the sleeves over wet epoxy...

Where there are only 3 layers here, it wasn't hard to massage the resin into the fibers. The sleeves expand when you compress them and contract when you stretch them, hence they fin the mandrel nicely. Also, the heat shrink tubing slides over the saturated glass quite easily. Just make sure the tubing is big enough. The stuff I used had a 4:1 shrink ratio. As far as using the US Composites fastest curing epoxy, the POT life is 15 minutes at 70 F. Once it's spread out, it takes considerably longer to cure. I'm also doing the lamination at about 32 F outside. I noticed the pot life was over an hour. Once everything is done, I brought the finished stuff inside to a cozy 70 F to properly cure. And speaking of cure! Here is the rough tube!

Going back in time to this morning, here is the tube after the shrink ray was applied to the heat shrinkable tubing. Made a nice puddle on the garage floor as excess resin oozed out of each end.

Oh yeah, the saran wrap serves no purpose here than to contain possible dripping epoxy so my wife doesn't kill me as this was relaxing in the bathroom all day to cure.

Tominator 2 said:

Because you can't put the sleeves over wet epoxy...

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I usually wet out the sleeve, and if it's a cardboard tube, I wet that out too. Then just do the finger trap thing to expand the diameter, and squeeze it out from the middle. Aeropoxy has a 2+ hour pot life.

Those tubes look beautiful! I like the red and black. How sturdy/smooth are they? I'm considering an order from soller composites for this exact reason.

Have you tried cutting this tube yet?

I have never had good luck cutting the carbon/kevlar material.

Tube is reasonably smooth. I will sand it down a bit today and for finishing will paint it with laminating epoxy then probably put it on the rotisserie to avoid sags. I'm told that's what's done with custom fishing rods anyway. As far as cutting, I was able to score the outer layer with the knife and then used the hacksaw to cut through. If I didn't have the kevlar stuff in there I'm sure cutting through with the knife would have worked just fine. Seemed to look good enough with the score/saw technique. Oh yeah, as far as smoothness goes, that outer layer was rather coarse. If I had done the kevlar or fiberglass as the outer, it would have been far smoother. It kind of bunched up at one end so for the lower airframe, I will probably tape one end on the mandrel, wet it out, slide the shrink tubing over from the taped end and begin shrinking from the taped end instead of working from the center out.

Tube is not to proper length yet. You can see the rougher bunched area at the right.

As for the "sturdiness" of the tube, well I can't quantify that either but it "seems" comparable to the 2.56" tube my Mad Cow Patriot is made from. For a tube such as this, I'm not sure anything was to be gained from my home fabrication except the pleasure and satisfaction derived from the process. It's probably just as or more expensive than a commercial tube. I have noticed, for big stuff, a substantial amount can be saved (big nose cones for example) assuming one has the equipment on hand alreadyand doesn't factor in HOLY S&%# UPS JUST RANG THE BELL AND MY 4" DARKSTAR HAS ARRIVED!!!! Anyway, gotta go!

Lower body tube is finished. Looks just like the upper tube but longer. Nothing too photo worthy. I gave the entire tube a good sand and got the fin areas masked off so I could sand them with 60 grit. For fin attachment, I'll use the Proline thick stuff.

Finally got the fins attached! At the root edge at least. Using the ol' digital calipers measured the fin thickness and airframe diameter and plugged the numbers into the fine tool at payloadbay.com.

I glued the printed papers to leftover foam board from the Bad Battle Axe and cut out waste with the xacto knife. I used a marking guide wrap tool as well do draw some lines up the airframe so I would know where to apply the tape. This enabled me to really rough up the fin mounting area with the 60 grit and not destroy the rest of the tube. I suppose it also keeps the adhesive off other areas as well.

After numerous test fits and contemplation I mixed up a 5 gram batch of Proline thick black goop. The little scale is indispensable for this task. Supposedly it's accurate to the nearest .1g. I found it on ebay for under 10 dollars and so far it's not failed me!

Once this is cured, I will pull off the tape and using the Wildman method will reapply the tape to fins and tube where a 1" PVC pipe will touch, to smooth the fillets. Once that is done, I need to paint the nose cone (What color? Red, Black? Suggestions please) and give the entire rocket a very thin coat of epoxy. I think I will try the future floor polish method and see how I like that for the final finish. Only parts I don't have yet are the streamer for apogee deployment and a parachute. I'm still waiting on the final weight. Oh yes, this bad boy begs to be tower launched but I'm going to use ACME rail guides. I've applied the lathe file to them to increase the coolness factor. You'll see.

Rail guides are attached! Recovery harness is installed! Just need the finishing touches and chutes! Here are the pics of the gory details. The aluminum channel keeps the aluminum rail guided lined up quite nicely while the epoxy cures.



For recovery, I did contemplate having the bolt mounted in a bulkhead that the motor would thread on to but finally decided against the extra weight and opted just the thread the bolt into the forward closure. The bolt will be cut down a bit. It is titanium and a notch was filed out to run the kevlar through (no sharp edges here!) The knot is a triple overhand bend as described in "On Rope". Isenhart (1974) claims that it is "as strong as the rope itself". Instead of attaching 2 ropes together, it's just tied to the bolt. The smallest bend the cord makes is about a radius of .25". Now looking at the picture and the book, I tied it wrong. Anyway, you get the idea. I'll wrap with electrical tape when done. That way I can undo and inspect after a flight.

Check out the pictures! I set up a rotisserie and mounted the airframe sections so I could paint them with US Composites 4:1 epoxy for that slick gloss look. I'll post a follow up when all is said and done. Then it will be awhile before I launch the beast. I think its name should be, "Speed of Money" Total weight comes in at 1.75lbs without propellent and an ultra light chute from Top Flight. Can't wait to stuff that I1299 up the tailpipe and let 'er rip. Assuming the motor doesn't CATO or travel faster than the airframe or any part below the nose cone tries to go faster than something else, we should have one fast ride! This has been one of my funnest builds yet.

That looks really sweet! I like the red and black!

Looks great so far! As for the nose cone, I think it would look great in black, possibly with a silver(or gold) metallic tip. Will you be taking this to the launch on Saturday, I would love to check it out.

Alex

Decided to go with black for the NC. Just threw on some primer, sanded it a bit and painted it with epoxy. If you look close, it's in the picture. I put a zip tie on the attachment point and dangled it off the rotisserie bar. Should be fully cured tonight! Will be going to the launch on Saturday but not flying this yet. I guess I could fly it on a F42 as the minimum size motor if I did my math right.

The work is finished! Behold, "The Speed Of Money". Actually I'm not entirely thrilled with the finishing coat. If I was to do it over, I would have used table top glazing epoxy instead of laminating epoxy. Oh well, live and learn.

Most excellent. I'll look forward to seeing it tomorrow.

Alex