Darkstar Series Build

[mtnmanak]

Finished a number of rocket projects recently, so planning on diving into some new ones.

One of my next ventures is to build out (most/all/some?) the Darkstar series rockets from Wildman. I feel ambitious enough to say I would like to culminate with a Jumbo build sometime in the future, but that seems a bit "out there" right now, if ever possible.

For now, I have a 2.6" (38mm) kit, a 3" (54mm) kit and a 4" (54mm) Dual Deploy kit sitting on the table ready to be built. Planning to start with the 2.6" kit and work my way up the chain.

 

[NateB]

I love Darkstars too and am also working on a whole fleet. I just built a Mini and Jr, and have a Mini that will be a minimum diameter and dual deploy when it is finished. I'm planning on a 3" for my L2 and maybe the 4" Extreme if I get ambitious. I'll probably have to call it there due to motor costs, but could always start scaling down too.

 

[tOD]

I've got a 2.6 and a 3, both are great rockets

 

[tim cubbedge]

I have the 3” and it’s a great flyer!

 

[mtnmanak]

I love Darkstars too and am also working on a whole fleet. I just built a Mini and Jr, and have a Mini that will be a minimum diameter and dual deploy when it is finished. I'm planning on a 3" for my L2 and maybe the 4" Extreme if I get ambitious. I'll probably have to call it there due to motor costs, but could always start scaling down too.

I've got a 2.6 and a 3, both are great rockets

Awesome! Look forward to any tips & tricks you guys have encountered along the way.

I did my level 2 with an Apogee Level 2 and am happy I did - it is a truly complete kit. For anyone just getting into HPR and/or fiberglass rockets, the Wildman kits could be intimidating. Some impressions I have of the kits off the bat:

- Very quality parts. Love the FG tubes Tim uses. I have already washed and sanded all the parts and can see that they are very nice. I have built a few Madcow FG birds and these parts from Wildman are much better. The nosecones are superb.
- The fins on the 3" bird and up are beefy 1/8" thick FG. Very nice. Many other vendors use 1/16" fins even for larger rockets and they just feel flimsy. These are solid.
- Love that the 4" DD bird came with aluminum bulkheads!
- For anyone not experienced in HPR or FG rockets, there are some things you should be aware of:
- You will need to buy/obtain extra stuff. What comes in the "kit" is just a bag of fiberglass parts. You will need to add things like hardware, recovery systems, AV Bay components, rail guidance, etc. For me, this is a bonus - I have all that stuff on hand and don't want to pay for those things. However, if you are using this as your Level 1 cert or first dual deploy, it may be a bit confusing to go out and find these things. I can distinctly remember a time when I thought "what the heck is an AV Bay and why do I need one?!"
- There are not explicit instructions for these rockets. Wildman has a number of methods and procedures posted that walk you through how to build the various rockets they sell, but the instructions are generic. This is definitely something that could cause stress/confusion for someone new to this. When I was building my level 1 for example, I would have been very confused about whether I should follow the "injection booster" method or the" open end booster" method for internal filleting. To make matters worse, these are double fin birds and I don't think the instructions for either method cover that. I plan to use a combination - injection for the forward fins, open end for the rear fins. For experienced builders, Tim's instructions are right on target.
- There are so many optional ways of completing a project like this, I would have been lost when I first started building HPR/FG birds.

I am not planning on any real "mods" to these builds outside of using my own techniques. Some planning factors:

- Will be building them out with both traditional DD and HED. Want to ensure I have room for telemetry, GPS, etc. For the smaller rockets, the HED may serve as the DD backup.
- Planning to use mostly Missile Works RRC3s and RRC2Ls in these, but may use a Raven in some smaller builds or as backup
- I have some of the MW printed sleds on hand, but want to get some of their dual altimeter sleds - they are sold-out right now, but should be able to swap them out later
- Never been a big fan of gluing the Y-harness to the motor tube. May have to do that on the smaller birds since there isn't much room in those, but for anything 3" or larger, I would rather connect the Y-harness looped to forged bolts or u-bolts on the forward ring so I can replace the kevlar down the road if it wears out.
- Not sure yet how I am going to approach the AV bay in the 2.6" bird. I have a Missile Works sled for an RRC2 that will fit in the AV bay, but the 2.6" kit doesn't come with a switch band, so not sure how I will approach the switch. I could add a switch band, but it may be time to try out the Raven AV Bay from Featherweight. It has an magnetic switch that may work great in the 2.6" build.

Other than that, these seem like pretty straight-forward builds.

 

[NateB]

For my Mini and Jr, I had to extend the fin slots and do a little sanding on the ends of the tubes for everything to fit square. It was very little effort to get everything to fit just right and way more enjoyable than filling spirals and sealing wood fins.

My Mini was built with the fin can foamed after double dipping the fins in epoxy. I only used 2 centering rings, the aft CR was used to center the motor mount when double dipping the fins and only glued on after the foam cured. The foam and fly technique is documented here in older threads and on the instructions for the Wildman mini series kits.

On my Junior, I decided to use fin pockets instead on injecting the internal fillets. I used scrap balsa and they weren't too pretty looking. I am pleased with how it turned out and will use them again on future builds where the motor mount is close enough to the body tube that the pockets and epoxy won't add too much weight. I injected the internals on my Punisher 3 and it was a messy process. Still working on cleaning that build up before flying it.

When I build a 3" Darkstar, I'm going to use fin pockets and try to build it to use HED or standard dual deploy depending on if I fly it with the payload section or not. Maybe I'll even try to fit a TRS and a quark for backup in the AV bay.

 

[mtnmanak]

For my Mini and Jr, I had to extend the fin slots and do a little sanding on the ends of the tubes for everything to fit square. It was very little effort to get everything to fit just right and way more enjoyable than filling spirals and sealing wood fins.

My Mini was built with the fin can foamed after double dipping the fins in epoxy. I only used 2 centering rings, the aft CR was used to center the motor mount when double dipping the fins and only glued on after the foam cured. The foam and fly technique is documented here in older threads and on the instructions for the Wildman mini series kits.

On my Junior, I decided to use fin pockets instead on injecting the internal fillets. I used scrap balsa and they weren't too pretty looking. I am pleased with how it turned out and will use them again on future builds where the motor mount is close enough to the body tube that the pockets and epoxy won't add too much weight. I injected the internals on my Punisher 3 and it was a messy process. Still working on cleaning that build up before flying it.

When I build a 3" Darkstar, I'm going to use fin pockets and try to build it to use HED or standard dual deploy depending on if I fly it with the payload section or not. Maybe I'll even try to fit a TRS and a quark for backup in the AV bay.

Great ideas, thanks!

Also, forgot to note above that another item on the agenda is to update or create necessary Rocksim files. I looked at the Rocksim files on the Wildman site and noticed they didn't quite match the materials that I got in my kit. Asked Tim about it and he said the Rocksim files on the site are old and he frequently changes vendors for the parts, so they won't match. As I go through this process, I will update and post as I work on the rockets.

 

[tOD]

For the JR I used an RRC2+ and the Missileworks 3D printed sled. Twist and tape for a switch and BP in glove fingers wired direct to the pyro outputs; pretty bare bones. There's an SMT designs nosecone bay with an Eggfinder Mini.
The 3" uses an AV bay setup from SMT designs and an Eggtimer Quantum as primary and a Quark for backup. I've flown it using the Lab Rat protective sleeve for Eggfinder Mini attached to the shock cord with a quick link

 

[Wayco]

Can't believe no one has referenced the "Bible" on building Darkstars:
https://www.rocketryforum.com/threads/how-to-build-a-stock-3in-darkstar-cj-step-by-step.55019/

Literally hundreds of rockets have been built using CJ's guide. My DS Jr., 3" DS, DS Extreme and Ultimate DS were all built using that thread as a reference, and those four rockets have well over a hundred flights. If you do your "Y" harness correctly according to that thread, you will NEVER have to replace it.

I did my Level 3 with a Darkstar Extreme and documented it for my TAPS with this thread:
https://www.rocketryforum.com/threads/wayco’s-dark-star-extreme.66950/

Here is my build thread for the Ultimate:
https://www.rocketryforum.com/threads/waycos-ultimate-darkstar-build.126244/
Only problem I have had on the six flights I have made with this rocket was the rail buttons came off when I flew the O3400 Imax motor last year at Airfest.

 

[mtnmanak]

Can't believe no one has referenced the "Bible" on building Darkstars:
https://www.rocketryforum.com/threads/how-to-build-a-stock-3in-darkstar-cj-step-by-step.55019/

Literally hundreds of rockets have been built using CJ's guide. My DS Jr., 3" DS, DS Extreme and Ultimate DS were all built using that thread as a reference, and those four rockets have well over a hundred flights. If you do your "Y" harness correctly according to that thread, you will NEVER have to replace it.

I did my Level 3 with a Darkstar Extreme and documented it for my TAPS with this thread:
https://www.rocketryforum.com/threads/waycos-dark-star-extreme.66950/

Here is my build thread for the Ultimate:
https://www.rocketryforum.com/threads/waycos-ultimate-darkstar-build.126244/
Only problem I have had on the six flights I have made with this rocket was the rail buttons came off when I flew the O3400 Imax motor last year at Airfest.

Thanks - great threads!

I should have noted up front that I read through CJ's build thread - essential Darkstar reading. GreenJello's index for that thread is very helpful as well.

https://www.rocketryforum.com/threads/how-to-build-a-stock-3in-darkstar-cj-step-by-step.55019/

 

[TheTank]

Nice! Ill be building a Darkstar 4 DD myself this winter. Look forward to seeing your fleet at the field!

 

[mtnmanak]

Can't believe no one has referenced the "Bible" on building Darkstars:
https://www.rocketryforum.com/threads/how-to-build-a-stock-3in-darkstar-cj-step-by-step.55019/

Literally hundreds of rockets have been built using CJ's guide. My DS Jr., 3" DS, DS Extreme and Ultimate DS were all built using that thread as a reference, and those four rockets have well over a hundred flights. If you do your "Y" harness correctly according to that thread, you will NEVER have to replace it.

I did my Level 3 with a Darkstar Extreme and documented it for my TAPS with this thread:
https://www.rocketryforum.com/threads/waycos-dark-star-extreme.66950/

Here is my build thread for the Ultimate:
https://www.rocketryforum.com/threads/waycos-ultimate-darkstar-build.126244/
Only problem I have had on the six flights I have made with this rocket was the rail buttons came off when I flew the O3400 Imax motor last year at Airfest.

I realize that Green Jello's post indexing CJ's Darkstar build is a sticky and is the golden source, but for anyone that wants that build or Wayne's builds in a streamlined PDF format, here they are. I like this format for my iPad to reference while I am working. I didn't do much editing - just copied over the actual build posts as they appeared in the threads.

Wayne - Thanks for the amazing build threads! Incredible!

 

[mtnmanak]

Been waiting on some parts before I begin these builds - in the meantime, created new Rocksim files since I couldn't find ones on Wildman's site that accurately reflect the parts you receive right now. These files represent what you get in the kit - no recovery, etc.

 

[mtnmanak]

Had a bit of a delayed start on these builds - we had a water leak in the workshop and had to have some work done to get it fixed. Back on track now.

Starting with the 2.6"bird. Mostly going to be following the "stock" build guidelines from Wildman's site and more closely following the excellent guides from CJ and Wayne posted above. A number of parts have changed in the kits since those build threads, I will try to point them out as I go. Most of the changes are small - just improvements from the old kits. For example, now the AV bay bulkheads are CNCed once piece step-downs instead of two pieces you have to glue together. Also, they have indentations for where to drill the holes (which line up perfectly with the MW printed sleds). Seems like a small change, but I welcome it. I always glue the AV end caps off just a bit or drill the holes just off a bit and end up spending an inordinate amount of time sanding and fitting them later so my sled isn't all cock-eyed. These one-piece end caps should alleviate that. The ones for the 4" bird are aluminum.

Starting off as any FG build should, I washed every part, completely sanded all the FG parts inside and out with 80 grit and washed again. This part of the build is dirty and dusty - I use a full respirator and large rubber gloves (the kind a veterinarian would use on large animals), so I like to get it all done at once. I don't want to have to sand much later, so I really concentrate on the areas around the fins and all glue points, etc.

As CJ noted in his thread, this is also the time to sand the ends of all the parts so they fit. This is really important. I found a lot of places where the ends of the tubes were not flat and needed to be sanded. As he said, many of the junction points fit best in only one way, so you also want to put witness marks around to know how to fit them back together later. And label everything.

Good example is shown below - the top of the payload bay tube had a significant bump. Some quick sanding with 180 grit on a sanding block achieved a perfect fit with the nosecone.

 

[mtnmanak]

Next step was to mark out the MMT for all the CRs and retainer. I am using a regular Aeropack 38mm L2 retainer (not aware of a 38mm to 2.6" tailcone retainer out there, but would have used one if I could find it). One difference in the way I am building these is that CJ/Wayne built their MMT tubes from the retainer and worked their way forward. I am going to glue the forward ring on first, then work my way backward, gluing each successive CR to the fins as I go. I will use the injection method for internal filleting.

For measuring and marking, though, you need to start with the retainer. It dictates how the entire MMT will be placed and fit. So, marked the retainer line, then taped the rear CR in place (nothing glued right now). Put on the forward ring and laid the tube out next to the lower body tube to determine best spot for the forward CR and marked that spot. An old Estes BT-60 tube marking guide helped to keep the CR straight for marking. Then taped the forward CR in place so I could insert the MMT in the fin can and use the fin slots to mark out the fin locations. Clamped the MMT in place to ensure it didn't move and used a drafting pencil to mark the fin locations. Drafting pencils have really thick lead - great for being able to extend the lead out enough to make markings like this without breaking the lead. Once I had the fin slots marked I took everything off the MMT and used a sharpie to make all the lines clear and label the front and aft ends.

 

[mtnmanak]

The forward CR needs notches for the Y-Harness. I am using 1/4" wide, 1200# test kevlar for the harness.

Used a center finder tool to mark an exact diameter line across the CR, then laid the kevlar across it to mark the width of the strap. The strap is about 1/16" thick, so marked the depth. A "fine" grain sanding rod from PermaGrit made short work of filing out the slots.

 

[mtnmanak]

Taped the retainer and rear CR in place securely - it will need to stay in place throughout the rest of the MMT build as I take the tube in and out of the fin can until it is time to install the middle CRs. I taped off the fin lines to ensure no epoxy gets on them while gluing the y-harness strap in place. Some Tamiya 10mm tape fit perfectly. The 38mm motor tube does not leave a lot of room to glue the straps exactly opposite each other. They will have to be glued very close to the fin lines, so will need to be vigilant on keeping it clean.

I re-measured the position of the forward CR and tacked it in place with CA. I measured out the kevlar to fit so I had about an inch or so loop protruding from the fin can. I am going to sew the loop on the end of the harness, so it should end up almost flush with the end of the fin can. To cut kevlar, I find it easiest to mark the spot, saturate that point with CA, then cut with a knife. Gives you a nice clean cut that won't fray and you can sand it so it will fit through the slots you made in the forward CR. I laid out the kevlar on the MMT, marked the end point and glued it in place with some Aeropoxy 6209. I am just gluing it in place right now, will completely cover it with Proline 4500 later. Once the glue was tacky, I removed the Tamiya tape so it wouldn't get glued in place then set the whole assembly in the "hot room" to cure.

 

[mtnmanak]

 

[mtnmanak]

While all that was curing, I decided to give some love to the AV Bay.

Started by drilling the holes in the end caps. Using 8-32 threaded rod for this build (fits in the MW RRC2 sled I am using) and 1-5/8" eye bolts, which also has an 8-32 thread, so all the holes can be the same diameter (11/64").

Made sure the sled fit on the rails then tacked the nuts onto what will be the front bulkhead using some blue Loctite. Using a Shurter rotary switch for this (sled is built for it). The RRC2L I am using doesn't have explicit switch ports, so the instructions tell you to wire the switch between the positive terminal on the battery wire. So I soldered a 22 gauge wire to one terminal on the switch, fed all the lines where they are supposed to go on the sled and soldered the positive lead from the battery connector to the other terminal on the switch. Installed the RRC2L onto the sled, trimmed the wires to fit and installed ferrules on the ends of the wires. Tested it and it is good to go.

 

[mtnmanak]

After messing around with placement of the sled in the AV bay, determined the switch band needs to be bit aft, not centered. This is to get the switch under the band. Could trim the eye bolt screw, but not worried about the switch band being aft. If you aren't going to center the switch band, you should have more room forward anyway. Once I determined the switch band placement, marked it and sanded the spot a little more then glued the switch band on with 5 min epoxy. Determined best hole placement for the switch hole, then drilled a small hole. There was some tear out (as usual). CJ recommends using a file for these kinds of holes - that works great. I reinforced the hole with CA then filed. Added some more CA and drilled out a bigger hole to accommodate the screwdriver I will need to fit through there to turn the switch. Some more filing and I ended up with a pretty clean hole in the right place. AV bay is almost complete, will add terminal block later and wire them to the RRC2L. Probably won't use charge wells for this small bird, I will just use disposable vials to hold the charges.

 

[mtnmanak]

The epoxy on the kevlar strap cured well, moved on to covering the strap with Proline 4500. Reinstalled the Tamiya tape on the fin lines and further covered the area with masking tape. The Proline can get messy. First tacked in the top piece of strap above the CR (in CJ and Wayne's threads, there is a robust discussion about whether the epoxy should go all the way to the end of the tube, so won't discuss here, but, from that discussion, decided to glue to about an inch away from the end). Then covered that portion of the strap and filleted the outer portion of the CR. Next, covered the strap with a healthy slathering of Proline. When tacky, removed the tape and set aside to fully cure.

 

[tOD]

I used CJ's method (pretty much) for both of my dark stars. Your additional comments are useful additions.
Could I ask about the terminals you used on your wire ends? Where did you get them, and do they require a crimp tool?

 

[Banzai88]

Could I ask about the terminals you used on your wire ends? Where did you get them, and do they require a crimp tool?

They're industry standard crimp ferrules.

You can get a kit, with crimpers, from ebay or amazon for under $25 on up to $400 crimp tools if you have a need for an industrial tool. Other favored sources are Mouser, DigiKey, and McMaster Carr.

After you get a crimp tool, a bag of 100 ferrules (they're wire gauge specific) will do you for about $5ish and is a near lifetime supply.

 

[mtnmanak]

I used CJ's method (pretty much) for both of my dark stars. Your additional comments are useful additions.
Could I ask about the terminals you used on your wire ends? Where did you get them, and do they require a crimp tool?

Tom is exactly right. Great items to have in your kit bag.

Here are the ones I use, for easy reference:

Tool and kit: https://www.amazon.com/gp/product/B07PJK2VNT/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

That will get you down to 22 gauge. Since I encounter so many different kinds of wire in a build, I also added:

24 gauge: https://www.amazon.com/gp/product/B07Z5QCB82/ref=ppx_yo_dt_b_asin_title_o06_s01?ie=UTF8&psc=1

26 Gauge: https://www.mouser.com/ProductDetail/644-FSD72-6-D

28 Gauge: https://www.amazon.com/gp/product/B00NVBGAEU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

While you are over at Mouser (like McMaster-Carr, I can't spend too much time on Mouser or I will have to take a loan out on my house for all the stuff I end up with in my cart), you may want to grab some 3M mini-connectors - love these for adding quick connects, like when you need to wire the terminal block to your removable bulkhead in an AV bay:

Female connector: https://www.mouser.com/ProductDetail/517-37304-A124-00EMB
Male Connector: https://www.mouser.com/ProductDetail/517-37104-2124-000-1

Those are 4-pin connectors, you can find 3-pin if you want smaller connectors.

 

[tOD]

Tom is exactly right. Great items to have in your kit bag.

Here are the ones I use, for easy reference:

Tool and kit: https://www.amazon.com/gp/product/B07PJK2VNT/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

That will get you down to 22 gauge. Since I encounter so many different kinds of wire in a build, I also added:

24 gauge: https://www.amazon.com/gp/product/B07Z5QCB82/ref=ppx_yo_dt_b_asin_title_o06_s01?ie=UTF8&psc=1

26 Gauge: https://www.mouser.com/ProductDetail/644-FSD72-6-D

28 Gauge: https://www.amazon.com/gp/product/B00NVBGAEU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

While you are over at Mouser (like McMaster-Carr, I can't spend too much time on Mouser or I will have to take a loan out on my house for all the stuff I end up with in my cart), you may want to grab some 3M mini-connectors - love these for adding quick connects, like when you need to wire the terminal block to your removable bulkhead in an AV bay:

Female connector: https://www.mouser.com/ProductDetail/517-37304-A124-00EMB
Male Connector: https://www.mouser.com/ProductDetail/517-37104-2124-000-1

Those are 4-pin connectors, you can find 3-pin if you want smaller connectors.

Thanks for the info. To wire from the altimeter outputs to the bullhead terminals I've been using the color coded pairs from Binder Designs.
https://binderdesign.com/store/locking-connectors.html

 

[mtnmanak]

While I am waiting for the Proline to dry on the MMT, went back to the AV bay for a bit. Working on securing it to the payload bay. Using these little PEM like nuts from LumaDyne. They have a coating on them that makes the epoxy adhere better. Using the 2-56 size for this rocket.

Used a piece paper to draw a circle around the payload bay tube about half way up the shoulder of the AV bay tube. Inserted the AV bay, lined up the witness marks and taped it securely. One nice thing about these red tubes is that they are very translucent. By holding it up to the light, you can see where the lines I drew on the AV bay coupler earlier intersect with the circle I drew on the payload bay tube. 3 evenly spaced marks.

The LumaDyne nut calls for a 5/32" drill bit. That was a hair too small, so I filed the holes a bit to get the nuts to fit perfectly, then glued them in with 5-min epoxy. Once I got everything lined up, it was easy to screw in the 2-56 screw and secure the av bay to the payload bay.

I only did one hole with these nuts. It is very secure and a slick solution, but getting them in and lined up right is a pain in the butt. I think I will just do one of these on each bird and plastic rivets for the other holes. 3 metal screws seems like overkill anyway. And these LumaDyne nuts are expensive.

 

[Banzai88]

While I am waiting for the Proline to dry on the MMT, went back to the AV bay for a bit. Working on securing it to the payload bay. Using these little PEM like nuts from LumaDyne. They have a coating on them that makes the epoxy adhere better. Using the 2-56 size for this rocket.

Used a piece paper to draw a circle around the payload bay tube about half way up the shoulder of the AV bay tube. Inserted the AV bay, lined up the witness marks and taped it securely. One nice thing about these red tubes is that they are very translucent. By holding it up to the light, you can see where the lines I drew on the AV bay coupler earlier intersect with the circle I drew on the payload bay tube. 3 evenly spaced marks.

The LumaDyne nut calls for a 5/32" drill bit. That was a hair too small, so I filed the holes a bit to get the nuts to fit perfectly, then glued them in with 5-min epoxy. Once I got everything lined up, it was easy to screw in the 2-56 screw and secure the av bay to the payload bay.

I only did one hole with these nuts. It is very secure and a slick solution, but getting them in and lined up right is a pain in the butt. I think I will just do one of these on each bird and plastic rivets for the other holes. 3 metal screws seems like overkill anyway. And these LumaDyne nuts are expensive.

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Based on price and spotty availability, I abandoned LumaDyne in favor of good old fashioned PEM nuts/screws/washers. When you order a bag of each from McMaster-Carr, buy the proper size drill bit for the PEM nut and a 'close fit' drill bit for screw and never look back.

Do 1 hole at a time and you'll never have a strange offset issue. Do one of the 3 holes 1/8 or 3/16 off from the others and you a have a pretty slick de-facto alignment key built in.

 

[mtnmanak]

Based on price and spotty availability, I abandoned LumaDyne in favor of good old fashioned PEM nuts/screws/washers. When you order a bag of each from McMaster-Carr, buy the proper size drill bit for the PEM nut and a 'close fit' drill bit for screw and never look back.

Do 1 hole at a time and you'll never have a strange offset issue. Do one of the 3 holes 1/8 or 3/16 off from the others and you a have a pretty slick de-facto alignment key built in.

Great recommendations Tom - I went that route for carboard tubes - the LumaDyne nuts weren't thick enough to use in those tubes, but I have a couple bags of these LumaDyne nuts in each size, so will try to use those up on my FG tubes until they are gone. Then it is back to good old PEM nuts and threaded inserts.

 

[mtnmanak]

The Proline on the MMT is cured. Before beginning the process to mount the MMT, couple steps I need to take.

First, I stitched the loop at the end of the Y-harness and reinforced the stitching with heat shrink tubing.

Next, need to drill the holes into the fin slots for the injection of the epoxy for the internal fillets. As noted above, CJ's advice on filing a hole vs. drilling it is a good one. Instead of drilling, I used a 3/16" round needle file to make prefect holes in the fins slots. That gave me just enough room to get a small Dremel sanding drum in there. On the lowest speed, the Dremel still cuts easily into the FG, but produces almost no dust (still wore a respirator and recommend recommend one anytime sanding/filing FG - especially if you are using power tools). I fairly quick fashion, I has two neat holes in the fins slots. You should make you holes sized to fit the syringes you will be using.

 

[mtnmanak]

Next, I dry fit the MMT again (the forward ring is tacked in with CA right now) and used an aluminum angle to draw lines down the whole body tube that bisect the fin slots perfectly. These lines are really helpful in lining up a fin jig later. Also, before I get the fins in place, I inserted the upper portion of the AV bay into the fin can and used the fin slots to mark out 3 evenly spaced lines around the coupler to use later for rivet positioning.

Just before I glued the MMT in place, I took the tape off that I was using to hold the rear CR in place and tacked it on with some mounting putty. I need that CR to stay put throughout much of the next few steps, but once the forward CR is glued in, the small diameter tubing makes it difficult to reach in and get tape off the MMT. The putty is good at keep the CR in place and easy to reach in and remove later.

With that done, I used a long stick to put a generous ring of epoxy right at the end of the fin slots (careful to avoid the fin slots themselves) and inserted the MMT tube until the forward CR was just peeking out from the front of the fin slot. I had already dry fit the fins a number of times and know the slot is about 1/8" longer than the fins, so the forward CR needs to be about 1/2 showing for things to seal up nicely. I am going to put this aside to cure.