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Wayco

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Prior to starting this build, I reviewed the instructions on Wildman’s webpage and decided on changes I would incorporate based on new techniques that have been developed since the instructions were written. I will note these as the build progresses.

Before I started this write-up, I weighed and measured all components and input them into Open Rocket. This will be adjusted as I refine the placement of avbay components and the Eggfinder in the N/C:


6-21-14
All parts were inspected and sanded to remove loose filaments, then washed and dried. Some parts won't fit into a sink or bathtub:



After wiping everything down with a microfiber cloth, I started the build.
Slid Avbay coupler into fincan and marked three lines for static ports and shear pins. All lines were drawn at top of slot:



Also did this with the N/C coupler. Transferred lines to top of payload tube and N/C:



6-22-14
Slid N/C coupler into N/C and marked N/C for 6-32 flat head screw placement. This is one of the changes I’m making to accommodate the Eggfinder GPS. I call it the metal-less anchor point for recovery. The coupler will be removable to access the Eggfinder on a sled in the N/C. The N/C coupler is 5.75" long, 2.5" will be the shoulder, 3.25" will be inserted into the N/C. The 3 screws will be 1.5" forward of the bottom of the N/C.
Here are some of the tools I use to install pem nuts:



First I drill one 9/64” hole through the N/C and coupler, and remove the coupler. Used a taper bit to enlarge the hole in the N/C so the flat head screw would lay flush:



Then switched to a 7/32 bit and drilled out the hole in the coupler. Cleaned up the hole with a rat tail file so the pem nut would fit. Don't want to remove much, the pem nut should press fit into this hole:



Then sanded around the hole inside the N/C. This is to improve adhesion when I add epoxy. Pulled the pem nut in with a 6-32 screw, nut and washer.To do this you first center the pem nut in the hole from the inside:



Then add a washer that has an inside diameter larger than the pem nut:



Tighten a screw and nut from the outside, making certain it is all perpendicular to the tube:



Tighten the nut with a wrench while watching or feeling the pem nut to be sure it's not turning:



It only takes about one rotation to snug the nut into the hole. It should look like this when done:





Slide the coupler back in and repeated the process for the second and third hole, doing one at a time and drilling each hole with the previous screw tightened down. Then I cleaned around each pem nut with acetone, and added some 5 min. epoxy around the outside edge of the nut:



Once I had the shoulder mounted to the N/C, I installed it in the payload tube and rotated it to find the best fit. Then I transferred the marks off the N/C onto the payload tube and marked the location of the holes for the shear pins, 1.5" down from the top of the payload tube. With a 5/64" bit, I drilled the first hole and reamed it out a little with my rat tail file:



I then inserted a 2-56 nylon shear pin and moved to the next mark, repeating the process for all three shear pins.
After all the pins were in place, I marked an index line with a dremel cutting wheel:




Finally, I removed the screw at the top of the N/C with a long handled phillips screwdriver and took off the tip. Reinserted the screw and marked where it came out the top of the N/C. Removed it again and popped out the fiberglass washer stuck in the top of the N/C. Replaced the fg washer with a large 1/4" metal fender washer that is the same OD as the fg washer, and added a nut, where I made the earlier mark. I glued the nut in place with red locktight. I added another metal washer that was 1/4" ID and 1" OD that fit the hole at the top of the N/C. Here is how it looks before installation:



When I re-installed it, I added a little more red locktite to the threads and surface between the tip and 1" washer. This will keep the tip centered in the top of the N/C.

Meanwhile, parts on order are starting to arrive:

 
Last edited:

daveyfire

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Excellent documentation job! I need to get going on my DS Extreme rebuild myself... you're inspiring me!
 

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I am looking forward to this do you have a date in mind when you will fly?

All I know is I want to be there!
 

Wayco

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I am looking forward to this do you have a date in mind when you will fly?

All I know is I want to be there!
I'm thinking you probably won't want to drive 1000 miles to Argonia, Kansas to watch this flight. This will be my L-3 attempt at Airfest in August over labor day weekend. If successful, I will fly it again at Octoberfest in Jean, Nevada.
I'm sending a link to this thread to both my TAPS so they can follow my progress and make (more) suggestions.
 

Wayco

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6-23-14
Started off by cutting a short piece of hardwood dowel for the anchor point in the N/C coupler. It would lay across the top of the fiberglass bulkhead mounted in the top of the coupler. I sanded down two sides of the dowel so it would lay flat on the BH and create a shelf to mount the sled for the Eggfinder. Good idea to wear gloves for this job:



Once I had a good 90* angle, I mixed up some Rocketpoxy and prepped the BH:



Wiped it off with acetone, spread the epoxy on, and clamped the dowel down:



After it cured, I fit the Eggfinder sled to the dowel and drilled two holes next to the antenna:


I will explain more about this in a later post, but the basic idea behind this setup is to keep any metal away from the antenna, thereby improving it's transmit performance.
Switching over to the switch band, I marked the position of the switch band on the Avbay coupler and fitted it in the payload tube and fincan to determine which way fit best. Marked “nose” on the top end of the coupler. Taped off one side of the coupler where the switch band goes and sanded with 220 grit sandpaper. I'm buying into the idea that a molecular bond is essential for good epoxy adhesion, so "exciting the molecules" with 220 grit is preferred to 80 grit for mechanical grip. This is one of the modifications I mentioned in my first post.
After I excited the molecules, I wiped the parts off with acetone and mixed up some more 5 min. epoxy. Spread it on the coupler and slid the switch band on with a circular motion. Wiped off excess epoxy and removed tape. Wiped it off again with alcohol and q-tips.
Just a note on procedure here, when I'm working with 5 min. epoxy you won't get any pictures. The stuff I use comes from Hobby Lobby and is "Hammerhead" brand clear epoxy. It truly is 5 min. epoxy and you have to be quick, no time for pictures. Anyway, fast setting epoxy and camera's are not a good mix.
Once the switch band was set, I slid it into the payload tube and marked the location of the 6-32 flat head screws that would hold the avbay to the payload. They would be located 3" above the switch band:



Same procedure as the N/C coupler, drill one 9/64" hole, remove avbay, drill coupler out to 7/32" and insert pem nut. Recess the hole in the payload tube for a flush fit of the flat head screw. After epoxy had set on the pem nuts, I re-installed the avbay in the payload tube and rotated it to find the best fit, then used my dremel to put an index mark at the joint, just like I did on the N/C payload joint.
Then I drilled 1/4" holes offset halfway between the screws centered in the middle of the switch band for static ports.

OK, confession time. I wrote that last sentence early this morning (3 am) because I sometimes have trouble sleeping when I'm involved with a big project. So I decided to get caught up on this build thread instead of laying awake in bed. When I wrote it, I realized that I couldn't remember offsetting the holes in the switch band. That was two days ago, and one of the things I lost as I got older was my memory, and I can't remember where I put it.....
So I went and looked and sure enough, I hadn't, the holes were right under the flat head screws. So I spent most of this morning regrouping, and after I fill you in on my progress for the last two days, I will tell you about my frustrating day today.
After drilling holes in the wrong place on my avbay, I did manage to drill holes correctly on the fincan and payload tubes. One 1/8" hole was drilled in the middle of the payload tube. 12" down from the top of the tube.This is to vent expanding air as the rocket ascends, and the same was done to the fincan tube, 16" down from the top of the tube.
Monday was a busy day, I spent most of the early morning doing yard work before it got hot, and the rest of the morning up in the office, setting up files for Sharon's business. That was all I got done on the rocket.
 

Wayco

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6-24-14
Yesterday was mostly taken up doing research for Sharon's business, but I did sneak in a couple of hours of sanding fin slots. Amazing how just a couple of thousandths of fiberglass can take up your time. Not much to take pictures of either, but I did figure out a little trick to make it easier:



A stir stick with some 120 grit wrapped around it gave me just enough leverage to get the last two slots done quickly. Then I took out a small rat-tailed file to make the notches with:



This is another modification to the original instructions. Instead of drilling 1/4" holes, file out a notch to inject your internal fillets. Drilling holes in filament wound fiberglass can be problematic, creating loose strands that will catch the carbon fiber additive recommended in the instructions and clog up the epoxy. Filing out notches doesn't fray the FG and keeps the holes closer to the fin, making it easier to cover with your external fillets.
When I finished that project, I had to go take a shower and rinse off all the dust....
Which brings us to today....

6-25-14
As I explained in the previous post, I didn't sleep well last night. Thinking about ejection charge cups, building a tower for my MD 54mm Blackhawk and all sorts of other spurious thoughts, I laid awake from 1 am to around 3 am when I got up and made a pot of coffee. That's when I discovered my mistake with the static ports. After I beat myself up for a while, and drank the pot of coffee, I got up and started fixing the problem.
Either I moved the pem nuts or I filled the holes. The only place where the joint between the switch band and the payload tube was flush all the way around was where I had it secured, so moving the pem nuts was out.

I mixed up some Rocketpoxy and added a few drops of black tint, prepped the bulkhead I built yesterday for the N/C coupler by sanding the aft edge with 220 grit sandpaper and wiped it off with acetone, then did the same on the inside of the coupler where they fit together (excite the molecules) wiped it off with acetone and ran a bead of epoxy inside the coupler and slid the BH in place. When that was done, the Rocketpoxy was getting thick. So I taped off the static ports inside the avbay and filled them with thick epoxy. As I rotated the tube, the epoxy still wanted to flow, but I stopped it by placing a piece of clear packing tape over the top. Then I set everything outside to cure. It was still early, so the AZ. curing oven was only at about 80*.
Moving back to the fincan, I started sanding again... These new centering rings (Cr's) are nice, not much sanding had them sliding onto the motor mount tube (MMT) nice and snug. Once I had them all fitting properly, I pulled the top one and laid the Kevlar strap across it:



Marked it with a silver sharpie for the slots:




Got out my trusty file, secured the Cr in a vise and with a few swipes got this:



Which I promptly slid back on the MMT with the Kevlar under it:



Whoops, looking at that pic, I realized I missed mentioning a previous step. In one of the fittings where I was sliding the MMT with Cr's into the fincan, I marked where the fin slots fit on the MMT with a long thin knife. You can see the marks in the above shot. It helps you situate the kevlar away from where the fin roots attach. You can also see that I have the AeroPac tailcone retainer attached. This is an important part to have on when fitting the MMT to the fincan. The tailcone has to fit flush with all the Cr's in the proper position as viewed through the slots:



You can just see the rear Cr right at the back of that slot. The forward slot looks like this:



A tight fit is essential when you are injecting fillets, any gaps would allow the epoxy to leak into areas you don't want epoxy in, if you get my meaning.
Once you have all the Cr's fitting, remove the MMT and put a fin between the Cr's:



After you get the rear fins snug, put a little drop of CA (super glue) in three places around the Cr. This will hold everything in place for the final dry fitting. Once you have the upper fins fitting snug between the Cr's, remove them and tape over the lines where they will be glued. This will prevent any glue from getting on them when you encapsulate the kevlar strap:



Now for the final fitting. Slide the MMT back into the fincan, making sure the tailcone is flush at the back. Check all fins in their numbered slots (Dang, did I forget another step?) for proper fit. If everything is good, take it all back apart and start gluing. I got all the way to this step and was looking at this:


Some of you may have already noticed, those fins don't fit! They were cut with the tabs 1/2" too long.
Regroup. Flash back to earlier this month when I posted up in the "What have you done Rocketwise" thread mentioning a soon to be released build thread for my DS Extreme. The reason this thread didn't get posted until now was due to the original fincan tube being cut with 1/8" fin slots. No way was I gonna ream them out for the 3/16" fins that came with the kit, so Wildman sent me another tube with the slots cut correctly. It got here right before ROCstock, so I didn't get started building until this week. NOW THIS! Sleepless night, stupid mistake discovered on the avbay static ports, just getting rolling and another setback. I wasn't really mad, just frustrated. So I took pics, and sent an email to Wildman. Does this look right to you?:


I waited about an hour and gave Tim a call. Got Jackie. She checked the kits that were bagged up and all the other Extreme kits had the same fins. Tim was in New York and wouldn't be back until next week, so I was stuck. I think I was whining a little, which I HATE to do, when I realized this was an easy fix. I apologized to Jackie and hung up.
Since this is a very long post, and I have been typing all afternoon, I'm gonna take a break now and get back to this later.
...
 

DizWolf

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Thought something looked off in the CR fitting photo. Ultimate DS fins or just long tabs?
 

jsargevt

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Thought something looked off in the CR fitting photo. Ultimate DS fins or just long tabs?
I'm betting a standard DS4" with a 54 mm mount fins were bagged incorrectly. Bummer!
 

Wayco

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Thought something looked off in the CR fitting photo. Ultimate DS fins or just long tabs?
Since I have a set of Ultimate DS fins, (another long story) I set them out to compare:



Nope, there half again longer and bigger than these. And you can see my solution, thanks to a generous neighbor that gave me his wet tile saw. All I had to do was mark off 1/2" from the bottom, whack it off with the tile saw, and viola! Back in business.



I'm betting a standard DS4" with a 54 mm mount fins were bagged incorrectly. Bummer!
I think you may be right. Not so much of a bummer, easy solution once I thought about it. I'm more bummed that I caught myself whining to Jackie on the phone. Sorry Jackie, next time we talk, you will get the smiling, happy Wayco that you remember from last years Airfest. :smile: But I still won't let Sharon go into Wildman's trailer without adult supervision....
 

BLKKROW

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Just to let you know, if you ever need a table/miter saw just let me know. I am more than willing to let you borrow my tools.

I am saddend I will not be able to see your L3 flight but I am sure I will see it fly in Arizona sometime.
 

Wayco

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So, being the stubborn, determined and slightly inebriated Irishman that I am, I jumped up, dusted myself off and got back on the horse this evening. (Theoretical horse) I attached the avbay to the payload tube and marked off half way between the screws, drew a line across the switch band and measured half way down it and put a mark with my handy little spring loaded punch. Then after checking for the third time that the marks were in the right place, I drilled a 3/32" pilot hole through the switch band:



Changed the bit to a 1/4" and drilled my static port. Rotated the tube 120* and repeated the process two more times to complete the task. Here is a shot of the new hole and the patched old hole:



I'm thinking now I will prime and sand that switch band until it's smooth, then paint it bright red.

Now that this day is drawing to a close, I decided to make a royal decree. Today is a dos Dos Equis day!

 

dixontj93060

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I'm betting a standard DS4" with a 54 mm mount fins were bagged incorrectly. Bummer!
Heck, that's what my DS Extreme was... A DS4DD. I swapped the 54 MMT for a 75 and re-cut/carboned everything in the fin can area. Not much trouble really.
 

stealth6

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Absolutely stellar build! What a great, detailed thread.
However, this pic scares me:

PLEASE be careful! I can just imagine that dremel tool skipping a bit, and your nice (ungloved) hand being in the path of destruction.
Yikes!!

s6
 

CarVac

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Absolutely stellar build! What a great, detailed thread.
However, this pic scares me:



PLEASE be careful! I can just imagine that dremel tool skipping a bit, and your nice (ungloved) hand being in the path of destruction.
Yikes!!

s6
Or the disc breaking and firing shards into your hand...
 

KenRico

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You are making quick work of this build..hope there are no more sleepless nights . Visions of CTI dancing in your head .

Fit fit fit , before you glue glue .. is serving you well. Nice catch on the fins and like your solution - - anything to keep things moving forward without having to wait for a shipment .

Bet you are having a blast simming this in ThrustCurve... with 75mm motors altitudes should START at 10k+ instead of stopping there !

Kenny
 

ChrisAttebery

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Dremel tools rotate clockwise as seen from the rear. Actually this applies to almost all power tools. The tool will pull away from his hand.

Absolutely stellar build! What a great, detailed thread.
However, this pic scares me:



PLEASE be careful! I can just imagine that dremel tool skipping a bit, and your nice (ungloved) hand being in the path of destruction.
Yikes!!

s6
 

Zeroignite

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Cutoff wheels do shatter at about a million miles an hour though, so I try to keep clear of the entire plane of rotation.
 

blackbrandt

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And wear safety glasses. I have 3 studs in the garage that I work in that have a shard of a cutoff wheel permanently embedded in the 2x4... :p
 

ChrisAttebery

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Are you guys using the fiber reenforced cutoff wheels? I've never shattered one of those in 20+ years of Dremel use.
 

Wayco

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Not quite sure how to reply regarding the dremel, it's an index mark, not like I'm cutting fin slots or other material that would put a strain on the wheel. Yes, it's a fiber reinforced wheel. No, it's not turning at 20,000 rpm. I wear poly carbonate glasses. I've had cut-off wheels shatter with no effect to my body, so not sure what the fuss is.

As far as the build goes, I got a few minutes free around lunch time so I put the Eggfinder into the N/C and added a piece of 1/2"Kevlar strap. I'm not sure what it's rated at, but you could probably tow a car with it, so it should be OK. Fortunately, the sled configured for the 5" Jart fits this rocket too, so no modification necessary:



The retention anchor point is the hardwood dowel, which is captured with two separate loops of kevlar:



The sled and antenna are held in place with a zip tie, with the antenna protruding through the bulkplate and into the N/C coupler:


I use overhand knots on all my shock cords, and the overhand loop at the end prevents separation if one strap breaks. The four holes in the bulkhead are 5/16" and all edges were rounded with a rat-tail file. Not that there's much chance of anything cutting through the kevlar.
That's about it for today, tomorrow looks good for a real productive session, might get the fins stuck and injected!
 

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Nice thread - minor question - which PEM nuts did you use and from where did you buy them?
 

Wayco

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6-27-14
Today I started off looking for my JB weld. After about a 15 min. search, I found it in the launch tool box. Not where it was supposed to be, but now it's back in the laundry/epoxy room. To finish up the MMT, I sanded down the aft end of the tube so the retainer would slide on smoothly, wiped it down with acetone and mixed up some JB weld:



Wiped out the inside of the retainer with acetone, and spread a thin layer of JB on the inside and on the outside of the MMT:



Slid the retainer on with a circular motion until it set flush on the back of the MMT:



Wiped of the excess inside and out with alcohol, leaving me with this:




Just to be sure, I slid a 75mm motor casing in:



Perfect fit, slides in nice and smooth.

Next step is to encapsulate the Kevlar strap. So I lifted up the strap and sanded down the MMT with 220 grit, wiped it off with acetone and repeated on the other side. Since I had some Proline 4500, and it has a pretty high heat tolerance, I used it to encapsulate the strap. It is mixed by weight, 5.5 to 1. I estimated what I would need for both sides and mixed 16.5 grams resin to 3 grams of hardener. Mixed well for two minutes and spread it on the MMT and underside of the strap:



Laid it down and smoothed it out:


Then put another layer on top:



That shot was taken after I lifted the tape off my fin slot marks. Repeat the same procedure on the other side and move on to the CR's.

 

Wayco

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When injecting fillets on two sets of fins, the CR's need to be flush up against the tabs on the fins, and the fins need to be flat against the MMT to prevent leaks. I'm using some of my 5 min. epoxy to hold them in place, once the internal fillets are injected, all the parts are bonded together in a solid piece, so the CR's are held in place by the internal fillets anyway.
Once again, I'm looking for a molecular bond, so I sand, wipe with acetone and apply the epoxy in the gap between the middle rings:


Wow, what happened with that picture? Must have set the camera wrong on that one.
Being careful not to put epoxy on the outside edges of the rings, or anyplace a fin goes. I also add some to the top CR, making sure I don't get any on the Kevlar strap:



Now all the rings are attached and we are ready for the final fitting:



I sanded everything between the rings where the fins attached, even the Proline that encapsulated the Kevlar strap. Wiped it clean with acetone and slid it back into the fincan. Checking the fit at the back of the tube with the tailcone, I had to sand the tube a little to make it perfectly flush. Fit the fins back into the slots to make sure nothing had moved and ran my piece of PVC tube along them to measure the gap for masking off the fillets. I'm using a 1" piece of PVC:




Although Wildman recommends a 1.5" piece for a bigger fillet. That was back before Rocketpoxy, and I think it will do the job with a little smaller fillet. After I removed the fins again, I marked off 3/8" at the top and bottom of each slot:




and used a piece of angle to run a line:




Taped off all of the slots:




and measured the mark on the fins. Those would be 7/8" from the root, marked them off, taped them off on the line and sanded the bottom and sides below the line of tape. If you hold your hand like this:



And hold the fin at the edge of the counter, you can sand the fin without damaging the tape. After all the fins are sanded, once more into the slot and tap them down to make sure they are solid against the MMT, then mark where they fit against the body tube with a pencil. That way when you put them in the last time with epoxy on the root, you can tell when they are all the way down.
Now I'm mixing up Rocketpoxy, nice thick goop that bonds so well, and clings to the root. Butter them up with lots of goop:



and slide them into the slot. I'm doing the front and rear fin like this:



After the first set, I decided that the little plastic fin holder wasn't doing the job, and switched to a piece of 1/2" angle iron, which was much more solid. Moved it outside into the AZ curing oven:



I also put a little epoxy on a card to check for when it's cured. After a few minutes, I took my new toy (infrared heat sensor) and checked it:



Yeah, I think 150* will cure it up quick! Sure enough 30 min. later it was solid.
So back into the epoxy room for another set, same routine two more times and the fins are in place.

It's past my bedtime now, and I still have more done than I have time to type up, so I'm offline for a while, post up the injection process tomorrow. Amazing what you can get done when you don't have any distractions all day!
.
 

jmight

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I just picked up an Eggfinder and was trying to figure out how best to mount it. Great idea! Looks simple and clean. Question: is the antenna extending through the bulkplate because it's too long for the nose cone, or for some other reason? Have you used that setup, or the Eggfinder, before?
 
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