"BOOF" Post-L3 Build Thread - Mad Dog - DD

[ClayD]

I recently took on a L3 project, and the time line was just not reasonable for a build thread. However, I thought some might find some of the information I have documented useful in their own builds.
I learned a good amount of information for my first L1 rocket from L3 build documents I was able to find on the internet. So, I would like to pay forward what I took from those great guys. This will take a few days to get updated! ENJOY.:wink:

I will start with the plan; I will probably attach better PDF files of the drawings as I post more detailed information.

View attachment Plan.pdf

 

[ClayD]

First, my wife would remind me that when I certified L1, I said; "I will probably never fly an M motor." :handshake:
But... oint: She knew better.

So, Second... the rocket . It was purchased from Rocketry Warehouse 3 weeks before AIRfest 19. So what ensued after that was a fun game of father of 3 building a level 3 in 3 weeks.

They graciously swapped the motor mount and centering rings out for a 75mm tube, and actually added some MMT length for me. A+ rating on the quality. The kits fit of components were top notch.

I pretty much had everything for this rocket in my build stock, even the AEROPACK retainer, so for a L3, the kit was really chosen to compliment existing hardware.

SO!, made a few calls, got a motor lined out from Scott at Loki Research; and was on my way.

Ohh, yeah this all began because a buddy and I were talking and he said he would loan me his 76/6000 case if I ever wanted to L3. I realized at that point there was little money required to build a kit, and buy a reload. So why not.

 

[ClayD]

The first order of business was to substitute the 76mm centering rings. I have 1/2in. 7 ply stocked I like using it much better than G10, however both were sufficient for this rocket. The birch makes it easier to mount brass inserts for rail buttons, and along with my method of secondary harness attachment was the reason it was chosen.

Some people say the birch gives a better epoxy bond because it has more surface area for bonding. The bond of the centering ring, in this rocket is not that important. The attachment of the fins to the MMT and air-frame are the primary load path in my opinion.

1. Drill holes in centering ring so that you can use screws to attach it to your plywood. Then use a router to follow the centering ring.

2. Hit them with some sand paper to clean them up.

3. Test fit.

 

[jpummil]

Thank for your efforts Clay!

I have been contemplating an L3 build over the winter and this will be a very useful reference :wink:

 

[ClayD]

Okay, so I used measurements taken from dry fitting all the fins, centering rings and AEROPACK retainer. This gave me the layout I needed to start gluing rings to the motor tube.

The first thing I did to the MMT was to get it ready for mechanical bond. A file works good, but something with carbide or a sharp hardened steel point is best and will "cut grooves". After that an aggressive use of 30 grit, same as you would use if your doing autobody to rough steel for Bondo.


Rough up the AEROPACK.

I used JB Weld and attached the AEROPACK while I was cutting centering rings. (So really it was the second order of business. Getting glue drying in a hurry was the first.)

you will see here there was a liberal application of JB Weld for the AFT centering ring. I believe in over application and then removing whats not required. A die-grinder and a sanding drum makes quick work as you will later see.

 

[ClayD]

Thank for your efforts Clay!

I have been contemplating an L3 build over the winter and this will be a very useful reference :wink:

Jeff, if there is anything I can do let me know! There will always be things that in retrospect you say, probably a better way. This idea has killed my last 2 big projects. I go so far and say, "I don't like the way this is going." So then I stop, and it falls to the side while I think about it. So, I firmly believe don't try things you haven't done before for a L3. You will hear this almost universally from taps, and is magnanimously great advice. This was a great time table for me otherwise, because I had a calendar for due dates, and I HAD TO HAVE certain components complete to fall in place with the amount of time I had to work with. About 20 hours total. So no over thinking it. In the end it worked for me.

 

[jpummil]

Jeff, if there is anything I can do let me know! There will always be things that in retrospect you say, probably a better way. This idea has killed my last 2 big projects. I go so far and say, "I don't like the way this is going." So then I stop, and it falls to the side while I think about it. So, I firmly believe don't try things you haven't done before for a L3. You will hear this almost universally from taps, and is magnanimously great advice. This was a great time table for me otherwise, because I had a calendar for due dates, and I HAD TO HAVE certain components complete to fall in place with the amount of time I had to work with. About 20 hours total. So no over thinking it. In the end it worked for me.

Thanks Clay! I'll likely take you up on that offer ;-)

I'm still fiddling with the aesthetic portion of the design...I mean, it's GOTTA look right :grin:

After I'm happy with that, I need to get the TAP situation squared away, make design determinations, etc.

 

[ClayD]

Thanks Clay! I'll likely take you up on that offer ;-)

I'm still fiddling with the aesthetic portion of the design...I mean, it's GOTTA look right :grin:

After I'm happy with that, I need to get the TAP situation squared away, make design determinations, etc.

Well good luck on the endeavor for your L3. There are plenty of great taps to help you with the process. I highly recommend having your paperwork done first. It just gives a common starting point for discussion.

I am not a tap, but if you want some outside input I am available. Just PM I'll give you my info if you don't have it.

 

[ClayD]

So the aft ring and Aeropack is installed on the MMT.

After this, I use the forward centering ring and the 3 fins to mark the MMT for location for forward centering ring.
I then align my ring, and secondary harness and use a jig saw to cut away enough room for the harness to pass through.
I scuff and prep the MMT, and install electrical tape along the line of the forward centering ring.
I cover the harness with electrical tape to keep epoxy from getting in the kevlar.
LOOKS LIKE THIS (note all the previous JB is gone from the aeropack, never mind the scratches, you won't see them later.)

I JB Weld attach the forward ring.

Here is the line, and tape being removed (before the JB gets fully cured)


Then the pieces that retain the secondary harness. They will take any recovery load, and are not attached to fins.
I usually notch the fins, and make a structural attachment. Here I did not want an anomaly to cause a load to my fin root. This is new for me, I am not sure I would do it this way again.
NOTE: marked the fins so I know the pieces would not interfere with attaching fins.

 

[ClayD]

View attachment fin start.pdf

Here is the layout of everything. This was done by measuring and dry-fit of everything. The CNC slots for the fins, I wish as 1/8" further up from the bottom of the tube. The roundness was distorted badly from the slots, and my 1/2" birch stuck out 1/16". (the distortion happens to any filament wound tube when cut.)

As you can also tell.. I did not cut of 11.5mm from the tang of the fin. I told myself it was unnecessary, since my fillets would take care of the front and rear of the fin root.

Made good measurements of centering ring locations so that I could measure and drill in brass inserts later.

 

[ClayD]

Some times crotchety things have bigger attitudes than they should... Squish!!!:eyepop:

This guy didnt get squished..... but he is a little big for his britches...

 

[ClayD]

So, this is a concoction of filler....

West epoxy, Aluminum Oxide(50micron in the baggy). 1/8" chopped CF, 1/32 milled FG, and Kevlar pulp.
all mixed up, and applied. Excess was ground out- kill the dead weight... Concrete substance.

 

[sodmeister]

Some times crotchety things have bigger attitudes than they should... Squish!!!:eyepop:View attachment 147179

This guy didnt get squished..... but he is a little big for his britches...

I believe that`s a type of Pine Sawyer Beetle......you should have given him the big "squish" ! LOL

Those SOBs are bad news to softwood forests along with their kin and Asian stowaways (hitching rides in wooden pallets and crates from overseas)

The Northwest pine forests as well as the East are being destroyed by these (well their larvae)....bad news.

Can centering rings ,fins and all things Balsa and Basswood be far behind :y:

That`s a superb photograph by the way ,I like it !!!!

Good to see you doing a play by play build ,good stuff !

Take care


Paul T (yah.....I like all things bugs and butterflies ,birds too !)

BTW -where do you get that Kevlar pulp if I may ask ,thanks.

 

[ClayD]

I believe that`s a type of Pine Sawyer Beetle......you should have given him the big "squish" ! LOL

Thanks so much for the compliments!

Yeah, they are bad news. I have lost 5 trees due a bug infestation. Ate up from just underneath the bark.

Still, I just am not a bug killer. I was dusting off and saw this guy, I just couldn't resist messing with him. He had quite the aggressive attitude.


oh yeah.. I purchased the Kevlar pulp from fiberglast.com

 

[sodmeister]

Thanks so much for the compliments!

Yeah, they are bad news. I have lost 5 trees due a bug infestation. Ate up from just underneath the bark.

Still, I just am not a bug killer. I was dusting off and saw this guy, I just couldn't resist messing with him. He had quite the aggressive attitude.


oh yeah.. I purchased the Kevlar pulp from fiberglast.com

I`ve been bitten by them rascals ,ouch ! I don`t think I`ve ever even killed a spider ,no need for that.Insects are indeed a much needed organism ,I love `em....comes in handy to know them when fly fishing ,which I`m doing all next week :clap:

Thanks for the tip on fiberglast.com ,I`m going to order some !

Cheers


Paul T

 

[ClayD]

The pulp was recommended by a friend. Add it in small amounts and mix thoroughly. It can make the epoxy have an almost gel-like characteristic. It is extremely strong.
Little bit does a bunch!

 

[ClayD]

Lee press-on fins don't exist in rocketry!
Not shown here, is that you need to sand, and prepare the inside of the air-frame for the mechanical bond. Solvents, take care you can permanently ruin the resin in the G12 air-frame if you use them.(I don't) Find what works for you, do what you think works, and learn from it. For this, don't pay attention to those who say "your wrong", even the tech papers you find say, "well, its very complex and you just don't know." This method is proven, and I base my reasoning on foam panel engineering, where the G12 air-frame does not need to be strong... Its filler.

At this point you pour the epoxy into the air-frame. I just pour it in the ends of the fin slots, and turn, rinse, repeat, pour.... you will get the idea.

Then you insert the MMT with the centering rings where the rings are visible through the slots and aligned properly so they don't interfere with the harness or the ring used to hold the harness in place.
Once that's done, dry fit your fins, and take a nap, after some catnip.

For through wall fin rockets, this method of setting fins is perfect. Surface mount it works too, but needs extra care to align them along the axis of the rocket properly. Most of my fins are tight in the slot, so there is no adjustment allowed of the in-axis alignment.
I draw this in Auto-CAD and print it to scale. The slotting of the G12 pulls the tube out of round at the slot since the fibers are released of tension... (this is bad for the G12, but okay for this rocket.)
So make sure its big enough to fit the air-frame in. SNUG as a little blue dune buggy in the sand...
6" calipers are what i use to get Max OD.
I attach 1 fin at a time, I try to place the new fin in the same slot cut out I used on the previous fin. This helps them all have the same exact angle. Oddly you would think it doesn't matter, but I have found better results this way, as opposed to doing all 3 fins in their own slots.
and your ready to glue them in.

 

[ClayD]

First I drill the air-frame, and inject epoxy to the root edge. This time I used Kevlar Pulp and Epoxy.
Here is the holes to inject (directly after injecting).


Next it's masked off for fillets, this just keeps the epoxy from running on the air-frame to the next fin.
As you can see, the front and back of the fin is flat, the fillet will have to be shaped here.


Note: the right side shows a build up of fillet already that was used to make the fin look "normal."

 

[ClayD]

Mix the epoxy, add the Kevlar pulp till it's a gel like consistency.

Then I added CF and Milled FG

Then Mix in Aluminum Oxide.


The structural fillets that were made are instant death to any carbide tool. I ruined 3 carbide files just "knocking them down" to be ready for the "cover fillet". :neener: So, its best to work before the epoxy fully sets.

Lay the fillets, they wont be smooth!:gavel:


When done, sand off the big bumps.
I used a half round file.. or 4. I also used a die grinder to shape the fillets in the front and back since there was not fin material to use for shaping.



Then mix epoxy with colloidal silica and give a nice smooth fillet. Over top of the bumpy structural fillet.

 

[ClayD]

There's tons on here about this so probably not much need to explain it. Her is how I do this..> excuse the messy garage.

1. I prep the rocket for mechanical bond, carbide file (or the like) 36 grit, then some 60 and 120...



2. I use a trash bag and cut out a pattern.
3. Make sure the cutout fits.



4. I put down the first layer, and let set, then work in the next layer to absorb the excess from the first. Then I work epoxy in on the second layer. If you place tape on the components, you can cut the fiberglass during cure to remove and have a strait line on the air-frame, its not shown here, but is my normal method. (this is only a 2 layer job.) I have done up to 4 this way and works well.

 

[ClayD]

So now we are built, tip to tip'd, and ready for final touches on the booster!
First use microballoons and epoxy to fill the weave *white milky stuff* - yeah...
Then use autobody glaze for the final thin finishes!


I love my vanilla sky clouds!!!! it's just in my mind!

(note 3 or 4 coats of primer! sanded, and you cant tell where g12 stops and Tip to tip begins.)

 

[ClayD]

I used my APCP box to set my drill press up. I set the rocket underneath with jack stands.

Marked my button locations then used the level to draw a strait line down the air-frame.

Drill, add JB weld, then install brass inserts. Install buttons to make sure the threads are clear...:no:

Its okay if you drill through the MMT.

 

[ClayD]

First, you have to break off the tip. I usually save this for after painting but, an early juggling episode did it early.. the funny part was it actually happened twice.


Epoxy in eyebolt. Cover threads and install nut. Then gridn down the nut, cut off excess threads, and cover with epoxy. Grind off extra epoxy when done.(not shown) excess doesn't do any good here.



Epoxy in the bulkhead. Then pour in Kevlar/epoxy fillet. If you spin the Nose cone, it makes a really good fillet.

 

[ClayD]

I have a 1" piece of 1/4-20 all thread I use to center the bulkheads, and epoxy them together. I use clamps to ensure a tight compression. I do the aft and forward bulkheads at the same time. Usually takes cutting apart with an X-acto knife.

Once the bulkheads are set use some 3m 77 adhesive to place this drill guide on them. (the pics on this post are confusing, I break them apart prior to this while they are still curing, then put them back together. It makes them easier to separate, but... re attach the two sides with all-thread before drilling for the sled.

Once I drill the bulkheads, I install the eye-bolts. Same method as the NC bulkhead. I put epoxy on the threads and shoulder, and then run in the lock nut.

Then I install the all-thread, and start placing the nuts exactly where they should go.

Here is a dry fit of the sled and altimeter to verify nothing is interfering.

 

[ClayD]

Here is the rest of the ebay.
First I had to drill and tap the bulkheads for the terminal blocks, I get these from Radio Shack, McMaster, and these came from AltusMetrum's Store.


Here is how the batteries are mounted, (4) 9volt batteries for dual ARTS-2.
The Z-shaped aluminum is from Lowes. Works perfect to hold batteries.

The switches are 2 6-32 brass nuts, with a piece of wire soldered onto them. The they are JB welded to a piece of 1/16 or 1/8" birch. I think this piece was in between.
you have to use a screw when moutning them , so that they are slightly tight threads just tighten them down a tad so they are not loose before the threads bottom out. You will probably have to start with a longer screw and cut down to the required length.

Then I carefully align them with the vent band holes. Measure twice , glue once. I had to cut one off and redo it.


As always, excess is not wanted, grind off extra epoxy.


Then build your rats nest as cleanly as you dare. Mine are always messy.... One of these days, my altimeters will be printed on the sleds, so wiring will be obsolete........

 

[ClayD]

It takes longer to lay them out than to drill them.

Not much explanation needed there....

 

[ClayD]

A fun candy coat..... Never do this in a dark garage, you wont like the results.
Duplicolor clear will never ever be used again. I will by horrible auto body 2k urethane clear before I buy a liquor clear ever again!!!!


I got heavy with the clear and it messed up the candy coat in a few places... OHH well, it still looked decent.

 

[dward]

2k urethane's can be pricey. How long did you wait before applying the clear? I have had trouble with the duplicolor clear when applied within 24 hours of the last coat of paint. If you wait a few days, I bet you wouldn't have those problems, but I could be wrong.

 

[sodmeister]

Looks pretty good to me !

I like the black and red fade ,looks very cool.

What happened to the clear ?


Paul T

 

[ClayD]

2k urethane's can be pricey. How long did you wait before applying the clear? I have had trouble with the duplicolor clear when applied within 24 hours of the last coat of paint. If you wait a few days, I bet you wouldn't have those problems, but I could be wrong.

Lacquer based paints will always re-constitute... one of the things I like about lacquer is that you add the lacquer thinner and go. No activator required. 2k urethane's, once activated are going to set up. If you wait for all the solvent to evaporate it helps a BUNCH... but wont remove the possibility that you re-constitute the base coats.
I have mixed lacquer and 2k urethane clear on projects, and the result is stunning. The duplicolor RTS Clear is about 26.00 for a quart, you can get a gallon of 2k urethane clear for about 100.00, you will see the gallon go way further because its not reduced like the RTS duplicolor. In this case I already had the clear, and wasn't willing to drop another 100.00 to replace the 2k clear I ran out on.

75.00 for black, silver base coat, and red candy coat cant be beaten!!! for the way it looks.(I have enough left over to do 3 more just like it, so I will probably repaint after 20 flights. Go back on with a righteous clear coat.

This paint job occurred at 1:30 am on a school night(work the next day) Wednesday night, and launch time was Friday. So this whole rocket was painted in 3 hours. I am not confident enough to fly naked, so this was a "good" solution.

The lacquer clear never got hard like 2k does, it has a lot of scratches and paint chips already. The dirt even scratches the surface.

Looks pretty good to me !

I like the black and red fade ,looks very cool.

What happened to the clear ?


Paul T

Thanks, I do like it, its a nice color and I was pleased in general with the paint. When I applied the clear, I went heavy in a couple areas, the clear soaked into the candy color coat and diluted it.
You can't see it inside, but in the sun, the areas are "clearer" than the other areas.