Scarab 54 vs Wild Thang Jr build challenge

The Additive Aerospace sleds are going to really help make for a clean electronics installation. But they are limiting on height. With an Adept22 altimeter installed, there is enough room but trying to get the more complex Eggtimer to fit just isn't going to happen in a 54mm tube. So it will be the Adept22 in the Wild Thang and an Eggtimer Quark in the Scarab.

Is it just me or, up close, do the Eggtimer vertical components look like buildings right out of Blade Runner?

First dual deploy installation complete. Mounting everything to the sled and having a terminal block to tighten down wires meant there was only need for one wire quick disconnect on the drogue chute end.

The fit of the Wild Thang tubes is incredibly precise. With the nosecone assembly finished, sliding on and off the sustainer tube takes no effort at all. In the accessory packet were 2/56 plastic shear pins.

Here is one screwed through the sustainer and the nose cone shoulder. Will separation forces be too much for just one? Is the .5 gram charge well going to be large enough to blow the nose cone?

Felt like a woodpecker drilling so many holes - two for pressure in the booster and payload sections, three through the payload and electronics bay for the plastic rivets and one to get a screwdriver in to turn on the altimeter, plus two more for the shear pins to hold the nosecone and lower electronics bay in place from the force separation drag. That's eight holes!

Those Altimeter sleds look super cool. Gotta get me some of those for my next project. Are they available from any large companies like Loc or Public Missiles?

The orange sleds come from Additive Aerospace (https://additive-aerospace.myshopify.com/collections/altimeter-sleds) with lots of mounting options for different altimeters. There are other 3D printed sleds that are for a specific altimeter such as from Missile Works (https://www.missileworks.com/store/#!/RRC2+-Modular-Sled-Systems/c/9045099/offset=0&sort=normal).

As much as I tried to have both rockets ready, only the Wild Thang made it to the LUNAR launch at Snow Ranch March 4th. This was to be a low level shake down flight so that all events could be observed easily. A 29mm Aerotech H268R was installed with an 29mm/38mm adapter. At ignition, a weak red flame was seen that then lasted, someone said, a minute before burning out. The Wild Thang never left the pad! The worst part was after flameout when visible flames were seen licking at the bottom of the booster tube. After putting out the fire, damage to the fiberglass was fatal as the motor mount deformed, leaving the retainer canted at an unacceptable angle.


Aerotech was informed of the motor failure. As only the booster section was damaged, I have to decide if I want to order just those parts and build up another booster section. I'm seriously bummed as the Wild Thang is an awesome design and I was really looking forward to seeing it fly.

Some consolation was achieved today when LUNAR offered a bonus launch opportunity at Snow Ranch for those of us suffering the long rainy winter. The Scarab was loaded with all the electronic, energetic and payload bay guts to of the Wild Thang and an H123W motor was installed. Everything went off without a hitch. The landing was spectacular as, with all the rain, there were two full channels of the steam bed and the rocket landed between the two!

Sorry about your WildThang issue.
FYI:

I have seen this type of motor burn [road-flare] many, many times over the years. In every instance I witnessed, it was caused by not inserting the starter/igniter all the way to top of motor. Sometimes the wire will catch in joint between the grains, making flier "think" he hit the top.

Motor grains starts burning down low, not developing enough pressure to lift rocket, it sits on pad burning like a road flare.

blackjack2564 said:

Sorry about your WildThang issue.
FYI:

I have seen this type of motor burn [road-flare] many, many times over the years. In every instance I witnessed, it was caused by not inserting the starter/igniter all the way to top of motor. Sometimes the wire will catch in joint between the grains, making flier "think" he hit the top.

Motor grains starts burning down low, not developing enough pressure to lift rocket, it sits on pad burning like a road flare.

Click to expand...

I always do a dry fit of the igniter to determine how far it needs to go in before securing it to the nozzle.

Also, this is why I don't like inserting the igniter when the rocket is on the pad. You are fighting gravity. The safety police will probably flame me for this, but I insert the igniter before putting the rocket vertical on the rail.

Here are a few photos of the damage.

A one-inch section of the 29/360 case and 3829 adaptor is just gone.


Amazingly, for all the heat, the the delay didn't ignite or even show signs of the event.


The once black retainer and adaptor ring turned bronze colored after being cooked for an estimated 60 seconds.

That's rough!

Just couldn't let this go, so purchased replacement parts from Wildman. Probably going to foam in the fins this time versus epoxy on the first one.

Like the Wildman way of attaching shock cord to both sides of the motor mount but spent over an hour at the field trying to untangle the shock cord when the loop fell through itself several times in handling.

Buckeye said:

I always do a dry fit of the igniter to determine how far it needs to go in before securing it to the nozzle.

Also, this is why I don't like inserting the igniter when the rocket is on the pad. You are fighting gravity. The safety police will probably flame me for this, but I insert the igniter before putting the rocket vertical on the rail.

Click to expand...

NFPA 1127 rule 4.13.5 simply says:
"An ignition device shall be installed in a high power rocket motor only at the launcher or within the prepping area."

It doesn't require that the rocket be vertical. 4.13.6 requires that the rocket be turned away from people, so depending on which way the rail folds down you may need to perform some gyrations.
However, when connecting the leads to the igniter, that should only be done once vertical.


Steve Shannon

Good to know. Thanks. I wish some of the overzealous pad managers would follow this common sense approach.

Back at it with the new components.


Pulled the motor mount down a bit this time to make sure there was enough clearance for the retainer.


Used the same foam board fin alignment tool. Rear CR, with screws temporarily inserted for a way to hold it, was dry fitted after epoxying the fins to assure everything was centered until cured.


Watched closely to make sure alignment tool didn't get caught up in any epoxy overflow on the body tube. Rubber band toward forward end of fins to assure fins stayed down against the motor mount tube.


"The Wall" where retired failures rest in clear view to remind me to apply lessons learned.

Got through building up the fin fillets with Rocketpoxy without too much mess. Its a smaller radius than the last one but I'm confident it will hold up given the robust fiberglass components and the internal foam coming. Again, black dye was added to match the fin color.


Next step will be adding expanding foam internally to further secure the fins. A test of the two years out of date bottles of two-part foam verified it still works. This was from 50 grams of material. It expands 10 to 1. This gave me a good idea of how much to mix for each space between fins, inner body tube and outer motor mount tube.


Getting closer to the finish line, the choice of motors is being considered. Kinda like the idea of going through a progression of Redlines to honor the Wild Thang's skin starting with an H268 and working up through I218, I285, I366, J420 and J825. Open Rocket sims the J825 to 6,847 feet at over Mach 1. Definitely will need to fit the Eggfinder tracker in that one.

Two part foam can be tricky in tight spots. On the first pour, the mixed contents didn't slide all the way across the base of the bottom of the space so as it expanded, a void was left. Luckily, it was relatively small.


Having seen the result, the next two pours were started more quickly while the mix was still most fluid with more attention to getting a straight shot to the bottom. They worked fine. It was really cool to watch the foam expand under the opaque red tube up and over the lip of the other end.


As an experiment, a piece of waxed paper was wrapped around the motor mount down to the fins. The first time, I used masking tape, thinking it would be easy to peel away afterward. Not the case. It took a long time to get the sticky tape up after clearing out the excess foam.

Was just going back to Crazy Jim's Wildman Sport build thread (
https://www.rocketryforum.com/showt...-instructions-thread&highlight=punisher+sport) to refresh myself on his building techniques. I was curious to compare what I just did with what I remembered reading some time ago from a Master Builder.

If you haven't had the opportunity to read/see what he can do, go look up "blackjack2564." It will save you a great deal of pain, frustration and expense as you struggle with the myriad questions that come up as you build your current project. It is nice to have a "brain trust" on TRF with experience in their travails to look back on and learn from, given there are few options these days to apprentice unless you are close to a large NAR/TRA club. And Crazy Jim is just one of many. Maybe there should be a TRF list of those who have provided significant useful content in different areas?

It took a bunch of tools to clear away the foam so the rear centering ring would fit on. Kinda was reminded of a dentist once that played havoc with my mouth trying to clean up a back tooth to fit a crown. I learned that on high speed, a metal Dremel tool cutting bit can gouge a fiberglass tube in no time.


With the foam cleaned up, the centering ring was epoxied in place. The translucent red tube made it easy to check to see proper fit and alignment.

Adding an Aeropack 38mm thin wall retainer and drilling several holes into the booster tube to match the previous ones finished the build (version 2). The comparison to the first booster section was striking considering the first booster took a minute of motor burnout on the pad.


Being able to see through the Wild Thang is really cool. Here, lined up with the rest of the day's launch fleet, the Wild Thang Jr has a completely different aura. Its long sleek lines with the distinctive W cut into the fins make for a mean looking dart. Several folks commented on the good looking rocket as I walked up to the RSO table for check in.


(Photo Credit: Rob Heil)
A previously assembled H178 Dark Matter motor, left over from a cancelled launch, ended up propelling the Wild Thang for its maiden flight to 1,900 feet at Snow Ranch. Launch weight was 5.4 lbs. The Adept 22 performed as intended blowing first the drogue at apogee and then the main chute at 500 feet. The tiny shear pins kept any chance of premature separation of e-bay or nose cone from happening although, with gentle acceleration forces, they probably weren't needed. It was more important to know that the ejection charges were sufficient to assure the pins would shear.

On retrieval, it was discovered that the metal nose cone tip had loosened up. There will have to be a more permanent solution to keep that from happening again.

Overall, the kit turned out to be as advertised - a rugged and handsome mid-sized performance machine. The metal tip, FWFG nose cone, translucent thin wall red tubing and distinctive 3/16" fins make this a feature rich kit with great value at a retail price of $125.99. Upcoming 38mm I and J motors should expand the performance envelope to its full potential. Anyone want to Drag Race?

Mr G said:

On retrieval, it was discovered that the metal nose cone tip had loosened up. There will have to be a more permanent solution to keep that from happening again.

Click to expand...

Here, Loctite is your friend. Purple, if you think you might take it apart someday. Blue, if you don't think you'll take it apart someday, but then have to anyway. Red, if you never want it to come apart even if you want it to. Green, if you never want it to come apart even after a Nuclear Holocaust (or just a bad day of flying and a core sample).

Thanks for the Loctite lesson, Adrian. I'll pick up some purple today. Not sure when I would ever use green.

Mr G said:

Thanks for the Loctite lesson, Adrian. I'll pick up some purple today. Not sure when I would ever use green.

Click to expand...

Purple may be hard to find, depending upon stores in your area. Purple is 221 or 222. Blue is 242 or 243. Red is 271 or 272. Green is in several forms; 290 wicking (after assembly), 620, 660 sleeve and bearing. Blue will work great for you. I have some green that once applied, sets in 5 minutes. We once used it to help retain a loose pulley on a shaft. I applied the stuff and my coworker installed the pulley; with the hub the wrong way out... We had to use a torch to soften the stuff up enough to get the pulley back off. We hadn't even tightened the set screws yet!

Put the finishing touches on the Scarab adding a shear pin to hold the electronics bay to the booster tube along with some vinyl.


I got Mark at Stickershock23 to make up the Scarab 54 logo using holographic characters.





In the shade, they look white or silver depending on the angle. In the sun, the full multicolor effect can be seen. I added chevrons to the fins made from a roll of holographic tape I picked up at Hobby Lobby. Since the plan is to put increasingly large motors in this, it was important to give it something that would glint in the sun as it was coming down. This should do the trick.

Slick holos!

Shiny decal in Gold Chrome from Stickershock23 finishes off the Wild Thang Jr look.



The pair of 54mm fiberglass rockets of different pedigree with their new logos sparkling in the California winter sun.

Next launch window is Mar 3 at Snow Ranch if the weather and business travel gods are quiet. The Wild Thang will go up on an I218 with apogee predicted 2,546 feet, so still easy to see. May try again with an I59 in the Scarab if the winds will be light. The Scarab is light enough to assure a reasonable initial speed off the rail and, if it goes, apogee is predicated for 3,759 feet.

Mr G said:

Next launch window is Mar 3 at Snow Ranch if the weather and business travel gods are quiet. The Wild Thang will go up on an I218 with apogee predicted 2,546 feet, so still easy to see. May try again with an I59 in the Scarab if the winds will be light. The Scarab is light enough to assure a reasonable initial speed off the rail and, if it goes, apogee is predicated for 3,759 feet.

Click to expand...

Looking pretty sweet man. You misspelled I600R

The Wildman credo will be upheld and a J825R is planned for a future launch. Just starting with Redlines on hand. That will make the Wild Thang a Mach Buster. I'll be doing some lower level tracker testing flights before that happens.