Gizmo XL DD "Extreme" Thoughts

Good Evening,

This thread is all about WILDMAN's Gizmo XL DD kit. It's pretty cool and Tim has them in stock right now... Okay this is not meant to be a build thread, and it's not exactly a full kit review either. But, this thread is all about how I modified mine (and I think you'll find it very "N"-teresting) and flew it last November to give you something to something to ponder. I mention this project because I've heard a lot of chatter about the Gizzy XL DD and wanted to share what I did with mine.

To begin, here's the unpainted bird getting ready for ejection charge testing last September,



And here is liftoff two months later, right after MWP in the sunny south west desert,



Now the motor was a CTI Pro75 6G XL case, M2080SK. Consider, that particular case pokes up pretty high in the booster. Stay tuned for the complete story from start to finish.

Jeb

My interest in the Gizmo XL DD goes all the way back to Midwest Power X (2012), when I was watching that big drag race. The "UP" part was really fun and I always though IF I could just make enough space in the garage THEN this would be a good 98MM kit.

So, after clearing out the space at home, I made this purchase around mid-2017. After dry fitting the parts, one realizes rather quickly that the annular Av Bay lets you fly longer motor cases, but at best it's a 4 (5?) grain 98. Just a little shy of being "N" as in nasty. Maybe that's "engineered restraint" in making your motor selection, only Tim knows.

Before getting too far on the build, I had Bill come over to look at this project. We decided to cut 12" off the payload tube (50/50 split, you start with 24") and then bought a coupler to attach one 12" piece to the booster. When all the surgery is done, you get something that looks like this,



I'll make a post about cutting the tube next.

Jeb

So for cutting the tube.

I actually remembered seeing CJ's post #678 in An "R"-powered rocket build, we ended up doing the same thing +1. We'll see if this link works or not, here is the post

https://www.rocketryforum.com/threads/an-r-powered-rocket-build.149574/page-23#post-1847648

Basic idea is to take a table saw and poke the blade up just barely above the thickness of the tube. Harder, fine tooth blades work best. Using the wood stops, work very slowly to roll the tube and make a complete cut.

This is really the only modification done to the kit, just build like normal and you get a smaller payload bay. The fully assembled payload section looks like this,



Shock cord, fire blanket, and drogue are rolled up and shoved into the annular Av Bay motor tube.

Now, on the booster you gain a lot of length. Now the Pro75 6G XL case doesn't look too long anymore,



Okay, end of this post I'll continue in a bit.

Jeb

Next part I'll mention is recovery. I flew with a SkyAngle C3 XXL main, and in this configuration the NC is more than big enough to fit the entire chute, with room to spare,



This loose fit, plus changing the attachment point and I never had any issues pulling the main out. You can see the payload vent hole in the NC shoulder, because the bottom of the shoulder hits the top bulk plate of the Av Bay. Used a key / shear pins so that the vent holes always line up with the air frame.

I did the static charge tests out in the desert on a previous club launch. I used (3x) Nylon 4-40 1/2 slot head (pan) screws from McMaster-Carr for shear pins, and pinned the boster and NC. This really showed me how much force is needed to move the recovery gear. Found that 6g 4F only pushed the NC (or payload for apogee charge test) about 4 feet. To really get closer to extending the shock cord I needed 8g 4F charges. Again, this is with the 4-40 1/2 screws and YMMV,



Nice and fully extended, without much (if any) jerk. But costs you 8g 4F in my configuration.

One more post to go, and that will be most of it.

On the day of the flight (11/10/18) we had great weather. Launch was a total success with recovery, too. Most of the pictures of the painted rocket are after the maiden flight, you can tell by the scuff marks.

So, M2080SK on Gizmo XL DD "Extreme" got me...

7190' (Stratologger)
7135' (MAWD)

I had a lot of time to think about this flight driving back from MWP in Princeton, IL. BTW-Quite the change in weather going from the Midwest to the South West. Anyway, we built this rocket a little bit at a time and it was a huge crowd please. I would love to push the "N"-velope for this kit. Okay sorry no more bad puns. But, a 98 6G case fits - yes that was a design requirement

Maybe the fins will stay on? I think they have a pretty good chance.

When I told the wife how much N's cost, I realized that I also needed a plan B. This is plan B and yes it fits,



(What you see was built in less than 5 hours at Tim's house on a Friday night...)

Okay, enough talk that's the Gizmo XL DD modification to "Extreme" mode.

Jeb

Almost forgot to mention that the loaded weight prior to launch was 59# on the nose. We had a crew of 3 getting it on the rail, certainly not a one-person job. Pad managers, where are you?

dekitte said:

Almost forgot to mention that the loaded weight prior to launch was 59# on the nose. We had a crew of 3 getting it on the rail, certainly not a one-person job. Pad managers, where are you?

Click to expand...

Wow, that definitely got my attention.

dekitte said:

This is plan B and yes it fits,

Click to expand...

I'll bite, What is plan B?

Hi Nytrunner,

Nytrunner said:

I'll bite, What is plan B?

Click to expand...

It's just another way of having fun, only with a 5" Gizmo kit and much less money. (The XL DD rocket is the 8" version).

Big idea is that a 54MM 6G XL case fits right up into the NC. So I will run motor eject, with tracker and Jolly Logic attached to the shock cord. The main parachute will actually pack below the motor case in the "donut space."

This configuration should be able to go up 9-10 kft, which is pretty outstanding for the humble Gizmo. Make sure your kit is well-built, with good internals.

I haven't flown this yet for a couple of reasons, but will add the flight(s) to this thread when they happen.

Jeb

Ah! I see now. I should have recognized the forward section for scale

My gizmo xl DD is a little different. I got an extra coupler and payload tube. Kept my standard ebay and left out the doughnut one. On short motors, flys like it was ment to. When I "go long" the extra tube goes in - with some 1/4 - 20 screws and nuts. It then will do a 98 6g XL

cbrarick said:

My gizmo xl DD is a little different. I got an extra coupler and payload tube. Kept my standard ebay and left out the doughnut one. On short motors, flys like it was ment to. When I "go long" the extra tube goes in - with some 1/4 - 20 screws and nuts. It then will do a 98 6g XL

Click to expand...

Hi cbrarick,

Thanks for contributing to this thread! Yes, that design makes sense to me. Has the added bonus of shifting the CG farther forward, and more "hand access" inside the regular Av Bay, too. Mind me asking what kind of altitudes you have achieved on the largest motors?

As always, no one way to build 'em.

The reason we went the way we did is that it is more like a head end deployment (HED) that has been gaining in popularity. There is very little wasted volume, and the thinking was that we could push 20 kft on the right motor.

Looking back at the thread (and because of the CG comment), I should say something about stability. It was calculated before flight somewhere between 1 and 1.5 body diameters, and this was flying without nose weight. But, certainly one needs to pay attention to the stability margin as you push the envelope on short, stubby Gizmos.

Cheers,

Jeb

Agent P got just over 11 k on a failed attempt to shoot down Micky Spain's "Certificationator" after he blew mains at apogee. Missed by about 60 feet, really hauling the mail. He flew a baby M to not very high....

Nice looking bird Rick.

every now and then I make a nice looking motor holder....