Wednesday, February 17, 2010

Thunderbolt 38mm FG kit from Giant Leap

Clearly most of the posts around here have been about professional rocketry and space matters (in addition to just random image posting from Google whenever something pretty or cool came up.) This is due largely to the winter season putting things on the back burner for a while. Even when active, however, I am lucky to do 3 or 4 launches a year. What a sad state of affairs - I don't own a car, and would prefer not to carry rockets and motors on mass transit.

However, there is one new item in the rocketry collection as of today:

I just got this kit in the mail, a 38mm minimum diameter rocket from Giant Leap. In fiberglass, this is actually the most expensive rocket I have ever purchased - around $170 shipped. That is pretty big money, but I figure you only live once and might as well fly in style before you die, perhaps as a result of starvation trying to pay down your massive massive rocketry debt. Hopefully this rocket lasts for a while, and it is rugged enough to survive quite a bit of use. (Flash forward to me climbing a 75 foot tree with a giant metal pole...)

As one can see above, the rocket arrived wrapped up as any normal kit would, which makes me think they may actually prepare these in advance rather than just setting up the parts each time someone places an order. It is funny to see such an expensive kit in what is basically the same old LOC style plastic bag with a label on top.

There is some relevant history for me regarding ACME fin cans. A recent post here discussed how I got my beginning in high power, essentially my BAR moment: I picked up the OuR edition of a rocketry magazine, and was totally blown away by this R motor flight to near space. Soon after reading the magazine from cover to cover (too soon, as you will see), I placed an order with Giant Leap Rocketry based on an ad.

I ordered one ACME 38mm Fin Can, one 38mm Airframe tube, one 29mm motor mount tube, one 38mm Nose Cone, and a length of nylon strap. In my novice mind at the time, these would make a nice D motor rocket. My thinking was that I could just adapt D motors to fit 29mm (how much could 5 mm be anyway?) motor tubes, and fly this rocket on D motors on my own. Boy was I in for a surprise. When the gear arrived, everything was pretty much as expected; the tubes and nose cone were all stocky, heavy, and larger than my model rockets, but nothing too out of the ordinary. (My instincts were not horrible; a small 38mm phenolic rocket could fly on D motors.)

But then came the shock: the acme fin can was a massive, dense hunk of plastic. I could only imagine the amount of power involved in rocketry that needed fins this strong! (Granted they are bulked up even by high power standards, but I didn't know that at the time.) If the OuR project got me started in high power, the ACME fin can made sure I was hooked for good!

That 38mm fin can was used to build a 72 inch x 38mm rocket that flew often during the late 90s on G125 motors. (The biggest I could fly before turning 18, though I don't think that was technically legal either...) After a few recovery problems, the rocket finally flew on a motor more appropriate for it - the I357T. This was in Jersey, and sadly the rocket was lost. Due to massive hobby inflation (prices have about doubled in the past 10 years), this rocket is more expensive than that first kit despite being shorter. However, hopefully it can go farther than the first and have a long and healthy high power career. There is no reason why this rocket can't fly on even full J motors, but I will probably keep it in the G-H range for now to keep it out of trees!

One more fiberglass kit is expected in the mail soon, with further posts to come. No construction images - my work is too sloppy to post online and no one need follow my example! However, once the rocket is finished perhaps a new post is in order, and again after painting and flying.

It is worth repeating, Giant Leap Rocketry is the best source for rocketry parts. They are second to none and have earned my loyalty time after time. (Can you tell I am fishing for a free 2nd fin can?!? :) )

Here is the exploded view of the kit. Boy are those 38mm airframe tubes heavy! The wall thickness is at least as thick as in 54mm if not thicker, for some reason. It feels about as heavy as a tube of glass would, but obviously much stronger. There are two lengths of tube, two 24 inches and a 4 inch coupler also fiberglass. The nosecone is plastic, longer than normal, and lighter than I am used to. It may be worth adding a bit of epoxy and weight to the tip just to make it stronger. Kevlar shock cords, two "hard point anchors" and tons of metal parts for recovery, everything is really strong and heavy the way I likes it. Now I did not expect the two hard point anchors in there, it looks as if this was a mistake on their end by sending two? Obviously the ACME fin can, a key part of the kit, two rail guides (my first time using rails rather than rods with a rocket, welcome me to the 21st century of rocketry), a 30 inch nylon parachute, a slimline retainer (yes it is the snap ring kind, no I wont start a scandal again with that topic), and a nomex chute protector that I will probably kindly set aside (I am a dog barf guy) rounding out the set of parts. There are good instructions, and a small decal as well. Yes as above this was a bunch of money, but the quality of parts helps justify that. The assembled weight will be high enough to make it appropriate only for G motors and above, but great for safe low altitude flights on G and H motors, which is what I want for right now. And, in the back of my mind, I am thinking of getting a pro 38 case and flying this on an H400 or so, and someday maybe even an I800?


Murdock said...

I've been pondering this kit lately also. I'm excited to see how your build/flights turn out.

R2K said...

I will provide feedback. I think the kit is great if you want this kind of rocket, at this high cost. It may not be right for everyone. There is something to be said for knowing your 38mm rocket can fly on ANY 38mm motor out there, even the pro 38 Js.