Friday, January 1, 2010

Quaddy

For now, I'll be calling my updated Big Daddy the Quaddy. A Q-car, also called a 'sleeper car', is one upgraded to higher performance without changing the outside appearance. Therefore, a Q-Daddy, or Quaddy, must be an upgraded Big Daddy...

I'll be improving or replacing almost every part of the original Big Daddy kit. Why? The original kit is designed for Estes motors - the C11, D12, and E9. All are low-thrust blackpowder motors that are 24mm in diameter, 2.75 or 3.75" long, and have flat frotns and small ejection charges. The stock kit has a 26" shock cord with a standard mount, a 24" plastic chute, thin centering rings, 1/8" balsa fins, and a 3.75" long motor mount with a motor hook and engine block. Fine for the blackpowder motors, so long as you use lots of wadding and fly in warm weather on soft ground.

Not for me. If I'm going to do something, I might as well overdo it.

The Quaddy will be able to fly on everything from 24mm D motors to 29/180 H motors. It'll be stronger, faster, more versatile, and more reliable than the stock kit, not to mention better looking. Because screw stock colors, I'm bringing back the classic Big Daddy colors. Or painting it scarlet and grey. Or something. Anything better than the new paint scheme, which looks like an anime art bus.

The biggest change is the ejection system. A 3" rocket needs a lot of wadding, and there's not a lot of room for wadding in the small chute space. Instead, I'm extending the motor mount tube to the base of the nose cone, and adding a 24mm stuffer tube that goes almost to the tip of the nose cone. That way, the hot gasses from the ejection charge will expand inside the nose cone, pushing it off, and pulling out the recovery system, rather than going off inside the tube half an inch from the meltable parachute.

How I'll take the Quaddy to the next level, component by component:

Nose cone: I drilled out the hole in the base to accept the stuffer tube, and I'll be adding nose weight - prolly around 3 ounces - so it's stable even on the larger 29mm motors.

Body tube: will remain stock, except for possibly adding a layer of wood glue to the outside for strength.

Fins: The 1/8" balsa provided with the kit was very high quality, and could prolly survive high-speed flight without extra reinforcement. However, a baby H will take the Quaddy to about 500 mph, and it'll surely have some hard landings. So I'm adding a layer of tissue paper for strength, then a layer of wood glue for strength and smoothness. The fin tabs will be reinforced with strong internal fillets. (I'll build it HPR-style, adding the aft centering ring last, rather than the LPR way of gluing it first to the motor mount. This allows me to make internal fillet for the through-the-wall fin tabs).

Launch lug: the stock 3/16" lug is just 2" long. Borderline for the stock rocket, which is just 5.3 oz stock, but not enough for the Quaddy which will be around 10 ounces. I'll add a second 3/16" lug in line for better balance, and possibly a 1/4" lug off to the side for HPR flights.

Centering rings: the stock rings are thin cardstock. Not great, but prolly okay once the TTW fins are in place. Still, I'll fillet them with epoxy clay, and possibly even get basswood rings from Balsa Machining Services.

Motor tube: The current tube is a 4" long piece of BT-50, which fits all currently available Estes and Aerotech 24mm motors. However, I'm going to upgrade to a 29mm tube 7" long, which will allow 29mm motors up to the 29/180 case and its G75J, H128W, and H165R loads, as well as the Aerotech 24mm G motors.

Engine block: Not used. For the 24mm blackpowder motors which, unlike composite motors, don't have a built-in thrust ring, I'll just use tape. Leaving out the engine block allows the huge range of motor selections.

Motor retention: The stock system is a metal engine hook, which again limits the selection to 24mm motors. I'll use the hook on something else and instead add a threaded-rod retention system, which I bought parts for on my hardware store run. I'll epoxy the rod to the motor tube.

Shock cord: the supplied length is 36" of 1/4" rubber band, which is inadequate even for the Estes "shotgun" ejection charges, and would be snapped by the stronger charge of composite motors. I'll add more - at least 3 more feet of tubular elastic, flat elastic, or kevlar thread.

Parachute: the stock 'chute is a 24" nearly-clear red plastic chute. Easily melted by the ejection charge, hard to get to open fully, hard to see in the sky, hard to remove from the shick cord, and liable to get extremely tangled in branches. I'll leave it off, and instead attach nylon chutes with a quick-link - everything from 18" chutes for windy days, to a 30" chute for calm days and heavier motor casings.

I'll post most of this on TRF within a day or two.

Other 29mm Big Daddy upgrades are available here and here.

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