Scratch Stage Tree Original Design / Scratch Built

Scratch - Stage Tree {Scratch}

Contributed by Moira Jean Whitlock

Manufacturer: Scratch
Stage Tree
(Contributed - by Moira Jean Whitlock)

[Rocket Pic]Height: 51 inches
Weight: 13 ounces unloaded
Width: 1 3/8 inches
Motor Mount: 29mm
Recovery System: 24 inch thin nylon chute

Brief description: This is a review of my scratchbuilt Stage Tree, an all wood rocket made from Retro Rocket Works parts. It's named for Larry Niven's stage tree, an alien plant that was genetically bred to make solid rocket boosters. The boosters disperse the tree's seeds as they blast off. Thia happens during natural prairie fires. Also, every century or so, a great stage tree grows that makes boosters that can launch seeds into space and to other worlds.

This is a single staged, 3 finned all wood rocket made from parts made by Retro Rocket Works, through Apogee Components. Its grain is visible and is used to accent the looks of the rocket. So, polyurethane furniture varnish was used to enhance the grain and provide a shiny protective finish.

Construction: I had the 3-inch long nose cone custom made by Retro Rocket Works (OOP). It's solid cherry or mahogany. As an inexperienced woodworker, I really do not know all of my woods. But I can say that this nose cone is pretty. It's medium dark hardwood, smooth, and precisely machined. It came with the beginning of a pilot hole in the base for me to drill in my shock cord screweye.

The shock cord is 1/4 inch thick bungee cording purchased from American Science and Surplus, who have a site on the net, and Rocketry Online. I used a 4 foot length of the cording. The parachute is a thin nylon Estes chute I found at my local hobby store. I chose it because its thin material packs well into the small body tube. Ever tried to stuff a thick chute into a 29mm tube and fret over whether it will eject? Well, the shock cord was tied to a loop of 1/8 inch thick Kevlar® cord, which mounts to the inside of the body tube via a square of 29mm paper tubing. This is curved just like the wooden tube, and fits smoothly. Epoxy was used.

The body tube is a similar color wood to the nose, with beautiful striping of grain. It's 48 inches long, the standard length of tubing sold by the Retro Rocket Works company. It appears to have been made in layers. It appears to be wood throughout.

There are two launch lugs, 1 inch long each by 1/2 inch diameter. I placed these at 20 and 40 inches from the aft end. The lugs started as standard 13mm body tubing. Once I placed them, I was bothered that they didn't have a wooden look, so I placed iron-on wood veneer strips around them, all around the areas that show. I chose a color like the body tube.

[Fins Pic]The fins are a clipped slightly forward swept delta shape, made from 1/8 inch thick basswood. There are also accents of reddish brown pekoe on top of each fin face. These accents are a smaller likewise shape of the fin, and accent the otherwise light color of the basswood.. I used epoxy to affix them on and fine sandpaper to smoothen rough transitions. They were aligned by sight. The fins were aligned by making marks on the body tube using measuring tape to trisect the tube in two places per fin, making a straight line to place the fins.

Finishing: Polyurethane furniture finish was used over the entire rocket to enhance the grain look and to protect it. I just couldn't paint it. The wood was too pretty. This project taught me real wood appreciation. Polyurethane made the job simple. All I needed to do was gently sand each of the three coats to get rid of drips and swirls. The result is a shiny finish like a coffee tabletop.

Flight: Prepping is a little tricky because of the small tube, so I use a long hemostat to grip the end of the chute and draw it down into the tube. Worm bed wadding is used to protect the chute. I discovered at the site that Econojet motors by Aerotech don't fit. The stick-on labels are too thick to allow the engine to go in. Oddly, the other Aerotech 29mm motors like the G40-7 do fit. So I went ahead and loaded that.

I'd have been better off with a slightly longer delay, according to my computer simulator, but this worked fine. I generally only try too-short delays if I mount the shock system STRONGLY, as I did here. The motor was retained via duct tape. My husband called it ineloquent, but I replied that ineloquent beats motor ejection followed by shovel recovery.

The model drew attention, to say the least. I heard a couple of people say, "Oh wow. A wooden rocket." Another said as it lifted off straight and noisily, "Well, will you look at that." Pictures were taken by the curious.

The rocket flew straight and stable, and recovered about right. As I said, a 10 second delay would have been better yet. I had to go downrange a bit, about half a mile, but I got it back intact and unhurt. I got approximately 2500 feet altitude, according to several onlookers. One of these days I just HAVE to get an altimeter and quantify heights exactly. I also experimented with my 29mm reloads, the G33-7, namely. Results were similarly picturesque.

My simulator predicts even better results with an H97, but because the fins do not go through the body tube, I don't feel comfortable with that. I'm gutsy, but do not want any shreds.

Project rating: Overall I rate my project a 4 for good success. I would have rated it higher if all my engines had fit and if the chute had fit in more easily. I think that paper tubes give more than wood so that the slightly thicher diameter of the Econojets won't pass in. This tube was PRECISELY machined without such tolerances.

General pros and cons: The body tube costs $24 and the nose cone was $13.50. The parts are pricy, but worth it. You'll just have to see it to know that. In fact, go to a hardwood store some time and look at woods to appreciate them. Anyway, the model is light but strong and gives very high flights.

I recommend wood if you'd like to get attention at a launch. I also learned at this launch that vaseline is not the best lubricant for reloadables because it can melt down into the propellant. It didn't happen to me, but a long-time flyer said that it can, especially with hotter motors.

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