Mini Tri Pak Build

[Fox Flyers Rocketry]

Greetings! I recently got some help from various members of the forum to find the instructions to clone the Estes Mini Tri Pak. I'd like to thank everyone for all the help pointing me in the right direction for the instructions and supplies. I thought I'd do my first build thread with these clones. I decided to upscale them to BT-50 size. I calculated that every inch on the minis would be 1.81 inches on my upscale. I dug out the parts I would need from my parts bin and ordered this nice set of decals from Excelsior Rocketry.

 

[Fox Flyers Rocketry]

There are 4 body tubes. 1 at 6 inches, 2 at 4 inches and 1 at 2 inches. My upscales to BT-50 came out to roughly 1 at 10 7/8 inches, 2 at 7 1/4 inches, and 1 at 3 5/8 inches long. I marked my body tubes and used heavy card stock wrapped around the mark to get an even cut. (Card stock is the same color as the body tube so it is difficult to see in the picture)

 

[Fox Flyers Rocketry]

All of the body tubes marked and ready to be cut.

 

[Fox Flyers Rocketry]

I sanded the ends that were cut with 400 grit sandpaper to smooth them up.

 

[Fox Flyers Rocketry]

I cut a 3 inch section of BT-20 tubing for a motor mount. I used the centering ring as a cutting guide on the 3 inch mark.

 

[Fox Flyers Rocketry]

I used a standard Estes motor hook. I glued the centering rings at 1 inch and 2 1/2 inches up from the bottom of the motor mount. A thrust ring was then glued in behind the motor hook slot. Here is the completed motor mount.

 

[Fox Flyers Rocketry]

I decided to build the S.C.R.A.M. rocket first. It was my personal favorite of the tri pak back in the day. I printed an upscaled copy of the fins. Making sure the 1 inch mark measured at 1 13/16 to match my 1.81 scale.

 

[Fox Flyers Rocketry]

I then cut out the S.C.R.A.M. fins with my straight edge. I used them as templates on my balsa sheet. I chose to use 3/32 balsa for my upscale.

 

[paul.nortness]

Nice!

I did a BT-60 upscale of the SCRAM last summer....what a great flyer on D12s. Gonna do a cluster BT-80 upscale this year.

Can't wait to see your completed rockets!

 

[Fox Flyers Rocketry]

Thanks! I think I saw your BT-60 S.C.R.A.M. on the forum. It got me reminiscing the old tri pac I had. I flew the S.C.R.A.M the most. I did loose the Sting Ray on the 2nd flight though. It went incredibly high on two stages! All 9 fins are cut out and ready for sanding.

 

[paul.nortness]

Yeah....I probably bought about 40 of these kits when I was a kid. That SCRAM....something about that rocket that was just awesome.

 

[HammerZ2008]

I been wanting to see the Star Seeker done. It is the one with the tricky fin setup.

Still think BT-20 would work out without having to gap stage the Sting Ray. I will still follow along with the build.

 

[Cosmotiger]

I've been thinking about cloning the SCRAM and Star Seeker at original size. I recently built the Sting Ray, and I have a compulsion to complete the set.

Should be good for a launch, and an afternoon of wandering around saying "I think it landed here somewhere." :blush:

 

[Fox Flyers Rocketry]

Yeah....I probably bought about 40 of these kits when I was a kid. That SCRAM....something about that rocket that was just awesome.

Yeah I like the fin layout. Simple but catchy. Can't wait to see that BT-80 upscale. 3 D12s should be impressive!

 

[Fox Flyers Rocketry]

I been wanting to see the Star Seeker done. It is the one with the tricky fin setup.

Still think BT-20 would work out without having to gap stage the Sting Ray. I will still follow along with the build.

I thought about that. Unfrotunately I had a boatload of BT-50 supplies. I figured I need some practice at gap staging anyway. It'll be a good experience for me.

 

[Fox Flyers Rocketry]

I've been thinking about cloning the SCRAM and Star Seeker at original size. I recently built the Sting Ray, and I have a compulsion to complete the set.

Should be good for a launch, and an afternoon of wandering around saying "I think it landed here somewhere." :blush:

I thought some original size clones would be nice. The tote full of unused body tubing as well as the fate of my last Sting Ray changed my mind though.

 

[Fox Flyers Rocketry]

I wanted a smooth surface on all of the fin area. Given the way the fins glue together I figured it would be a good idea to sand seal them before assembling them. I used Elmers Wood Filler slightly watered down to make it paintable.

 

[Fox Flyers Rocketry]

While the sand sealer was drying I figured I'd mark out the body tube. Instead of using the tube marking guide on the downloaded instructions, I went with a standard Estes BT-50 3 fin tube marking guide.

 

[Fox Flyers Rocketry]

Yeah.... I'm a door jam bum I've seen some nice tube marking tools on the forum. I just haven't got around to getting one yet. May have to stop by the Hobby Lobby....

 

[Fox Flyers Rocketry]

I used a standard Estes shock cord set up with paper mount and elastic cord.

 

[Fox Flyers Rocketry]

I then glued in the motor mount using Gorilla Glue and a scrap piece of balsa to get the glue inside the body tube.

 

[Fox Flyers Rocketry]

Next I glued in the shock cord mount 1 1/2 inches inside the body tube, using Gorilla glue again.

 

[Fox Flyers Rocketry]

Once the sealer dried I sanded all of the fins giving all of them a nice smooth finish. Now down to business. The instructions call for marking 3 of the fins 1/8 of an inch up for placement for gluing. Upscaling came out to 29/128. I decided to live with 7/32 being only 1/128 off.

 

[Fox Flyers Rocketry]

I then connected the marks using my straight edge.

 

[Fox Flyers Rocketry]

The instructions then say to glue the fins together matching up on the line and slightly back from the root edge. I wanted consistancy with all 3 of my fins so I chose to mark another line there 1/16 of an inch up. My straight edge just happens to be 1/16 of an inch thick.

 

[Fox Flyers Rocketry]

Fin with both marks.

 

[Fox Flyers Rocketry]

I then test fit the fins. I made a mark along the trailing edge of the center fin as well.

 

[Fox Flyers Rocketry]

I then knew exactly where the fin went on. I carefully sanded the area inside this perimeter, removing all of the sealer. This allowed me to get a good glue joint wile still having the rest of the fin remain smooth.

 

[Fox Flyers Rocketry]

I put a mark on the center fins as well so I knew exactly how much fin area needed to be sanded.

 

[Fox Flyers Rocketry]

After sanding I glued the first set together.