My Semroc Orbital Transport Build

[astropilot]

As a kid the Estes Orbital Transport was always my favorite rocket. Now forty-some years later I find myself still fascinated by the gracefully lines of the bird. So when I came across the Semroc version of the Orbital Transport, I knew I had to have it. So I placed an order with Semroc,and a few days later it was sitting on my doorstep.

I must say that dealing with Semroc was painless. They acknowledged the order, and updated me on every step of the process from the time they received my order until it was shipped.

When the box arrived I was dismayed to see that it looked like it had been stepped on. The box was crushed, and the packing tape was ripped and hanging loose. I just new that the contents of the box, my rocket, would be a bag of crushed parts. Well, I opened the box and took out the bag, and to my surprise the only damages was a slight crushing of the booster's body tube at about 3/4 of the way from one end of the tube. The damage was not so severe, that it couldn't be repaired with a little CA and some Elmer's FnF. So I repaired the body tube, and today I commenced the build.

This thread will document the build process, and I'll update it as the build progresses.

To get started I laid out all of the parts of the kit.

The balsa parts of the kit are very nice. The fin stock is smooth and the surfaces are well sanded. The nose cones in this kit are IMHO a work of art and will require very little in the way of preparation before finishing. Well done Semroc, and your suppliers.


The first step in the assembly was to layout the parts to assemble the wings. Each wing is composed of two parts that are glued together

Here they are glued together and drying. I like using Aleen's tacky glue, as it "grabs" fast and when dry forms a tight bond between the parts.

The next step was to layout the parts for the ScramJets and their nacelles.

Next the parts were glued together for each wing.

Here I have added the ventral rudders to the wings.

And hold them in place with my "poor mans" assembly jig

Next came the motor tube and shock cord. Here are the parts for the motor tube. Assembly is straight forward and the parts are well matched and fit together perfectly.

Here is the completed motor tube assembly with the Kevlar shock cord attached.

At this point I decided that was enough for the evening. I must say again that the parts in this kit are a joy to work with. As the build continues I'll add to this. Please feel free to jump in and discuss this build, or the Orbital Transport in general.

 

[rockets2000]

Nice build so far, and great looking rocket! You're pretty organized, aren't you?

 

[astropilot]

Nice build so far, and great looking rocket! You're pretty organized, aren't you?

Thanks. Yeah I don't know how that happened, usually my shop area is a disaster :blush:. But somehow this bird deserves the best attention to detail that I can give her, and to do that I have to be organized .

 

[Peartree]

Looks good so far. I like using Testor's paint bottles like that too. You know they'll hold a good 90 degree angle.

 

[NjCo]

Looks great so far. Has anyone NOT used Testors paint bottles like this!

I also have a Semroc OT to build one of these days. I never built one as a kid so now that I'm in my 2nd round as a BAR I just have to get this thing built. One thing I'm wondering about is the knot holding the Kelvar to the engine mount. I was thinking about wrapping the cord around the engine mount before tying it off to give it some added strength. I'm worried that after several flights it might pull through the ring. Anyone have any experience with this?

Another thing I've decided to do is cover most of the fin surfaces with paper. There are soooo many fin/wing pieces that filling and sanding will take forever and the added strength certainly won't hurt. I decided to do this with a Big Daddy I bought earlier this year but I had a sheet of warped fins and it took the Big E the better part of 3 months to get some replacements to me . So I first tested it on a Estes EAC Viper clone I was building. I loved the way it turned out and the process was so simple.

Here's my process. Just pop out the fins and toss them onto the sticky side of full sheet labels without any sanding. Then cut around the fins and be sure the adhesive is well attached to the fin. Then just harden up the edges with some very thin CA to cover about 1/8" around the edge of the paper to make sure the adhesive doesn't peel up during sanding. It takes about 20 - 30 minutes for a set of fins before I'm ready to round off the edges. Light years faster than the normal two coats of FnF with sanding in between and the end result is the same if not better. The only thing I'd do differently with the Orbital Transport is to be sure and cut the paper off the sections where another piece of balsa will be attached so that I'm attaching balsa to balsa and not balsa to paper that is held in place by an adhesive.

Looking forward to more of your build thread. Thanks for taking the time to do this.

 

[astropilot]

Looks great so far. Has anyone NOT used Testors paint bottles like this!

I also have a Semroc OT to build one of these days. I never built one as a kid so now that I'm in my 2nd round as a BAR I just have to get this thing built. One thing I'm wondering about is the knot holding the Kelvar to the engine mount. I was thinking about wrapping the cord around the engine mount before tying it off to give it some added strength. I'm worried that after several flights it might pull through the ring. Anyone have any experience with this?

Another thing I've decided to do is cover most of the fin surfaces with paper. There are soooo many fin/wing pieces that filling and sanding will take forever and the added strength certainly won't hurt. I decided to do this with a Big Daddy I bought earlier this year but I had a sheet of warped fins and it took the Big E the better part of 3 months to get some replacements to me . So I first tested it on a Estes EAC Viper clone I was building. I loved the way it turned out and the process was so simple.

Here's my process. Just pop out the fins and toss them onto the sticky side of full sheet labels without any sanding. Then cut around the fins and be sure the adhesive is well attached to the fin. Then just harden up the edges with some very thin CA to cover about 1/8" around the edge of the paper to make sure the adhesive doesn't peel up during sanding. It takes about 20 - 30 minutes for a set of fins before I'm ready to round off the edges. Light years faster than the normal two coats of FnF with sanding in between and the end result is the same if not better. The only thing I'd do differently with the Orbital Transport is to be sure and cut the paper off the sections where another piece of balsa will be attached so that I'm attaching balsa to balsa and not balsa to paper that is held in place by an adhesive.

Looking forward to more of your build thread. Thanks for taking the time to do this.

Thanks!! Yeah the OT is a great bird. I too was a bit leery about how the shock cord is attached to the motor tube at first, but now after the assembly is fully set up and dried I don't think it will ever pull out. It is absolutely rigid, and IMO the motor tube will fail before it pulls loose.

Your technique of using paper to cover the balsa is really a good one, and I may try that for the orbiter. The balsa for the wing and vertical stabilizer are pretty thin and flimsy. Any added strength to them could only help, provided it doesn't change the center of gravity on the orbiter and make it impossible to trim.

 

[NjCo]

Your technique of using paper to cover the balsa is really a good one, and I may try that for the orbiter. The balsa for the wing and vertical stabilizer are pretty thin and flimsy. Any added strength to them could only help, provided it doesn't change the center of gravity on the orbiter and make it impossible to trim.

Coating fins with paper is a pretty standard method of strengthening fins and I certainly wouldn't take credit for it. In my hands using the full sheet adhesive labels is a better method than coating the fin with glue and using regular copy paper over that. Less mess, a more consistent result and less weight (glue is heavy!).

However, I'm not sure I'd do this on a boost glider. I'd think the weight would make the glider very hard to trim. I was planning on not coating the glider and just using a coat or two of white primer (sanded off after each coat) followed by a coat of gloss white. Then again this will be my first glider of any sort so what do I know! Anyone have any feedback on finishing the glider portion of the OT?

 

[foose4string]

Coating fins with paper is a pretty standard method of strengthening fins and I certainly wouldn't take credit for it. In my hands using the full sheet adhesive labels is a better method than coating the fin with glue and using regular copy paper over that. Less mess, a more consistent result and less weight (glue is heavy!).

However, I'm not sure I'd do this on a boost glider. I'd think the weight would make the glider very hard to trim. I was planning on not coating the glider and just using a coat or two of white primer (sanded off after each coat) followed by a coat of gloss white. Then again this will be my first glider of any sort so what do I know! Anyone have any feedback on finishing the glider portion of the OT?

I used label paper to strengthen my booster fins and went lightly on the primer and paint(just like you described) for the glider portion and did not cover the wings with paper. I do think you could get away with papering the glider surfaces, but I be would be mindful how much weight you add and be prepared to trim it later. It's a great glider design and hard to screw up. I still needed a bit a nose weight in the glider despite my efforts to keep it light. It might take away slightly from the overall appearance, but I don't glue the nose cone on the glider as the instructions would have you do. This will allow you to add trim weight later to the nose if you need to. Much better than adding an ugly glob of clay to the outside of the bird or drilling a hole through your fresh paint job! Make sure you have a good friction fit on the glider cone should you choose not to glue it.

 

[NjCo]

However, I'm not sure I'd do this on a boost glider. I'd think the weight would make the glider very hard to trim.

I did a quick test to see about what the weight of the paper on my fins would be. Granted, I only have a kitchen scale accurate to 0.1 gms. I took the fins from the Big Daddy I've been working on. These fins have a 5" root edge. extend out from the body tube about 2.75" and are 1/8" thick. There are 4 of them. I weighed the ones I coated with full page labels and the weight was 30.0 gms (for all 4). I then weighed the set of untouched, warped fins that I originally had in the package and the weight was . . . . . . 30.0 gms. I had rounded the edges of the paper covered fins, nothing drastic but otherwise the fins were identical. Maybe there wouldn't be a huge difference. It would suck if you covered the fins and there was a difference though. Maybe just cover the underside of the glider fins since that's the area that you would expect to take the greatest abuse.

 

[NjCo]

Excellent pics foose4string!! :clap:

Are those stills from a movie? How did you get such nice pictures?

The last two in the sequence are the perfect proof for why you need to extend the shock cord length on many kit rockets. Check out where the nose cone is in both pictures. In this case it looks like the shock cord is longer than stock - maybe about 2x the length of the body tube.

 

[foose4string]

Excellent pics foose4string!! :clap:

Are those stills from a movie? How did you get such nice pictures?

The last two in the sequence are the perfect proof for why you need to extend the shock cord length on many kit rockets. Check out where the nose cone is in both pictures. In this case it looks like the shock cord is longer than stock - maybe about 2x the length of the body tube.

The pics were taken the a digital SLR-the Canon 40d. It has a very good burst rate. Resolution is better than most consumer grade movie cameras.

My OT was made from Semroc parts and was cloned before the kit was available. I supplied my own shock cord material , so it might be longer than comes with the with the kit. I'm a firm believer that the shock cord can never be too long. The decals were made on my inkjet.

 

[astropilot]

Coating fins with paper is a pretty standard method of strengthening fins and I certainly wouldn't take credit for it. In my hands using the full sheet adhesive labels is a better method than coating the fin with glue and using regular copy paper over that. Less mess, a more consistent result and less weight (glue is heavy!).

However, I'm not sure I'd do this on a boost glider. I'd think the weight would make the glider very hard to trim. I was planning on not coating the glider and just using a coat or two of white primer (sanded off after each coat) followed by a coat of gloss white. Then again this will be my first glider of any sort so what do I know! Anyone have any feedback on finishing the glider portion of the OT?

I'm not too worried about the overall additional weight that would be added to the orbiter/glider. I think that would be negligible. What I am concerned about is shifting its center of gravity to far aft, then having to add a ton of weight to the nose to get it trimmed out again.

 

[astropilot]

I did a quick test to see about what the weight of the paper on my fins would be. Granted, I only have a kitchen scale accurate to 0.1 gms. I took the fins from the Big Daddy I've been working on. These fins have a 5" root edge. extend out from the body tube about 2.75" and are 1/8" thick. There are 4 of them. I weighed the ones I coated with full page labels and the weight was 30.0 gms (for all 4). I then weighed the set of untouched, warped fins that I originally had in the package and the weight was . . . . . . 30.0 gms. I had rounded the edges of the paper covered fins, nothing drastic but otherwise the fins were identical. Maybe there wouldn't be a huge difference. It would suck if you covered the fins and there was a difference though. Maybe just cover the underside of the glider fins since that's the area that you would expect to take the greatest abuse.

That's encouraging. It looks like the weight of the paper is less than the resolution of your scale. My concern over the additional weight is probably unfounded, as your quick experiment has shown -- Thanks

 

[astropilot]

Foose those pictures are just fantastic. What size lense did you use to get that close to the action?

 

[astropilot]

I got a little bit more work done on the OT this morning. First thing was to tie the Kevlar and the elastic shock cords together. I then set the knots with a bit of CA.

Next motor mount was installed and the body tube was marked for the attachment of the wings, launch lugs, standoffs, etc. The use of an aluminum angle makes this a snap.

I then cut the parts for the launch lugs and their standoffs. I always like to cut the LLs leading edge at an angle. I just think it makes the model look better. Of course this is jut a personal preference

Finally I decided that I had to do something with the ScramJets nacelles. IMO it just looked bad with the gaps between the tubes and the nacelle. So what to do about that??

I took some tissue paper soaked in whit glue and carefully worked it into the gaps between the tubes and the nacelle. Then using a flat metal spatula I smoothed out the tissue/glue filler. When dry, a light sanding will be done, and if all goes according to plan it will be smooth and 100% better looking than it was.

Well that's it for now. More to come...

 

[Fred22]

The build is looking great. Your build area however is a disaster. You need glue blobs on the matt and at least three pop cans hanging around the edges not to mention the required scrap balsa in an untidy heap nearby Seriously this is a great looking build
Cheers
fred

 

[astropilot]

The build is looking great. Your build area however is a disaster. You need glue blobs on the matt and at least three pop cans hanging around the edges not to mention the required scrap balsa in an untidy heap nearby Seriously this is a great looking build
Cheers
fred

Thanks!!! Yeah, I know what you mean. My shop is normally a disater area looking for a place to happern.

 

[astropilot]

I got just a bit more done this evening. I rounded all of the leading edges to the scoops of the nacelles and the nacelle housings. At this point the instructions call for attaching the wings to the fuselage, and then attaching the strakes. I deviated from the instructions here somewhat, in that I attached the strakes to the wing,and will then attach the entire wing assemblies to the fuselage.

Also at this point I cut out the wing alignment template. I then glued it to a piece of card stock and made some card stock "stands" that were glued to the back side of the template. This will allow the template/marking guide to stand freely on the wings while they are adjusted for level. The template can bee seen in the background of the first image.

More to come...

 

[astropilot]

A bit more progress on the Semroc Orbital Transport. This evening I attached the wings and the strakes to the fuselage. and the fillets on the top surface of the wing have been applied, but not yet blended and smoothed out.

Here I've gotten everything squared up, the fillets are smoothed and blended and now I'm waiting for the glue to dry. Note the wooden mixing spoons being used to lift the fuselage and wings the proper height to maintain level on the wings.

More to come.

 

[RocketsNorth]

Awesome pix. I had a great time building mine this summer.
Can't wait to see the rest of your build and some flight pics!

 

[astropilot]

Awesome pix. I had a great time building mine this summer.
Can't wait to see the rest of your build and some flight pics!

Thanks. Yeah this so far this build has been a lot of fun. Of course I haven't gotten the glider flight trimmed yet either . I remember that being the most difficult part of the build, when I built the last one way back when.

 

[RocketsNorth]

Actually that went quite smoothly. I just used the trim template provided and a couple of "throw tests" before I glued the the fins into final trim position.

I've only flown the OT with glider once, but it was a near perfect flight and landing.

 

[U812]

Very nice clean work. I just got to do one of these some day.

Steve

 

[astropilot]

Not much to report on the progress of the OT. I have all of the wings, canards, strakes, fences, rudders, and ventral fins in place, and the first coat of filler applied (Photos later) and sanded. Over the next few days I'll continue the sanding of the balsa, and filling in more where needed.

This thing can be a bear to sand with all of it's angles Anyway just a quick report on the progress so far. The glider assembly has not started yet but will get underway soon.