New Year, new build thread - Mach 1 Karman, US Rockets Trident, K&S Orion Starfighter

[les]

If you've followed my other threads, you know I build multiple rockets at one time.
I initially thought I had 3 mid-power rockets selected, but....
The Mach 1 Karman Line Transport is really a low/mid power (for 24mm D~G motors)
The US Rockets has a 29mm motor tube - so definitely mid-power
I initially was going to do a different K&S kit, but I don't have vinyl for it. And with the current situation with Stickershock, I switched kits and didn't realize I had picked a high power kit (38mm motor). Let me know if I should split it off into its own thread under the high power section.....

Obligatory part shots....

Mach 1 Karman Line Transport. This is a new company with fiberglass kits. This kit has a central tube and two side pods.


US Rockets Trident. This is a new kit from US Rockets. In fact, so new I discovered I am actually a Beta tester (which I did not realize at the time that it was not a production kit). It does not show up on their web site yet. I found out about the kit via their Facebook page.



And the K&S upscale of the Estes Orion Starfighter

 

[les]

Some more kit comments..
The Karman has some really thin fiberglass tubes. But since it is supposed to fly on a D motor they do need to keep it light. The nose cones are plastic. The parts appear to be well made.
I gave them a bath but didn't take pictures. The kit did not come with instructions, but you can download them from their website. You have an option for a launch lug or they also supplied micro-buttons.

The Orion Starfighter has cardboard tubes, plywood fins, and plastic nosecone. The kit came complete with shock cord, chute protector, and AV bay HW. The kit came with a CD that contains a copy of the Estes instructions and a Rocksim file of their upscale version.

Last, the Trident. Frankly - I have to admit I am a bit disappointed. As I previously stated, this is a beta kit - but I was not informed that it was still in the beta stage. The only instructions are a copy of the Estes instructions. The kit includes a note stating it "doesn't officially exist yet" and that the kit contains "No custom parts and only used stock parts". As such, the Trident is, well, Trident-ish. One issue is the scale. The tube diameters are 2.26x the BT5 and 2.31X the BT50. But the lengths range from 1.88x to 2.22x. The nose cones are a bit confusing. There are 3 pod cones made of plastic and 3 pod cones made of balsa. My first thought was to use the balsa on the rear where the balsa fins would glue. But the balsa cones are shorter than the plastic cones and the longer cones belong on the rear. Even if I use the plastic on the rear, the cones range from 1.55x to 3.28x.
Now, there was some cleverness in the design. The original Trident used a 5E nose cone, 18" BT5 tube, and 5W tail cone for a total length of 22.13. The US Rockets Trident has a 3.75" nose cone, 36" of tube, and a 4.25" tail cone for a total of 44", or about a 2x scale. Similar for the passenger pod (works out to 1.98x). However the motor pod works out to 2.49x. Bottom line, since there are different scales and no real instructions, I will be needing to decide where to cut the ducting ports. The other issue is a blown up copy of the Estes Fin template is provided. However, since the cones are not scale the pattern will not line up. Again, I am going to need to "fudge" things. The fin material is 1/4" thick x 6" wide balsa.



But to give an idea on how it will look, here are the parts laid out next to an Estes Trident....

 

[les]

But some actual build effort!

First - spiral filling for the Orion. BUT - the tube came all pre-marked.


My concern was after applying the filler and sanding I would erase the lines. I wrapped the tube with paper and marked it where the lines are and recorded the distances. And the spirals got filled



For the Trident, the pods consist of 3 12" tubes, and they are the same size as the motor tube - so 10 tubes. I can set up a bowling alley!



And adding the passenger and motor pods

 

[les]

You know how we rocket builders LOVE sanding (well, not really). Sanded many feet of tubes - my arm is sore

Did some cleanup of the Trident rings. A before and after picture. Still want to fill the edges for the exposed rings.



On the Karman, sanded inside the tubes and the fins, and then epoxied the fins into the side pods

 

[les]

Karman - marked the tubes for the next step. When I glued the fins into the pod I used the "double butter" method. You can see the internal fillet that method creates



Orion - most of the lines remained after sanding, but I did go over them to make them stand out better. I did discover that one of the original marks was done wrong so I corrected it.
At work I blew up the cockpit template, copied it onto cardstock at home, cut it out and test fitted it. Below you can see the size difference and the test fit. But I doubt cardstock will work at that size. I need to look into another approach....

 

[Nytrunner]

Double layered paper. Shape one, then overlay and glue?

 

[les]

Double layered paper. Shape one, then overlay and glue?

Perhaps.... Was thinking of filling it with expanding foam to give it some strength....
And another option that I ordered some parts to try - will see how well it works before I divulge that approach............

 

[les]

Trident - made some decisions - and need to make more - Comments welcome!

First - I did not like how the pod tail cone was so short and didn't line up with the fin pattern. So I ordered some other cones from eRockets. Man they got here fast!. Shipped Thursday. Initial tracking stated they would be delivered Tuesday and showed up today! Here is how the new cones look.



But now my next decision. Based on the tube diameters and the fin, I'm going with a 2.25x scale factor. Used the dimensions from the Estes kit to mark and place the rings on the engine mount. Not bad looking....


But then I thought to check the engine mount to the body/nose cone - whoops. You can see that the cone won't seat fully. And no path for the exhaust gasses.



I see 3 options:
1) Make the body tube longer - but it is already at 2.22x. Making it longer will become non-scale
2) Just shorten the motor tube. I presently have CTI 3G and 6G cases with spacers. The motor tube is presently 12". The 6G case is 12.6". So I can shorten the motor tube and limit myself to 3G motors max. Although I could still be set up to allow a 5G case if I ever wanted more power - just need to buy the case.
3) Move the motor mount back by at least an inch. I got 2 extra rings so I could even add a 5th ring to fill some of the space (see pix below)



Personally, I am leaning for #2 but as I stated, looking for comments/thoughts.
(I did consider trying to hollow the nose cone but felt I would just mess it up)

 

[les]

Karman - Worked on the motor mount. Sanded and "scratched" the tube and Estes motor retention

 

[les]

Orion - Started cutting the slots for the fin tabs



Also made a new cockpit - how does it look?



Emboldened by the thread on Adam Savage working with Styrene. I purchased some .040 sheets. This was my first try with that medium and it didn't come out too bad!



Trident - My next question/issue.....

The pods are about 1.22 diameter x 36 long. For all 3 pods that is 126 cubic inches. The Passenger pod is about 2.25 diameter x 17.87 for an additional 71 cubic inches. Total is about 200 cubic inches. For now I have excluded the motor pod (not a lot of spare space in there) and any detrimental effects of static pressure passing through the ports. For even just 12psi that will require slightly over 1.2grams of BP. I believe this is more that what is normally provided in a commercial motor (I normally use CTI).... Can someone confirm how much BP is provided with a 29mm 3G motor?

One option would be to block off 1 or 2 of the tubes. If only one has ducting than that reduces that volume to 42(ish) cubic inches. Adding back in the passenger pod of 71 and we are at 113 which reduces the ejection charge to 0.7grams.

BUT - for the pod connection I can lengthen the cutout but I can't make it wider - there are still two circular tubes meeting tangentially. Do I now risk blowing up the motor compartment with having only one vent to get the pressure up to the passenger compartment?????

 

[les]

Something else I plan to change. There are 3 pod tubes, each 12" long for a total of 36". If I use the 2.25x scale they should be 40.5" long. I have a spare 29mm motor tube. So I am going to use the supplied tube and cut it into 3 sections of 4" each. Adding these to the supplied tubes will give me a total of 40" - close enough.

I also am concerned about fitting this thing into my car, so I would like to be able to separate it - only adds to the challenge of ducting the ejection charge.
Along with the replacement cones, I got a 34" long section of coupler tube from eRockets which I cut into 3 pieces. The plan will be to glue one end in and be able to slide the other end over and secure the tube to the coupler (probably with screws)

 

[les]

Trident - I modified the supplied balsa cone for the top of the pod. Here are the pods as supplied and how I modified them.

 

[les]

I see 3 options:
1) Make the body tube longer - but it is already at 2.22x. Making it longer will become non-scale
2) Just shorten the motor tube. I presently have CTI 3G and 6G cases with spacers. The motor tube is presently 12". The 6G case is 12.6". So I can shorten the motor tube and limit myself to 3G motors max. Although I could still be set up to allow a 5G case if I ever wanted more power - just need to buy the case.
3) Move the motor mount back by at least an inch. I got 2 extra rings so I could even add a 5th ring to fill some of the space (see pix below)

Personally, I am leaning for #2 but as I stated, looking for comments/thoughts.
(I did consider trying to hollow the nose cone but felt I would just mess it up)

Weighed up the mess of parts. Presently around 2 pounds 4 oz (and that included the motor casing and full sheet of balsa for the fins. Excluded parachute and actual motor.
Based on the weight I want a motor with at least an average thrust of 50N. Looking at the CTI site all of the 2G & 3G motors (except the mellow yellow) meet this requirement so I feel good with limiting myself to a 5G case size.

Further, I checked their instructions and they state that all the Pro-29 motors have 1.2g of ejection. Since 3 pods will require a bit over 1.2g and only using 1 pod would require around 0.7g, I think I will split the difference and have 2 of the pods active for ducting....



Meanwhile - motor retention. Looking through my junk, I mean scratch build stockpile, I found a long piece of straight metal similar in size to an Estes engine hook. I have no clue where I got it from. But I bent and cut it to size and notched the tail rings. Here it is dry fitted together. A piece of tape will help secure the sping clip to the motor when I go to fly.




PS - any comments to date? ...... chirp ......chirp ...............

 

[les]

Orion - sanded the motor centering ring to remove some of the laser charring. Dry fitted the wings to the body tube

 

[les]

Orion - I need to get to the store to get some parts for the motor mount. Now I did not round the leading edges, but I did break the edge some



Karman - glued nosecones onto pod. Started attaching small fins to main body tube.



Trident - This was just getting picky, but sanded the motor section cone to more match the original Trident. You can see the difference against the passenger section cone which was the same. Finished sanding the other 2 pod nose cones.

 

[les]

Trident continued - cut about 2" off the motor tube. The top centering ring is positioned to make sure it clears the pod duct cutout (see the pencil lines)



Started gluing rings to the motor tube



Last problem - the passenger section should be 21.375" The supplied tube is 17.875", so it is about 3.5" short. I will probably have to live with it.

 

[neil_w]

I love these multi-builds.

 

[Nytrunner]

Further, I checked their instructions and they state that all the Pro-29 motors have 1.2g of ejection. Since 3 pods will require a bit over 1.2g and only using 1 pod would require around 0.7g, I think I will split the difference and have 2 of the pods active for ducting....

Good info. I'd like to di a similar check in their pro24 ejection charges, do you have a link to where their info is?

 

[les]

The 24mm has 0.6g. See their instructions
https://www.pro38.com/pdfs/Pro24Instns.pdf

 

[les]

Busy Day - and a good day for motor mounts.

Karman - All fins and pods installed. Plus installed the motor mount. I used some tape to protect the cord while epoxying the mount in.




Orion - Cut and mounted so T nuts onto the centering ring. I also glued the ring to the motor tube but neglected to take a picture.



Trident - Sealed the cones. Why? Because we love to sand!



And got the last of the rings onto the motor tube.

 

[les]

Orion - No real activity - Just lucky at last moment I realized I was on the verge of totally mucking it up!
Partly due to "Go Fever", I was about to epoxy the motor mount into the main body. Even mixed up the batch of epoxy. Then I realized - I hadn't done anything to secure the shock cord!!!
At least I had not applied the epoxy yet.......

Trident - Glued the pod tubes together. I did find some of the couplers were a bit lose and had to be built up with tape. I did sneak into the kitchen to use our nice flat counter to roll the tubes to ensure they were straight. Also, I soaked the ends where the pods are meant to disconnect with thin CA. When dry, I sanded a chamfer onto the end to make the installation easier.



BTW - any so OCD that they align the spirals when gluing 2 tubes together? Never mind. Then a bit of FnF for the joints.



The cone for the motor section got a coating of epoxy to protect it from the ejection charge.

 

[les]

I made up some alignment templates that I glued to foam board and cut out



And then I just had to see it all together. Dry fit for the picture. Quickly slid it together. The slots are not cut yet and the positions for the pix are wrong. But starting to look good!.

 

[les]

Orion - Sanded a notch in the top CR. Tied the supplied strap around the tube and epoxied in place. Later attached the first small wing. I did find some of the wings the plywood splintered when they were cut.



Trident - Started marking the tubes and cutting the first slots for the ducted ejection charge.

 

[les]

Orion - Installed second wing. Had to do alignment by eye as the first wing interfered with the jig



Trident - cut a few of the spare CR and glued together. Just sitting in place but my thought is for it to be the mount for a rail button

 

[les]

Trident - Since I changed the nose cone I needed to verify the template for the fin. Of course it doesn't line up. I adjusted the pattern by eye and only had to do a second try. Dumb luck! It lines up fairly well now.



But now it is too big for the sheet of balsa supplied. So I cut a corner off and glued it back on. Some water for weight while drying.
I also discovered that cutting 1/4" balsa is not easy. Cutting the curves will be "fun"

 

[les]

Orion - Installed the large wings. One has warped a bit so using some angle irons to help hold while the epoxy is curing.



Trident - Well - have more spare width than I need....

Glued my rail button "target" onto the motor tube

And put a little thin CA on the couplers where I plan to tap them

 

[les]

Trident - Received my tap set and got drilling. Verified I hit my "targets"



Cut out the fins - just have the fin sitting on the tube to verify the fit.




Orion - Removed assembly from jig. Alignment looks OK. The dowels for the wing tips are supposed to be 2 different lengths (2.5" and 2"). All four dowels were the same length in the kit so I cut 2 down. Also sharpened the forward tip.



Glued the dowels and forward fins to the rocket.



And added the fins to the "auxiliary motor tube"

 

[les]

Orion - Figured I needed to fillet the fins on the "auxiliary motor tube" before I installed the tube to the main body. Anyone ever use 5 min epoxy for this? I did - just smoothed it like using Titebond with my gloved finger. Not too bad.



The .040 thick styrene was a bit too stiff, so I made another from some 0.020 I picked up. I wanted to strengthen the joints so I mixed some epoxy and created some fillet. The cockpit needed to bend/flex to fit the body tube, so I taped the cockpit to the tube while the epoxy cured. I placed a sheet of wax paper underneath so it would not accidentally bond to the tube.



Trident - I was still concerned with the ejection charge "Blowing up" the motor tube so I widened and lengthened the slots. You can see the original lines in the pix. I only widened the slot from 3/32 to 1/8".



I also had purchased a "grab bag" of styrene pieces that came with a thick piece. I cut off a section to use as a guide when gluing the tubes together.

 

[les]

Trident - finally time to bond some tubes together. I mixed up some Rocketpoxy and added some milled fiber.
I was about to bond everything together when I realized I had not made clearance cuts in the guides to keep them from getting glued to the rocket. I quickly adjusted one set (top left).


I smeared some epoxy on both tubes and installed my styrene block and used the jigs to align everything. The block also helped keep the slot from being blocked by excess epoxy. I cut some 1/12" dowel that I epoxied on the tube joint for more strength. I then removed the guide block. Now it is curing time - need to do these tubes one at a time....

 

[les]

Orion - DUMMY ME!!! I was looking over the cockpit and it didn't look quite right. I glued one of the side pieces on upside down. Sigh...Time to try again

Trident - Attached the second ducted pod - no new pix - looks the same as the first one. I tried placing the cone on the Motor pod - it was a little difficult with two of the pod tubes in place. I decided to permanently install the motor mount and nose cone before I installed the last, UN-ducted pod.

First drilled and installed wood insert into the target block



I applied epoxy in the tube and on the leading edges of the internal rings, slid the mount into place, re-installed the rail button screw to ensure the holes were aligned, and then hung it by the jigs so the epoxy would flow downhill.



After waiting a few hours, I turned the rocket over and applies epoxy to the top and installed the nose cone. Then I applied some Elmer's F&F to the nose cone/body joint



Final step for the day - I won't say I rounded the fins but I did break the edges of the "chunky" 1/4" thick balsa fins.