Mach One “Alien Interceptor” build

[downhill_D]

Well the I205 seemed a bit much today so I gave the Alien Interceptor something to do with an H250-14 Mojave...yeah! Perfect flight at 3968 ft and 355mph (jolly alt2) with a 500ft main.

 

[downhill_D]

Post flight inspection was today. Be careful packing. I overpacked and think I almost destroyed this rocket at apogee. Found bubbled paint and a crack almost through the body tube. Gonna repair this and finish the design for dual deploy-I have been using motor ejection.

To clarify-the crack is just above where the motor charge is. I normally use an 1/8” rod to carefully pack an 18”rocketman chute ina. 6”nomex blanket above dog barf followed by a 30” thin fabric chute with a jolly logic chute release. This is a 38mm airframe so it will need to move about the cabin easily. I did not use a packing rod this last flight. Big lesson learned.

 

[downhill_D]

Bubbled paint and crack. I will set up dual deploy after repair.

 

[Arsenal78]

I would contact Steven and see if he has any tips to prevent that in the future. Mention it cracked because that’s very surprising.

 

[downhill_D]

I’ll hive him a call/email-good idea.

 

[crossfire]

Post flight inspection was today. Be careful packing. I overpacked and think I almost destroyed this rocket at apogee. Found bubbled paint and a crack almost through the body tube. Gonna repair this and finish the design for dual deploy-I have been using motor ejection.

To clarify-the crack is just above where the motor charge is. I normally use an 1/8” rod to carefully pack an 18”rocketman chute ina. 6”nomex blanket above dog barf followed by a 30” thin fabric chute with a jolly logic chute release. This is a 38mm airframe so it will need to move about the cabin easily. I did not use a packing rod this last flight. Big lesson learned.

I have never seen a FG tube break like that. I don't think the charge would cause it. Is the crack right near the top CR? How did deployment and the landing go? If you can I would cut tube at the break point and put in a coupler tube. Would be a easy fix.

 

[downhill_D]

That is the repair plan-I will have to double check but I think it is above the jb welded forward motor ring. I’ll run an inspection light inside and see after brushing the tubes out completely. Easy fix just a little surprised-it’s a 29/240 casing and you can run these with a 38mm motor if you build it that way so I dunno.

 

[downhill_D]

I wanted to have stained wooden av-bays originally-forgot how much wood filler does not like stain but it still looks cool to me! I gave it ample days to air out in case the solvent of the stain was still evaporating. I realized this might cause issues with electronics or the plastics-anyone have experience with stains and electronics?

 

[Nytrunner]

Its the vintage ebay sled you unearthed from your attic!

 

[downhill_D]

Its the vintage ebay sled you unearthed from your attic!

That is exactly what it looks like! Red Oak stain over SIG aircraft ply. It would look awesome in a steam punk themed rocket maybe

 

[downhill_D]

OKay! Coupler ordered so I should have this repaired well before next launches are allowed. Come on NSL! It is hopefully not gonna be cancelled...and I205 is waiting patiently.

 

[caveduck]

I wonder if that was some heat damage followed by an impact crack. I had a fin break completely off -- right through the middle of the G10 -- on a nominal landing of a Vindicator 2.0 under chute, apparently due to the weight of the 4g 38mm casing whacking the fin can into the ground. Impacts are annoyingly good at exploiting even small weaknesses.

 

[downhill_D]

True. I will need to check my chute fall rates. I have an 18" rocket man chute drogue followed by a 30" round main that seems to bring it down gently. My true thought from working in an industry with carbon fiber is if it is thin enough heat, stress or expansion will make it crack, break or just plain fail. This is a good example of two things to learn from this:

1. Mach 1 fiberglass tubing on this particular airframe is very thin, strong, but very thin. Heat will eventually overcome this barrier in time.
2. In a future build I will add a longer coupler (maybe 8") just above the Ejection charges to prevent this.

*as a side note I would also consider adding support for any dual deploy utilizing charge wells on fiberglass this thin. I always use a JLCR with this model.

It is the only problem I have had and it has a lot of flights on it. This H250 (mohave) was a real kicker though so I need to consider that as well.

 

[downhill_D]

I am installing the coupler today. I will make a cut just above the crack and use a 6" coupler and just epoxy it in, fill the edges and sand and paint the section again. I may leave paint off the area for now and just sand it smooth to see what happens in the area after the next flight.

 

[downhill_D]

I finally got around to repairing this and it will be ready for flight...whenever that will be. I sanded a 6” piece of coupler and prepped (cleaned with soap and then alcohol) before adhesion with rocketpoxy. I did not die the epoxy black so I could see the seam. The seam afterwards was cleaner than expected with a regular japanese razor saw and some masking tape with a line to follow. I cleaned the ejection residue out with alcohol and a quick acetone wash and dry and installed the new coupler...everything went back together almost seamlessly. I will paint over it and it shouldn't ever be a problem again. In future build with this thickness I would consider a coupler here for blowout protection anyway. The crack is right above the forward centering ring-I almost couldnt repair this properly but the coupler went just over and beyond the crack.

 

[mbeels]

Nicely done, that will be solid.

 

[downhill_D]

Nicely done, that will be solid.

Thank you! It was nerve racking when the first dry fit...didn’t go beyond the crack.

 

[gldknght]

Nice looking build so far!

 

[downhill_D]

With this rocket repaired now I might get to fly this soon. I am still determined to fly the I205 if conditions are right. This will easily fly ~6,000 ft.