Min Diameter drag racer

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conman13 said:
Looks cool. Can't wait for a flight report.
Click to expand...

If there is one. I still have a lot of av-bay work. Then a clear coat after everything is done. Also the launch tower still needs a lot of work before that's ready. Also winds are supposed to be in excess of 25mph. You aren't allowed to launch if the winds are above 20mph.

So as a whole, it's not looking good for launch tomorrow. But at least I can get my L2 (if the winds are good).
 
ImageUploadedByRocketry Forum1409366109.988891.jpg

I just lopped off about 4.5" from the av-bay tube. This is the ACTUAL size now. Will run some sims in OR once I have the av-bay completely assembled.
 
Av-bay complete!!!! Rocket just needs clear coat now. Just did an ejection charge test (last time I do that at 1/4 to midnight) and it seems I measured the perfect amount. Everything is a go flight!

Except the tower that is. That still needs to be assembled at least once before I take it to the range. If I can't get it done in time I will just epoxy rail buttons to the side. :(
 
T34zac said:
Av-bay complete!!!! Rocket just needs clear coat now. Just did an ejection charge test (last time I do that at 1/4 to midnight) and it seems I measured the perfect amount. Everything is a go flight!

Except the tower that is. That still needs to be assembled at least once before I take it to the range. If I can't get it done in time I will just epoxy rail buttons to the side. :(
Click to expand...


Haha the test must have been pretty load with no other sounds outside!
 
FINALLY!!!! MD-38 Sky Punch is done!!!! Right now it's sitting in my garage with clear coat drying over it. Now I have to go to bed so I can be up at 5:00 to deliver newspapers if I want to be on time for my ride to Berwick.
 
ImageUploadedByRocketry Forum1409397805.149763.jpg
Clear coat makes this thing look good!

Now I'm waiting for my ride to Maine. On the way I can study for my l2.
 
So the launch tower is not ready. When I get to the field, I'm going to epoxy some rail buttons to the side of this thing (sadly). When I do finally get the tower ready, I will take the rail buttons off, sand it down and repaint.
 
T34zac said:
So the launch tower is not ready. When I get to the field, I'm going to epoxy some rail buttons to the side of this thing (sadly). When I do finally get the tower ready, I will take the rail buttons off, sand it down and repaint.
Click to expand...

See if the will allow you to tape in some launch lugs for this flight so you don't have to permanently attach buttons.
 
This rocket did not see flight yesterday. Mainly due to the lack of drag race participants. They decided to hold it at the next launch. That's great for me because that gives me time to get my tower built, and to finish a couple things on this rocket.

But I did get my L2 yesterday, just a month and a half after I got my L1, and two months after the biggest motor I had flown was an estes C6-5.

ImageUploadedByRocketry Forum1409485295.157741.jpg
It was an awesome flight. Everyone was speechless until we couldn't see it anymore. I want to do it again!
 
This rocket will finally see flight this Saturday in Berwick Maine. My dad and I spent the day building the launch tower and are very happy with our results:
ImageUploadedByRocketry Forum1410318919.989039.jpg
It's a bad picture I know. Will get a better one with the whole thing mounted up outside once I get pet stakes.
 
Got the rocked prepped to fly. Touched up the paint as well, now it looks really nice. Too bad the paint will like horrible after the tower scrapes the sides, small price to pay for performance I guess.
 
This rocket has finally flown.

It looked awesome on the ground.
It looked awesome on the pad.
And it looked awesome as it shredded at Mach 1.
ImageUploadedByRocketry Forum1410625642.058476.jpg

I got everything expensive back in working order which is good. Apparently phenolic is no good past Mach. I will rebuild with CF.
 
Are you sure it was the tube and not your fins? That shape looked susceptible to flutter.

Alex
 
Aksrockets said:
Are you sure it was the tube and not your fins? That shape looked susceptible to flutter.

Alex
Click to expand...

I agree. Even if it didn't flutter, the length of the fin relative to the root length makes the attachment weaker. Perhaps a fin fell off first and then the tube snapped.

It doesn't look like you reinforced the fin-tube joint.
 
I am sure that the fins liberated themselves and the subsequent left turn at Albuquerque did the tube in.

I bet it was exciting on that I800. The one I flew in my 5" Jart resulted in some silly acceleration off the pad.

Screen Shot 2013-03-16 at March 16, 20137.18.02 PM.png
 
Aksrockets said:
Are you sure it was the tube and not your fins? That shape looked susceptible to flutter.

Alex
Click to expand...

It could have been fin flutter. It also shredded almost as soon as it left the pad. But when I rebuild, I will also reconsider fin design.
 
Well some kids from a local university are setting up an MD right now. It's a 38mm with fins a lot smaller than mine. I can't wait to see this shred...
 
conman13 said:
did it shred.
Click to expand...

Well it didn't shred. I found out after that they fiberglass wrapped the fin are so it stays on. They still haven't found it yet. They didn't have any sort of tracking, so I don't think they will find it.
 
T34zac said:
Well some kids from a local university are setting up an MD right now. It's a 38mm with fins a lot smaller than mine. I can't wait to see this shred...
Click to expand...

Fin based failures are generally based on 3 things: Fin Shape, Fin Material, and Fin reinforcement.
A clipped delta with a short span is generally the best when it comes to keeping the fins on. So "smaller fins" wont mean more probability of a shred, it'll generally mean the opposite.

A stiff fin material will also help with flutter and vibrations. Stiffer fins mean that less force is put on your fin attachments during flight. You used 1/16in G10, which is acceptable for a 38md. I've personally flown 1/16 G10 to ~Mach 1.8-2.0 in a 38md. However, that was a fin shape designed with a high stress flight in mind.

Of course fin reinforcement is also important. Those tiny Jb weld fillets won't do much. The bigger the fillets, the better (within reason). I don't think you'll need any "tip to tip" in the 38mm size so fillet strength is very important.

Looking forward to the rebuild!

Alex
 
Aksrockets said:
Fin based failures are generally based on 3 things: Fin Shape, Fin Material, and Fin reinforcement.
A clipped delta with a short span is generally the best when it comes to keeping the fins on. So "smaller fins" wont mean more probability of a shred, it'll generally mean the opposite.

A stiff fin material will also help with flutter and vibrations. Stiffer fins mean that less force is put on your fin attachments during flight. You used 1/16in G10, which is acceptable for a 38md. I've personally flown 1/16 G10 to ~Mach 1.8-2.0 in a 38md. However, that was a fin shape designed with a high stress flight in mind.

Of course fin reinforcement is also important. Those tiny Jb weld fillets won't do much. The bigger the fillets, the better (within reason). I don't think you'll need any "tip to tip" in the 38mm size so fillet strength is very important.

Looking forward to the rebuild!

Alex
Click to expand...

Thanks for the info. When I rebuild I was planning on a clipped delta for the fins. My friend also has a way to attach the fins (that he has used before) that I will use for the rebuild. I will also build the av-bay shorter as I now have a Raven 3 to use instead of the RRC3.
 
Aksrockets said:
Fin based failures are generally based on 3 things: Fin Shape, Fin Material, and Fin reinforcement.
A clipped delta with a short span is generally the best when it comes to keeping the fins on. So "smaller fins" wont mean more probability of a shred, it'll generally mean the opposite.

A stiff fin material will also help with flutter and vibrations. Stiffer fins mean that less force is put on your fin attachments during flight. You used 1/16in G10, which is acceptable for a 38md. I've personally flown 1/16 G10 to ~Mach 1.8-2.0 in a 38md. However, that was a fin shape designed with a high stress flight in mind.

Of course fin reinforcement is also important. Those tiny Jb weld fillets won't do much. The bigger the fillets, the better (within reason). I don't think you'll need any "tip to tip" in the 38mm size so fillet strength is very important.

Looking forward to the rebuild!

Alex
Click to expand...

Thanks for the info. When I rebuild I was planning on a clipped delta for the fins. My friend also has a way to attach the fins (that he has used before) that I will use for the rebuild. I will also build the av-bay shorter as I now have a Raven 3 to use imstead of the RRC3
 
Aksrockets said:
Fin based failures are generally based on 3 things: Fin Shape, Fin Material, and Fin reinforcement.
A clipped delta with a short span is generally the best when it comes to keeping the fins on. So "smaller fins" wont mean more probability of a shred, it'll generally mean the opposite.

A stiff fin material will also help with flutter and vibrations. Stiffer fins mean that less force is put on your fin attachments during flight. You used 1/16in G10, which is acceptable for a 38md. I've personally flown 1/16 G10 to ~Mach 1.8-2.0 in a 38md. However, that was a fin shape designed with a high stress flight in mind.

Of course fin reinforcement is also important. Those tiny Jb weld fillets won't do much. The bigger the fillets, the better (within reason). I don't think you'll need any "tip to tip" in the 38mm size so fillet strength is very important.

Looking forward to the rebuild!

Alex
Click to expand...

Sometimes "root-to-root" is important so that the tube doesn't peel up.
 
I think there is something to be said about the MW RRC3 if it was able to survive a shred at Mach 1.1 (according to the altimeter) and a free fall from 973'. That's a durable altimeter if you ask me.

Also in the case of lipos vs. 9v batteries. My lipo stayed connected through the entire flight. I've heard of routine (non Mach) flights that lose connection on their 9v batteries.
 
Ok, so I've decided on almost everything I'm doing for this rebuild. The final design will feature swept back fins with a MUCH longer root edge than before, and a carbon wrapped tube.

I'm probably going to get a thin-wall LOC tube to be wrapped. The is the only thing I'm really having trouble with is deciding what to get for carbon fabric.

I'm also going to stuff most of the recovery system inside the nose cone to help save on space. Also decided on getting a featherweight 38mm av-bay for my raven3 to further save on space and weight.
 
T34zac I been experimenting with carbon fiber sleeve from ACP. composites. https://www.acpsales.com/Carbon-Fiber-Tapes-and-Sleeves.html And using shrink wrap that I picked up from jo-anns craft store. I've been trying to keep things as lite as possible. I made some tubes with two layers. But it came out lighter with just one layer on the tube. I also peeled the first layer of paper from the tube. this is what they look like.
 

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