Wildman Rocketry Blackhawk 38 build thread

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After mixing up a small batch of JB Weld, it was time for tacking on the first fin.

Everything worked out great!

IMG_3979.jpgIMG_3980.jpg

The fin guides did a great job!

Here's a closer look:
IMG_3981.jpg



Isn't that the best feeling, when you glue a fin on a rocket, and you don't have to keep checking it every couple minutes? That's the great thing about fin guides!! :)




Thanks,
 
Nice work! So how far forward did you set your fins from the aft end of rocket? Can't tell from your pics.
 
Did you rough up the body and fins? You want to rough up the area where the epoxy will be with some 60 grit sandpaper to help the epoxy stick.

cheers - mark

what mark said, something like this. easier to do before you tack them on too!

IMG_2082 (2).jpg
 
Nice work! So how far forward did you set your fins from the aft end of rocket? Can't tell from your pics.
1.75 inches, like what the instructions say to do.
Did you rough up the body and fins? You want to rough up the area where the epoxy will be with some 60 grit sandpaper to help the epoxy stick.

cheers - mark
I sanded the root edge of the fins, and the body tube, where the fins will go.
what mark said, something like this. easier to do before you tack them on too!

The only thing I sanded on the fins was the root edge.

I will also sand them like you did, in the picture.

Thanks,
 
I forgot to post these the other day. Oops!


I measured the 1.75 inches up the tube, where the bottom of the fin will go. And measured up the tube, where the top of the fin will go. This will tell me where the fins will go, and where I need to put the fin guides! :)
IMG_3968.jpgIMG_3967.jpgIMG_3969.jpgIMG_3970.jpgIMG_3971.jpg
I then sanded the areas where the fins will be attached, and where the fillets will go.

After that, I wiped off the excess dust with a paper towel.
IMG_3972.jpg

And here's all of that dust:
IMG_3973.jpg

All cleaned up:
IMG_3974.jpgIMG_3975.jpg



Thanks,
 
Very Cool kit..................be careful with the fins...(if they are CF..graphite G10, whatever) it may not be as insidious as sanding straight up CF layup, but I'd keep your hands clean and not get it anywhere you'd not want it...

I keep my pets out of my work area when sanding CF...and not let the residue get anywhere you don't want to answer for....(don't ask me how I know.....the wife didn't appreciate the black nasty dust stain)
 
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Very Cool kit..................be careful with the fins...(if they are CF..graphite G10, whatever) it may not be as insidious as sanding straight up CF layup, but I'd keep your hands clean and not get it anywhere you'd not want it...

I keep my pets out of my work area when sanding CF...and not let the residue get anywhere you don't want to answer for....(don't ask me how I know.....the wife didn't appreciate the black nasty dust stain)

I always wash my hands very well after sanding any composite rocket parts.

And I also wear a mask as well.



Thanks,
 
Well, before I glued the other fins on, I sanded the sides of the fins, (see picture) so that the fillets will stick better.
IMG_3982.jpgIMG_3983.jpg

And fin #2 was glued on:
IMG_3984.jpgIMG_3985.jpg

After about 6 hours later, I glued on fin #3.

IMG_3986.jpgIMG_3987.jpgIMG_3988.jpg



And after all these dried, and I removed the fin guides, all seemed well until I realized a :facepalm: mistake. :mad:
Apparently when I taped up the body tube, so I'd know where to glue the fins on, I somehow made a mistake.
I have NO idea how this happened, because I measured it twice but, I did, so I might as well tell you....
The fins were glued 1/2 inch higher up the tube, like they were supposed to.
In other words, the bottom of the fin should be 1.75 inches (45mm) above the bottom of the tube. I glued the bottoms of the fins 2.25 inches above the bottom of the tube.

I tried running a simulation on OpenRocket, but I couldn't because I can't seem to move the fins forward 1/2 inch more forward. Does anyone know how to do this on OpenRocket?
I know how to do it on RockSim, but I don't have RS anymore.


So, I can basically do one of these two things. (Unless you have another idea)

1. Run simulations on this mistake, if all goes well, keep it the way it is, and fly it on a G motor to start.

2. Cut 1/2 inch of the bottom of the body tube.


_____________________________________

Anyway, I have no idea how I made this mistake. I wasn't in a hurry when building it, and I wasn't distracted either.
But, hopefully all goes well with this!






BTW, fillets will be done mid-to late next week.






Thanks,
 
You will probably be ok but here is a screen shot of adjusting fin position. Click on "fin set" under your booster (body tube), depends on what it's called in your file.

fin bh.jpg
 
You will probably be ok but here is a screen shot of adjusting fin position. Click on "fin set" under your booster (body tube), depends on what it's called in your file.

Thanks!! :)



I ran the simulation with the fins 2.25 inches up the body tube.


Everything seems to be OK.

I'll start at the smallest motor possible, just to be safe.



Thanks,
 
I removed the fin guides, all seemed well until I realized a :facepalm: mistake. :mad:
Apparently when I taped up the body tube, so I'd know where to glue the fins on, I somehow made a mistake.
I have NO idea how this happened, because I measured it twice but, I did, View attachment 344879

Hmmm...and you measured twice. Curious.
I'm assuming those slots cut in the fin alignment guide are there for a reason (one of the good things about a fin guide).

If the rear fin alignment guide was set where it is supposed to be....were the rear TE of fins supposed to be inserted a 1/2 inch further INTO the rear fin alignment guide (see your last posted picture ) instead of the TE lined up with the FRONT of the fin alignment guide ?
That would have the fins in the correct location from the rear of the BT.
 
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Hmmm...and you measured twice. Curious.
I'm assuming those slots cut in the fin alignment guide are there for a reason (one of the good things about a fin guide).

If the rear fin alignment guide was set where it is supposed to be....were the rear TE of fins supposed to be inserted a 1/2 inch further INTO the rear fin alignment guide (see your last posted picture ) instead of the TE lined up with the FRONT of the fin alignment guide ?
That would have the fins in the correct location from the rear of the BT.

FIN_MESSUP.png






Thanks,
 
You should be fine anyway...CP location might only be very slightly altered forward....easy fix for that w/o cutting the BT shorter IMHO.
Have you decided on motor retention method….?
 
You should be fine anyway...CP location might only be very slightly altered forward....easy fix for that w/o cutting the BT shorter IMHO.
Have you decided on motor retention method….?

It really depends on available funds.

Right now I'm looking at doing friction fit, but if you don't think that's a good idea, I'll do a AeroPack motor retainer.


Thanks,
 
Friction fit works. Masking tape on the motor until it is snug and then use aluminum tape over the end of the tube and motor.
 
friction fit.jpgThis is my BH-38 that I had prepped for our club launch yesterday that was cancelled. I friction fit my 29-38mm adapter with masking tape inside and aluminum tape at/over the end. My first couple flights are planned for 29mm G-76's as I'll be testing a new T-3 tracker.
 
It really depends on available funds.
Right now I'm looking at doing friction fit, but if you don't think that's a good idea, I'll do a AeroPack motor retainer.
Thanks,

Just curious...I have a Mongoose 38 kit (the Performance Rocketry version - very similar to this) that I have yet to build and fly, so I'm always looking see how people do motor retention on a MD.
I've heard horror stories of motor heat making spent motor extraction on a taped friction fit a royal PITA.

There are internal methods that seem logical.....but require motor hardware end closure eyebolts.
 
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I received the scale from Amazon today.
I'm Hoping to start the first set of fillets tomorrow.


Thanks,
 
Good work, Andrew. Having good tools for the job makes life so much better.
 
Well, I have finished the first set of fillets.
After weighing the glue with my new scale, I mixed it up, and put it on.

But, before any of that, I taped the parts of the rocket, so I'd know where to put the glue for the fillets, and it would also prevent the glue from running all over the body tube.
IMG_4104.jpg
All taped up and ready for glue.


And here are the fillets:
IMG_4105.jpgIMG_4108.jpgIMG_4109.jpg
I have to admit, this glue was very easy to work with!

And I now need to remove the tape.



Thanks,
 
Umm. Did you smooth the fillets with a tool of some sort then remove the tape a few minutes later?

Here are the fillets from yesterday.


All dry, and pretty much 100% smooth!

IMG_4110.jpgIMG_4111.jpgIMG_4112.jpg
There are a couple of small bumps, but that's from the JB Weld. Otherwise, it's very smooth!





Thanks,
 
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