Wildman 3" Saab RB 05A

I bought one of the Wildman Saab Sports during the BSS. Once I received it and started looking at the sims I was torn. I liked the look of it, but I didn't want to buy any 38mm hardware and the 29mm motors that would fit only put it up to about 3000'. I wanted something with more wow factor. I thought about the 4" version but I didn't want the temptation to get into 75mm motors. I really wanted one with a 54mm mount and 3" seemed to be the Goldilocks zone. I scaled up the Saab Sport in OpenRocket using parts from the 3" Punisher. I had planned on cutting my own fins on my CNC mill. I called Tim and told him what I was up to. The next thing I know Tim offered to cut the fins and slot the tube if I'd provide him with the design files. Tim will be offering this kit in the near future. I got a call from Jackie this morning and the box is on the way.



View attachment Wildman_SAAB_3.ork

I happened to be at Wildman's on Saturday when he was away at a launch and got a glimpse of your 3 inch Saab, very very nice.

That's not fair. That's like my brother telling me that he saw my Christmas presents but he won't tell me what I got. :neener:

Interesting to see how it stacks up to my 3" version which was scratch built about 12 years ago.. I had forgotten about till; found it when I moved about year and half ago.


JD

I received the kit on Friday. The parts look pretty nice.

The centering rings needed to be sanded inside and out before they would fit. I used a 2" sanding drum on my drill press to open up the inside of the rings. Then I stacked all of the rings on the MMT and sanded the OD on my belt sander. I marked the fin tab locations on the MMT and then I tacked the rings into place with thick CA. I also installed the AeroPack retainer with JB Weld. My order was missing a yard of 1" Kevlar I was going to use for the recovery harness, so I can't install the MMT into the body tube until it shows up. I placed another order with WildMan for a couple more 12x12 parachute protectors. Hopefully it will show up before the weekend.

I'm using 24" and 60" Top Flight Ultra X parachutes for this project. I just thought they'd look better on this bird. The 60" along with a 12x12 Nomex protector is about as big of a chute as I can pack into the nose cone.

The mock up with a CTI 54mm 3 grain case.


The 54mm x 14" MMT. Ring tacked into place and AeroPack installed.

How thick are the fins? .062 or .093?

Looks cool, Chris! Don't forget the noseweight!:wink: She's a neat little critter!

-Eric-

Justin,

The fins are .125". I was planning to cut them from .093" stock, but I think Tim has a set system for his kits. Not a big deal. It's not a deal breaker as far as I am concerned.


Chris

Thanks Eric. This is partially YOUR fault. :wink:

I'm looking at about 18-24 oz depending on how heavy all the epoxy turns out.

ECayemberg said:

Looks cool, Chris! Don't forget the noseweight!:wink: She's a neat little critter!

-Eric-

Click to expand...

ChrisAttebery said:

Thanks Eric. This is partially YOUR fault. :wink:

I'm looking at about 18-24 oz depending on how heavy all the epoxy turns out.

Click to expand...

Cool! First thing I thought when I saw your 3" thread was...Oh no, not another Saab *I need*!

Looking forward to watching your build progress!

-Eric-

I have good news and bad news on this build.

The good news: I've made some progress over the last week. I epoxied a 36" length of 1" kevlar strap to the motor mount as a recovery attachment. The MMT is ready to glue into the body tube.

The bad news: I started beveling the fins. I made an angle plate for my mill a while back. It puts the fin at a ~4.5 degree angle (.040" over .500"). Here's where I made a series of mistakes. I wanted to bevel .050" on each side of the fins leaving a .030" edge. I set up the cut to use a single pass with a 3/4" HSS end mill. I did a test cut on a piece of scrap and it looked great. Then I beveled one side of on the first fin. The bevel only measured .040" so I set the cut depth to .060" and tried again. This time it measured .050" so I did the other three fins. Then I noticed that the corners on the end mill were severely rounded off.

Mistake #1: G10 is way too abrasive to cut with HSS.
Mistake #2: Adjusted the cut depth even though the test piece came out fine.

So, I mounted up a 3/8" 3 flute carbide end mill and used 4 passes per bevel instead of one pass. Now the bevels looked great, but they were .060" leaving a .010 edge. Hmmm, well I can live with that. I flipped the fins over so that the leading edge was at the start of the cut. I was clamping the fin about 3" from the leading edge so that the clamps didn't get into the tool path. That was fine when i was starting at the wide end of the fin. When I started milling from the unclamped narrow end of the fin the end mill lifted the edge and took off a big chunk. It was all my fault I should have seen that coming.

Mistake #3: Failed to ensure that the part is securely clamped along its full width.

The good news is that I have the material to cut another set from. I updated the fin design drawing. One change I made was to make the front fin tab full depth so I can use it to clamp the fin down. Once I have the bevels done I'll cut it down to 1/16" depth. I'll get another set cut and beveled this week. :blush:

Hey Chris, I gave up on G10 a long time ago. It's machinability stinks and the dust is toxic.

Well part of my business relies on me machining G10, so I'm not going to drop it anytime soon. I'm still getting used to machining it though. I use a vacuum hood hooked up to my shop vac to pick up the dust. I also have a fine filter in the vacuum.

I cut a new set of front fins yesterday. I also designed the altimeter bay bulkheads and sled (none came with my semi kit). After a lot of thought about a stressed aluminum sled/carrier I decided to stick with the gold standard 2x 1/4-20 rods. I'll post some pictures soon.

I made a little progress over the last few days. I dry fitted the ballast in the nose cone and found that I needed a 4.5" extension on the eye bolt. That left about 9" for the main and shock cord. I decided that I wanted to inset the front bulkhead 2" from the end of the coupler to allow for more room. I cut another altimeter bay sled and a new front bulkhead this morning.

Altimeter mounting plate set up for an RRC2+ on the left. Battery mounting plate for a 9V battery and Missile Works screw switch on the right.


Assembled with the altimeter mounting side up.

I assembled the altimeter bay last night. Everything fit together perfectly.

Very nice!

Thanks Jim!

I epoxied the forward bulkhead into the altimeter bay. I also glued the motor mount into the rocket. I only used epoxy on the rear centering ring. I figure that the ~32 linear inches of fin tab should have plenty of strength to hold the MMT in place.

I got the PEM nuts installed for the rail guides and started looking at how I'm going to use my fin jig on this beast.

I epoxied the first set of fins onto the booster this morning. I set the fins in place and then clamped the them into my fin jig.

I got the second and third sets of fins epoxied into place. I'm really impressed with how stiff they are. I can't even detect the slightest amount of flex the small "steering" fins.

I got the last set of fins epoxied in place this morning. I need to get started on the fillets.

Chris how much nose weight will be needed?

~18-24oz.

crossfire said:

Chris how much nose weight will be needed?

Click to expand...

I added my OpenRocket file to the first post if anyone is interested.

I've been making parts for my business for the last week or so, but I got a little work done on this one this morning. A few months ago someone on the TRA mailing list posted that they used these nylon rivets for shear pins. They have a .125 shank and the head is only .062" tall. I've used similar rivets in the past. I drilled holes for 4 pins on the nose and 2 on the booster. I'm more worried about the nose coming off when the drogue deploys than drag deploying the drogue.

Hi
I have used some what close to the same thing for years. McMaster Carr is where I purchased them. They have one other style that I use on rockets 5" and above. I just can't remember what they call the style. I like the fact there so easy to use. The type you show work very well.

I bought some from a rocketry vendor in the past that looked like these arrow shank rivets.

I added fillets for the Saab today. Since it is already pretty porky I decided to use .2" radius (AKA popsicle stick) to keep them from adding too much weight. I used about 32g for all 8 fins.

All that's left at this point is paint and recovery harness rigging.