Madcow Seawolf Build Thread

geof · Jan 10, 2013

Hi folks. Been a long time since I've posted here, so I figured I would post a few projects I'm working on. This one is a (mostly) stock 38mm Madcow Seawolf.

The rocket requires a pound or more of nose weight (!) due to its fin shape, and the kit I bought did not include motor retention or parachute. Those are a few of the minor twists I'll tackle later. I love making my own chutes. Also, I'm thinking of stretching the body another 9.5 inches to achieve stability with less nose weight, but we'll see about that when the time comes.

I'm mostly a scratch builder these days. Among kits, this is my first Madcow Rocketry kit ever. (And, coincidentally, my first semi-scale kit...I'm more of a creative fantasy guy).

The Madcow box was extremely well packed with lots of protection for the fragile bits. The parts are all standard materials provided by all high-quality kit sellers, and the laser cutting is precise.

I must admit that the price is a little steep, in my judgment, since there is no retention, no chute, no nomex protector, no decals, and no extraordinarily high-quality parts. For example, I could get two 4" Binder Design Thugs (with chutes and decals) for nearly the same price. I'll stop complaining, however...the Seawolf has a lot of interesting fin bits and should be a very enjoyable project.

Geof

geof · Jan 10, 2013

Here is a photo of the kit parts. I added a bunch of metal bits for motor retention to the picture even though they weren't in the kit itself. The first thing I did was mark one centering ring for the motor retention bits and sand away the glassine around the airframe slots and on the motor tube.

Glasspack · Jan 11, 2013

Good luck ........... That is such a cool looking model.

neond7 · Jan 11, 2013

Nice looking kit, I look forward to seeing your build progress.

How much nose weight does this bad boy recommend?? I imagine having big fins that far forward really wrecks the CP/CG relationship?? My Mad Cow Phoenix needed quite a bit in the nose and I still don't launch it on windy days. It tends to fly with the wind.

JordanT · Jan 11, 2013

By the way...I found a 38mm retainer at WalMart for $1.50. :clap: It will require just a touch of sanding, and I installed my first one too short (on a test piece of tube). Here is it - look in the travel area of the toiletries section to find the 1.1 oz Palmer's Cocoa Butter Formula. You need to leave enough depth past the bottom of the engine tube for the retainer ring (which I didn't do) and, of course, cut a hole in the cap.

Oh, and if you want a logo to go on that bird, these are the guys who make them now: https://www.dropbox.com/s/xe2679jhn5xdt99/MBDA.JPG (edit: make the real missiles, not the stickers)
My SeaWolf is in the garage waiting for it to warm up this weekend so I can shoot a coat of white on before I send it aloft. Now, back to your regularly scheduled build thread.

Aksrockets · Jan 11, 2013

JordanT said:
By the way...I found a 38mm retainer at WalMart for $1.50. :clap: It will require just a touch of sanding, and I installed my first one too short (on a test piece of tube). Here is it - look in the travel area of the toiletries section to find the 1.1 oz Palmer's Cocoa Butter Formula. You need to leave enough depth past the bottom of the engine tube for the retainer ring (which I didn't do) and, of course, cut a hole in the cap.

View attachment 112061

Oh, and if you want a logo to go on that bird, these are the guys who make them now: https://www.dropbox.com/s/xe2679jhn5xdt99/MBDA.JPG (edit: make the real missiles, not the stickers)
My SeaWolf is in the garage waiting for it to warm up this weekend so I can shoot a coat of white on before I send it aloft. Now, back to your regularly scheduled build thread.

Cool! Thanks for sharing.

Good luck with the build, Geof. I'll be watching.

Alex

neond7 · Jan 11, 2013

JordanT said:
By the way...I found a 38mm retainer at WalMart for $1.50. :clap: It will require just a touch of sanding, and I installed my first one too short (on a test piece of tube). Here is it - look in the travel area of the toiletries section to find the 1.1 oz Palmer's Cocoa Butter Formula. You need to leave enough depth past the bottom of the engine tube for the retainer ring (which I didn't do) and, of course, cut a hole in the cap.

Is a plastic retainer?? You might have problems with heat melting it if it doesn't outright catch on fire!

JordanT · Jan 11, 2013

neond7 said:
Is a plastic retainer?? You might have problems with heat melting it if it doesn't outright catch on fire!

Maybe, maybe not. I couldn't get it to even warm up much with a 2300F torch flame 1/4" away for 5 seconds (same burn time and proximity for an engine). I don't know how hot the retaining ring on a 38mm gets from a full burn - I don't think I've ever recovered one fast enough to see if the edge the motor (which is thermopastic for CTI) gets too hot. As I understand, 200C is the limit for the case temp, but the nozzle end, outboard of the screw threads, should be quite a bit cooler. Guess there's only one way to find out!

Green Jello · Jan 11, 2013

I'm looking forward to your report Jordan as I saw these in Walmart when I went to lunch.

geof · Feb 17, 2013

Found some time the last couple weekends to work on this.

Marked 3/8 inch lines on each leading edge for sanding the fins. I usually sand by eye, using pencil marks and the plywood layers as a guide. The transition between two layers appears as a dark line in the wood when it is sanded at a bevel. Through experience, I know that (for .25in ply) a fin bevel is almost ready when the second such line appears about 1mm in from the edge. I'll show the results in another post.

I also sanded the motor tube and attached for forward ring, harness bolt, etc.

geof · Feb 17, 2013

The kit has little winglets at the trailing tips of each large fin. Looking at photos of real seawolf missiles, I noticed that they had something more like a pod at the fin tip. To me, the kit version was kind of crude. First, the winglet piece is .25 ply, so it creates a very blocky, unfinished look. Second, the forward end of the winglet touches the leading edge of the fin. When the fin's leading edge is rounded or beveled (see above), then the square surfaces of the winglet will not fit nicely with the fin. I debated what to do for several weeks before diving in.

First, you'll notice in my previous post that I made some marks where the winglet tips hit. I beveled the fin edges only as far down as the top of the winglet; this will be clearer in the photos. Then I tacked on the winglets with CA. Then I glued scrap balsa together to form blocks, then used wood glue to glue the balsa blocks into the *outer* seams between the winglet and the fin. (Again, see the pix). When this was dry, I used a Dremel and palm sander to sand away excess material to create 45-degree surfaces that end flush with the various plywood corners.

When that was done, I painted the whole thing with diluted Elmers wood filler and sanded it down to get a smooth look. Touch-up (not yet done) will consist of several iterations of spraying with grey primer in order to detect blemishes, then wood filler + sanding, until it is perfect. I also put tiny wood glue fillets on the inside seams just for the heck of it.

geof · Feb 17, 2013

JordanT said:
By the way...I found a 38mm retainer at WalMart for $1.50. :clap: It will require just a touch of sanding, and I installed my first one too short (on a test piece of tube). Here is it - look in the travel area of the toiletries section to find the 1.1 oz Palmer's Cocoa Butter Formula. You need to leave enough depth past the bottom of the engine tube for the retainer ring (which I didn't do) and, of course, cut a hole in the cap.

View attachment 112061

Oh, and if you want a logo to go on that bird, these are the guys who make them now: https://www.dropbox.com/s/xe2679jhn5xdt99/MBDA.JPG (edit: make the real missiles, not the stickers)
My SeaWolf is in the garage waiting for it to warm up this weekend so I can shoot a coat of white on before I send it aloft. Now, back to your regularly scheduled build thread.

I am extremely interested in this and would like to hear how it works. Scorching or melting? I've seen other people posting threads with PVC tubes, but have never attempted it due to concerns about heat. Has anyone seen a thread with pix & convincing proof that it's not a problem?

For the Seawolf, I had already begun another approach. I use inset T-nuts and bolts. The motor is retained by small aluminum clips I'll show later. First, I fill the threaded chamber of the nuts completely with modeling clay. Then I drill 3 holes in the aft ring, being careful to start with a very small drill bit to avoid splintering the ring. When the holes are enlarged to the correct size, the T-nuts are tapped in with a hammer, after smearing the holes with just a tiny bit of epoxy. Wipe it all clean. Then use some epoxy on the forward side of the ring to anchor the nuts more securely. Finally, I clean out the threaded chamber. The results are shown in the photo. The clean side will be the aft, visible side. You can see a tiny speck of orange clay that's not removed yet. A bolt and retaining clip will go in each of these. For display, the bolts can be removed for a very clean look.

geof · Feb 17, 2013

Also, Jordan, can you post a photo with the motor casing inserted, but the cocoa butter cap *not* present? Thanks!

Geof

halcro1 · Feb 17, 2013

I have this rocket and I love it. Probably 8 flights.. one of my favorites

geof · Apr 13, 2013

Made some more progress. I installed the motor mount (more later), and epoxied the fins. It's my first chance to get an idea of what the rocket will look like overall.

geof · Apr 13, 2013

A couple more pix.

The instructions said to build the entire motor mount and then insert it in the body. I decided to attach only the upper ring to the motor tube. Then you can glue in the motor mount with the aft ring only dry-fit for alignment. After the epoxy dries, I removed the aft ring to get access to the inside. I put some fillets only on the back set of fins. The forward ones were to hard to reach and, I figured, they are so long that there is already a lot of surface contact between the fin and the body tube (exterior fillets) and the motor tube.

The other thing I did was paint the entire rocket with goop, which I make by diluting Elmer's wood filler with water until it is a little thinner than ketchup. It sands easily when dry.

geof · May 18, 2013

Finished the rocket, but not the thread! Catching up....

Big oops: I was done sanding, priming, etc. when I realized that I had forgotten both the side panels and the rail buttons. Boy did I feel stupid. Since I had nice fillets on the aft fins, the slotted side panels wouldn't fit anymore because the slot was too narrow. So I cut out bigger slots and glued on the panels. Since the tube is round and the tube is flat, there are huge gaps between the edges of the panel and the surface of the tube. There were also various gaps due to my slot widening and fin beveling.

I ended up filling all this with goop (see post above). Didn't like the solution, and required a lot of sanding, refilling, etc., but eventually got it done. The second pic is all primed and ready for painting.

MasonH · May 18, 2013

Finished result looks like something to be proud of!!

geof · May 18, 2013

The big launch sneaked up on me, so I had little time to paint. Worse, my in-laws were in town

Everything that can go wrong with painting, did. I had paint peel off. Leakage under the tape (despite the trick of painting a coat of clear, first, to seal the tape). Alligatoring. Ugh. I did not want to miss this launch, so I hurried things, making compromises. I sanded off and repainted (to no avail) some of the worst alligator skin. (Does anyone know how to solve -and prevent- that?). I touched up some of the edges with a steady hand. I painted "white-out" over some bad white spots. I skipped the final clear coat. From 10 ft away, it looked acceptable, but up close it was a mess!

But, I made it to NCR's "Mini Mayhem" launch.

Note those red and green rings on the body. The red is the CP, and the green are each +1 caliber (tube diameter), so you can check stability in the field.

I flew it on a H250G-7, which gave a nice, low flight (simmed ~1100 ft). Big chute was tough to fit but brought the bird down nice and easy. The nose has so much nose weight that it actually "lawn darted" about 1.5in. One of the motor retaining bolts got bent/loose. I'll need to fix that. What's up next, I don't know, but I'll probably sand and repaint the nose and touchup the body by hand.

The end.

PS. Someone asked how much nose weight was required. I used 21.5oz + epoxy, and I think the instructions said 18-24oz. I used bb shot in the very tip of the nose. My father-in-law helped. However, the instructions also said to sink some screws through the nose cone to hold the epoxy/bb wad in place. I did this, but it was a major pain to grind the screws down while keeping them in there tight.

MasonH · May 18, 2013

One thing a lot of people do is to just run a dowel through the nosecone from one side to the other. It is easier to sand down flush, and gives even more for the epoxy to grab onto. Also very sturdy!!

dr wogz · Mar 29, 2016

What size chute did you eventually go with?

What was your overall final weight?

legranddudu · Mar 31, 2016

geof said:
The big launch sneaked up on me, so I had little time to paint. Worse, my in-laws were in town

Everything that can go wrong with painting, did. I had paint peel off. Leakage under the tape (despite the trick of painting a coat of clear, first, to seal the tape). Alligatoring. Ugh. I did not want to miss this launch, so I hurried things, making compromises. I sanded off and repainted (to no avail) some of the worst alligator skin. (Does anyone know how to solve -and prevent- that?). I touched up some of the edges with a steady hand. I painted "white-out" over some bad white spots. I skipped the final clear coat. From 10 ft away, it looked acceptable, but up close it was a mess!

But, I made it to NCR's "Mini Mayhem" launch.

Note those red and green rings on the body. The red is the CP, and the green are each +1 caliber (tube diameter), so you can check stability in the field.

I flew it on a H250G-7, which gave a nice, low flight (simmed ~1100 ft). Big chute was tough to fit but brought the bird down nice and easy. The nose has so much nose weight that it actually "lawn darted" about 1.5in. One of the motor retaining bolts got bent/loose. I'll need to fix that. What's up next, I don't know, but I'll probably sand and repaint the nose and touchup the body by hand.

The end.

PS. Someone asked how much nose weight was required. I used 21.5oz + epoxy, and I think the instructions said 18-24oz. I used bb shot in the very tip of the nose. My father-in-law helped. However, the instructions also said to sink some screws through the nose cone to hold the epoxy/bb wad in place. I did this, but it was a major pain to grind the screws down while keeping them in there tight.

View attachment 129772 View attachment 129770 View attachment 129771

Such a cool bird full of fins and a great design... and a great post...congrats!
Just dreamin of it upscaled... I always loved madcow's creatures

)

Madcow Seawolf Build Thread

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