Madcow Patriot Build Thread

I picked up this 4” x 52.5” kit from Madcow and opted for the 54mm Motor Mount. Also, I purchased the 8” AV bay to set up dual-deploy.

I really like the Patriot 4 fin minimal-surface-area design. However, I expect I will need to add significant nose weight to stabilize the rocket against some of the aggressive reloads I plan to pack in it. Also, the fins are 1/4” thick, which means they should be PLENTY strong and will not require additional FG reinforcement. I am, however, fiber-glassing the body tubes.

The payload bay is a bit small for my taste (12”) which gets condensed to about 5” with the AV bay and nose cone shoulder. So, STEP 1 - - take advantage of the space inside the nose cone. I used my Dremel to remove the Nose cone base…







Once I figure out the nose weight calculations (towards the end of the build), I will epoxy a spare bulk plate into the cone. This will process will add 3”+ to the payload section.

I like the ‘boxy’ look and feel of the ¼” fin design. So I decided to only bevel the leading edges…

Some other prep work - - secured a welded eye-bolt on the upper center ring…



And added wood blocks to both center rings (to evenutally install rail guides)...

I will be injecting internal filets through the 1/4" fin slots. So, I pre-built the entire motormount (fully equipped with an AeroPack 54m retainer)





Next Step - - Fiberglass Body Tubes...

Maybe it's just an optical illusion, but did you orient the grain on those wood blocks so the screw for the rail guide would be biting into the end grain?

mdoering said:

Maybe it's just an optical illusion, but did you orient the grain on those wood blocks so the screw for the rail guide would be biting into the end grain?

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It is entirely possible - - I worked with some scrap wood and shaped it to fit the center rings. I can't check as the MMT is now installed. I'm not concerned though - there's not a lot of stress on rail guide screws (especially when mounted behind a fiberglass wall).

I figured it was too late on this build, but it's definitely something I'd pay attention to on the next round... It's like trying to put a screw in the end of a broom... It looks like you were working with a square length of material, if you had rotated it 90º you could have grabbed onto some face grain with the threads...

The body tubes are now Fiberglassed using 2 wraps of 5.79 oz. fiberglass cloth and finished with Teflon Release Film. I am really pleased with the results...

first needed to remove the outer film on the tubes for better adhesion...



I started with the mainframe tube...



And then the Payload Bay...



Once dried, I removed the Release Film and used a Dremell to trim the ends and recreate the Fin Slots. As far as I can tell, there are very few flaws and no bubbles to contend with.

Looking good Chris! I wish I had the patience to FG a tube, I would have done the same to my AGM-33

mdoering said:

Looking good Chris! I wish I had the patience to FG a tube, I would have done the same to my AGM-33

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I know – it can be a tedious process. But, in the end, you get a lot of added strength and a really nice finish. I’m mostly doing it on these smaller rockets to gain experience as I head towards my level 3. I’m now leaning towards the HyperLOC 1600 with tip-to-tip fiberglass.

As I mentioned earlier - - the motormount has been installed. But first, I needed to attach 15' of kevlar shock cord...



On to the fins...

Normally, I might have pre-built the entire fin-can with fins attached and then cut the slots all the way through to the bottom. Or, I might have used wildman's technique of injecting internal filets. However, it just didn't feel neccesary to me with such stubby fins and easy access to the motor mount through the 1/4" fin slots.

Instead, I simply used tape to avoid a mess and injected a heavy bead of Aeropoxy 6209 directly on to the motormount and attached each fin. Of course, I will follow up with heavier external filets.





Here's my high-tech 4" dia fin jig...

Here it is pieced together.



Next on the agenda...

1. External filets
2. Cut off 1" vent/switch band
3. Construct AV Bay

Great job fiberglassing; and boy those are stubby fins! Do you know, is the Madcow true scale? Of "sport" scale?

dixontj93060 said:

Great job fiberglassing; and boy those are stubby fins! Do you know, is the Madcow true scale? Of "sport" scale?

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Thank you and great question! I really didn't research the actual dimentions of a patriot missile. I just assumed it was a scale build. Regardless, I crafted my own Open-Rocket configuration and will balance the rocket based upon the CP of my actual build. I expect lots of nose weight to be required.

Maybe somebody else has something to add about the size and scale of this kit.

Made a lot of progress on this build over the past few days…

Cut 1” off the top of the main body tube to use as a vent/switch band on the AV Bay.

Worked on the external fin filets as well... I started with West Systems epoxy and plenty of High Density Filler to get a Peanut Butter Consistency.

I sanded the epoxy filets and then applied a layer of Elmer’s Wood Filler.



With a little sanding, the fillets look really good.

I also did some work on the AV bay.

Drilled holes for two separate switches





Also drilled 2 static port holes



Installed blast caps and terminals



Finally, I cut an extra-large altimeter sled and secured 2 StratoLogger SL 100 Altimeters (not very sophisticated set-up, but it always gets the job done)…

That is one nice build...thanks for sharing!!

Lookin' good. Nice job on the fillets. I would sand down the BT a little to get rid of that peel ply texture though.
I LOVE that teflon peel ply from aircraft spruce.


Alex

Very nice!!

Spooks said:

That is one nice build...thanks for sharing!!

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MasonH said:

Very nice!!

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Thanks Guys!

Aksrockets said:

Lookin' good. Nice job on the fillets. I would sand down the BT a little to get rid of that peel ply texture though.
I LOVE that teflon peel ply from aircraft spruce.

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Agreed - - I still have some work to do to get the BT's where I want them... filling/sanding/priming/filling/sanding/priming. But, I am pleased with the way they turned out after the peel ply. It shouldn't be as much work as my last project.

This thing is pur-dy!

I will likely utilize a 54/852 case on most flights with this Rocket. However, I want to be able to pack a 54/1280 when conditions are right. So I calibrated the CP to CG ratio based on the heaviest load (most likely a J415W).

With the rocket pieced together and all build-weight accounted for (with the exception of paint), I loaded the recovery materials and hardware to identify the Center of Gravity. I then adjusted my Open Rocket design to exact specifications and started to add nose weight. To get to a simulated CG/CP calibration of 1.2 with a fully loaded J415W, I need 12 ounces.

First, I needed to prep the nosecone - - So, I used a dowel with sandpaper and roughed up the interior.



I set aside 10.3 ounces of #8 lead shot and 2 ounces of Aeropoxy 6209. Then mixed it all together...







Simply pour all of the above into the nosecone as shown here...

Once I determined the nose weight was fully cured and the balance points met my specs, I secured the nosecone bulk plate. This actually came off of a retired AV bay so it's not pretty. But, it wil do the job!

To make sure it is 100% secure, I started with an internal filet of Aeropoxy and let it cure. Then I flipped it over for the more important outer filet. A little messy, but I want to make sure it was solid as a rock.



Utilizing the Nosecone space will allow me to significantly upsize my chute.

Good job on the build! Nice looking model.

csoechtig said:

I will be injecting internal filets through the 1/4" fin slots. So, I pre-built the entire motormount (fully equipped with an AeroPack 54m retainer)

View attachment 102121

View attachment 102122

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Quick question - any reason to mount the forward CR that far back? I usually attach them within an inch of the front of the MMT. When I want extra stability I'll add a third CR so the middle and back CR can be attached directly to the sides of the fin tabs. I usually overbuild, so I save my fiberglass scraps so I can use those little pieces for securely attaching the fin roots the MMT and CR's. Was there any JB Weld on the Aeropack?

I envy your av-bay skills, I'm still working (procrastinating) on finishing up my first one.....

Can't wait to see it fly! Think it will be ready in time for the November TTRA launch? I've got a few builds I'm trying to get finished up. Next weekend is booked up with the RUSH concert in Tampa, so not much will get done. Next week will be more productive, my wife will be out of town on a business trip so I can play with the rockets all evening every night.

neond7 said:

Quick question - any reason to mount the forward CR that far back? I usually attach them within an inch of the front of the MMT. When I want extra stability I'll add a third CR so the middle and back CR can be attached directly to the sides of the fin tabs. I usually overbuild, so I save my fiberglass scraps so I can use those little pieces for securely attaching the fin roots the MMT and CR's. Was there any JB Weld on the Aeropack?

I envy your av-bay skills, I'm still working (procrastinating) on finishing up my first one.....

Can't wait to see it fly! Think it will be ready in time for the November TTRA launch? I've got a few builds I'm trying to get finished up. Next weekend is booked up with the RUSH concert in Tampa, so not much will get done. Next week will be more productive, my wife will be out of town on a business trip so I can play with the rockets all evening every night.

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Hey Jeff,

Typically, I like to build with 3 center rings as well. This kit only came with 2 and I didn't take the time to order a 3rd. I positioned the forward ring where I wanted the upper rail guide. That picture might make it look lower than it really is. The tube is 15" and I believe I'm about 4" from the top.

Yes - it will be ready for the November launch. In fact, I'm only going to bring this and one other. I am duck hunting in the morning and expect to arrive a little later than normal. How's that for being a die-hard rocketeer?

patelldp said:

Good job on the build! Nice looking model.

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Thanks Dan!

Installed 3 removable rivits to secure the Payload bay to the AV bay...