L3 Winter Build Thread - 3/4 Scale PAC-3 Patriot

Nytrunner said:

Meaning came through loud and clear when I read it . This should turn out really solid. Won't have to worry about breaking the waiver either!

The Estes Patriot (SAM) was my first rocket built at home, and I did my L1 with the 4" Madcow version (Big SAM vv). It'll be cool to your big one as an L3.

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Yes. I'm not so interested in maximum height. I love slow lift offs and being able to watch the rocket the whole way. I'm targeting about 5,000' with this on an M3400 75 mm engine. I'm building this solidly enough (by the match anyway) to take up to an O3400 that tops out at mach 1.2 and 10,000'. That's why I'm setting it up with reinforcement from thrust plate up to the payload bay bulkhead so it can take a big push.... if I want to go that big down the line.

I do have machbusters and high altitude model on the drawing board for learning and building through this year.

Recent trip to the US Space and Rocket Center gave me a chance to see their PAC-3 display again.

It was the standard PAC-3 from the video below, not the MSE version you're building. Any particular reason you chose this variant?
[video=youtube;xU9C2iLm764]https://www.youtube.com/watch?v=xU9C2iLm764[/video]

Nytrunner said:

Recent trip to the US Space and Rocket Center gave me a chance to see their PAC-3 display again.

It was the standard PAC-3 from the video below, not the MSE version you're building. Any particular reason you chose this variant?
[video=youtube;xU9C2iLm764]https://www.youtube.com/watch?v=xU9C2iLm764[/video]

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I like the Patriot. However, I've seen a ton of the standard Patriot, so I wanted to make one a bit different. I like the look of the MSE version with the Nike fins and the forward fins.

Weekend progress was made. The fincan was completed and set aside while I glass the tubes.

As per my experiment before, instead of sanding the outer layer or peeling it, I used an adhesion promoter primer. It worked very well in my previous test to allow the expoy to stick well to the tube without turning the tube into a massive epoxy sponge. The end result is a much lighter tube that still has great adhesion of the fiberglass, so no worries about delamination. This stuff is awesome.



I have a home made rotisserie system. A 1/2" wood dowel is inserted into some 8" wood discs. Those hold the tube in place on my PVC rack for easy rotating and layup work.



I put on two layers of 6 oz. fiberglass using US Composites laminating epoxy with 3:1 medium hardener. Using an angle iron to mark a straight reference line, I started layup and pulled the fabric using a cheap chipping brush. I don't think I'm doing anything here that special or different from others.






The whole thing was then wrapped with mylar to keep it dust free and smooth.



This was left to rotate overnight. I peeled off the mylar this morning, and it looks nice. A few spots where the fabric texture is visible, but nothing too bad that I can't smooth out with filler primer at the finishing stage. I'll put up a pic of the glassed tube tonight.

Mylar peeled off and edges trimmed. The mylar left a slight silvery tint in some areas. The mylar is off. Just some tinting left. Shouldn't affect the priming and painting I think. Weights for a 48" tube are:

Bare tube (inner wax lining peeled off): 919 g
Primed with adhesion promoter: 919 g
2 x layers 6 oz. fiberglass: 1568 g

So the total estimated mass of my rocket will now be 42.4 lbs.

I'm thinking a 75 mm Loki M2550 (10:1 thrust to weight) simming to 5900'.
Or
A 75 mm Loki M1969 (8:1 thrust to weight) simming to 6358'.

Here's the tube without the mylar. Note the silver color that was transferred. Shouldn't be a problem. The mylar came off completely intact. Next time, I'll look for clear mylar.

The ends here were just trimmed with a utility knife. I'll cut and sand level when fitting the frame at a later time.

mccordmw said:

Here's the tube without the mylar. Note the silver color that was transferred. Shouldn't be a problem. The mylar came off completely intact. Next time, I'll look for clear mylar.

The ends here were just trimmed with a utility knife. I'll cut and sand level when fitting the frame at a later time.

View attachment 309588

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Finish looks nice and smooth. Question though, I have found the Sonotube outside wrap to be waxy and not amenable to epoxy at all. How is your adhesion to the fiberglass? Any peeling/bubbling? Normally I remove the yellow wrap.

dixontj93060 said:

Finish looks nice and smooth. Question though, I have found the Sonotube outside wrap to be waxy and not amenable to epoxy at all. How is your adhesion to the fiberglass? Any peeling/bubbling? Normally I remove the yellow wrap.

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The epoxy stuck well to the tube. I used adhesion promoter on the tube. That stuff is awesome. Adds no weight and lets the epoxy bond at the molecular level. I tested it on scrap tube with some drain sleeve fabric. Not much epoxy soaked into the tube, so overall weight was low. Yet the bond was strong.

mccordmw said:

So the total estimated mass of my rocket will now be 42.4 lbs.

I'm thinking a 75 mm Loki M2550 (10:1 thrust to weight) simming to 5900'.
Or
A 75 mm Loki M1969 (8:1 thrust to weight) simming to 6358'.

Click to expand...

I used the Loki M1882 in the 76/6000 case for my L3 that was 55 lbs at launch. Worked great and the 6" rocket got 6870 ft.

The Spitfire would be awesome, but if you want to go with the smaller case and like the smoke and flame of the Loki white, the M1882 should work just fine in a 43 lb rocket.

Handeman said:

I used the Loki M1882 in the 76/6000 case for my L3 that was 55 lbs at launch. Worked great and the 6" rocket got 6870 ft.

The Spitfire would be awesome, but if you want to go with the smaller case and like the smoke and flame of the Loki white, the M1882 should work just fine in a 43 lb rocket.

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I believe sparkys are ok at MWP, so if the weight is ok, I'll go with that. Would look amazing.

The weekend brought some more minor progress.

I finished the fin can by epoxying on the kevlar bridle. I also filed two notches in the top centering to fit around the kevlar bridle. The top ring is still just a dry fit. The reinforcing stringers were also sanded flush with the rings and tested for fit into my first fiberglassed body tube. The fit was nice and tight.



I also got around to fiberglassing the second of three airframe tubes. Not much to see here. Same as the last time.



And with the left over laminating epoxy, I painted the inside 3 inches of the last tube to strengthen the ends.



This morning, I peeled off the mylar from the second tube. Same as last time; no bubbles or issues with solid attachment to the paper. I still don't do the greatest with getting the mylar to adhere all around. There are a few spots where the weave shows due to the mylar not holding down. I might switch to polyester peel ply for the third tube, but I'm not sure that will be smooth enough to simply prime and paint.

Yes, I wouldn't go to polyester peel ply if you want to stay close to "finish state." Polyester peel ply is meant to provide a "tooth pattern" for subsequent layers and is thus rougher in finish.

dixontj93060 said:

Yes, I wouldn't go to polyester peel ply if you want to stay close to "finish state." Polyester peel ply is meant to provide a "tooth pattern" for subsequent layers and is thus rougher in finish.

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Exactly.
When I laminate a phenolic or cardboard tube I always use filler to smooth the surface. It's quick and easy and sands beautifully.


Steve Shannon

dixontj93060 said:

Yes, I wouldn't go to polyester peel ply if you want to stay close to "finish state." Polyester peel ply is meant to provide a "tooth pattern" for subsequent layers and is thus rougher in finish.

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Thanks. I've always either done no wrap (for internal parts where I don't care about finish) or mylar. So I wasn't sure about how rough peel ply was. I'll stick with the mylar. I have TotalBoat TotalFair Epoxy Fairing Compound that I've used in the past to fill up any weave texture with good results. I roll it on, smash on some mylar, and squeegee smooth. Works pretty well with minimal sanding to help blend it in.

Steve Shannon said:

Exactly.
When I laminate a phenolic or cardboard tube I always use filler to smooth the surface. It's quick and easy and sands beautifully.


Steve Shannon

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What filler do you use? I like the one I use, but it's not perfect.

I'm planning the steps to build out my payload bay and my coupler for the lower airframe section. I have a section of Quiktube that fits inside my airframe tube, but it's a bit loose. Measuring the OD of my coupler, it's about 1/16th of an inch too narrow. I have some 1.5 oz chopped strand fiberglass. If I do one wrap with this and two wraps of 6 oz fiberglass cloth, I'll be nearly perfect in size (by calculations at least).

I've never epoxied with chopped strand mat. Although it's light at 1.5 oz., it's thick. Anyone know how much epoxy weight this adds? I wonder if I'm better off cutting a coupler that already fits perfectly and adding a couple wraps of fiberglass cloth on the inside of the coupler for strength. I'm always leery about cutting a coupler since I worry about getting the cut perfectly straight.

If it doesn't add too much weight, I'm inclined to go with building up with the mat. Hmm...

mccordmw said:

What filler do you use? I like the one I use, but it's not perfect.

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I bought a gallon of generic "lightweight body filler" at the local NAPA. It was $11 when I bought it in 2004. I still have about half.
I like that I can begin sanding in half an hour. If I use a squeegee to apply it I don't usually get pinholes.

I bought Super Fil at the same time but never used it. Someday I'll try it.

dixontj93060 said:

Yes, I wouldn't go to polyester peel ply if you want to stay close to "finish state." Polyester peel ply is meant to provide a "tooth pattern" for subsequent layers and is thus rougher in finish.

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Its smooth really, I dont know where you are getting that its rougher. I've never had one come out with a rough finished texture.

These are a couple of carbon tubes I did for someone that were finished with polyester peel ply.



Not rough at all


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SinfulDarkLord said:

Its smooth really, I dont know where you are getting that its rougher. I've never had one come out with a rough finished texture.

These are a couple of carbon tubes I did for someone that were finished with polyester peel ply.

Not rough at all


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Thanks for the image. I can see the peel ply fabric texture in the epoxy. That doesn't print through high build primer? Looks significant enough that it would.

mccordmw said:

Thanks for the image. I can see the peel ply fabric texture in the epoxy. That doesn't print through high build primer? Looks significant enough that it would.

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Havent tried it to be honest with you, but I've coated it with clear gloss before with no issue. The texture is sandable, so as you apply primer and wet sand etc, the texture should disappear when sanding the paint smooth.


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I found this fiberglass tube that has the textured finished and I have some black primer. I will give it a few shots with black primer and see what it does.




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SinfulDarkLord said:

Its smooth really, I dont know where you are getting that its rougher. I've never had one come out with a rough finished texture.

These are a couple of carbon tubes I did for someone that were finished with polyester peel ply.

Not rough at all


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The suede finish when removing the polyester ply is the tooth designed for next layer application. Yes, if you are making tubes you can add epoxy, but that's just extra unneeded weight compared to SuperFil or some other aircraft filler. Compare that suede finish to a Mylar peel ply application next time and you will see there is no comparison.

dixontj93060 said:

The suede finish when removing the polyester ply is the tooth designed for next layer application. Yes, if you are making tubes you can add epoxy, but that's just extra unneeded weight compared to SuperFil or some other aircraft filler. Compare that suede finish to a Mylar peel ply application next time and you will see there is no comparison.

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What Tim said. Read Jim Jarvis's report, he cleans up the field that will be exposed by applying epoxy and polishing. He leaves the peel-ply texture where his fins will be adhered and tip-to-tip will be applied. "Smooth" or "rough" is relative, but raw peel ply finish is probably close to 200-400 grit sand paper, from my experience.

dixontj93060 said:

The suede finish when removing the polyester ply is the tooth designed for next layer application. Yes, if you are making tubes you can add epoxy, but that's just extra unneeded weight compared to SuperFil or some other aircraft filler. Compare that suede finish to a Mylar peel ply application next time and you will see there is no comparison.

Click to expand...

I know the difference I have a giant leap magna frame I glassed with mylar awhile back. Where are you getting at that you can add epoxy as your primer? This is only handy for carbon tubes, but for a glassed cardboard tube or a fiberglass tube you are going to paint it. Its just a matter of getting it smooth enough to paint. Mylar just presents a few issues that require a few extra steps to get it finished for primer and paint. Little less with peel ply. You just sand and prime.


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patelldp said:

What Tim said. Read Jim Jarvis's report, he cleans up the field that will be exposed by applying epoxy and polishing. He leaves the peel-ply texture where his fins will be adhered and tip-to-tip will be applied. "Smooth" or "rough" is relative, but raw peel ply finish is probably close to 200-400 grit sand paper, from my experience.

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I'll repeat, only for carbon fiber, glassed tubes or fiberglass tubes are going to be painted. You need only sand away at the texture and prime, sand, repeat. No fuss no muss.


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Looks great! What happened to your idea about using drain sleeve instead of fiberglass?

BDB said:

Looks great! What happened to your idea about using drain sleeve instead of fiberglass?

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I'm using drain sleeve for all the centering rings and the payload bulkheads. The drain sleeve soaks up too much resin and weighs a bit too much for my liking. It is the perfect fit for the rings and bulkheads, though.

Also, my qualitative testing on crush strength gave me the impression that the drain sleeve was not quite as strong as the 2 x 6oz. layers of glass. Close, but not quite. I could hold a 12" length of tube and squeeze it hard enough to crack the drain sleeve epoxy work. I couldn't really do that with the fiberglass layup. Maybe if I tried really hard, I could.

mccordmw said:

I'm using drain sleeve for all the centering rings and the payload bulkheads. The drain sleeve soaks up too much resin and weighs a bit too much for my liking. It is the perfect fit for the rings and bulkheads, though.

Also, my qualitative testing on crush strength gave me the impression that the drain sleeve was not quite as strong as the 2 x 6oz. layers of glass. Close, but not quite. I could hold a 12" length of tube and squeeze it hard enough to crack the drain sleeve epoxy work. I couldn't really do that with the fiberglass layup. Maybe if I tried really hard, I could.

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That makes sense to me. I was amazed at how much strength 2 wraps of 6 oz glass provided. That, combined with the adhesive primer, looks like a great method.

I've been reading about boat fiberglassing techniques. Those guys do layups over wood and wind up with glassy smooth surfaces. Many just recommend going back over the fiberglassed surface with a skim coat of the same laminating epoxy. I tried giving that a shot.

I mixed up some of my 3:1 US Composites laminating epoxy. Using a chipping brush, I lightly brushed the tube with one thin layer. After all the exposed weave was covered, I went back over with a teflon squeegee. The squeegee pass removed all the epoxy from the smooth surfaces and pushed it into any exposed weave. Keep a paper towel handy to wipe off the squeegee every few passes. In the end, an almost immeasurable amount of epoxy was added.

I left this to rotate on my rotisserie overnight. I check it this morning and it's still a little tacky, but the weave was filled in quite well. There are still slight depressions where the weave was. I imagine another 2 skim coats will fill those in nicely to the point where normal high build primer and sanding will give me a smooth surface. I'll post close up shots once it's all done in a couple days.

If anyone is curious, I've been documenting the materials and costs to insert into my L3 packet. Here's what it's taking and what it's costing. Some are estimates, and I've probably missed a little bit. I also rounded to the nearest dollar. I didn't include common tools.

Total including engine hardware and propellant is about $1,862.

If I drop all the parts needed for a scratch build and assume I buy a fiberglass kit, I'm at about $1,400 plus the cost of a 7.5-8" fiberglass rocket kit. So this scratch build is saving me what...in the neighborhood of $200-600? (cough...let's not factor in the build time, shall we?)

Luxury extras like the aluminum thrust plate and Aeropack retainers and adapters did add up quite a bit.