"K" sock

[Johnnie]

Anyone had the pleasure of working with Giant Leaps Kevlar sock? I just received 16' of the mustard color fabric for my 5.5" AGM-78 Standard Arm. This high quality Blackhawk R&D kit will be used for a future L3 attempt. Along with the Kevlar I also received 16' of their Glass sock, that should work great for a "veil" to cover the weaves of the kevlar.

Just curious to know of anyones good or bad experiences working with this stuff...

 

[AlexNUMB]

Hi Johnnie--

I made my Level 3 rocket out of the same Kevlar(r) sock and some 6oz S-glass. I made all composite tubing by stretching the kevlar over a 6" full length coupler and wrapping it with glass.

Working with it is pretty easy. Start from the center and work your way out. Plan on using an excessive amount of epoxy to get it wetted out. The sock is a knit fabric, not woven, and as such will literally drink the epoxy by the cup!

Due to the knitted nature of this stuff, it doesn't stiffen up much at all. It probably won't add much stiffness to your final laminate.

Hence the subject of the post...

Why do you feel you need Kevlar(r)? What properties are you going after?

Kevlar(r) offers superior abrasion and penetration resistance. If you feel that your rocket may get dragged along by wind, develop road rash, or you want to shoot at it with your .45, then Kevlar(r) is the way to go.

However, if you are trying to stiffen up your aifframe and prevent tubing kinks, shredding, etc, then glass is going to be a better solution.

Carbon, of course, is the cat's meow for stiffening and strengthening tubing.

Part of this is a function of how wide your airframe is going to be. In your case, 5 1/2" will make your "hoop" a little large. the larger the hoop, the less stiff the Kevlar(r) sock becomes (because it stretches out, making a thinner layer of material.

My L3 bird (The Kevlar(r) Kritter)was 6" diameter, with 2 layers of S-glass over the top. The final tubing was so flimsy that you could squeeze it out of shape with your hands easily. My L3CC guy questioned weather it would be able to stand up to the thrust of L3 motors. We found out that in compression, it was very strong. Especially after adding the substructure (98mm mount, fins, centering rings, couplers and bulkheads). It ended up living a glorious life of big Ms and small Ns until it's 18k swan dive last year.

YMMV...

--Alex

 

[Johnnie]

Alex, great post, thanks...

The rocket I am "socking" it too, is a little on the light side for one, so the epoxy soak will not be a big deal, it is the easiest way to add weight and spread it out over a wider area. Also, the Kevlar will be added 1st, in hopes that it will help deter the dreaded zipper from deployment. Since the AGM-78 has the long strakes, making a multi tube deployment rocket is kinda tuff. Cutting up the strakes to give the rocket the ability to break into multiple segments adds complexity issues I would rather work around.

For the mounting of the fins and the strakes, I will use a heavy kevlar fabric, and a 6oz. glass combo to attach everything permanently. The hopes is to get the rocket to put on weight without adding 20 pounds of shot to the nosecone, (thus making it a rocket launched lead shot put) and keeping it strong at the same time. For the nose weight, I have a piece of 3/8" all thread embedded in 4 pounds of rubbery silicone, that basically gives me a rocket launched "super" Ball.

Parts alone, I am in the 15 pound range, the hopes is to hit a dry weight of 37 to 45 pounds, and fly the re-certified/new M1297 from Aerotech, or maybe the new AMW Skidmark squirels when they come to certification. keep it in the "baby" M range, so I can fly all of my larger EX motors as well. Even with the baby M's, I am looking at a mile...I kinda wanna see the whole L3 flight if you know what I mean.

 

[rocwizard]

Originally posted by Johnnierkt
The hopes is to get the rocket to put on weight without adding 20 pounds of shot to the nosecone, (thus making it a rocket launched lead shot put) and keeping it strong at the same time.

I had the same thought process with my 2x Sumo, using kevlar sock and all that (much construction still to be done though) and i still am going to have to add 20 pounds of weight in the nose. Then again, i am putting 4 ex M2400s in it as well.

Anyways, my dad and I are fans of the kevlar sock, never have tried the glass sock though. My dad is using it in a similar manner as you are, with his LOC Magnum for L3. the tubes have only been covered with the sock so far, and they are feeling much tougher than before. Two layers of glass have yet to be applied. We build 'em tough out on the left coast

Best of luck on your project! Keep us updated!

 

[Johnnie]

Magnum as an L3 was my first choice...but a 5.5" kit with a 3" motor mount for $139.00 is hard to beat. I wish Blackhawk had not gone away, as their kits are and were quality.

Sumo on (4) M2400 EX motors??? That is awesome!

I will walk the walk and graduate from college on May 13th (age 39 ) and on May 14th @ 4:30 AM in the morning, I will begin construction of the Standard ARM. That will be the beginning of a gift to myself...Level 3.

Good luck tp your dad on his Magnum L3 project, and we want to see some good shots of all of these birds in action.

 

[Johnnie]

Thirsty is right...

It took 4 days, but I was able to laminate 5.5" X 90" long of the AGM-78 Standard ARM this weekend. The tubes were broke down into (1) 30" long tube, and (1) 60" long tube. Each tube received (1) layer of Kevalr sock, and (1) layer of the glass sock...and all 90" drank (4) pints of Bondo brand Marine epoxy.

The amount of epoxy has definetly added a fair amount of weight to the tubes, as I had originally planned. The 30" tube is fully cured, so I was able to trim it up. This tubes stiffness has increased significantly, as I hope the 60" will too.

For the 60" tube, I doubled back the Kevlar about 4" at the end where the 30" tube will couple in. This is to increase the protection of that end of the tube from the dreaded "zipper."

So far I have a $139 kit, with $75 worth of Kevlar and Glass sock, laminated with $28 worth of epoxy.

Noted advantages:

The Glass sock is some tough stuff once laminated, and the Kevlar sock does not deform like the cross hatch type of Kevlar fabric. The Kevlar can get a snag, but it stretches forever, and is very forgiving...the most noteworthy advantage of using thse two products is that there is no overlap seam to sand!!

 

[hokkyokusei]

Originally posted by Johnnierkt
I will walk the walk and graduate from college on May 13th (age 39 )

Congratulations. It's never too late for further education.

 

[Johnnie]

...thanks, after a Summer break I may seek a Mechanical / Aerospace engineering degree...maybe.