Launch Pad Hawk MIM-23A upgrade

[dixontj93060]

Finally got to start working on my next mid-power kit. It is a Launch Pad kit I found cheap on Ebay. I always liked the look of the Hawk-M with the long fins and tailcone. Reviews I have read said it was underpowered with the stock 24mm motor. That plus after receiving the kit and seeing some paper (yes paper) components (tailcone and nosecone extension), I decided to do the full upgrade.

I went to a 29mm motor mount. Added retention in the new plywood aft centering ring. Added a field serviceable kevlar shockcord design. Deviated from instructions by not using CA to reinforce the paper tailcone/nosecone extension, but instead used epoxy on the nosecone and 2-part foam on the tailcone (internal). In addition, I'm fiberglassing the whole thing. This is my first glassing experience and I must say it is going well and much easier than I expected.

-Tim

 

[dixontj93060]

Here is a picture (not so good picture) of the motor mount upgrade...

 

[dixontj93060]

Standard clip motor retention and aluminum tubing to access shock cord from rear (sorry about pic quality here too)...

 

[dixontj93060]

Paper tailcone being foamed...

 

[dixontj93060]

Finished tailcone (Dixie cup)...

 

[dixontj93060]

Standard nosecone with paper extension installed (notice black trace lines). Whole top end filled with epoxy. This will ultimately be glassed also to get rid of the paper edges...

 

[dixontj93060]

And finally the glassing. Vacuum bagging. Picked up a Foodsaver 550 model on Ebay cheap and it really works well. Looked at the "Pro" models but the specs and construction seemed the same (only didn't have a cutter).

Anyway the body first... Notice I'm using the technique where you pull the bag through the body cavity to get air pressure on the inside of the tube and not crush it. I tried another method at first (that I read on some other bulletin board) with balloons (three hotdog) blown up inside the tube. DIDN'T WORK. Always wanted to both smash the balloons and the tube.

 

[dixontj93060]

A little tricky cutting the fiberglass for the fins. The points along the root edge wanted to shread...

 

[dixontj93060]

But finally got them on the fins. Once "wetted out" with epoxy the everything was fine. Two fins per 11" wide bag...

 

[dixontj93060]

Body tube with wrapping and 1/2 coupler tubes removed and into final cure state. Also first wrap on nosecone...

 

[dixontj93060]

The body came out so smooth looks as though I'll need very little sanding...

 

[Ryan S.]

very nice, I have been interested in getting a vacuum bagger, but its alot of money, and I am not sure if I can get bags for larger rockets, I wrapped tape around the end of a rocket the other day and the FG came out smooth, maybe I will do that instead.

How did you do it? what is wrapped around the body tubes to keep them from touching tthe plastic?

 

[Stones]

Nice building techniques Tim. I'm currently doing a scratchbuild (4") of a Bullpup AGM-12C based on the TLP kit which Missleman was kind enough to send me plenty of info on.
Your ideas about the tailcone/hat parts will help me out. I bought a Foodsaver not too long ago and will be trying my hand at bagging parts. I have access to all the necessary cloths (pre-preg) wicking felts, West Systems epoxy, etc.. How long are you keeping the parts vacuumed? Also, are you placing the fins under weight in the bag or will they hold shape on their own through the vacuum?

 

[dixontj93060]

Originally posted by Ryan S.
very nice, I have been interested in getting a vacuum bagger, but its alot of money, and I am not sure if I can get bags for larger rockets, I wrapped tape around the end of a rocket the other day and the FG came out smooth, maybe I will do that instead.

How did you do it? what is wrapped around the body tubes to keep them from touching tthe plastic?

Ryan,

I was able to pick up the vacuum bagger for ~$45 on Ebay. Bags I've seen standard are 8" and 11" so there is a limit--probably about 7" airframe. But... Two weekends ago I saw a monster M-class rocket at the DARS (Dallas Area Rocket Society) meeting that was fully vacuum bagged (carbon then fiberglass). He had used an 18" bag (but I stupidly didn't ask him where he got it) and funneled it down to 11" to fit in the Foodsaver. Really nice results!

In the bag over the fiberglass application you have first release fabric. I went ahead and purchased the 879 Release Fabric from West Systems. I think some people just use straight nylon fabric but since it was my first fiberglass job, I didn't want to take chances. Over that you put polyester batting (equivalent to West System 881 Breather Fabric). You get that cheap by the yard at Walmart or a fabric store. You can reuse the plastic bag and release fabric after each layer of fiberglass, but you trash the breather fabric.

-Tim

 

[dixontj93060]

Originally posted by Stones
Nice building techniques Tim. I'm currently doing a scratchbuild (4") of a Bullpup AGM-12C based on the TLP kit which Missleman was kind enough to send me plenty of info on.
Your ideas about the tailcone/hat parts will help me out. I bought a Foodsaver not too long ago and will be trying my hand at bagging parts. I have access to all the necessary cloths (pre-preg) wicking felts, West Systems epoxy, etc.. How long are you keeping the parts vacuumed? Also, are you placing the fins under weight in the bag or will they hold shape on their own through the vacuum?

Stones,

I pretty much followed the "Kitchen Vacuum Bagging" instructions on John Coker's site (https://www.jcrocket.com/kitchenbagging.shtml). My deviations were to not use the coupler reinforcement technique described and instead thread the bag through the airframe and then around it to support the body tube under vacuum (I found it best to turn the bag inside out before starting this procedure). Also for the first layer of fiberglass I found it easier to use a light spray of 3M 77-type glue to tack up the fiberglass and get it in place. Regarding timing, I also found that for me that instead of 12 hours cure as recommended, about 10 hours was good between fiberglass layers (they cured in an insulated, air conditioned garage at 75 degrees). Regarding the fins, they are not under weight. The vacuum bagging provides all the pressure required to laminate the glass effectively (was that your last question?).

-Tim

 

[Stones]

Originally posted by dixontj93060
Stones,
...
The vacuum bagging provides all the pressure required to laminate the glass effectively (was that your last question?).
-Tim

Yes, that was what I meant. Thanks for all the rest of the info as well.

 

[dixontj93060]

Originally posted by dixontj93060
Pics of finished fins and nosecone. Amazing how strong balsa fins become with two layers of 4.5 oz. fiberglass (and of course the epoxy). Will need to do some triming and filling on these. Notice the nosecone mistake? Forgot to tape/cellephane off the shoulder and got layers there. But with some careful Exacto-knife whittling I got it back body tube I.D.

OOPS! Forgot attachment on previous post... Here it is...

 

[dixontj93060]

Speaking of filling, anybody every use SuperFil? I read of the reference on the Shadow Composites website and then on: https://www.polyfiber.com/epoxy/. A Bondo for airplane builders. And it seems to make sense, why sand down and ruin the integrity of the layers of fiberglass you just put together, better to build up--but build up light! Anyway, I got some in and I'll try it here--let you know the results...

 

[dixontj93060]

Almost forgot. Before I do the SuperFil on the outside I needed to add more than 4.5 oz. of compensation. This might seem large for a mid-power rocket, but with the very long root edge on the fins (over 15") combined with the bigger motor (G64, G80, whatever...) I need this much.

I decided to improve on the nosecone attachment at the same time, so I did the following: 1) snipped off the existing molded parachute attachment, 2) cut a 1.25" hole in the aft end of the nosecone, 3) ran an ~8" 1/4-20 all-thread with a T-nut (T-nut was positioned toward the forward end of the nosecone to give a mechanical anchor for the epoxy and weighting) down through the middle of the nosecone, 4) plungered in some 5-minute epoxy just to set things in place, 5) inserted small lead fishing weights and encased them with 15-minute epoxy (this was done in ice so as to not overheat with the epoxy and melt the nosecone--see picture), 6) screwed on a 1/4-20 coupling nut (with a drop of epoxy to secure), 7) screwed on an eyebolt, fender washer and lock nut combination (with drops of epoxy to secure).

The picture is the middle of the process of encasing the lead weights--nosecone in ice. What you see sticking out of the nosecone aft end is some cardboard tubing used to center the all-thread in the middle of the nosecone while applying epoxy.

 

[dixontj93060]

Not your Dad's Estes nosecone...

Finished nosecone weighed in at 7.7 oz. Made up of about 2.4 oz. for BT-80 nosecone, nosecone extension and two wraps of fiberglass, 2.8 oz. for new shock cord attachment hardware, 2.0 oz. lead fishing weights and probably the rest epoxy fill for securing the weight. Total is just a little over what I have in my SpaceCAD simulation so should give me a little leeway on my CP/CG and be fine for any G-motor I throw at it.

 

[dixontj93060]

Semi-finished product. You can see the nice eyebolt upgrade. Fender washer covers the larger whole made to insert the all-thread assembly and plunger in the epoxy. If you look closely on the top right side you can see the flashing where the old puny shock cord attachment used to be located.

 

[dixontj93060]

Its beginning to take shape now. This is after full epoxy fill of tailcone and sanding of first layer of SuperFil bonder on nosecone and body. Major rough build items left are second layer of SuperFil on nosecone, a layer of fiberglass on the fin fillets and two layers of fiberglass on the tailcone (it's going to have to be tough)...

 

[dixontj93060]

This angle gives you a good view of the large fins on the Hawk.

 

[dixontj93060]

With that length and size of fin it was important to get the alignment just right so picked up some aluminum angle stock at the local Tractor Supply store cheap.

Also I said I'd comment on the Superfil. Real easy to work with. A little goes a long way. Although very light, it seems harder than regular Bondo. A little tough to sand. Going on it spreads alot like cake icing so you end up with having a lot to sand through.

Next comments will be after final fiberglassing. Right now I'm making a jig to hold the fins so I can fiberglass the fin joint. I'll let you know how it goes...