Laminating a fin

Discussion in 'High Power Rocketry (HPR)' started by REK, Aug 18, 2012.

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  1. Aug 18, 2012 #1

    REK

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    I decided to take the spare Mariah 38 fin I beveled not to long ago and glass it as to get the hang of glassing. Materials I used are: 20 minute epoxy, 6oz fiberglass cloth, wax paper, and a bag filled with some sand.

    IMAG0574.jpg
     
  2. Aug 18, 2012 #2

    REK

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    So I went ahead and layed down a layer of 20 minute epoxy and then layed down the 6oz fiberglass cloth.

    lam fin 2.jpg

    I then placed the wax paper over the fin.

    lam fin 3.jpg

    Right after that I placed the bag of sand to apply pressure.

    lam fin 4.jpg

    Then I play the waiting game.
     
  3. Aug 18, 2012 #3

    REK

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    After waiting nearly 3 hours I went ahead and peeled the wax paper off. Unfortunately since 20 minute epoxy has a water like viscosity it wet through the wax paper and it stuck to the fin like it was a sticker. The lamination was a success however.

    lam fin 5.jpg

    If you all have ideas please Im all ears.
     
  4. Aug 18, 2012 #4

    MuddAmateurRocketryClub

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    Unfortunately in our experience the quality of the final product is proportional to the amount of money spent on it in consumable material. I'd do this with a piece of dacron peel ply the shape of the fin plus an inch or so in every direction, and a layer of airex breather cloth or a nice non-textured paper towel (several, actually) on top of that, then the wax paper or a real nylon release film. The bag of sand is, however, an excellent compression method we have used many times before.

    Also, it looks like that is red paint-it's doubtful that the epoxy will adhere to paint well, I'd sand all the paint off, then scuff the G10 with 60grit sandpaper as roughly as I could.
     
  5. Aug 18, 2012 #5

    edwinshap1

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    In addition to what is stated above, I would recommend parchment paper. I've used it for pressing fiberglass plates and it creates a near perfect finish. It also doesn't seep through. I have used wax paper and it does seep through, but not parchment paper. Quite cheap for a large amount.
     
  6. Aug 18, 2012 #6

    G_T

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    You want water like consistency. Actually you want a laminating resin, which will be quite a bit thinner than what you used. You also want more working time so you do not have to rush.

    Epoxy does not stick very well to plastic. It stick rather poorly to waxed plastic. Mylar sheets are a good choice, waxed.

    You cannot pile enough sand on to get the result that you likely want, which is a compressed laminate. Let's say your surface is 6" x 4". This is 24 square inches. If your sand bags weighed 24 pounds, then the resulting pressure is one pound per square inch. That is, not much. This is why people use vacuum bagging methods. Even a poor vacuum system will get many times the pressure you can achieve with sand.

    Alternative methods:

    Vacuum bagging. Probably the best method. If you have a food saver around, you can use that to do the job. Search for food saver vacuum bagging wings.

    More pressure. Get some thick slabs of plywood or metal. Get some sheets of the spongy foam that used to be used to wrap receivers in RC planes. Make a sandwich of your fin, surrounded by your fabric and epoxy, layered between waxed plastic sheets, layered between sheets of spongy foam, layered between solid plates. Use a big vice and/or several big c-clamps, and squish it. Hard. You can get adequate pressure this way.

    Stick then laminate. Get a can of 3M77 spray contact adhesive. Lay a piece of fabric larger than your fin on top of some newspaper, preferrably outside. Spray a rather light coat of 3M77 on one side of your fabric. This should be a mist coating, not a layer. You are not painting it. You are making it tacky, like a weak tape. Lay your fin on top of this, squish it down, then pick it up. Flip it over, and smooth the fabric down to full solid contact. Now do the same for the other side. Trim the excess. Now that the fabric is where you want it, you can brush on laminating resin with an acid brush. Wet out the fabric but be gentle with it. Epoxy softens 3M77. Once wet out, blot up all excess epoxy with paper towels. Leave to dry. You will have filling to do with this method, unfortunately. Note that ideally you want fabric to wrap around the leading edge of your fin. You can do that with this method, using one larger piece of fabric.

    Gerald
     
  7. Aug 18, 2012 #7

    REK

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    Thank you for your opinion. Like I said the lamination was a success. It still adhered to the painted area. As much as I know its better to have sanded it off. I didnt want to waste time. I am only practicing for my next project. I just want to hear all the alternatives to use in place of wax paper. The bag of sand trick is nice and I enjoyed using that technique because my advantage on this is that I live in the desert lol.
     
  8. Aug 18, 2012 #8

    REK

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    Parchment paper you say? I will look into it :).
     
  9. Aug 18, 2012 #9

    REK

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    20 minute epoxy is very good in water like consistency. It soaked in pretty well. I even managed to spread it nicely with my finger. I had no brushes available :(. I had plenty of working time. 20 minute epoxy likes to harden after 1 hour. Im sure that is more than enough time. As for the mylar sheets it seems like something to try as well. I want to try vacumm wrapping but I do not have the stuff for that so my only method is the bag of sand which worked perfect for me. Also this is a G10 fin not plastic. After I had finished laminating the cloth looks like its apart of the fin. It was a success. I believe I can place another layer and it will still apear unoticable.
     
  10. Aug 18, 2012 #10

    G_T

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    Adhering to the paint is unfortunately not a measure of success, unless you are only looking for cosmetics. Failing to adhere would be utter failure!

    The test is to bend your part until it breaks. What is the failure mode? If the failure mode is delamination at a force lower than what the core can take, then you have achieved negative progress. You've added weight without an increase in strength. That is, the fabric separates from the core but the core doesn't break at that load. So the added fabric was useless.

    If the failure mode is breaking of the fabric and the core pretty much simultaneously, then you've probably added strength or at least stiffness.

    If the failure mode is breaking of the outer fabric but not the core, then you've done an adequate job of laminating. Unfortunately, the material added to the core was of inappropriate structural properties for the job.

    I hope this is of some help. I'm not intending to be critical. I'm presuming the reason you are working this out is that you plan to make a rocket that will require such reinforcing.

    When working with composites, one of the goals should be to have the part, when it comes out of the mold or bag or whatever laminating tool is used, be as close to a finished part as possible. Already painted. Glassy surface. Etc. Pop it out and it is done.

    There is a very good reason for this (other than just saving time). Epoxy sticks to cured epoxy by mechanical bond. Epoxy sticks to uncured epoxy (of a compatible system) by both mechanical and chemical bonds. This is stronger. Use of peel-ply to leave a surface suitable for the next laminating step, is a tool used when one cannot for some reason perform the whole lamination at one time. The result is inferior, but probably better than not using peel ply in such situations. If this is the outer layer, then one has to sand the surface or at least fill the surface. It is easy to sand the fibers and damage their structure. I would say that peel-ply on the outside of the final layup should be considered a no-no. Besides, with proper prep work, one can achieve a painted finished result with near perfect glass like surfaces, all as part of the layup process.

    Gerald
     
  11. Aug 18, 2012 #11

    UPscaler

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    Another option is the way Crazy Jim told me to do it, granted this is a GLR kit, and I'm not sure if they come in bags. (I'd really like to grab a talon 4 to find out though :wink:) The wildman kits come in a thick plastic bag that is perfect for smooth and shiny finishes with composites.



    Braden
     
  12. Aug 18, 2012 #12

    REK

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    I hate to say it G_T but you are being critical. You are more experienced. I am merely seeking alternatives to the wax paper. Also I will not break the fin. It is the only spare I have. Also this was just one layer. I am going to add another. I just need to seek other materials that will work more better than the wax paper. I thank you for your ideas and opinions.
     
  13. Aug 18, 2012 #13

    REK

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    Thank you all for the ideas and opinions. I know I am stating that I only want advice on alternatives to wax paper, but I did say I am all ears to your advice :). I appreciate this greatly. By the way I have only glassed one side of the fin. When I aquire some thing mylar sheets I will laminate the other side. If the thin myler works more better than the wax paper I will add another layer of glass to both sides to see if I can feel the strength incease. Like I said I wont break the fin it is my only spare. I plan to get another Mariah 38. I am going to bevel the fins and instead of fiberglass. I will be using carbon fiber. I am sure that carbon fiber will be incredibely strong compared to fiberglass and less weight if Im not mistaken. Remember this just all practice for me. I am still a rookie learning on how to do this. Practice makes perfect :).
     
  14. Aug 18, 2012 #14

    HyperSpeed

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    I have got perfect fins using regular wax paper and I'll share with you how this is done.

    You purchase the 1.5" pink foam board insulation at T.H.D. (if you are doing non-airfoiled fins, you can use the thinner board than 1.5"). Slow epoxy is used, it is not allowed to get hot during the mixing process. I cut the bottom off a plastic party cup and mix one pump of West System epoxy and one pump of their #206 curative.

    I lay the carbon up and I use foam brushes don't use regular paint brushes because the epoxy thickening will pull bristles off and have fun with bristles in your finish. :) I mix the epoxy after I use each cup so epoxy stays cooler. You could get it to 58 degrees minimum in the fridge first if you want to use more epoxy at once and prolong your thickening time but mix more vigorously ever when cooled.
    Now use excess epoxy so there are surely no voids in the end when you wet your fabric out. Lay your top piece of wax paper be sure the paper has no kinks and is smooth. Roll on your wax paper in all directions outward from the middle of the fin. Going back to the earlier stage, wet your lower piece of wax paper first with epoxy, lay the cloth on the flat pre-wetted wax, then wet out that cloth piece fully. You always do this so air is not pushed from the top of the cloth down to the bottom and form voids you cannot see. This is not required with the top because you can see through the wax paper and can roll them out.

    Put on your top foam piece, I typically use fin-area roughly times two or say a overhang of 1.5" on a 7" root cord fin, for foam square area. Put a flat board on your foam, then put about your fin's square area multiplied by 8 and use this as an approximation for required weight to set on top of the wood board/foam/wax/fin-laminate.

    Go to bed for 8 hours. :) If you sleep well, time will have morphed into the future and you can now carefully peel your wax paper. :D

    Never heat this process! Think, wax melts. Wax will melt and epoxy will replace it in the paper. Bad news! Cure your fins only overnight at room temp and be sure to peel at 8 hours. This is when the epoxy is stiff but still uncured completely; 8 hours using #206 @ ~ 70 F. Now you may carefully lay your peeled fins on a surface and harden them the rest of the way at 140F for a few hours.

    This is how I have made wax paper work when in a rush and having no Mylar.

    Sorry about a poorly organized writeup its hard in a rush on a cell phone while I'm driving to type all this. I'm joking I'm not driving! But am on a cell phone.
     
    Last edited: Aug 18, 2012
  15. Aug 18, 2012 #15

    troj

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    For small items like this, I'm surprised I haven't seen the ultimate in easy suggested yet -- a Food Saver.

    Not only are the bags plastic, so the epoxy won't stick, but it also is an inexpensive vaccuum-bagging method. And it safely serves a dual purpose, with having kitchen uses, as well!

    Cut your fiberglass exactly like you did, brush on the epoxy, then apply the cloth. When you're done with that, instead of placing it on waxed paper, slip it into a Food Saver bag, vaccuum out the air, seal, and let it cure.

    -Kevin
     
  16. Aug 18, 2012 #16

    El Cheapo

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    All good tips. The fact of the matter is you don't know until you know. There is a difference between structural epoxy and laminating resin. Just Google it. Nice effort. It's more than I've been able to fit in the last couple months.
     
  17. Aug 18, 2012 #17

    cwbullet

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    I highly recommend a food saver. I have used one on multiple project and it has never failed me.
     
  18. Aug 18, 2012 #18

    DRAGON64

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    You stated that the fin was a spare fin... so what you are doing here is teaching yourself how to laminate correct? Here is what I would add to your experience.

    Wax paper aside, let's start with what you must have:

    Applicator; Get some disposable horse-hair brushes or the $ .50 black bristle brushes from Wally-World. I prefer the black bristle, so I can pick out the bristles as they come loose.

    Gloves: You do not want to build up an allergic reaction to epoxy, I hear it is bad. Get some of the purple gloves (also found at Wally-World) to use when working any epoxy.

    I'm assuming the dishes and food ware removed from the table before you started...(?)

    The fin was red... I assume that it had been painted. This surface would need to have been removed, otherwise you are laminating a structural system to the paint surface, which is a removable layer. Your glass laminate need to be adhered to a properly prepped structure (the fin) in order to gain the best benefit. Sanding a rough textured surface on the fin would be best. Gives the epoxy something to get a hold of.

    Using thin epoxy; if you are planning more than one layer of glass, then add the layers you intend to lay up. Since the Mariah fin is G10, your epoxy can only soak in one direction, and that is towards the glass laminate you have applied. Multiple layers save much work and extra prep, but also adheres all layers into one structural system, not two or three seperate systems. You may also find that you use less epoxy over the course of the project.

    You are learning, and that is good. Do not take what experienced members are saying as being negative towards you, it is constructive criticism...we can learn much from this to.

    Lastly I will say that you should never work from a diningroom table, there are multiple reasons for this, the most important is it is not safe for anyone who may eat from there.

    Good luck, and please post your progress.
     
    Last edited: Aug 18, 2012
  19. Aug 18, 2012 #19

    REK

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    El Cheapo,

    Do not mistake me for a complete rookie lol. I know the difference. The 20 minute epoxy is very good for laminating since it has a water like viscosity. I am very sure you do not want to use 20 minute as a structual use otherwise it will run on you.
     
  20. Aug 18, 2012 #20

    REK

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    A food saver bag eh? Sounds interesting. I will look into this.
     
  21. Aug 18, 2012 #21

    flynfrog

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    I think you will find that a real release film is not that expensive and wont contaminate you part with wax https://www.airtechonline.com/econo/econo_a.html

    Not sure what you 20 min epoxy you are using it should be a laminating resin such as west systems or aeropoxy. Not a bonding epoxy such as the hobby stuff.

    The first prep would be to clean the fin with acetone or iso propyl alcohol and sand the fin with 120-240 Grit paper to expose the tops of the fibers without going through them. Grit blast works really well for this part.

    Now wipe the fin with acetone and/or iso propyl with a clean lint free cloth. You should keep doing this until you get a clean wipe.

    Wet the surface of you fin with a thin coat of epoxy

    Wet out your fabric I use a bondo spreader but a popsicle stick works. It should be almost transparent if you are using glass.

    Lay the fabric over you fin so that you dont trap any air work out the air bubbles if needed with a speard or stick.

    Apply your release layer.

    Apply your compaction this could be weight as you used. I have vacuum pumps so I use those this requires a vacuum bag. Make sure you have a resin trap so you don't suck resin into your pump.

    Wait for the epoxy to cure.

    Remove compaction.

    Admire beautiful fin.

    Celebrate!
     
  22. Aug 18, 2012 #22

    REK

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    Thank you Dragon I like all your ideas. No worries okay I had one last spare of gloves. I think using my finger was better than a brush lol. This will save on those little strands of the brush on the epoxy. Also do not worry about the kitchen table I was well prepared for that. The kitchen is my only working area :(. Id use my grandfathers garage but man talk about chaos. Its all greasy everywhere and full of dirt so yeah not your place to work in when it comes to glue. I like all these Ideas so far. They are all very helpful and I enjoy it. Also yes that was red paint. I did not want to take the time to sand it off. I know very well that the G10 must be roughed up for great adhesion. I for sure wont do any painting until the model is completed. I found all these ideas and opinions great. I was just letting G_T know that he was being a little critical in asking too much of me when there is very little I can do. I had only just laminated one side of the fin and already asked me to break it. Thats no way to test it. He assumed too much and so I was only letting him know that he jumped the gun a bit. I do very well appreciate his advice and therefore am learning from all this. Thank you Dragon.
     
  23. Aug 18, 2012 #23

    cwbullet

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    Nice follow on Dragon. There is a lot to be learned from on this thread. There are many ways to do something. I am glad to find a few more to try.
     
  24. Aug 18, 2012 #24

    REK

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    Thank you flynfrog. I will be using some aeropoxy laminating resin. I am just using the 20 minute epoxy for practice. I gotta say however it worked nicely to my delight. The glass turned transparent and I had plenty of working time I had no rush. The fin was very perfectly laminated. All that was really annoying was the wax paper stuck to the fin like a sticker. You can feel the strength it added as well. I will laminate the other side when I get some other materials. I might go for the mylar sheets that seems like it might work more better.
     
  25. Aug 18, 2012 #25

    kenstarr

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    Did some fins for my scratch Blackhawk 38. I used a core of the Giant Leap Nomex honeycomb and carbon cloth over the outside. For the laminating, I used USComposites 4:1 laminating epoxy. After the fin was laid up, I put it in a quart(?) size bread bag (thinner than a ziploc). using a sharp knife tip, I poked as many holes as I possibly could through the plastic (this was my peel ply). Covered that part with paper towels or maybe it was toilet paper to act as the breather material. Finally I put it in the seal a meal device. After it was vacuumed tight, I sandwiched the fin/bag/paper towel/bag package between 2 flat hard surfaces to keep things straight. Worked fantastic. surely not as good as using real peel ply, breather material, vacuum bag material, but hey the whole thing worked as planned. Much better than the aluminum foil/sand attempt awhile earlier! Also, I once tried to glass some Aerotech plastic fins.... Worked great until I tried to trim the glass and popped off some nice fin molds, but it was a good learning experience.
     

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