Composites 201

Discussion in 'The Garage' started by harcus, Nov 16, 2011.

  1. harcus

    harcus Long timer

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    The purpose of this thread is to pass on some techniques accumulated over the years on building real parts out of composites. In this case, motorcycle parts. Our friendly inmate HickOnACrick provided a good overview of composites in general. Let's take a look of how to apply some of that knowledge.

    Disclaimer 1 - About me - First, I do not claim to be a composites genius. So don't get upset if I say something that may conflict with your views. I do claim to be a retired aerospace engineer & program manages spen=ding the last 21 years in the composites industry building struture for rockets, F35s, commercial aircraft n the like.. Sadly, only small segments of that world translate well to our world. The aerospace materials, processes & equipment are not available to us. Luckily, we don't really need them.

    Disclaimer 2 - I am a vendor. I make these parts & sell them via Globetrottin.com. If that offends you, don't read this.

    The project
    I will walk you through how I build many composite motorcycle parts using one of the latest - a bash (skid) plate for a new KTM 500 EXC.

    1. How do I start?
    I start with a problem. The problem in this case is... How do I provide protection for the engine case on the bike?

    2. Requirements
    This leads me to what are the requirements.
    Many bash plates are made for bike but most only cover the bottom of the engine. I live in Utah where we have many rocks that like to reach out & bash a hole in your rotor or clutch cover. So I like to make the bash plate cover this area as well as the bottom.
    We also have many sticks & brush out here so i like to keep the holes in the bash plate to a minimum. I don't believe I need a oil plug access hole so that's out. I will attempt to put a shrouded hole in any large panel area to facilitate air flow.

    3. Vision
    So what is the part going to look like? Hard to say at this point. Lets go to the bike.

    I am a hands on guy. I like to use the CAD system in conjunction with the bike to develop a product. They go together as far as I am concerned.

    4. The process
    Since I plan to make more than 1 part & I want a commercial quality part, I will build a mold. This will be a female mold so that I get a smooth (tooled) surface on the outside mold line (OML).

    To build the female mold I will build a male part (plug) that exactly looks like the part I want in the end. I will finish the plug smooth with the proper surface, wax it & layup the mold. The plug with then be removed, the mold cleaned & waxed & prototype part made. This part will be fit checked on the bike, measured & inspected to verify if this part will meet the requirements. If all is good, it's off to production we go. If not, changes are made.

    5. Plug fab
    Many materials can be used to fab the plug. For this type of part
    (& many other MC parts) I like to used .25 in thick ply wood. Why plywood? Because it can be easily cut, shaped and bonded together.

    Let's get started.

    Here is the starting of the plug on the bike as seen from the LH side...

    [​IMG]

    How did I get here?

    I started with the bottom surface. I cut a piece of plywood approx the size of the bottom I pushed it up against the frame with a small floor jack. I then added the front lower panel.

    I like to use Bondo to glue the pieces together. I keep a piece of glass on the table for mixing. I scrape off the semi cured Bondo with a scraper blade ...

    [​IMG]

    Let's take a break for a minute.
    #1
  2. harcus

    harcus Long timer

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    Notice that I hold the plug in place with clamps, etc.

    This part of the job is much like sculpting - you have to fit each puzzle piece in place & see how it works. Does it maintain the line you want? does it fit as it should? Are you meeting your requirements?

    Notice the bulge in the LH side of the pic? I was considering whether I wanted to protect the exhaust pipe with the bash plate. It looked like this from the other side...

    [​IMG]

    It was ugly. So I chopped it off. I shaped the plate to cover the water pump area instead...

    [​IMG]

    Once I get the shape where I want it, it's time to blend. At this point, reinforcements may be necessary. I put splices or fiberglass patches on the inside to maintain structural integrity while finishing.

    Remember - The plug only has to stay together through the mold process.

    Here is the unblended plug...

    [​IMG]

    Here is the inside...

    [​IMG]

    Here I have blended the surfaces & rounded the corners. I use a bench type belt sander for the big stuff & use various oscillating sanders for the blending. I like 40 grit zirconium at this stage. Notice that I have started filling the surfaces here...

    [​IMG]

    Here we are a little further in the process...

    [​IMG]

    Check the plug to make sure all joint bonds are sound. If not, repair them. If a joint is cracked I will apply some resin in the crack & clamp it together. Resin curing can be accelerated by use of a light bulb and / or mixing it hot (hi catalyst ratio). Once the surface is good it's time for the sealing coat. I like to use gel coat because it builds up faster than laminating resin. When spraying gel coat in these applications thin it with acetone. I always mix it hot (2.7 cc MEKP per 4 oz resin) & cut (thin) it about 2/1 (2 parts gel / 1 part acetone). Blow the dust off the plug & coat it being careful to not create drips. That just increasing your sanding effort. Make sure you get good coverage.

    Tip - Use contrasting colors of gel so you can verify coverage. Example - I want this part to be black so the mold will be light colored (I like grey) so the plug will be black. Got it?

    Let it cure for about 1/2 hr. Spray the surface with PVA. Why? Gel coat is made to provide a tacky surface for layup. When exposed to air it will remain tacky. The trick is to seal it from the air so it will cure tack free.

    It's best to let it set over night if possible. Wash off the PVA with warm water & a brush or scotchbrite. Inspect for imperfections.

    Sand the surface with 120 grit & watch the bumps & divots show up. Fill 7 sand as required to get everything nice & smooth.

    BTW - It is good to have a dust evacuation system on your sander or table to keep it out of your sinus & lungs.

    Here it is during coating....

    [​IMG]

    Here it has been sanded once...

    [​IMG]

    [​IMG]

    Recoat & repeat. Typically I get a decent surface on the third coating.

    I sand with 320 / 400 wet on the final surface & finish with 600.

    Once the surface is acceptable it's time to wax. I use Johnson's floor wax. Put on several coats & set the part in the sun. If there is no sun, use a heat lamp. Let the wax soak in to the pores. Repeat until everything is sealed

    Warning - This is a key step. If you don't get the plug sealed you will have a door stop!

    [​IMG]

    [​IMG]

    Notice here that I went thru the gel locally but the plug is still sealed. The key is sealing.

    Next - Mold fab - Later :D
    #2
  3. tmotten

    tmotten Lefthand ride Dutchy

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    :clap:clap:clap

    :lurk

    How about for your next project a 'under the seat fuel tank/shock' guard/fender?? :deal

    Is the sealing purely to get a nice finish on the mould??
    #3
  4. harcus

    harcus Long timer

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    No - It's to keep the resin from sticking to the plug when the mold in made. It's a "release agent".

    There is actually a composite subframe / airbox / rack system on the list tho.

    Stay tuned. :D
    #4
  5. harcus

    harcus Long timer

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    The next step is to make the mold. As I noted earlier, the mold color should contrast with the part color so that you can verify coverage when spraying the gel coat. Since the part will be black I will make the mold gray. I create grey by mixing my standard black "tooling gel coat" with some standard white gel.

    As before, thin the gelcoat with acetone to facilitate use in your gun. I usually thin about 2 parts gel to 1 part acetone to get the right consistency. Spray the plug with a good coat of gel. The acetone flashes off quickly so keep layering it on. It looks like this once coated...

    [​IMG]

    Set it aside to cure. Remember it will be tacky but will not stick to your finger when cured.

    Next, we apply the glass. Many types of glass are available for this purpose - fabrics & mats. For this purpose I prefer to use mat.

    Why mat? On small parts like this there are many contours. Orientation of fabric over these contours to prevent wrinkles is challenging. If you do decide to try fabric use a lighter fabric of about 5 oz.

    This part is small & doesn't have large panels that would require stiffeners to maintain contour. For this part we will use 3 plies of mat. Ply 1 will be a 1/2 oz with ply 2 & 3 will be 2 oz plies. I like 1/2 oz on the ply next to the gel coat to minimize the step at the edge of the ply. This minimizes the possibility of gel chipping.

    Decide on the ply arrangement before you start layup. It is virtually impossible to lay a 1 piece ply in a part like this necessitating cutting the ply into pieces.

    On this part I chose to lay one large ply down the middle of the part from end to end with the width of the ply flashing up the sides about 1.5 inches. I then pieced in the sides.
    I precut the 1/2 oz & 2 oz large pieces as well as some smaller pieces that I custom cut on the fly.

    Mix up the resin & catalyst. I prefer to use a cool mix (lesser amount of catalyst) at this stage to provide more pot life during layup. Using a 2 inch chip brush apply resin onto the mold. Lay the main piece of 1/2 oz glass onto the wet mold. Roll it out with a standard glass roller. For small parts I use a 1/2 in dia x 3 in roller to access the corners. Roll the mat pushing the resin up thru the mat until no "white" dry mat is visible. Allow 2-3 minutes for the resin to dissolve the sizing in the mat. You will note that the stiffness of the glass disappears & the ply conforms to the contours as the sizing dissolves.

    Note - It is possible to lay the glass onto the mold dry & wet it from the outside surface. I find this method unsatisfactory.

    [​IMG]

    Cut the edges of the ply (called a dart) at the corners to allow the ply to lay flat. Continue to lay in pieces to cover the entire plug. Overlap the pieces approx 1 inch. Flash them over the edge of the plug by approx 1/2 inch max. Trim excess as required to allow the ply to conform.

    [​IMG]

    Next, apply Ply 2 of 2 oz mat using the above procedure.

    [​IMG]

    [​IMG]

    Applying a ply piece to a vertical surface is problematic because the dry ply will slip from position & the resin drips causing a mess. I like to lay the ply flat & prewet it then move it to the plug & roll it in place. You can use a flat surface on the plug or a piece of window glass. The window glass is extremely handy for this since several pieces can be wetted & staged for application. Then, as the resin sets, it can be scraped clean with a razor blade.

    [​IMG]

    Apply all ply pieces to get the 3 planned plies & let them set up...

    [​IMG]

    [​IMG]

    Trimming
    Let the mold cure. Rough trim to within 1/8 inch of the plug with a band saw.

    Stiffeners
    I chose to stiffen 2 areas of this mold to maintain contour:
    a. the portion that extends over the rotor
    b. the portion that extends over the clutch

    I use 1 1/2 in x 3/4 in wood for this. I measured & cut material for (2) L shaped stiffeners. I bonded them together at the corners with Bondo & (2) grabber screws. Fit them onto the outside surface of the mold to get the angle correct. Pot each L stiffener in place on the outside of the mold with Bondo & let it set. "Wet rag" the stiffeners to the mold using strips of 1/2 oz mat about 2 in wide. The strips should flash up the wood & down on to the mold to form a structural connection. Let it all cure...


    [​IMG]

    Once the mold is cured, it is time to pull the plug. The plug can be loosened from the mold by gently tapping the outside with a rubber mallet. Separate the plug from the mold at the edges by carefully inserting a knife. A "separator" tool can be made by blending the edges of a flat blade screwdriver. Insert the separator tool between the plug & the mold & carefully break it loose.

    If you did a good job waxing the plug there will be no drama.

    Once the mold is off of the plug, finish the trimming. I use a coarse belt sander (40 grit) to sand down to the mark from the plug. Blend the edges & knock off the fuzzies with a orbital (I like the Mouse) sander.

    You now have a mold.

    [​IMG]

    [​IMG]


    Next - Building a part.

    :D





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    #5
  6. VonHelm

    VonHelm soggy doggy

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    Excellent write-up. I've seen a few of finished molds, and while understanding the process of building a plug and making the mold, I've never seen the process detailed so thoroughly. I was surprised when you used Bondo to glue the all the plug pieces together, but it makes perfect sense: thick, quick setting, bridges gaps, easy to sand and blend. It is glue and filler in one step. Brilliant!
    #6
  7. muddywater

    muddywater Been here awhile

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    More Please!!
    #7
  8. tmotten

    tmotten Lefthand ride Dutchy

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    Ok, guess I'm just surprised it takes that many coats to achieve that. I would have thought that the PVA would fill in those tiny holes.

    Like the idea of reinforcing. I'm always a bit nervous with the vertical release angles thought, particularly for mould where the part will end up relatively thick such as a bash plate where there will be a minimum flex in the part to pull out from the part.

    Keen to see your future projects. I've yet to find out how I'll make a plug for my fender under the tank as it's one of those upside down areas.
    #8
  9. harcus

    harcus Long timer

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    You might have missed it. I didn't use PVA for a release. I only used it to to seal the gel coat I put on the plug for sealing.

    PVA certainly can be used but it is hard to get a good finish with it. The pro shops only use wax or a similar release agent.

    Plug for your fender? Take it off the bike! Make your life easy. Of corse I am assuming you are doing a copy of the OEM fender, etc. You may need to explain the project.

    :D
    #9
  10. anonny

    anonny What could go wrong?

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    I too was a little surprised about using bondo as a glue, thought the part would be too fragile.

    Good stuff, keep it coming :clap
    #10
  11. Gary B.

    Gary B. Older than dirt...

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    :smile6
    #11
  12. tmotten

    tmotten Lefthand ride Dutchy

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    http://www.advrider.com/forums/showthread.php?t=726679

    That's the problem. I've rebuild bike with a new subframe and the old fencer doesn't work any more. I'll have to have a look at how much of the OEM one I can use. But that's for later.
    #12
  13. harcus

    harcus Long timer

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    It is now time to build a part.

    Well, almost.

    Once the mold is trimmed to the "mark off" from the plug & the edges deburred & slightly rounded, they need to be sealed. Otherwise, the resin from the part can seep into the edges & bond causing quite a mess.

    Mix up some laminating resin (hot), put on a rubber glove, and using your fingers, dab resin on the edges. Be careful to not slop the resin on to the inside of the mold. If you do, use some acetone on a paper towel or toilet paper to wipe it off. Let it cure.

    Next, inspect the surface of the mold by running your hand over the surface. If you find any imperfections you may want to sand them out with some 600 grit. Or fill them. Sometimes you may find local delaminations at the edges where the layup or trimming was not up to par. These can be filled with a little gel coat. Be sure to sand locally or it wont stick. After filling the divot / imperfection, apply a piece of tape onto the surface of the mold. Any tape will work. This will help to keep the resin in profile. Sand & blend after it is cured. If you are going for a very shiny surface (think Harley saddle bags) then wet sand the entire mold with 1200 & finish up with rubbing compound. With a little elbow grease you can make the mold shine like a mirror.

    Since this is a bash plate I am not going for that finish.

    Lastly, we need to wax it. Apply the wax just like we did before when waxing the plug. Put on 2-3 coats, use the heat lamp to cook it in & buff it out. Repeat. Don't forget the edges.

    Part thickness
    The target thickness on this part is .12 in (3 mm). Why? We don't need more....
    1. Due to the limited size of the flat panels we can stop most any rock with this thickness of glass (based on past experience ***).
    2. The contours, angles, & ribs tend to stiffen the part
    3. We are wanting the lightest part possible

    ***Note - I make composite bash plates for the KTM 990. It has much larger panels & the bike weighs 2x the weight of this bike. I build the edges at .12 inch (3 mm) & the center to .18 inch (4.5 mm). I have yet to have any rock blast a hole in the plate.

    Part fiber material
    Now that we have a mold, we can make the part out of several different fibers. There are many materials but they cook down to only a few to be seriously considered....

    Fiberglass cloth - This was discussed in the previous section a bit. Glass cloth comes in many weaves & many weights. On small parts like this, I would stay with 5-6 oz cloth max to get the plies to conform to the contours.
    Pros - Might save a few ounces in weight since the resin can be worked out of the cloth easier than the mat.
    Note - Optimum resin content of any layup with any fiber is 32 - 36 percent by weight. This figure is near impossible to acheive with hand layup room temp cure resins. But it is a good target!
    Cons - More time consuming, more wrinkles / delaminations possible
    Impact resistance - High. Commonly used in vehicle armor.
    Cost - Low


    Fiberglass mat - Use the same material for the part as we did for the mold. Same layup procedure. Commercial chopped mat has fibers about 1.5 in (40 mm) long arranged in a random manner held together by sizing that will dissolve with polyester resin.
    Pros - Easier to layup. Faster. Less chance of wrinkles / delaminations.
    Cons - Part may be slightly heavier since the mat tends to hold the resin more.
    Impact resistance - High. Commonly used in vehicle armor.
    Cost - Low

    You may wonder why not graphite or kevlar. There are several reasons. Graphite
    <style> <!-- /* Font Definitions */ @font-face {font-family:Cambria; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:3 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin-top:0in; margin-right:0in; margin-bottom:10.0pt; margin-left:0in; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Cambria; mso-fareast-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --> </style> (Carbon) seems to be the rage today particularly if you want to add bling. Carbon fabric has all the limitations of glass fabric with the additional issue of stiffness & fracture resistance. Because it is stiffer, it is very challenging to use on small part like this with out vacuum bagging / autoclaving. Carbon mat is also available but it too is stiff & challenging. The high strength of carbon make it prone to fracture - not good in this application. In short, the attributes that make desirable for primary structure on an airplane, make it undesirable in this application. Much of the same can be said for Kevlar. Kevlar has much better fracture resistance but is extremely hard to work with. Both are extremely expensive materials that bring little to this application.

    Resin - Epoxy vs Polyester
    In a laminated structure, the purpose of the resin is to hold the the fibers in position so they can carry the load. There are several criteria thae drive resin selection but the two at the top of the list are ..
    a. temperature environment
    b. translation - the ability of the resin to adhere to the fiber

    The temperature continuum looks like this...
    a. Polyesters (several variations) - good for 160-180 deg F
    b. Epoxys - good for 250 - 280 deg F
    c. BMIs (bismalimide) - good for 300 - 330 deg F
    d. Cyanate esters - good for 440 - 480 deg F
    e. Polyimides - Good for 550 - 600 deg f

    These are approximate temps where the strength of the resin is starting to degrade. The resin strength does not "fall off a cliff" as the temperature goes up. It just gradually gets softer & every thing falls apart.

    Resin strength is typically in the range of 5000-6000 psi where fibers are notably higher. ..
    Fiberglass - 30,000 - 40,000 psi
    Carbon - 200,000 - 800,000 psi

    Note - Fiber strength are not to be confused with impact strength.

    So, what is the punch line for this part?

    It is near a water cooled engine (180 deg F max) but out in the air so it should not get past approx 140 deg F so polyester resin should be fine. Fiberglass has much better impact strength than carbon ( it stretches elastically rather than fracture) so glass should be sufficient. The only question is format - mat vs cloth. I chose mat because there is very little weight advantage of fabric over mat & the layup effort of mat is about 1/2 that of mat. (History says this part weighs about 2 lbs 3 oz in mat).

    So it will be polyester / fiberglass mat layup of a .12 inch (3 mm) thickness (based on past experience). This can be done with a hand lamination or a chopper gun. The beauty of the chopper gun (used by the pro shops) is that is provides a seamless layup & it is fast & low cost. The disadvantage is that the operation can go to sleep & use too much resin thus making a heavier laminate. Since I am doing this in my shop & I have no chopper gu, I will use mat just like the mold.

    Let's get going
    - Your mold is clean, smooth & waxed - Check
    - You mat (1 ply 1/2 oz + 2 piles 2 oz) is precut in the shapes you need (see the mold fab) - Check

    Mix up the gel coat (like in the mold fab) a little hot & spray it on. I used black. Let it cure to the finger tack test level (no stick to the finger).

    Mix up the resin a bit cool
    (like in the mold fab) & do the layup just like before. Let it cure.

    Remove the part from the mold using a separation tool & trim it like we did before on the mold. Here is what it should look like...

    [​IMG]

    On the bike ...

    [​IMG]

    [​IMG]

    In this case, I liked the way it fit on the bike but I decided to make 2 changes...
    a. add a stiffening rib on the transition of the bottom to the back lip
    b. add a small vent in the large LH side o encourage airflow

    I modified the part & made a new mold accordingly. You can see the changes here...

    [​IMG]



    [​IMG]

    This plate is a quick release design that is held in place by a single bolt inserted into a small bracket at the front of the engine. With that item fabbed, the project is complete.

    [​IMG]

    Hopefully, this exercise has been helpful. A you can see, it is not cost or time effective for 1 part. But for production quantities of high quality parts it is quite useful.

    Later :D :D :D


    #13
  14. tmotten

    tmotten Lefthand ride Dutchy

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    Wow, good detailed info. :clap

    I actually struggle the most at the moment getting the edge right. Particular with the joint between 2 panels. Have you got any tips for that? I thought using steel edges clamped to the plug to I don't sand past a certain point, and 'glue' a piece of flat glass to the inside of the plug so I can join the other panel to it flush when finished like OEM panels. Would that be the way the pro's do it?
    #14
  15. VonHelm

    VonHelm soggy doggy

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    Could you tell us a little more about spraying resin, i.e., gun type, tips, pressures, saftey, and cleaning?
    #15
  16. harcus

    harcus Long timer

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    T
    Not sure I understand your question. Can you post a pic of the panels and edges that you are trying to fabricate?

    Thanks
    Jim
    #16
  17. harcus

    harcus Long timer

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    Spraying resin? ....Hmmm....OK

    Spray guns - Several types of spray guns will work. Pressure feed guns work the best for heavy liquids.

    The pro guys use pressure pots with remote guns. The resin / gel coat is place into the pot & the top clamped down to restrain the pressure. The resin exit tube extends into the resin. Air pressure is applied to the pot which forces the resin down the hose to gun.

    Like this...

    http://www.harborfreight.com/2-1-2-half-gallon-pressure-paint-tank-66839.html

    These are great for large volumes of gel. The bad news is that they require more acetone to clean since you have to clean all that hose.

    I use a pressure cup gun like this (may be a different model but similar)...

    http://www.harborfreight.com/industrial-paint-spray-gun-43760.html

    Look at the specs for the gun...

    Specially designed for auto body and industrial jobs. External mix gun gives professional results and a mirror-like finish.

    • Conventional material transfer
    • Designed for automotive and industrial use
    • Siphon feed
    • One quart cup
    • Regulator available separately
    • Fine spray adjustment
    • All metal construction with powder coat finish
    • Reinforced base with cam-lock closure
    <table class="data-table" id="product-attribute-specs-table_1"><colgroup><col width="100%"> </colgroup><tbody><tr class="first odd"><td class="data last">Required pressure: 20-55 PSI</td></tr><tr class="even"><td class="data last"> Air consumption: 6 CFM (stated), 1.5 CFM @ 30 PSI suggested</td></tr><tr class="odd"><td class="data last"> Nozzle size: 1.7 mm</td></tr><tr class="even"><td class="data last"> 1 quart paint capacity</td></tr><tr class="odd"><td class="data last"> Air inlet: 1/4''</td></tr><tr class="even"><td class="data last"> Hose size: 3/8"</td></tr><tr class="last odd"><td class="data last">Shipping Weight: 2.50 lbs.</td></tr></tbody></table>
    The 2 key numbers are the air flow requirements & the nozzle size.

    Make sure your air compressor can provide more than the required air flow at the required pressure reliably.

    The nozzle size indicates how much you will have to thin the resin to push it thru the nozzle. Pick a gun with the largest orifice you can find. Expensive guns are not required since you are not going for a high quality finish, just coverage. I have a Harbor Freight gun like this and a similar Campbell Haulsfield gun . Both work well with properly thinned resin.

    Pressure feed

    External mix

    As I noted previously, I thin the gel coat about 2 parts gel to 1 part acetone. Experiment with this ratio, plus & minus, using your gun. If it is too thin, it will run easily. If it is too thick, it will look like orange peal.

    I use an old metal box about 3 ft hi as a stand. I cover the top with newspapers. Set a block of wood on top like a 4 x 4 to hold the mold off the paper. Make sure you can access all the surface & edges.

    Spray on a thin coat moving in one direction. See if it runs. Apply a light coat all over. Let the acetone flash off. This takes seconds. Repeat. Build up the surface by many thin coats. You may have to reposition the item to access the edges. Make sure you end up with a consistent coat all over the part.

    Be sure to always clean the gun after each use.

    Remove the cup. Put in a small amount of acetone. Put the cup back on the gun. Shake it up. Spray a small amount thru the gun into a trash can. Open the cup. Use a 1 inch chip brush to reach inside & loosen the resin film from the cup. Brush off the feed tube on the end. Dump it.

    Do it again verifying that all resin is absent. Remove the ring nut holding on the mix head. Put it in a cup of acetone. Remove the valve body under the mix head & put it in the cup of acetone. Brush the resin from the gun. Clean the parts & lay them on a newspaper to dry.

    Use a air filter / pressure regulator between the compressor & the gun. Like this...

    http://www.harborfreight.com/industrial-air-filter-regulator-68247.html

    or

    http://www.harborfreight.com/12-air-line-filter-regulator-with-gauge-68281.html

    DO NOT spray around open flame or spark sources. I use an exhaust fan in a window to pull fumes out of the room while spraying. Open a window across the room to create a draft. Keep the vapor dissipated!

    Why? Acetone is extremely volatile particularly as a vapor.

    It is best to wear an air filter mask when spraying to keep the vapor out of your nose / sinus. Some people are allergenic to solvents so figure out if you are & act accordingly.

    Wear laytex or vinyl gloves while handling resin. Like this...

    http://www.harborfreight.com/pack-of-100-industrial-vinyl-gloves-medium-8934.html

    These vinyl glove have better resistance to acetone than the laytex or nitrile and they are cheaper.

    Hopefully this helps. :D:D:D
    #17
  18. tmotten

    tmotten Lefthand ride Dutchy

    Joined:
    Jun 28, 2006
    Oddometer:
    2,502
    Location:
    Calgary
    No worries. Appreciate the help.

    This is the type of joint I was thinking of because I figured it would be easier to use than 2 flanges butting up against each other. Because there is better access to the bolt head.

    [​IMG]

    The blue is the bolt which in this case will be a DZUS type with a clip receptor. The orange are the 2 panels for which I've already sanded the fairing side straight and smooth. I am now trying to figure how best to build up the black bit. No idea how the pro's do this. I was thinking of glueing a pre-made piece of cured glass but I wonder about being able to get the cloth of the part to really follow the step down nicely. I imagine that instead of making a more straight edge down it'll be more 45 degree at best which will make the joint a lot wider.
    #18
  19. beechum1

    beechum1 Grimace Soup

    Joined:
    Oct 14, 2007
    Oddometer:
    8,685
    Location:
    Not home in Tijuana
    I used to work for Cheetah Racing Bodies doing R&D/moldmaking for YEARS. what I would do for a joint like that is splash a mold of the edge (on the outside of the part that is smooth already) where the flange is to go and make it about 2 inches above the edge. I used freekote NC770 to coat before laying up, and also on the plug. I'd pull it off, secure it to the back side of the plug and finish appropriately to ensure proper fit of the bottom part of the fairing to the top where the flange is. I probably made 200 molds over the years and this is how I would do EVERY set of race bodywork needed, for CBR's, GSXR's, ZX's, and YZF's.

    The freekote line is VERY expensive for one off's, but in my opinion, THE VERY BEST RELEASE for this type of work. It flashes in seconds and you only have to wait a few minutes between coats, and for plugwork, I'd always use 7 coats. We've gotten away with 3 in some cases, but when dealing with making a production mold, there's not reason to rework the mold at 1-5 hours because we were too lazy to do 10 more minutes of work. I've NEVER had a stuck plug/mold/part when treated properly. I liked the smell too.
    #19
  20. tmotten

    tmotten Lefthand ride Dutchy

    Joined:
    Jun 28, 2006
    Oddometer:
    2,502
    Location:
    Calgary
    I'm not quite getting you there. What do you mean splash 2 inches high?
    #20