SMC repair - not so scary example
pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» Jobs

» wallpapers

Results 1 to 7 of 7
  1. #1
    PWCToday Regular TimeBandit's Avatar
    Join Date
    Jun 2016
    Location
    Tampa
    Posts
    78

    SMC repair - not so scary example

    I see SMC repair questions posted often. I recently had my go at it, so I thought I'd share how things went. Although this demo is on an 05 four-stroke, most SMC hulls will apply.

    If I could summarize things for those of you that are already familiar with fiberglass layup & repair . . . it's the exact same thing – only exception being that epoxy is the resin of choice verses polyester ! Otherwise technique and creativity is the same. That said, epoxy resin does add some changes. 1) it's very fluid, it runs, it creeps. Add the long setup/cure times, and it can be a challenge to keep put in place.

    Test subject : 05 FX HO (SMC hull material) with bow damage, missing edge/lip pieces.


    (pics of damage)

    Ok, so the craft I am salvaging has had some past collision damage up front – minor, and likely a very common issue. The stbd 'lip' or edge where the front bumper and trimming pieces bolt up to is missing a few chunks right where the bolts would go, and therefore won't stay in place. The plan is to knock off the loose stuff, and then rebuild the lip.


    (pic of supplies)

    Ok, so epoxy is the name of the game because epoxies like to stick to other epoxies, and that is the resin type used in the complex SMC sheets. I went with the Total Boat epoxy kit with hardener. It's a 5:1 mix ratio and you have a good 30 min of working time. The other two products are fumed silica (used as a thickening agent) and loose chop-strand glass. The aluminum foil will come into play for this project.



    The best way to knock-off all the loose stuff is with a wire-brush or wire wheel. SAFETY 1st ! SMC has embeded glass fibers - goggles/respirator required.


    (aluminum foil backing form)

    ok, so here's where my foil technique comes in. . . On the 'good' side I press-form this foil against the inside lip. I'm trying to form the backside contour. I also get the thickness of this edge. Next, wax/mold release the foil form, then move it to the damaged side where I affix it in-place. This is going to serve as a backing so I can simply “fill in” the missing lip sections.

    (sorry – didn't get a shot of the foil in-place)

    Ok, since everything is vertical here, & epoxies just love to run & drip, I'll need to create a “putty-like” recipe. Here how :

    Unlike polyester resin (fiberglass), use can only add fillers AFTER you have mix both parts epoxy, so there is going to be a time-factor in thickening step. I kept adding the silica until the epoxy resin just started to stop flowing (if that made sense). Next was to add the chop-strand glass. Keep mixing until we have a “hairy peanut butter” texture. You should be able to put some on the end of a small putty knife and not fall off or run. Ready to apply . . .

    So I simply used a small putty knife to smear this into the missing sections. The foil backing provided support and gauged the correct thickness to build up. In about 3 hours things were setup enough to remove the foil.



    So after a day to cure, I drilled new holes to mount the trimmings. The edge/lip is super soild again. I'd even say its stronger than oem, becuase this edge is actually the two halves of the SMC upper & lower bodies seam - and no, I have no plans of ever separating the two bodies.

    All that's left is to sand/level the correct shape, maybe some paint, then remount the bumper and trimmings.

    Hope this took some of the mystery out of SMC.
    Nano-cell ?? That might be for another thread-topic
    Last edited by TimeBandit; 08-15-2016 at 08:50 PM.
    -- Just another Time-Traveler stuck in real-time forward

  2. #2
    PWCToday Guru alaski's Avatar
    Join Date
    Apr 2015
    Location
    Alaska
    Age
    68
    Posts
    337

    Re: SMC repair - not so scary example

    Wow-great info TB!

  3. #3
    PWCToday.com Is My Home Away From Home WFO Speedracer's Avatar
    Join Date
    Aug 2006
    Location
    Al-ugh-bam-ugh
    Posts
    26,778

    Re: SMC repair - not so scary example

    Actually SMC is polyester based , the reason it can't be repaired with polyester resin is because the SMC material contains mold release which comes to the top anytime you heat it up by sanding or grinding, this is why Epoxy resin is used to repair it.
    Y'all know me, still the same O.G. but I been low-key
    hated on by most these &^$$@s with no cheese, no deals and no G's, no wheels and no keys, no boats, no snowmobiles, and no skis, mad at me cause I can finally afford to provide my family with groceries

    I was 300SXing when 300SXing wasn't cool !

  4. #4
    PWCToday Regular TimeBandit's Avatar
    Join Date
    Jun 2016
    Location
    Tampa
    Posts
    78

    Re: SMC repair - not so scary example

    Well, to balance your assertion, epoxies have equal trouble sticking to mold-release and waxes - aka either resin type would have trouble if there were a wax substance in the substrate. Yet epoxies don't exhibit the wax-skin issues often common with polyesters. I won't split hairs with you, but SMC is more the sandwich manufacturing process of materials and technically several resin formulas can exist. However, I can tell you these non-nano Yamaha hulls are indeed epoxy-based - which is the classic formulation :

    "Glass Fiber Reinforced Sheet Molding Compound (SMC) Epoxy is a subcategory of Epoxy. The additative is added during the manufacturing process. Its elastic modulus ranges from 2000 to 4000 MPa. Its flexural modulus ranges from 1500 to 2500 MPa. Its tensile strength ranges from 20000 to 35000 MPa at break. Its flexural strength ranges from 50000 to 70000 MPa. Its compressive strength ranges from 20000 to 30000 MPa. Its Izod Impact strength ranges from 30 to 40 J/cm. Its elongation at break ranges from 0.5 to 2 %. Its hardness ranges from 55 to 65 Shore B. Its molding pressure ranges from 0.5 to 2 MPa."
    source: http://www.efunda.com/glossary/mater...nd_smc--67.cfm

  5. #5
    PWCToday Regular TimeBandit's Avatar
    Join Date
    Jun 2016
    Location
    Tampa
    Posts
    78

    Re: SMC repair - not so scary example

    Quote Originally Posted by WFO Speedracer View Post
    ... the SMC material contains mold release which comes to the top anytime you heat it up by sanding or grinding, this is why Epoxy resin is used to repair it.
    Remember, my thread topic here is on the older 2005 SMC hulls. Yamaha's newer NanoXcel hulls have waxes impregnated within the substrate to offset resin weight. Sanding, grinding, etc... exposes & spreads the wax making repairs very difficult with high failure rates.

  6. #6
    PWCToday.com Is My Home Away From Home don37725's Avatar
    Join Date
    Jan 2006
    Location
    Smoky Mountains TN
    Age
    76
    Posts
    3,233

    Re: SMC repair - not so scary example

    Its Izod Impact strength ranges from 30 to 40 J/cm.
    I did not know that!

    ***
    Democracy is two wolves and a lamb deciding what to have for dinner***
    *******************Liberty is a well-armed lamb.*****************

    **********Lotteries are created by those who understand math**********
    ***************to take advantage of those who do not****************

    ***************As government expands, liberty contracts**************

  7. #7
    PWCToday Newbie
    Join Date
    Apr 2017
    Location
    Texas
    Posts
    5

    Re: SMC repair - not so scary example

    What about using marin tex on Nano? It's worked well for me on SMC.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBadvanced CMPS v4.2.0