Results 1 to 18 of 18

Thread: Sikaflex 291, how to apply over large area to bond plywood

  1. #1
    Join Date
    Aug 2009
    Location
    New Hampshire
    Posts
    1,805

    Default Sikaflex 291, how to apply over large area to bond plywood

    Bonding together two pieces of plywood. Is there a pattern for the bead during application? UP/DOWN every 2 inches? Three inches? Do I spread it around with a squeegee or leave it in bead form?

    I can do epoxy all day, this stuff I am new to.

  2. #2
    Join Date
    Oct 2000
    Location
    Padanaram, MA USA
    Posts
    10,059

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Why not epoxy or even Titebond III?

  3. #3
    Join Date
    Feb 2017
    Location
    Seattle, W.A., U.S.A
    Posts
    241

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Don't use it. It's terrible for that application. Instead use epoxy or a panel adhesive. I have had too repair large areas that used sika as an adhesive in that manner and it had been an endless delight of new and creative failures. The volume the sika occupies creates voids, it's much the same issue as 5200, only easier to demo when it is necessary. Also the per volume price of sika huge compared to nearly any other method.

    Nicholas

  4. #4
    Join Date
    Jun 2003
    Location
    Central Coast, Ca
    Posts
    31,949

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Sika makes a very durable bond on plywood. When making a repair I have found that removing and replacing a panel put on with Sika is a big job basically splitting and finally planing/scraping off the old plywood panel. With an epoxy joined panel you can often just break the joint apart with a chisel.
    From a time standpoint, I cringe at the challenge of replacing a large Sika join, it is a rather permanent solution, more so than epoxy (I like it for that reason) Be careful of "pillowing" when fastening or clamping.
    To apply it I have used plastic disposable notched tile adhesive spreaders (fine) and smoothed out the adhesive with disposable squeegee or a putty knife.

  5. #5
    Join Date
    Aug 2009
    Location
    New Hampshire
    Posts
    1,805

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    I'm building a LYS. It's specified in the plans to build the boat with Sika 291. I built my first Brockway with a mix of epoxy and PL Premium and this time I'm building Walt's and I want to try a new product/method for my own experience. I'm not interested in mixing and thickening miles of epoxy in the summertime anymore and it was cheaper than the equivalent epoxy from my calcs.

    Thank you Canoeyawl, will do.

  6. #6
    Join Date
    Jan 2000
    Location
    Portland, Maine
    Posts
    21,677

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Notched trowel. Like the tile guys use. You’ll get a precise thickness of Sika that way. And complete coverage.

  7. #7
    Join Date
    Nov 2006
    Posts
    9,338

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Quote Originally Posted by StevenBauer View Post
    Notched trowel. Like the tile guys use. You’ll get a precise thickness of Sika that way. And complete coverage.

    Here's what an eighth inch triangular notched trowel produces...



  8. #8
    Join Date
    Aug 2009
    Location
    New Hampshire
    Posts
    1,805

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Thank you Steve and Jim. Exactly what I was looking for. I had a hard time searching online for good technique. Beautiful work, Jim.

  9. #9
    Join Date
    Nov 2006
    Posts
    9,338

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Quote Originally Posted by callsign222 View Post
    Thank you Steve and Jim. Exactly what I was looking for. I had a hard time searching online for good technique. Beautiful work, Jim.
    Don't forget that you need to make sure the panels are pulled together. Clamps around the edge, weight in the center. Better than weights, if you can, are small temporary bolts. Remove them after everything's set up and fill the holes with epoxy. When you clamp, make sure air can escape, plan your clamping pattern with this in mind.

    Jim

  10. #10
    Join Date
    Jan 2000
    Location
    Portland, Maine
    Posts
    21,677

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    A big pile of lead ingots would come in handy here.

  11. #11
    Join Date
    Aug 2009
    Location
    New Hampshire
    Posts
    1,805

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Everything is screwed down and the screws remain. I'll have everything screwed down dry at first and then work from one side to the other, like epoxy work.

  12. #12
    Join Date
    Nov 2006
    Posts
    9,338

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Quote Originally Posted by callsign222 View Post
    Everything is screwed down and the screws remain.

    Depending on the thickness of the plywood, I like to fasten the whole thing together in a grid pattern. If your rows of screws are, say, a foot apart, as might be the case with deck beams, then there will need to be some additional clamping between. For instance, no screw more than six inches from the next.

    Which is the reason for the removeable bolts.

  13. #13
    Join Date
    Jan 2011
    Location
    Norwalk CT
    Posts
    1,955

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    You can screw through big ass fender washers until everything sets and then lose the washers. Dry fitting and pre drilling is a smart approach.

  14. #14
    Join Date
    Jun 2010
    Location
    PNW, an island west of Seattle
    Posts
    2,918

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Sikaflex cures with a reaction with moisture. So if applied to a large surface, where will the moisture come from? On a small surface or a built up bead, the cure can begin at the edge and work into the middle quickly. But on a large surface that could take quite a bit of time. But I don't know... just a lot of conjecture by me. But backed with personal experience of having poly glue fail on a project because of a poor cure. Gorilla Glue, for instance, recommends that one surface be slightly moistened before assembly.

    Jeff

  15. #15
    Join Date
    Sep 1999
    Location
    Armada, MI, USA
    Posts
    358

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    I helped my son laminate some thick bench tops using Titebond. Like Steve said, a notched trowel does a great job. We started out with a rather course trowel, maybe 1/8" notches, and had glue gushing out everywhere when we started clamping and weighting it. We changed to finer notches until we ended up with the finest notched trowel we could find. It still pushed some glue out the perimeter, but not nearly so much.
    We then switched to vacuum bagging instead of weighting and clamping. Highly recommended, and the equipment and supplies cost a lot less than I thought they might.
    Here's a question for someone, anyone:
    I believe Titebond is an air-dryng adhesive. The vacuum gage eventually showed a rather impressive level of vacuum. I became concerned that the glue wouldn't harden. But it did. Just like normal. How did that happen?

  16. #16
    Join Date
    Nov 2006
    Posts
    9,338

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Quote Originally Posted by Gordon Bartlett View Post
    How did that happen?

    There's a small amount of air in the wood itself. Moisture as well, even in kiln dried, because any wood will absorb moisture from the atmosphere given the chance. The wood might feel dry but the glue or adhesive is going to have a helluva time staying liquid for long.


    Glue it up and walk away. Leave it sit for a week if you can. I never do really, but I should.


    Jim

  17. #17
    Join Date
    May 2015
    Location
    Oakland, California
    Posts
    246

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    If you decide to use Sika 291 buy "Sika 291 LOT" LOT= long open time. It's necessary to use the LOT on large areas. I've often bonded ply with Sika 291 LOT and if you can get enough clamping pressure it works fine. I coat both side of the ply - one a skim coat & the other 1/8 V notched trowel & use screws if it's too big to use screw clamps. Weights work ok on small pieces & I 1/8" V trowel both sides but you're never sure...Moe

  18. #18
    Join Date
    Mar 2019
    Location
    Rushworth, Australia
    Posts
    808

    Default Re: Sikaflex 291, how to apply over large area to bond plywood

    Quote Originally Posted by MoePorter View Post
    If you decide to use Sika 291 buy "Sika 291 LOT" LOT= long open time. It's necessary to use the LOT on large areas. I've often bonded ply with Sika 291 LOT and if you can get enough clamping pressure it works fine. I coat both side of the ply - one a skim coat & the other 1/8 V notched trowel & use screws if it's too big to use screw clamps. Weights work ok on small pieces & I 1/8" V trowel both sides but you're never sure...Moe
    I second that, 291 skins over in about 30 min(dependant on atmospheric condition) There are also primers available from Sika and the best thing you could do is ring their advice line. That goes for any product actually.
    Last edited by Andrew Donald; 07-01-2021 at 10:43 PM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •