Modifying epoxy to secure a machine bolt.

Discussion in 'Wooden Boat Building and Restoration' started by missinginaction, Jul 14, 2012.

  1. missinginaction
    Joined: Aug 2007
    Posts: 1,054
    Likes: 225, Points: 63, Legacy Rep: 512
    Location: New York

    missinginaction Senior Member

    I'm plugging along and am now installing the flybridge on my 73 Silverton. I'm using epoxy to fill oversize holes and then boring smaller holes through the middle creating an epoxy "bushing" as many here have suggested.

    So far so good.

    There are a couple of railing stanchions that fall over a heavy beam that supports the roof of my cabin along the cabin sides. These beams are too thick to drill through. I don't want to use a lag bolt though as I don't trust them.

    I'd like to use a Forstner bit and drill a 1/2" hole down about 2 1/2 inches. I'd then fill this hole with epoxy and when the epoxy sets, drill it out and tap for a 1/4" - 20 machine bolt.

    The question... Should I use "neat" epoxy or modify the resin with some silica (or other substance) in order to improve it's ability to hold the machine bolt?

    Thanks,

    MIA
     
  2. sean-nós
    Joined: May 2010
    Posts: 157
    Likes: 30, Points: 0, Legacy Rep: 392
    Location: Dublin,Ireland

    sean-nós Senior Member

    I would add 404 high density filler or 406 colloidal filler, if it's a big hole add some chopped strands of glass also wet out the edges of the hole with neat epoxy first. Remember with the high density filler it's harder to sand so get it as smooth as you can or put a pice of clean plastic over it till it sets.
     
  3. pauloman
    Joined: Jun 2010
    Posts: 268
    Likes: 10, Points: 18, Legacy Rep: 151
    Location: New Hampshire

    pauloman Epoxy Vendor

    fill the holes with an mixture of epoxy and sand (epoxy cement if you will) then grease the bolds and place into the epoxy sand mixture. when the epoxy gets hard you can unscrew the bolts from their perfectly threaded 'rock' filled holes.

    paul oman
    progressive epoxy polymers inc.
     
  4. tunnels

    tunnels Previous Member

    Also add a little micro fibfes helps to hold things together !!:D
     
  5. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 484, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I'm a bit surprised at Paul's comment of sand, it's not what I would do in a wooden beam. I would consider it if lagging to a garage floor, but not here.

    Silica to control viscosity, milled fibers and 403 (cotton flock) and/or 404 (calcium metasilicate) to bulk it up. I'd drill the flat bottom hole, just as Bart has mentioned and fill with this mixture, flush. While still green, but hard, drill out just a little over the thread diameter and slightly deeper then the bolt is long, then insert the bolt, heavily coated with a similar mixture, just a bit runny. If the bolt is intended to remain well stuck and removed only very occasionally (every five to ten years or so), is should be clean, but unwaxed or greased. If you do plan of removing this bolt regularly, then coat the bolt with regular paste wax, like that used on your better half car. Coat the bolt with wax (3 coats) let it dry good, then insert in wet goo. This will permit it to be removed regularly. To remove the unwaxed bolt, just a little heat is needed. If it's a hex head, take a torch to a socket and extension, until and slide it over the bolt head. In a minute or two, you can twist it out, without harm. If a slot of cross point, torch the tip of a screw driver, insert into the head and wait until it heats up before turning.
     
  6. missinginaction
    Joined: Aug 2007
    Posts: 1,054
    Likes: 225, Points: 63, Legacy Rep: 512
    Location: New York

    missinginaction Senior Member

    Thanks for the replies. I see that the drill and tap method is not the preferred one. I'll be able to install all the rail bases with through bolts except one port and one starboard so getting the alignment straight should be pretty easy. I'll have to pick up those additives as all I've been using is silica, quartz spheres and plastic minifibers on occasion. BTW has anyone any thoughts on using aluminum powder as a strengthener?

    Thanks again,

    MIA (Bart)
     
  7. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 484, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Aluminum powder is typically used to improve heat resistance, not strength. Aluminum isn't very strong anyway.

    You can tap the epoxy too, but it's better if you cast the threads, instead of cut them.
     
  8. pauloman
    Joined: Jun 2010
    Posts: 268
    Likes: 10, Points: 18, Legacy Rep: 151
    Location: New Hampshire

    pauloman Epoxy Vendor

    the sand acts as a heat sink limiting the epoxy exotherm kick. Also makes the epoxy - rock hard -. You can pretty much hit and epoxy/sand mixture with a sledge hammer and nothing happens. It is the common fix for fixiing runways, anchoring cables in dry conditions and underwater (with an underwater epoxy).

    The epoxy part of the mix will bond as well to wood as any other surface and with the sand in it, you will never crack, compress, (or maybe even chip) the mixture.

    so the key features of sand epoxy is 1) heatsink, 2) compression strength.

    Give it a try, it's the closest thing to imbedding into granite! - plus it increases the volume of the epoxy by about 85%.

    give it a test (all of you) let cure for a week or so and then 'attack' it.

    paul
    progressive epoxy
     
  9. tunnels

    tunnels Previous Member

  10. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 484, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I've used sand before Paul and a few other ground stones (pulverized granite, limestone, quartz, etc.) as well. I've just never tested it on wood with a metal fastener buried in it, nor would I have thought to try.
     
  11. tunnels

    tunnels Previous Member

    I cant find it just yet but there are simular type fitting used in the furnature trade theses days as well and the one i saw a while back could be excilent to bury and wrap in glass and resin . was really rough on the outside and should get really good grip !! :?:
     
  12. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 484, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    My concern isn't compressive strength, but pull out resistance, which is what I think is called for here. A blind nut will do, but it's a sin to have to drill all the way through a beam for this. The bonded bolt trick works well, but I suppose you could bond in about anything with some threads on it if you want. I don't suspect the fly bridge will be removed very often, so a I might consider casting a stud in the beam, maybe just a bolt and washer, so the fly bridge can be lowered over it and dogged down with a lock nut and washer. You'd be able to remove it, you wouldn't have drill through the whole beam and it would have good pull out strength.
     
  13. bntii
    Joined: Jun 2006
    Posts: 731
    Likes: 97, Points: 28, Legacy Rep: 1324
    Location: MD

    bntii Senior Member

    Keep a weather eye to future repairs when you select materials. A 1/4-20 will break off if tapped into hardwood before tearing out.
    Don't over do the fill material used or you or another will be fighting it when the part next needs service.

    MissImagine- just use West 404 or Pars custom mix. You can either set the bolt in wet or cut threads after cure.

    I prefer to drill and tap as I can run along the rail in one go doing all the bedding work with sealant, while the fasteners can be snugged down on a bedding film in the same manner on all sites- whether drilled through or tapped into fill.

    Mind in your installation that the plugs are covered by the base- holes in a timber filled with epoxy will not protect the wood if the joint is exposed.
     
  14. LP
    Joined: Jul 2005
    Posts: 1,414
    Likes: 58, Points: 58, Legacy Rep: 584
    Location: 26 36.9 N, 82 07.3 W

    LP Flying Boatman

    My concern would be that sand would impede future maintenance if it was needed in that area. I think I would choose to use materials that would not dull my tools in the future.
     

  15. missinginaction
    Joined: Aug 2007
    Posts: 1,054
    Likes: 225, Points: 63, Legacy Rep: 512
    Location: New York

    missinginaction Senior Member

    Thanks for all the feedback gentlemen. I don't ever expect to remove the flying bridge or the rails so I'm going to use West 404 with my System Three epoxy as System Three doesn't appear to market a product comparable to 404. My goal is eliminate (or at least minimize) the chances for the hardware to pull loose and equally to keep water out of the cabin roof. It's a little more tedious to do the job right but I've come this far and don't want to cut any corners.

    Thanks again,

    MIA
     
Loading...
Similar Threads
  1. weedeater64
    Replies:
    15
    Views:
    2,676
  2. manos mit
    Replies:
    21
    Views:
    5,052
  3. tonyg99
    Replies:
    6
    Views:
    2,218
  4. flyingvranch
    Replies:
    10
    Views:
    3,925
  5. RMMager
    Replies:
    14
    Views:
    3,414
  6. aaronhl
    Replies:
    11
    Views:
    3,485
  7. Skookum
    Replies:
    14
    Views:
    2,938
  8. abosely
    Replies:
    44
    Views:
    7,425
  9. Pete Cross
    Replies:
    0
    Views:
    1,301
  10. NoEyeDeer
    Replies:
    18
    Views:
    3,874
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.