deck beam without screws?

Has anyone installed the deck beam without screwing into the hull to do so?  I'm wondering if a tight pressure fit is enough to hold it while the epoxy is kicking.  I guess the main issue is whether there is enough strength in the epoxy alone to hold all the latent tension caused by the deck camber.  

 I'm planning on installing it either Sunday or Monday, so any advice would be great. 

 Thanks,

~Chris 


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RE: deck beam without screws?

Chris,

I did, yes and yes :-)

It was on my wife's CH16LT which is still going strong after 3 years. I used woodflour alone for the thickening agent. The main thing to make sure of is that the beam is immobilized (might need to use tape in addition to the hull compression since epoxy is such a good lubricant at first).

In general, a properly done epoxy bond is stronger than metal fasteners through wood. The force is distributed more smoothly over more surface area, the wood fibers are not cut and you don't have metal screws with their sharp threads in the center of the joint, expanding and contracting at different rates than the wood.

Have fun,

Laszlo

 

 

RE: deck beam without screws?

Thanks Laszlo, that's exactly what I was thinking.  Any fastener screwed into end-grain wood (especially ply) is inherently pretty weak.  Plus, I'm going through the trouble of glassing in the studs for the foot braces, so why would I want to screw through the hull for deck beams :-).  

 After five (very thin) coats of epoxy, I have the weave filled on much of the hull.  I'm thinking one more coat today should do it, then I'll be flipping her over to work on the deck beam and sheer clamps this week.  I'm hoping to have the deck on by the end of next weekend.  I ended up adding glass tape to the bow and stern ends of the keel, and will probably coat the keel panels with graphite before I varnish.  Clear packing tape on either side of the keel allowed me to cut off the selvedge after the resin cured, and a little sanding of the edge allowed a smooth transition into the 6oz glass.  

Still hoping for an end of August splash...

 

~Chris  

RE: deck beam without screws?

Sounds good, Chris. You leaving off the deck nails, too? I did and never missed them.

Laszlo

 

RE: deck beam without screws?

I was thinking about it.  I really don't like the idea of fasteners entombed in epoxy (plus there's something about pounding nails into the deck of a kayak that rubs me the wrong way!).  How did you hold down the deck while it was curing?  Straps and packing tape?  Did you do the stern one day and the bow the next, or the whole shebang all at once?

 ~Chris    

RE: deck beam without screws?

This is an interesting posting to me because I am ready for installing the deck. I am debating ordering the brass ring nails and here I see that laslo has mentioned not using nails at all. I am excited to read more on this.  My only concern is that those ring nails have a great grip to them and would add some security to the scary idea of the deck delaminating from the sheer clamps had they not been there. 

RE: deck beam without screws?

Yes, lots of straps - 17 or so, if I recall correctly. I used nylon ratchet straps for the main grip and nylon cam-cleat straps in between for additional support. The ratchets were good in that they let me make incremental increases in the strap tension.

I did a dry fit attachment first just to work out how many straps and to get some practice in putting it all together while not rushed by curing epoxy. Once I got it the way I liked it, I let it sit for 3 days to let the decks get used to their new shape. Before I removed the dry decks, I also drilled eight 1/4" holes through the decks and into the sheer clamps at the "corners". Then once the decks were off, I glued dowels into the holes. These served to align the decks during final assembly, after wihich they were cut off and sanded flush with the deck.

As far as strength goes, the epoxy joint is much stronger than the nails are. The nails actually weaken the joint, acting as stress concentrators. Even with the nails, though, the joint is plenty strong so no one should worry about their boats falling apart.

Finally, letting the deck glass overlap onto the hull for 2 inches or more provides a large retaing force in addition to the epoxy glue joint. That deck isn't going anywhere.

Laszlo

 

RE: deck beam without screws?

Thanks Laszlo.  I was thinking a combination of ratchet straps, cam straps, and a weave of tie-down lines would work pretty well.  I'm glad you mentioned the dowels.  I think I'll make mahogany bungs from some scrap stock I have, that way the colors will match pretty well.  So, I would assume you cut the butt-joint at the cockpit during the dry fit?  Makes the most sense since all the close alignment is taking place during that stage. 

 I'm hoping to be decking next week, as I'm still working on filling the weave of the glass, need to install the deck beam and do a bit of planing.  A wise man once said that a boat decides the pace at which it gets built.  So true...   

RE: deck beam without screws?

Laslo,  Thanks for the great description!  I really feel confident that I can do this now.  I am off to go buy some straps now!

One more question,  If I am understanding correctly, I will  install the deck and still need to trim the deck and plane the edges since I am building from plans right?  I am assuming that I would not trim the deck to size prior to the application of epoxy and going through those steps.  The reason I ask is because you mention the dowels for allignment and if the deck is not precut you would not need so much in place for alligment right?  Sorry for the questions, I am thinking too much.  Thanks in advance! 

 

sail114 - "A wise man once said that a boat decides the pase at which it gets built. So true..."

Yes, I agree, So very true!

RE: deck beam without screws?

Danno,

Plans or kit, you always need to trim and plane. The decks in the kits are closer to the correct size, but still cut large since the final shape varies from boat to boat.

The dowels are there to easily get you back to the dry fit positions. They also keep you from accidently slipping while gluing, when the epoxy is acting as a lubricant. Builders who use nails don't have the slipping issue (one of the reasons in favor of using nails). The fit over the dowels also makes sure that you get the same camber you had while dry fitting. So plans or kit, I'd use them.

Chris,

Yes, I cut the butt joints while dry fitting. That's another reason to use the dowels - to make the butt joints join tightly again while gluing. Also, there's no reason not to attach the deck before filling the weave, if you'd rather do that.

Finally, check out my WD12 assmbly pages for a different way to build up the coaming that results in a smoother joint with less sanding (again, not my original idea). Click on the picture to get there.

 

 

RE: deck beam without screws?

Laslo,

Once again, thank you for such a good description. You have made my deck install much more simple and I will probably be using the idea for the coaming too!  Thanks, I can' wait to post pictures when its done.

Dan

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