Mast lamination

[Memphis Mike]

I've got most of my mast lumber scarfed into twenty foot sections for my Windsprint. They will later be cut to sixteen feet after lamination.

Should the lumber be coated with CPES or anything before I glue it up?

Is it imperative that I use epoxy in the process or can I use PL Premium? I used PL Premium in the scarfs.

What about staggering the scarfs? I'm a little bit befuddled on that principle.

Thanks in advance for any replies.

[John Teetsel]

Couple of questions Mike.

How many pieces will be used to make the mast? Are you going 8 stave birdsmouth or just a couple of pieces glued together?

Coating w/ CPES isn't necessary. In fact it may impair the adhesion of the glue unless you go with epoxy for the glue up. Regardless, I'd skip it.

Epoxy vs PL is your call. I haven't used PL but I've seen it after application and it looks messy which means it's good for a "loose" joint. I'm an epoxy guy, but that's just my preference.

On the stagger business, you want to make sure the weak spots (joints) are not adjacent to each other. This is a ROUGH idea of what you're aiming for. No joints in line.

__________________________________________________

________________________|_________________________

_______|______________________________|___________

_______________|_____________________________|____

______________________________|___________________

Hope that helps.

[Barry Pyeatt]

Mike,

If I recall correctly you are laying up a birdsmouth mast. I would encourage you to use epoxy rather than PL Adhesive for this process and coat the inner side of each stave with epoxy as you are laying it up, that way it is all done on the inside.

Now then, question about your mast and its structure. Have you planned on blocking any attachment points on the mast. That is installing a plug on the interior so that the mast is essentially solid at that point or any point that you will be thru bolting anything to it? Also at the top and bottom of the mast itself so that that portion doesn't have any possibility of collapsing under stress.

Might just think about that before you assemble it. Easy enough to cut some plugs and install them in the appropriate places as you build it, harder than all get out to do it afterwards. I would also recommend that you consider the epoxy on the inside for protection rather than trying to glue up a bunch of Cetal coated staves. If you want to use Cetal use it on the outside of the mast for easier maintenance.

Try to stagger any joints with shorter pieces as much as possible and none of them adjacent to one another to maintian as much integrity as possible in the overall length. In that long a mast try to keep them spread out as far as possible based upon the length of the pieces. Also try to avoid having more than one joint on any cross section within about a foot of each other. You will have a much better structure that way.

[Charlie Jones]

It's actually really simple to add blocking inside a birds mouth mast AFTER part of it is glued up. When I built the 22 foot mast for the Windjammer out in Florida I didn't glue the opposing mouths. I hgad tape inside so no glue cuold stick, just in case. Then I popped the two resulting halves apart, cut and fitted the blocking and then glued the final joints.

Definitely use epoxy for building a birds mouth spar. By the way- this one was number 7 for me to build

Here's a pic of the two halves after I popped them apart.

[Craig]

Slick Cj. That ay you can insert the plugs and lay the lighting wires in the mast at the same time. Great tip

[Memphis Mike]

Thanks for the replies guys. It's going to be a solid spar. This is my first mast project so I'm a little intimidated by the birdsmouth type. It seems like an awful lot of trouble.

I think I'll use epoxy on this rather than the PL.