PDA

View Full Version : First Scarf



PAComet
04-13-2009, 07:15 AM
Hi all-

I'm scarfing a 1x6 of wrc with a step. Got the 8/1 dimensions, but it is not going to be a "pristine" fit. I've heard epoxy adhension for joints get "starved," by too tight a squeeze, and through epoxy soaking into the wood.
Question: would 5200 be a better bond, after cpes-ing? It would avoid the two epoxy problems above, right?
Second query: should I reinforce or draw together the scarf with screws?

Thanks

DGentry
04-13-2009, 07:32 AM
WRC scarfs well with epoxy. Just paint the joints, first, with unthickened epoxy before you add the thickened epoxy glue. Don't overclamp the joint (there should definitely be squeeze out, though) and your scarph will be stronger than the wood. No need for screws, esp as you have a step, which will keep the joint from sliding apart under pressure.
The thickened epoxy will fill any small voids in your non-pristine joint, but of course, you want it to dry fit as close as possible.

Good luck!
Dave Gentry

ishmael
04-13-2009, 07:52 AM
What Dave said. I'll just reemphasize DON'T OVER CLAMP. You obviously want your faces to line up, but that's about it. Number one cause of failure in epoxy scarfs is a starved joint caused by squeezing all the googe out.

Practice on a couple of pieces of scraps is never a bad idea, until you've got the hang of it.

Good luck. You'll do fine.

Ray Hurley
04-18-2009, 10:54 AM
BHOFM,

I'd like a copy of the plans for your scarfing set-up. Thanks.

Canoeyawl
04-18-2009, 11:27 AM
Why use a step?

DLW
04-18-2009, 01:54 PM
This is the finished mast, can you find the scarf??



Not to be a jerk, but covering up a scarf with paint etc is not exactly a huge accomplishment. If you could see the scarf through a red paint like you have, that would be bad news bears.

BobW
04-18-2009, 06:59 PM
BHOFM - thanks for sharing the plans/details of that scarfing jig.

That red paint is Rustoleum? Looks pretty good... whether there is a scarf under there or not!

Bob

CundysHarbor
04-19-2009, 01:46 PM
I've been making stepped scarfs 12 inches wide in 4 mm occume. My jig has the stock stationary and the router moving across the workpiece. The advantages of the step are fixed alignment of the pieces and minimum epoxy showing in work finished bright. To keep the plywood solidly down on the fixture, I used a vacuum produced by the shop vac. It worked very well. I have taken pictures of the result but they are really fuzzy. I guess if the camera is close enough to catch detail, it becomes out of focus.
Dave

pcford
04-19-2009, 02:26 PM
Why use a step?

If the scarf is going to be finished bright, I prefer a step scarf. If you don't use a step scarf...the glue line is stretched out and uneven as it is feathered. Also, it will not stain well.

On a 1/4 scarf, I did a step of about 1/32 or so...can't remember truth be told.

Scarfs cut freehand with LN block planes.

BobW
04-19-2009, 07:50 PM
BHOFM -

What bit do you use to cut the scarfs with your jig?

Bob

BobW
04-19-2009, 08:21 PM
Thanks.

Bob

Bruce Hooke
04-19-2009, 10:40 PM
Not being an epoxy person, I use Titebond III for every thing water related.

For the record, I just think it is worth noting that I don't think using Titebond III in marine applications is what would be considered "standard practice." I know various people seem to have done it successfully. I am not suggesting that it should or should not be done, just noting that to the best of my knowledge there is not general agreement on whether Titebond III should be used in marine applications. Of course a lot also depends on the particular application as well -- a glue joint in a mast is a very different matter from, say, a laminated keel.

Titebond III is also, to the best of my knowledge, not as good at filling gaps as thickened epoxy.

Longbow
04-20-2009, 07:15 AM
How much clamping is too much? The pictures above don't seem to show a band of epoxy between the two pieces and those that I've seen of plywood seem to show one continuous ply accross the scarf with no epoxy apparent. So the epoxy band in the joint must be very thin. I scarfed two 4 X 8 panels this weekend. Since it was my first time I decided to err on the side of caution and used 4 oz. of T-88 along the 4" wide scarf. I use screws to secure the ply to a piece of scrap about every 8" and a weighted 2 x4 accross the top to press the joint down. There was plenty of squeeze out, but the panels seem solid. I can lift the 16' long panel at the seam without it breaking. Is the only way to tell if it's truly solid to use an offcut and see if the wood gives before the joint?

BobW
06-16-2009, 07:58 PM
I wanted to say, "Thank you" to BHOFM for sharing the photos and link to his scarf cutting jig.

Using that information as a guide for putting this together:

http://farm4.static.flickr.com/3160/3633539313_ca72f2f901_o.jpg

It is narrower and uses a laminate trimmer for power but seems to work ok. My first test joint has been cut and glued up. The pieces mated pretty well on the dry fit.

Thank you.

Bob

RodB
06-16-2009, 10:54 PM
BHOFM

I sure would like the link to that scarfing jig...

Thanks...

RodB

BobW
06-16-2009, 11:57 PM
I think this is going to work just fine...:)

This is my test joint. It isn't perfect but it is pretty darn good for the first attempt. Well, at least I think it is.

http://farm3.static.flickr.com/2481/3634065799_76f4f54c4c_o.jpg

Now I need to work on improving the quality of my pics.

Thanks again.

Bob

Candyfloss
06-17-2009, 03:59 AM
Thanks guys, that looks absolutely terrific & just what I need. When I get sober I'll have a closer look at it, but meanwhile, how do I modify it to cut gains in lapstrake planks, & while we are about it, how do I cut the bevels in the edges of lapstrake planks with a router, or a power plane, or anything, using the adjacent ribband as a guide, a la Tom Hall? Doing it with a hand plane is wrecking my no-hard-physical-work ethic. Please?:)

Tylerdurden
06-17-2009, 05:21 AM
When doing plywood I still use the West system jig for the circular saw. I have used the router set up but for quick easy and accurate on ply nothing beats the circular saw setup. I use epoxy and have not had a failure in 15 years.
http://www.westsystem.com/ss/assets/products/_resampled/ResizedImage400358-scarfer-reflection.gif

AndreasJordahlRhude
06-18-2009, 07:32 AM
12:1 machine cut scarf in nominal 2" solid lumber, circa 1984.

http://i232.photobucket.com/albums/ee189/ThompsonBoat/SlopeScarf01.jpg

Andreas

hightop
06-18-2009, 08:37 AM
http://img524.imageshack.us/img524/6452/scarfinggig.jpg

Thanks for posting that! I'm going to make a copy this weekend.