beginner - scarfing

I read the instructions and watched the video.  I am building a Chesapeake 16LT from a kit.  The manual says that you don't want the blunt end of the scarf to potrude above the panel's surface. It also says that they should overlap about 1 1/4".

 I noticed that if I overlap them 1 1/4" then the end potrudes above the panel's surface. If I pulled them back then they overlap about 1 1/8" or less.

 How do I reconcile this?  What's the minimum overlap I want and what is the most I would want the scarf to potrude obove the pane's surface? 


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RE: beginner - scarfing

Hector,

The correct amount of overlap has been determined by the bevels already cut in the panels. so don't worry about the 1 1/4" - 1 1/8" business.  Do your very best to keep the total thinkness thru the scarf the same as the individual panels.  This is a bit fussy, but it's important to spend some time on it.  If one panel protrudes above the other then when you sand it all out you will sand thru the outer layer of plywood and be left with a big black spot where the second layer shows.  If your lap is short you will have a pocket that you will need to fill and then you will be looking at a big sploch of filler.  Lap teh panels at what loos right and then lay a straight edge across the joint.  It should lie flush on both panels with no gaps underneath.  If, in the end, you are going to paint, neither of these are big issues, but if you plan to varnish, take your time and do it right.

 

Just one more caution:  Be sure to stack the port and starboard panels when scarfing so you end up with good mirror images of the fully assembled panels.

Good luck and happy building

Paul

RE: beginner - scarfing

Thanks,

  I will move ahead by measuring to make sure the thickness of the scarf is the same as the rest of the panels.  But there will be a small pocket since the end of the scarf is blunt. I don't expect this to be a problem since it is very shallow and will probably disappear with sanding.

Hector 

RE: beginner - scarfing

Hector --

It won't disappear when sanding -- not unless you sand a whole lot of wood away (and get the problem Paul mentions, plus a significant depression in the wood).  The bevel should end in a feather edege, not a blunt one. 

Stack all the pieces being beveled so that the beveled edges are up (being mindful of Paul's warning about mirrored sides) and the panels are staggered by the length of the bevels. The bevels should form a nice, smooth ramp which serves two very important functions: 1) you make sure the bevels are all cut at the same angle, and 2) the bevels end in feathered edges.  It helps to put a piece of scrap under the bottom piece while cutting the scarfs, as you can then carry the bevel into the scrap and get a nice feathered edge on that last piece. 

At least, that's how I did it, and it worked rather well.

  -- Jim

RE: beginner - scarfing

Hector,

The kits come with a "blunt" scarf because those feather-edged ones you can make in the shop are going to get damaged in shipping. I've built a few of them from CLC kits and the blunt scarfs are no problem. The most important thing is to have the thickness at the scarf the same as the plywood and this was pointed out earlier. If you start messing with the scarfs, trying to make them feather-edged, and you haven't cut scarfs before you're more than likely to screw them up. Trimming them will reduce the length of the finished panels if you're not careful. There won't be that much of a gap when you glue them up and it'll be filled with epoxy/cellofill mix. Sand it smooth and after fiberglass, epoxy and varnish you won't be able to feel it.

George K.

RE: beginner - scarfing

 Thanks for all the help. I have just one more question. This will be my first time using epoxy as well and I was wondering how much to mix to glue the scarfs.

 I don't expect that I will need that much. Maybe 1 pump of each.  I still need to follow the instructions for priming the pumps.  As far as the Cell-o-fill is concerned I will add until I get a mustard consistency as I have read.

Hector 

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