Scarrfing question CS17#272

[Mainewinds]

So, I just got my plans recently, and I've been reading them over and starting to formulate my plan of attack.  Which is the preferred method of joining the hull panels, butt joints or scarrfing?  Scarrfing seems like it would create a much cleaner joint.  I guess my question is do you scarf the plywood sheets first and then do your layout?  Thanks in advance for the info.

Jake

[Ray Frechette Jr]

Butt joining is plenty strong enough.  But>>>  In some environmental temps humoidtity whatever...  The seam will telegraph through the paint like a sore thumb.

Scarf Joins do not do this in my experience.

I cut out the panels and then scarf them.

It involves layinh out the panel overlapping correctly to loft them out,  Cut them and then scarf them.

Or even better , order the Kit from Graham withthe nifty step scarfs cut out for you to perfection....

[Mainewinds]

Ray, thanks for the reply.  Yeah I was looking at the way Grahams kit goes together, and it looks pretty cool.  This boat however, I'm committed to building from scratch.

Would it make sense to scarf the whole width of the full sheet of plywood, dry fit the scarfs, tack everything down and then do the layout and cut?  Just wondering if it's awkward to spring a batten over the overlapped sheets of plywood and mark out the hull panel shapes accuratley.  Any thoughts are greatly appreciated.

Thanks,

Jake

[Ray Frechette Jr]

I overlap the sheets the appropriate amount, and strike witness marks on the sheet.  IE: pencil in where the edge of the sheet lies.

I also screw the sheets down into substrate while I spring the batten and draw the edges of the panels.

You can of course scarf the 4 x 8 sheets of ply  together first and then draw the panels and cut them out, but I find it much handier to have smaller individual sheets to worlk with.

[PAR]

The best and most accurate way would be to rough the shapes onto over lapping plywood, leaving a couple of inches around the perimeter as a fudge factor, then join the panels. The joined panels can be then finally marked for the actual cut line.

A butt joint is much faster and easier to make then a scarf and doesn't eat into the length of the stock either. Both joints are stronger then necessary and taped seam building methods require enough fairing to make any differences easily hidden under fairing compound.

[John Burritt]

If you scarf the sheets together before doing the panel layouts/cuts, you don't have to worry about getting the scarfs accurately aligned.

[Mainewinds]

Thanks to everyone who responded for the guidance.  It is very helpful.  The kayak in my profile pic I built from a kit withy pre scarrfed panels, so this will be my first attempt at scarrfing, and I want to make sure I get it right.  There will be plenty of practice on scrap before I get after the marine ply.

I'm thinking about purchasing the John Henry scarrfing attatchment for the Makita hand planer.  Does anyone have any experience with this set up?

[Ray Frechette Jr]

A butt joint is much faster and easier to make then a scarf and doesn't eat into the length of the stock either. Both joints are stronger then necessary and taped seam building methods require enough fairing to make any differences easily hidden under fairing compound.

Yes and no in my experience.

Yes it is hidden when painted.  But it is not always hidden.  Some temps humidity whatever days and the seam is visible due to differential swelling contraction etc.

Fact is I have a CS 20 outside my house with but seams and some days the seams are plainly visible,  and some days you can't find them no matter how hard you look.

[Ray Frechette Jr]

The best and most accurate way would be to rough the shapes onto over lapping plywood, leaving a couple of inches around the perimeter as a fudge factor, then join the panels. The joined panels can be then finally marked for the actual cut line.

In practice very little issue with laying out the panel on overlapped ply and cutting out.

I do take precaution to not cut the tedge immediately adjacent to the facotry straight edge of the plywood sheet as I use that as a reference line when gluing up the panel.  It is accurately marked though prior to gluing up the scarf.

Once panel scarf is securely glued up I then cut that edge and plane down to the line.

[Ray Frechette Jr]

I'm thinking about purchasing the John Henry scarrfing attatchment for the Makita hand planer.  Does anyone have any experience with this set up?

Scarfing is a subject that seems to cause a lot of trepidation for people untill they have done it several times.

Then they sit there and wonder why it freaked them out.

For myself, I can't imagine taking the time to set up a scarfing jig ona  power handplaner every time I wanted to scarf up a panel.  Way too time consuming.  I would ave to have a dedicated power handplaner just for that purpose if that is what I was going to do,  and I am too cheap to spend that much money on a tool that would see too little use...

It may be a fine attachment, but for me it falls into the more trouble than it is worth category.

[John Turpin]

Scarfing is a subject that seems to cause a lot of trepidation for people untill they have done it several times.

Then they sit there and wonder why it freaked them out.

Exactly.