Hey all,
I installed 2 mohogany ply stringers in this blank, I’m going to glass it this weekend. I’m having an issue with the dark plywood discoloring the foam a little when sanding. I’ve tried blowing it and vacuuming. It’s not like western red cedar, the mohogany is really leaving some streaks on the foam.
What’s the best way to clean this foam up so it’s perfectly white?
Thanks.
Use a sharp hand plane to take the stringer down lower than the foam. Then when you final sand you’re not hitting any wood.
Excellent! I think I’m going to invest in a better spokeshave 
No, the proper tool is a Stanley Mini Plane. Cost is less than ten dollars, last time I looked. If you can find one, an older Stanley model 60, low angle hand plane is really worthwhile. LOW ANGLE is the important feature.
I don’t recommend a Spoke Shave for that final pass. Use a Stanley Mini Plane and plane at a slight angle across the stringer from tail to nose or vice versa. If the wood doesn’t plane smoothly, plane in the opposite direction. A couple of passes with no more than medium pressure will Plane the stringer below the foam without tearing the foam. Then screen the stringer area with a worn out piece of 220 and a hard block. Always take the wood down first and then bring the foam down flush to match. I actually like to leave my stringer below the foam just slightly. Even if you do tear foam, it will usually clean up with a final screen. Also on a Poly blank you can lightly hit the stringer area with a heat gun. The foam expands and fills the tears. A Stanley Mini Plane is one of the only planes I have ever used that is sharp enough out of box to evenly plane a stringer. The small spoke shaves sold at the supply shops are notoriously Dull with a capital “D”. They will chunk the $#!+ out a stringer if not sharpened before use.
PS. The problem you are having is the main reason Mahogany is not used for stringers. It also does not hand plane or sand well. Having said all of the above; It looks to me that you did a pretty decent job on that Arctic glue up.
Many thanks! Yeah, the mohgany ply looks REALLY cool with glass on it; very high-end looking, but I’m only going to do this again if I have a really radical stringer like a box agave, balsa or checkered pattern setup. The amount of work to cut perfectly straight and true up all the pieces is a little overkill.
So, Stanley mini plane seems to be the consensus. I’ll go pick one up tonight.
Thanks agian.
If your cutting straight lines just get a piece of thin aluminum or even a clean strip of plywood will work. Clamp it at the nose and tail (bottom works best) and run your circular saw up against it. Clean and straight. If you can’t get the full dept come back with a hand saw and all you got to clean up is a little section.
I’ve never heard of using a circular saw to take down the stringer but it makes sense. Bold but it should work if you’re careful. I spend a lot of time eyeballing the top and bottom edges of my stringers. They can tell you a lot about the surface of the foam. With multiple stringers, you can eyeball for symmetry.
I’d definitely take down the stringers on your shaped blank. I think I see a couple of spots in the tail area that are a bit proud. Maybe up towards the nose as well(?) Try to make sure the top and bottom edges of your side stringers are following the same curves…
Just trying to be helpful here, not critical…
John hahaha I must have made that confusing.
My previous post was in relation to the OP stating cutting the blank for the stringer glue up was a pain.
I’d say using a circular saw to knock down a stringer is far beyond bold haha - straight crazy haha
Maybe I misread his post?? Ehh anyways…
With reference to WA’s circular saw method for splitting a blank. I have found that on a longboard blank the 7 1/2” Skilsaw will saw thru the blank for about 1/3 of the blank at nose and tail. Leaving only the thicker mid sec. if I turn the blank over and change sides with my saw guide or use a straight edge to align my cuts and mark the middle; I can Skilsaw the mid section from the opposite side. Gives me a clean cut. No planing or joining necessary. And no handsaw cut to clean up. Lowel
Haha! Okay that makes sense now. Yeah, I’m past that part. The board is shaped. I’m down to final shaping details; shaving the stringers and prepping for laminate.
the issue is the stringers I installed are mahogany plywood, which looks really good but doesn’t sand well. It’s very hard.
What’s the length of that Arctic? At first I thought it was a 9’3, but then I realized that Mahogany Ply usually only comes in eight foot.
I own a carpenter’s Makita with a 100 mm depth of cut that will go through the majority of blanks I know (with the exception of a few SUP blanks) in one pass. Pretty useful.
It was an 11’0 blank, now a 10’0. I was able to get 10’ mahogany plywood at Frost in Mira Mesa.
As for splitting the blank; you hands-down best bet is to have your supplier do it for you if possible.
Here’s more pics of me toiling away with the glue-up. I used a hacksaw blade to split the blank by hand. I marked top and bottom and just made sure both ends of the blade were on the top and bottom lines all the way through the cut. To go faster I did a ///\///\///\///\///\\ cut and that’s how the pattern on the foam looked after it was cut. Then I slightly planed all 4 cut sides. Had to redraw new measurements/depth lines, of course.
When the board was all in pieces, I traced the outline for the stingers on the plywood and cut as close as possible so there wouldn’t be a ton of cleanup necessary.
I misread your post… I have heard of guys using a router to knock down a box install so not that far fetched(?) If I feel ambitious and inclined to adding my own stringers, I just ask USBlanks to make the cuts. The blanks arrive with plastic stretch stuff wrapped around holding it all together. I’ve sliced up a blank or two for stringers and glue lines but it’s pretty much high anxiety for me. That said, I have a couple of blanks in stock that I may take a saw to. I have one of those ‘beam saws’ like what Guilhem Rainfray shows below. Scary!
Wait just a goldarned minute… you sliced a longboard blank in two places by hand using a bare hacksaw blade?! I am in awe.
…just the blade, no handle. I wanted to be real careful. I have weird-level patience.
What’s the diameter? Must be 10” or the Metric equivalent? What guys call a “Beam Saw” I think. Once you get used to splitting a blank with a Skilsaw, it’s actually easier than a Band Saw. Using a Band Saw is really a two man operation.
Good old Frost. A solid source still.
