recessing the sole of a plane

[M. Moore]

An afterthought about the blade modifications.
You will only be able to cut in one direction so if right handed then you would have to cut away the right side of the blade as you will be working from right to left, and the opposite if you are left handed like I am. Assuming that the weld bead is on the edge of the part.
If you want to work in both directions then you could grind away from both sides leaving a small blade in the middle which allows bi-directional planing. If you make the plane handed then you will have a larger non cutting sole area to rest on the plastic.

 

[stoneaxe]

Maybe a stupid question, but can you perfect the weld?
Then you would not need to plane it at all.

 

[Trboatworks]

I am late to the party- how did the work turn out?
I am with Richard- around boat there is heavy plastic tape used in shrink wrapping boats.
I use it for all sorts of shielding and skid operations around the shop and would use a couple of strips on the plane sole for this.

 

[DanielG]

We did some experimenting with a few different regular planes and never got them cutting as well as I would like in HDPE. Rather than wasting a bunch more time, I ordered the Bridge City plane that memphisjed suggested. The lower angle definitely made cutting easier. We set the blade depth on some scrap material and then set the side fences using the surface plate and some shim stock. I think we ended up with a .003 chip thickness and set the fences at .005. Theoretically this would leave the weld .002 high; in practice, it's a bit more because weld distortion makes the surface wavy.

We just finished welding up the first part, and the plane worked beautifully. Much easier than the way we were doing it before.

Thank you all for your advice, especially memphisjed.