G10 vs HDPE

[dalekidd]

Clint's plans for the CIY 16 call for plates made of 1/4" G10 to secure the lifting rudder blade to the rudder head. For a third of the cost, just curious as the comparable strength of a sheet of 1/4" high density polyethylene. I have never heard of, let alone handled a piece of G10. We're talking about saving $20 so may not even be worth a discussion, but $20 is $20. If not of equivalent strength, would 1/2" HDPE compare? Maybe a couple pieces of 3/8" left over meranti would suffice???? Before you answer, I know that no one wants to lose their rudder! TIA!

[JimConlin]

The tensile strength of G10 is roughly ten times that of HDPE. Other mechanical properties compare in the same way.

G10 is a strong structural material that bonds well with epoxy, can be tapped for fasteners and needs to be painted. It’s good for providing a hard point in a softer material.

HDPE and its cousins have the virtues of low friction, impact tolerance and tolerance of UV.
It does not bond well. G/flex epoxy works, but not all that well.
It’s good for surfaces that will be whacked, slid on or scraped.

Use the G10.

[Jim Ledger]

There's something else...G10 needs to be cut with a diamond router bit. Not cheap and the bits don't last long. Carbide will dull very quickly.

HDP, though, I don't know if that's the stuff for the job.

Plenty of boats have been built without either, the large majority, actually.

How about a nice piece of bronze plate, pricey, but you can cut it and it looks good.

Jim

[Edward Pearson]

Build exactly to Clint’s plan. Pay the extra $20. Isn’t the rudder blade supported externally on the rudder head? That needs structural material not a low friction hdpe (chopping board material). Thats normally only used for low friction washers or keel rub strip. Clint will have his reasons. Its always quicker and easier to just build to Plan A, years of cogitation, rumination, experience and calculation is what you already paid for in his planset.

[JimConlin]

There's something else...G10 needs to be cut with a diamond router bit. Not cheap and the bits don't last long. Carbide will dull very quickly.
<SNIP>

Jim

G10 can be cut with carbide grit (tile) blades or metal cutting blades in a jigsaw and refined to shape with a belt sander.
I’ve even cut it with a woodworking blade on a table saw. Painful.

[willin woodworks]

How about 1/4" duraluminum? You probably buy a decent piece at a local scrap yard. It machines nicely and wont need painting.

[JimConlin]

How about 1/4" duraluminum? You probably buy a decent piece at a local scrap yard. It machines nicely and wont need painting.

Duralimin is an aluminum copper alloy and is subject to galvanic corrosion in salt water.

[willin woodworks]

Id go out on a limb and say there's not a lot of salt water in northwest Georgia.

[Autonomous]

I don't know now much left over resin and glass cloth you will have but consider making plates at least partially from leftovers.

[peb]

Id go out on a limb and say there's not a lot of salt water in northwest Georgia.

No, but its not that far from several bays he may want to trailer the boat to and do some venturing out.

G-10, IMO, works for a lot of things. It makes very good backing plates. It can be threaded and will hold a bolt pretty well, which occasionally comes in handy for lower load hardware such as hinges. I use tubes of G-10 for bearing of bolts through wood, this has worked really well for me in the past when the bolt is in shear, as it increases the diamater load bearing surface against the wood, makes for a very good water intrusion barrier, and provides a consistent thickness to counterbore into the hole so that the sealant or butyl tape works well.

It is a pain to cut. For plates I use a carbide blades that I keep around just for this purpose. They haven't dulled too bad so far. But its not always fun.

Its not cheap, but it seems to go a long way.

[Yeadon]

Clint knows what he's doing. I'd consider following his plans. That said, some 6mm joubert okume plywood glassed on both sides has worked out well serving the same purpose for my HV18's rudder cheeks. But definitely do what Clint says.

HDPE would be the correct material for a skid shoe on the keel.

[Pete Bergquist]

G10 needs to be painted... that caught my eye. On my CIY16 I have the G10 posted but left them unpainted. Will it deteriorate from UV?

[Mike V.]

G10 is fiberglass and epoxy, the epoxy breaks down in sunlight. You'll first notice that the surface of the G10 will turn chalky and then get worse from there.

[JimConlin]

G10 needs to be painted... that caught my eye. On my CIY16 I have the G10 posted but left them unpainted. Will it deteriorate from UV?

My earlier statement that G10 needs to be painted was incomplete. I should have used the word eventually. G10 is epoxy based and epoxy is sunlight sensitive, to a degree.

Over ten years ago, I launched a boat that had a few beefy G10 parts that weren’t painted and were exposed to weather. They’ve been outdoors nearly year-round since and they’re now slightly weathered and would look better if painted. They’re not structurally affected at all.
I’d keep an eye on parts of 1/4” or lighter material.