Hobie Cat Forums

Has anyone tried making their own sheave using a router? I need to replace the masthead (non comp tip) sheave and was thinking of playing around with a cove bit and a scrap of corian solid surface material.

Thought about it too..not with router though. Hole saw, take the hole cutout and put bolt through the center hole, lock that down with a nut, put the bolt in an electric drill and clamp the drill while you use a rounded chisel to create the rope track in the outer edge. Only thought about it though.

I think you have something there Chris. I was thinking a router with a circle template but you would have a hard time cutting the groove with a router. Amazon.com has a 5" hole saw which would be the perfect size (the diameter of the sheave is 4 7/8"). I don't think the diameter is that critical, it's the diameter of the inner groove which looks to be about 4 3/8" that has to be the same as the original. I have a bench top grinder that has a tool rest, so mount the cutout in the grinder and cut the groove with a rounded chisel. The problem with the grinder is that the arbor is 1/2", and the original sheave uses a 3/8" pin. I suppose the mast head could be drilled out to 1/2" though. I was also thinking of buying an inexpensive plastic cutting board instead of buying delrin online. The cutting board could be run through a bench top planer to get to the required thickness which is about 3/8". Or I am still thinking of trying to work with the corian.

Thanks for the great ideas!
Don

No reason not to drill to 1/2 like you said and stick a bolt through the mast head and new pulley. Then you could mount a telltale to the top of the mast using the bolt. Consider asking on this site if anyone has a good mast head to offer. Loads of bent or just old masts with good heads on them out there though I'd be covered in milled plastic with buying one as a backup plan.

Thanks for the advice Chris. I was able to make a sheave (a prototype anyway) using the method described in our previous posts. I used a 1/2” thick plastic breadboard and planed it down to 3/8” on a benchtop planer. The 5” hole saw created a cutout that was a tad too small, so I went with a 6” (5 ½” would have been perfect but I didn’t have one) and turned it down to 4 7/8” using a 1” chisel while the disk was spinning on a benchtop grinder. Once I had the diameter right, I used a ¼” chisel ground down to a round shape, and carved the groove. The grinder worked well because it has a tool rest that is adjustable and can be positioned close to the disk. I call this a prototype because I don’t think the plastic breadboard material is rigid enough to withstand the cable tension if the cable should ride up too far on the ‘fin’ if you will of the sheave (the thin part at the outer diameter). I ordered a piece of delrin from amazon.com and will try this method with that material. The sheave also needs to be a bit thicker than 3/8” to match the original which is closer to 13/32”. The groove on my prototype is a bit too narrow does not allow the crimped on bead on the halyard to seat properly as it travels over the sheave. I’ll post the results after I play around with the delrin.

Don


By shadmeall at 2010-08-01

By shadmeall at 2010-08-01

By shadmeall at 2010-08-01

By shadmeall at 2010-08-01

By shadmeall at 2010-08-01

Don, that's one sweet job. Now we all know who to call to get a good deal on masthead pulleys! I know its a bit late but check this link at Harbor Freight for a 'circle cutter'. I have one and for the money it's a give away. Old school and infinitely adjustable.
http://www.harborfreight.com/catalogsea ... =&q=circle

Thanks for the compliment Chris. I don't know if I would have got this far without your ideas. Yeah, I guess I should go into the sheave business! The circle cutter looks like a great deal. Think I may go check it out. The delrin should be delivered today so it's not too late for a better method for cutting the circle. Sure wish I had a drill press though.

Well, the homemade sheave worked out pretty well. I bought a 1/2" sheet of delrin from amazon.com, planed it down to a bit over 3/8", and used the same method described in my earlier post to shape the sheave. The first one broke during the turning process (I angled the chisel up at too steep of an angle). I ended up using the 5" hole saw after all even though the cutout diameter is slightly less than the original. The depth (or diameter) of the groove is what is critical. I also opted for a 3/8" chisel rounded over instead of the 1/4" chisel that I used for the prototype. The sheave ended up with a 1/2" hole rather than 3/8" like the original, so I drilled out the masthead hole to 1/2" and used a stainless steel bolt and nylon locknut for the axle. Took the boat out yesterday, the main went up easier than ever before!

By shadmeall at 2010-08-28


By shadmeall at 2010-08-28


By shadmeall at 2010-08-28

Great work! You should make several and sell them.

_________________
'88 Nationals Blue
Hobie Alter Signature Model
Sail #11

Hobie Mirage Classic

I wouldn't mind having one on hand. I'm sure the clock is ticking on my '82.

Thanks guys. I do have enough delrin to make a few more. Maybe if I have some spare time...

Sign me up! Seriously.......

_________________
'81 H16

If it ain't a blowin', I ain't a goin'

I just got a newer, straighter mast for my old 16 but the masthead sheave is toast.....I had to hunt for this thread, but I remembered what a great looking product you had turned out....would you consider making me one?...do you still have leftover material?... And of course what would it cost?. If you are still at all set up,( like do you still have the altered 3/8 chisel ) ... it would make more sense for me to pay you than to start from scratch...although thanks to you and the great pictures you put up...we all are better informed as to how we could.
BTW , had a piece of Corian and started working with it. It's too brittle, I believe the thin edges of the pulley V would crack off during machining or use. I've made a lot of stuff out of poly cutting board, but I think your delrin is the way to go. Contact me at adams429 at yahoo dot com and let me know if you even saw my post.

Check out this video on youtube http://www.youtube.com/user/getwetsaili ... r8eLgiqVEE. The guy has one machined out of aluminum and looks to wsork well.