wood block construction ?

[c.grillo]

I am a novice here and searched the forum first but found nothing. I will be rerigging a 42 ft schooner and want to make rope stropped blocks. Yes, it's winter and I'm looking for indoor projects, have time and not enough money but want wood anyway. I would be interested in hearing the pros and cons of built up vs solid construction and any tricks to each method...and/or a good book/article on specifics. I will have aprox 30 for 1/2" line (about 1/2 of those doubles), 30 for 3/8 and a half dozen 5/16.

I have access to local elm or ash and several sawmills within spitting distance...any other recomendations for wood?

Anyone have a good source for durlin in 5/8, 1/2, and 3/8?

Rules for axle diameter? (I plan on bushing the sheave)

Rules for sizing the diameter of line for the strop grommet?

I recieved some samples of "spunflex" and like working with it better than dacron. I don't find much written about it except it isn't as strong or chafe resistant. Does anyone have recomendations on sheave size? On the spunflex in general?

I appreceate any direction available.
Conrad

[Brion Toss]

Hello,
You'll find directions for making rope-stropped blocks in the "Apprentice". Also sheave size recommendations. As for the grommet materials, what are the loads? A properly-made grommet should be close to twice the strength of the rope it is made from. How does that compare with the loads on the block?
Is it "Delrin" you are after? I'd go to Zephyworks; they make fine bushed Delrin sheaves.
Fair leads,
Brion Toss

[c.grillo]

Thanks Brion,

"Apprentice" has been helpful. So is your post.

Any thoughts on solid vs built up construction? Seems commercially available rope stropped blocks are made from, solid. For one without milling equiptment it would appear that glueing and pinning the bodies might be easier. Any suggestions from those that have done it?

[allene]

google "stropped blocks" and find a couple of helpful articles addressing your question. For example, this one:
http://www.duckworksmagazine.com/02/...odenblocks.htm

Allen

[c.grillo]

Thanks for the link. I've seen that one. Running the grain as he does in the cheeks worries me for strength. A good bump to the side looks like a split waiting to happen. With the grain the other way it would appear to be much more robust. And, yes, this is just the sort of info I seek...Those ones are for a dinghy of course and not as critical.

[allene]

Looking at the forces it looks like the wood is in compression due to the strop. My first thought is that you want the grain running across the strop like he has it. Also, the pin should probably be relative to the grain the way he has it. Just my 2 cents.

[Scott McDonald]

I looked at the pictures, and my initial thought was the grain should run parallel to the load. After thinking about it, I think the author got it right. If you visualize it under load with the rope stropping, you will see that the wood will be in compression between the pin and the lower part of the stropping. If the grain was parallel to the load, there's a significant chance the block will eventually split as the force of the pin bears down on the end grain. As shown, the block may be a more susceptible to damage from physical abuse, but should not split under load.

- Scott

[UnlikelyBoatBuilder]

This is a timely thread for me, because I would like to make a new set of blocks for my Tom Gilmer "Blue Moon" yawl.

I've been trying to find information on building both metal and rope stropped blocks (I need both). So far, Brion's book has the most comprehensive info (the reason I found this forum), and there is some info on the Wooden Boat forum and Duckworks, but it seems to me someone must have written a book back in the 30s or even earlier that gave detailed info on building blocks, various kinds of cleats, etc.

Unfortunately, I haven't found one, yet!

In particular, I'd like to see something that showed how to build something more complicated than a single, rope-stropped block. I need to build at least one metal-stropped triple, with becket, for example.

I *think* I know how to make one, just by inspecting a few from the outside, but it sure would be nice to have a book that showed some of the tricks that may not be obvious to non-experts. For example, why does Davey & Co put the becket off-center on their double and triple blocks? That makes no sense to me, but I am guessing they have a good reason. Maybe an old book would explain it.

So, anyone know of such a book? Even an out-of-print one?

TIA: John

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Check out my blog: http://unlikelyboatbuilder.com

[c.grillo]

As for the grain, I can only imagine the thing cracking in two when it hit something if made up like the ones in the duckworks aricle. All commercially made blocks run the grain the other way as far as I can make out. But axle pin size probably is significant so as to lessen the chance of splitting. Sure would be nice if one of the experts would chime in! Brion?

I've been thinking of ordering one from Ording. They use elm as was traditionally used (traditionally as far as I have found -H.G.Smith I think it was). They hog out the slots from a single piece on the rope stropped ones but it is my guess that they have the milling equiptmet and it saves them man hours. For larger blocks and a bunch of them, I'm thinking it would probably be easier to build them up, Any suggestions from those that have done it both ways?

Just talked to my friend with the mill and millworks. He has some dry white oak and suggests using it for it's durability in the intended environment. Any comments?

[c.grillo]

Originally Posted by UnlikelyBoatBuilder

For example, why does Davey & Co put the becket off-center on their double and triple blocks? That makes no sense to me, but I am guessing they have a good reason.
TIA: John

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Check out my blog: http://unlikelyboatbuilder.com

If you think about the way the line will be rove, I think it makes sense. Straight pull to the next sheave removing one coss. Even if right angle reeving is used.