[Public-List] [EXTERNAL] Public-List Digest, Vol 3920, Issue 2

[Gordon Laco]

Right on Matt… and the white oak spreader would be much more durable with regard to it’s superior rot resistance.   Another issue is the strength of the very hard oak where pins or fastenings go through it.

In my Folkboat days I once tore the gooseneck traveler track out of the mast in a wild downwind surfing match while racing.  I didn’t want to see that happen again, so the following winter I inlaid white oak where the track was fastened, in effect to ‘armour’ the mast with hardwood for the fastening screws to go into.  That hardwood is still in her.

When I was Executive Director of Toronto Brigantine, one of the things I noticed was that when we had spar failures over the years in our two 50 ton brigantines, the breaks tended to occur toward the ends of the spars where iron collars etc were.  So as we replaced spars due to usual maintenance, I had them built up with sitka spruce, but with white oak worked into the centres of the yardarm ends.  As the spars tapered the spruce thinned out so that the iron collars bore against the oak.  We never broke one of those.

White oak tends to be a little acidic, and glues tend not to age well with that, but the trade off of greatly increased strength where the properties of white oak made dealing with it worth while, was, well, worthwhile.

Well back to work… 

Gordon Laco
www.gordonlaco.com




> On Sep 17, 2019, at 12:17 PM, Greenhouse, Matthew A. (GSFC-6650) via Public-List <public-list at lists.alberg30.org> wrote:
> 
> Hi Gordon,
> 
> Interesting discussion (although tangential to the advantages of aluminum). Sitka spruce is used extensively for masts. For spreaders, a key property is the compressive strength parallel to the grain. One can find this for a number of woods here: https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr190/chapter_05.pdf  See table 5-3a.
> 
> You are right that white oak is about 30% stronger than Sitka spruce in this regard. This just means that, if one were to make two spreaders of equal strength, one of oak and the other of spruce, then the oak spreader would need less cross-sectional area.
> 
> Cheers,
> Matt
> 
> From: R Kirk <isobar at verizon.net>
> Sent: Monday, September 16, 2019 6:35 PM
> To: public-list at lists.alberg30.org
> Cc: mainstay at csolve.net; Greenhouse, Matthew A. (GSFC-6650) <matt.greenhouse at nasa.gov>
> Subject: Re: [Public-List] [EXTERNAL] Public-List Digest, Vol 3920, Issue 2
> 
> Gord… Wasn't Sitka once used extensively for masts at some time? I'm not sure. But I agree white oak is very rot resistant and great for spreaders. Hearts of Oak and all that. I wonder why Whitby switched to aluminum. Costs? Easier to construct? At any rate, Isobar had its original white oak masts that lasted for years. I was going to make new spreaders when I took the mast down one year but found them in good shape. I just refinished and painted the tops white... Bob
> 
> 
> -----Original Message-----
> From: Gordon Laco via Public-List <public-list at lists.alberg30.org<mailto:public-list at lists.alberg30.org>>
> To: Alberg 30 Public List -- open to all <public-list at lists.alberg30.org<mailto:public-list at lists.alberg30.org>>
> Cc: Gordon Laco <mainstay at csolve.net<mailto:mainstay at csolve.net>>; Greenhouse, Matthew A. (GSFC-6650) <matt.greenhouse at nasa.gov<mailto:matt.greenhouse at nasa.gov>>
> Sent: Mon, Sep 16, 2019 5:20 pm
> Subject: Re: [Public-List] [EXTERNAL] Public-List Digest, Vol 3920, Issue 2
> Sitka spruce?  I don’t think any boatbuilders in any period in history used that wood for spreaders.  Too soft, too rot prone; white oak is what Whitby used... earlier, black locust or elm.  Spreaders require very hard wood, very stiff with high durability.
> 
> If a boat had Sitka spruce spreaders, that would be an error by a well meaning but ill informed subsequent owner.
> 
> Sorry for the over-long rather adamant response... rigging classic yachts is my trade.
> _______________________________________________
> These businesses support your Association:
> http://www.alberg30.org/store/A30supporters.html
> Please support them.
> _______________________________________________
> Public-List mailing list
> Public-List at lists.alberg30.org
> http://lists.alberg30.org/listinfo.cgi/public-list-alberg30.org