Two paths two boats? AS 19 scantlings
It begins,
"DESIGN #550, AS 19, KEY TO PLANS
The specified scantlings are very heavy for the size of the boat and ought not to be increased. She could be built with 1/2" total bottom and 1/4" everywhere else and still stand up if not abused. Apart from the first cost savings, she could then carry more ballast, be stiffer under sail, therefor faster in strong wind. The natural wood fastening frame and stringers could be slightly reduced if care in driving mechanical fastenings was adequet (sic).
Plywood as designed is all 1/2". About 22 sheets wil be the maximum number needed; this figure could be reduced, perhaps to 18 or even 16, by careful use of scrap including use of more butts in deck, bulkheads, and elsewhere."
DISPLACEMENT is shown as 2100lbs. BALLAST: 500lbs (metal or concrete)
Bernie Wolfard's old CSD catalogue has:
EMPTY WEIGHT: 1200lbs (approx.)(Presumably, Bernie got his numbers straight from PCB. I believe that this empty weight must be just the hull plus ballast, yet...);
SLEEPS: 2 adults;
DAY SAILS: up to 6 adults
Now, those who have built a number of ply boats from various sized plywood scantlings, weighed them, and then accounted for the number of sheets consumed may be able to help guide how an AS 19 may come together. For example, I'm somewhat confused by Jim Michalak's estimates for final boat weight based on number of plywood sheets needed. Early on he said he worked on 1/4" @ 35lbs, 3/8" @ 50lbs, and 1/2" @ 7olbs and that this included an allowance for typical framing scantlings required per sheet. Recently, he has simply used figures for the plywood sheet weight of 25lbs for 1/4" and 50lbs for 1/2".
If 18 sheets of 1/2" are used then weight per JM will be either 1260 or 900lbs. Then there's the 500lbs ballast...
If 18 sheets of 1/4" are used then weight will be either 630 or 450lbs.
It seems that B Wolfard is using the figures (more or less) for 1/4" plywood scantlings.
If the designed 1/2" ply is used then empty hull plus ballast is going to be somewhere around 1600lbs! Add a motor and fuel, sail rig, safety gear, and ground tackle, and the light ship weight will be around 1800lbs! This before 2 to 6 crew, provisions, and personal gear. I think it could be gotten away with as she may just settle on her lines with a crew of 2 plus their minimal provisions for only a 5 day cruise. What to do for a longer cruise?
What scantlings were Mike S's old boat built to, the one from the "Bolger on Design" AS 19 article? What amount of ballast?
I recall that PB&F wrote that the boat was mainly designed to carry the large day sailing crew, to provide much lounging deck space, hence the small cuddy. If so, how does that sit with the original heavy ply scantling spec?
Here's another rub I have to consider: currently I can obtain 1/2" marinewood seconds (beyond excellent for cheap boats) for AUD80 per sheet. The 1/4" is rarely available due to high demand from large distributors and is not a lot cheaper at around AUD50 (slowly getting a few - for BW1!). There are other options in lower grades but those are merely good, still...
Wolfard's lighter hull weight for more sprited sailing sounds good to me, but then so to does solidity and strength. Trailer weight is the same I suppose, more or less, given PCB's suggestion to increase ballast.
Anyone any thoughts about scantlings?
Graeme
You beauty! Plans received Nels. Yer blood's worth bottlin'.
"DESIGN #550, AS 19, KEY TO PLANS
The specified scantlings are very heavy for the size of the boat and ought not to be increased. She could be built with 1/2" total bottom and 1/4" everywhere else and still stand up if not abused. Apart from the first cost savings, she could then carry more ballast, be stiffer under sail, therefor faster in strong wind. The natural wood fastening frame and stringers could be slightly reduced if care in driving mechanical fastenings was adequet (sic).
Plywood as designed is all 1/2". About 22 sheets wil be the maximum number needed; this figure could be reduced, perhaps to 18 or even 16, by careful use of scrap including use of more butts in deck, bulkheads, and elsewhere."
DISPLACEMENT is shown as 2100lbs. BALLAST: 500lbs (metal or concrete)
Bernie Wolfard's old CSD catalogue has:
EMPTY WEIGHT: 1200lbs (approx.)(Presumably, Bernie got his numbers straight from PCB. I believe that this empty weight must be just the hull plus ballast, yet...);
SLEEPS: 2 adults;
DAY SAILS: up to 6 adults
Now, those who have built a number of ply boats from various sized plywood scantlings, weighed them, and then accounted for the number of sheets consumed may be able to help guide how an AS 19 may come together. For example, I'm somewhat confused by Jim Michalak's estimates for final boat weight based on number of plywood sheets needed. Early on he said he worked on 1/4" @ 35lbs, 3/8" @ 50lbs, and 1/2" @ 7olbs and that this included an allowance for typical framing scantlings required per sheet. Recently, he has simply used figures for the plywood sheet weight of 25lbs for 1/4" and 50lbs for 1/2".
If 18 sheets of 1/2" are used then weight per JM will be either 1260 or 900lbs. Then there's the 500lbs ballast...
If 18 sheets of 1/4" are used then weight will be either 630 or 450lbs.
It seems that B Wolfard is using the figures (more or less) for 1/4" plywood scantlings.
If the designed 1/2" ply is used then empty hull plus ballast is going to be somewhere around 1600lbs! Add a motor and fuel, sail rig, safety gear, and ground tackle, and the light ship weight will be around 1800lbs! This before 2 to 6 crew, provisions, and personal gear. I think it could be gotten away with as she may just settle on her lines with a crew of 2 plus their minimal provisions for only a 5 day cruise. What to do for a longer cruise?
What scantlings were Mike S's old boat built to, the one from the "Bolger on Design" AS 19 article? What amount of ballast?
I recall that PB&F wrote that the boat was mainly designed to carry the large day sailing crew, to provide much lounging deck space, hence the small cuddy. If so, how does that sit with the original heavy ply scantling spec?
Here's another rub I have to consider: currently I can obtain 1/2" marinewood seconds (beyond excellent for cheap boats) for AUD80 per sheet. The 1/4" is rarely available due to high demand from large distributors and is not a lot cheaper at around AUD50 (slowly getting a few - for BW1!). There are other options in lower grades but those are merely good, still...
Wolfard's lighter hull weight for more sprited sailing sounds good to me, but then so to does solidity and strength. Trailer weight is the same I suppose, more or less, given PCB's suggestion to increase ballast.
Anyone any thoughts about scantlings?
Graeme
You beauty! Plans received Nels. Yer blood's worth bottlin'.