Re: [bolger] More Mast Alternatives
Had a look through some old 'How To Build 20 Boats'. In with
the mix between runabouts with fins and Sea Scout cruisers
by William Garden and other serious boats there are lots of
drawings re: rectangular box spars.
I actually didn't find more than one plywood mast. Which
makes me think these might really be more of a Sam Rabl
innovation than I thought.
The examples in the 3 mags mostly specified the purest Sitka
Spruce, and none was free standing. I noticed that, while
they had various fillers here and there, none had a big
solid plug at the bottom. That's further confirmation to me
that for a freestanding wooden mast, a substantial solid
plug is very important.
There was one boat showing another way to have a plywood
mast. This was 'Guppy', cuter than a Swan shaped pedal
boat. a 5' x 32" children's sailboat. Meticulously laid out,
deep keel, washboards, paddle and all come from one sheet
each 3/4 and 1/4 inch plywood. The rig is is the four sided
sprit, something under 16 sq. ft.
A pair of blanks for the 5' x 2 1/2" mast come from one
edge of the 3/4" sheet. Glued together and tapered
for'n'aft, it isn't kidding for this little boat.
Keep safe,
Mark
the mix between runabouts with fins and Sea Scout cruisers
by William Garden and other serious boats there are lots of
drawings re: rectangular box spars.
I actually didn't find more than one plywood mast. Which
makes me think these might really be more of a Sam Rabl
innovation than I thought.
The examples in the 3 mags mostly specified the purest Sitka
Spruce, and none was free standing. I noticed that, while
they had various fillers here and there, none had a big
solid plug at the bottom. That's further confirmation to me
that for a freestanding wooden mast, a substantial solid
plug is very important.
There was one boat showing another way to have a plywood
mast. This was 'Guppy', cuter than a Swan shaped pedal
boat. a 5' x 32" children's sailboat. Meticulously laid out,
deep keel, washboards, paddle and all come from one sheet
each 3/4 and 1/4 inch plywood. The rig is is the four sided
sprit, something under 16 sq. ft.
A pair of blanks for the 5' x 2 1/2" mast come from one
edge of the 3/4" sheet. Glued together and tapered
for'n'aft, it isn't kidding for this little boat.
Keep safe,
Mark
Or then, there's the stitch-n-glue spar:
Cut thin plywood staves on given taper. Fix to four sides of
plug. Pull together full length. Putty and tape to round the
corners. Plug at the top.
Mark
Cut thin plywood staves on given taper. Fix to four sides of
plug. Pull together full length. Putty and tape to round the
corners. Plug at the top.
Mark
--- Inbolger@egroups.com, Mark Albanese <marka@o...> wrote:
snip
>
> Not even an amateur scientist, I can only ask:
> Isn't plywood strong enough to replace a plank twice its
> thickness?
Not unless you mean across the grain of the original plank. With the
grain the plank is stronger. Wood is much weaker across the grain. If
you need strength in both directions at once, plywood is better. If
you are making a mast, I think you would end up with a lot more
weight
with plywood than with regular planks. Also, the thickness, position,
and grain direction of each layer matters a lot.
Isn't there more strength in the size and shape
> of a section than in the mass of material involved?
>
That's not very precise, but I'd give it a yes, sort of, unless the
load is pure tension. That's why you don't see hollow stays.
snip
Sam Rabl was very esteemed, a Bolger of his day. The plywood
spars in his book all have shrouds, hence the plug to help
one stand alone.
Not even an amateur scientist, I can only ask:
Isn't plywood strong enough to replace a plank twice its
thickness? Isn't there more strength in the size and shape
of a section than in the mass of material involved?
Wood inserts for aluminum tubes are seen in Stevensen designs.
Mark
hwal@...wrote:
spars in his book all have shrouds, hence the plug to help
one stand alone.
Not even an amateur scientist, I can only ask:
Isn't plywood strong enough to replace a plank twice its
thickness? Isn't there more strength in the size and shape
of a section than in the mass of material involved?
Wood inserts for aluminum tubes are seen in Stevensen designs.
Mark
hwal@...wrote:
>Jim Goeckermann wrote:
> In a message dated 8/2/2000 8:33:08 AM Eastern Daylight Time,
>marka@...writes:
> I have a borrowed copy of this same book - and remember seeing the section on
> plywood masts - and at the time I wondered if this was for real! It hardly
> seems like it would strong enough. Wow - what a great idea - if it works. I
> mean - if it's in a book it has to work right? Steve Anderson ( the notorious
>
> Regarding mast alternatives, thought the source eludes me, I recall seeing
> an aluminum tube reinforced by a wooden "X" that was driven down the
> center. If you have access to aluminum tubuing this sure merits
> considering. Anyone else recall where on the net this was detailed?
>
>
>
> Bolger rules!!!
> - no cursing
> - stay on topic
> - use punctuation
> - add your comments at the TOP and SIGN your posts
> - add some content: send "thanks!" and "ditto!" posts off-list.
Regarding mast alternatives, thought the source eludes me, I recall seeing
an aluminum tube reinforced by a wooden "X" that was driven down the
center. If you have access to aluminum tubuing this sure merits
considering. Anyone else recall where on the net this was detailed?
Jim
an aluminum tube reinforced by a wooden "X" that was driven down the
center. If you have access to aluminum tubuing this sure merits
considering. Anyone else recall where on the net this was detailed?
Jim
In a message dated 8/2/2000 8:33:08 AM Eastern Daylight Time,
marka@...writes:
<< Looking at Sam Rabl's old 'Boatbuilding in Your Own Back
Yard' got me thinking that, in the same way plywood is
partly an alternative to scarce, great timber for planking, it
might again do the same for hollow, wooden masts. >>
I have a borrowed copy of this same book - and remember seeing the section on
plywood masts - and at the time I wondered if this was for real! It hardly
seems like it would strong enough. Wow - what a great idea - if it works. I
mean - if it's in a book it has to work right? Steve Anderson ( the notorious
MJ Landroval)
marka@...writes:
<< Looking at Sam Rabl's old 'Boatbuilding in Your Own Back
Yard' got me thinking that, in the same way plywood is
partly an alternative to scarce, great timber for planking, it
might again do the same for hollow, wooden masts. >>
I have a borrowed copy of this same book - and remember seeing the section on
plywood masts - and at the time I wondered if this was for real! It hardly
seems like it would strong enough. Wow - what a great idea - if it works. I
mean - if it's in a book it has to work right? Steve Anderson ( the notorious
MJ Landroval)