Re: Ideas for shaving 20% of weight.
--- In bolger@y..., "rnlocnil" <lincolnr@m...> wrote:
True, I can easily see *more* than several pounds of "coating" on the
boat. I now wish I had weighed the boat before coating. There is
more than half a gallon of epoxy (4 lbs+) and the cloth might weigh
nearly 2lbs. Plus, a quart of varnish 2 lbs. Almost 1 pound of
Bondo too. The "cab-o-sil" filler seems to weigh nearly nothing.
Probably 9 pounds of coating total which I bet could be reduced by
half.
The coating is heavy, but the strips, nails and bulkheads are
heavier; they must weigh 35 - 40 pounds. They could probably be
reduced by 25%, which would save nearly 10 pounds.
A 36 pound final weight might be possible.
It is hard to guess how much epoxy came off with my sanding, perhaps
a pound.
bulkheads was to give the boat shape during the buildup, not
strength. The "shell effect" strength of the glued up strips is
remarkable. I would have tried to remove the bulkheads after glue-
up, but there is no easy way to do that.
> I seem to remember you slobbered all sorts of epoxy and thickened<sniping> costing you several pounds.
True, I can easily see *more* than several pounds of "coating" on the
boat. I now wish I had weighed the boat before coating. There is
more than half a gallon of epoxy (4 lbs+) and the cloth might weigh
nearly 2lbs. Plus, a quart of varnish 2 lbs. Almost 1 pound of
Bondo too. The "cab-o-sil" filler seems to weigh nearly nothing.
Probably 9 pounds of coating total which I bet could be reduced by
half.
The coating is heavy, but the strips, nails and bulkheads are
heavier; they must weigh 35 - 40 pounds. They could probably be
reduced by 25%, which would save nearly 10 pounds.
A 36 pound final weight might be possible.
It is hard to guess how much epoxy came off with my sanding, perhaps
a pound.
>I got the distinct impression, that the main function of the
> I would hesitate to use paper in a boat, unless totally saturated
>
bulkheads was to give the boat shape during the buildup, not
strength. The "shell effect" strength of the glued up strips is
remarkable. I would have tried to remove the bulkheads after glue-
up, but there is no easy way to do that.
I seem to remember you slobbered all sorts of epoxy and thickened
varnish on it. Wouldn't it be better to make a nice surface with
sandpaper? If you use .55oz glass, it's a bit of a pain to work with,
but you can blot off the excess with paper towels and then lightly
sand. That's how we sometimes finish model airplanes, so it's plenty
light. Latex paint will stick well after washing, but go easy. Or
maybe you can just use latex in first place? Probably will save
weight if you can spray it, very lightly. The bright finish may be
costing you several pounds.
With the heavy glass, I've just done a SWAG which predicts it will
weigh between 2 and 3 pounds if put on carefully, more if not, and you
ought to be able to save quite a bit.
I can't recall how thick your strips are, but that might save weight.
Of course if thicker strips mean you don't need heavy glass, it might
actually be lighter that way. A model airplane trick I've heard of is
to use bands of glass tape periodically to prevent splits. If the
inside and outside bands are at the same place, it would be stiffer,
but of course outside bands will make a small bump.
I would hesitate to use paper in a boat, unless totally saturated with
some kind of resin. How about really thin marine ply? And can you
remove some of the bulkheads? Thin glass and epoxy on either side of a
dense foam ought to make a light bulkhead, too.
varnish on it. Wouldn't it be better to make a nice surface with
sandpaper? If you use .55oz glass, it's a bit of a pain to work with,
but you can blot off the excess with paper towels and then lightly
sand. That's how we sometimes finish model airplanes, so it's plenty
light. Latex paint will stick well after washing, but go easy. Or
maybe you can just use latex in first place? Probably will save
weight if you can spray it, very lightly. The bright finish may be
costing you several pounds.
With the heavy glass, I've just done a SWAG which predicts it will
weigh between 2 and 3 pounds if put on carefully, more if not, and you
ought to be able to save quite a bit.
I can't recall how thick your strips are, but that might save weight.
Of course if thicker strips mean you don't need heavy glass, it might
actually be lighter that way. A model airplane trick I've heard of is
to use bands of glass tape periodically to prevent splits. If the
inside and outside bands are at the same place, it would be stiffer,
but of course outside bands will make a small bump.
I would hesitate to use paper in a boat, unless totally saturated with
some kind of resin. How about really thin marine ply? And can you
remove some of the bulkheads? Thin glass and epoxy on either side of a
dense foam ought to make a light bulkhead, too.
--- In bolger@y..., "brucehallman" <brucehallman@y...> wrote:
> I am left guessing how he shaves the weight.
>
> _Small Boats_ makes no mention of cloth or resin, so now I wonder if
> that is absolutely required.
>
> So, I am wondering how, on 2nd attempt, I can shave off weight:
>
> Thinner strips. If I rely more on glue to edge hold the strips, by
> using Raka ultra fast epoxy and 3/16" thick strips, I bet I can
shave
> several pounds in wood weight.
>
> Fewer nails. If I do more clamping, while the glue sets, I can save
> 1 pound (or more) of nails I bet. The problem I found, was that I
> need some way to hold the "sprial twist" in battens, while the glue
> set. A thinner batten would twist easier, though I lacked anything
> solid to clamp to. Edge nailing ring shanks solved that problem at
a
> cost in weight.
>
> Thinner ribs. I think the bulkhead ribs, if edge "T" reinforced,
> could be much thinner and lighter. The edge reinforcement, could be
> used to attach a spring loaded clamp to hold the twist in the
> batten. I think that ribs made of cardboard, corrugated or
> posterboard wrapped around the circumference with 1" glass tape or
> cardboard, and brushed down with thinned epoxy resin might work.
> [see sketch at:]
>http://www.hallman.org/bolger/Kotick/rib.gif
>
> Thinner cloth [or no cloth?], and I might be able to save 1 pound.
I
> used 5 oz cloth. I wonder if those glass microfibers in resin would
> provide enough tensile strength in the skin? Or, Raka sells a 0.55
> oz/yd cloth.
>
> Lighter wood. Redwood seems like an very light weight wood, but
there
> might be a lighter wood still.
>
> Give up on the brite finish, and use epoxy resin with lots of
> microballoons instead.
>
> Helium floatation bags...
I test floated my bastard Kotick last night...it feels nice, I still
need a spray skirt before venturing out in the cold water.
I also weighed it yesterday; 49 pounds. Light enough, but in _Small
Boats_ PCB says that Dynamite Payson's Kotick weighs "under 40", and
I am left guessing how he shaves the weight.
_Small Boats_ makes no mention of cloth or resin, so now I wonder if
that is absolutely required.
So, I am wondering how, on 2nd attempt, I can shave off weight:
Thinner strips. If I rely more on glue to edge hold the strips, by
using Raka ultra fast epoxy and 3/16" thick strips, I bet I can shave
several pounds in wood weight.
Fewer nails. If I do more clamping, while the glue sets, I can save
1 pound (or more) of nails I bet. The problem I found, was that I
need some way to hold the "sprial twist" in battens, while the glue
set. A thinner batten would twist easier, though I lacked anything
solid to clamp to. Edge nailing ring shanks solved that problem at a
cost in weight.
Thinner ribs. I think the bulkhead ribs, if edge "T" reinforced,
could be much thinner and lighter. The edge reinforcement, could be
used to attach a spring loaded clamp to hold the twist in the
batten. I think that ribs made of cardboard, corrugated or
posterboard wrapped around the circumference with 1" glass tape or
cardboard, and brushed down with thinned epoxy resin might work.
[see sketch at:]
http://www.hallman.org/bolger/Kotick/rib.gif
Thinner cloth [or no cloth?], and I might be able to save 1 pound. I
used 5 oz cloth. I wonder if those glass microfibers in resin would
provide enough tensile strength in the skin? Or, Raka sells a 0.55
oz/yd cloth.
Lighter wood. Redwood seems like an very light weight wood, but there
might be a lighter wood still.
Give up on the brite finish, and use epoxy resin with lots of
microballoons instead.
Helium floatation bags...
need a spray skirt before venturing out in the cold water.
I also weighed it yesterday; 49 pounds. Light enough, but in _Small
Boats_ PCB says that Dynamite Payson's Kotick weighs "under 40", and
I am left guessing how he shaves the weight.
_Small Boats_ makes no mention of cloth or resin, so now I wonder if
that is absolutely required.
So, I am wondering how, on 2nd attempt, I can shave off weight:
Thinner strips. If I rely more on glue to edge hold the strips, by
using Raka ultra fast epoxy and 3/16" thick strips, I bet I can shave
several pounds in wood weight.
Fewer nails. If I do more clamping, while the glue sets, I can save
1 pound (or more) of nails I bet. The problem I found, was that I
need some way to hold the "sprial twist" in battens, while the glue
set. A thinner batten would twist easier, though I lacked anything
solid to clamp to. Edge nailing ring shanks solved that problem at a
cost in weight.
Thinner ribs. I think the bulkhead ribs, if edge "T" reinforced,
could be much thinner and lighter. The edge reinforcement, could be
used to attach a spring loaded clamp to hold the twist in the
batten. I think that ribs made of cardboard, corrugated or
posterboard wrapped around the circumference with 1" glass tape or
cardboard, and brushed down with thinned epoxy resin might work.
[see sketch at:]
http://www.hallman.org/bolger/Kotick/rib.gif
Thinner cloth [or no cloth?], and I might be able to save 1 pound. I
used 5 oz cloth. I wonder if those glass microfibers in resin would
provide enough tensile strength in the skin? Or, Raka sells a 0.55
oz/yd cloth.
Lighter wood. Redwood seems like an very light weight wood, but there
might be a lighter wood still.
Give up on the brite finish, and use epoxy resin with lots of
microballoons instead.
Helium floatation bags...