Re: [bolger] Re: Compound Cut - Match Curve
The tic board will not get the bevel for you that's for sure but it will get
the curve. Depending on how much stress is anticipated and the glue used,
and material thickness, you may get by with just getting close to the bevel
with a sander and using thickened epoxy to bed down the joint. Using a good
fillet of epoxy then glassing the joint with tape it should be just as
strong as having and exact bevel. If you going for the craftsmanship
approach, by all means, Ray's is the best.
Jeff
the curve. Depending on how much stress is anticipated and the glue used,
and material thickness, you may get by with just getting close to the bevel
with a sander and using thickened epoxy to bed down the joint. Using a good
fillet of epoxy then glassing the joint with tape it should be just as
strong as having and exact bevel. If you going for the craftsmanship
approach, by all means, Ray's is the best.
Jeff
----- Original Message -----
From: <Shorty@...>
To: <bolger@yahoogroups.com>
Sent: Wednesday, September 19, 2001 8:15 AM
Subject: [bolger] Re: Compound Cut - Match Curve
> Jeff & Ray --
>
> I had to read your posts a few times to understand them, but I have the
> concept in my head now.
>
> Thank you so much for illuminating the solution to this problem! This
> is just the greatest list, without you guys I would be totally lost.
>
> Shorty
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
> - pls take "personals" off-list, stay on topic, and punctuate
> - add your comments at the TOP and SIGN your posts, snip all you like
> - To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA,
01930, Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject tohttp://docs.yahoo.com/info/terms/
>
>
Jeff & Ray --
I had to read your posts a few times to understand them, but I have the
concept in my head now.
Thank you so much for illuminating the solution to this problem! This
is just the greatest list, without you guys I would be totally lost.
Shorty
I had to read your posts a few times to understand them, but I have the
concept in my head now.
Thank you so much for illuminating the solution to this problem! This
is just the greatest list, without you guys I would be totally lost.
Shorty
Hi Shorty,
Jeff gives a good explanation of using a tic board to pick up the
curve. If your boat's V changes along it's length you'll also need
the bevel along the curve. I'd like to give a couple of other
methods you might want to try.
The first is a series of arcs. You'll need a pattern, a batten, a
compass, a sliding T-bevel and a little practice before you cut up
good wood. The hardest part will be finding the perfect compass. It
should have for it's "pointed leg" a straight leg with a farily fine
point, not the dog leg style of the typical grade schooler's
compass. When the compass is folded closed both sides should be
parallel. The best kind has a screw for fine radius adjustment. I
found mine in an antique shop, they haven't been made for many
years. Stick a pencil in the holder and with your sharp knife
whittle the outside of the pencil down such that when the compass is
open about 1/2 way the pencil lead is the widest part of the radius,
rather than the wood of the pencil.
The pattern needs to be long enough to cover the area you from which
you want to pick up the curve and wide enough to fit the arcs.
You'll have to fiddle around with this till you get the hang of it.
I like to use thin ply or door skins for the patterns. That way my
mistakes don't break the bank.
If you are dealing with a lot of curve you can even rough out the
pattern to the approximate curve. Or cut short straight pattern
pieces and overlap and fasten to make a segmented pattern that
somewhat follows the curve.
Now you've got to use a fair amount of creativity, the object is to
get the pattern to stay in place where the bilge keel goes, stable in
all three axis. This will probably require additional hands.
Now the fun part begins. Open the compass to a radius that reaches
from the center of the pattern to the contact point on the hull.
Place the pencil lead against the hull and swing the pointed end
about till you find the top of the arc. Push the point firmly
against the pattern to make a dent and now swing the pencil leg to
make sure it exactly touches the hull. This is where the fine radius
adjustment of the antique compass comes in handy. Without moving the
sharp point swing an arc from the dent across the pattern, remove the
compass, darken the dent and sketch a line from the dent to the arc
on the pattern. The reason for this last bit is that you may have to
change the compass radius as you work your way down the pattern so
you'll need to be able to reset the compass to the correct radius.
Repeat the process till you have a series of arcs close enough
together to recreate the hull shape.
Now take out your sliding T-bevel and a straight pattern. Mark the
curve pattern at regular intervals and placing the T-bevel against
the curve pattern and hull pick up the angle between the pattern and
the hull. Place the thick part of the T-bevel against the hull and
let it find it's own resting point. Once you are happy with the
angle place the bevel against the straight pattern and record the
angle and label it. It doesn't matter which side of the pattern you
work on, but be consistent.
Remove the pattern and place it flat on your workbench blocking under
it such that it is the same height off the bench as the thickness of
the stock you'll be cutting. Fiddle with the relationship between
the pattern, the stock and the radii of the arcs to so that you'll
get the curve reasonably close to the edge of the stock. Tack
everything down with finish nails.
Get the compass out again. At each arc put the sharp point on the
dent, set the radius to the arc on the pattern matching that point
and swing an arc on the stock. Repeat this for all the arcs.
Get your batten, some finish nails and and a bit of patience.
Lightly drive a finish nail at the "top" of each arc. Spring the
batten across the nails and fair it. You'll want to find a smooth
curve that will touch all the arcs. Fiddle with the placement of the
finish nails till you're happy. Draw the line.
You now have the first part of the compound curve.
Now study the straight pattern with the bevel marks. Look out for
the "bevel monster". It can make you do all kinds of stupid things
at this point. Think about how the bilge keel will sit on the hull,
which side of the curve pattern you measured the angles, and which
side of the stock you are looking at. Pick the most severe bevel and
set your saw to that angle. Sharp curves with lots of bevel are best
cut on a band saw. Gentle curves with shallow bevels can be cut with
most any saw. Experience will teach you which is the best tool. If
you have to use a saber saw use the widest hallow ground blade it
will take, and if your saw has an adjustable orbit set is as small as
will work with your stock. Cut wide of the line and fair the cut by
hand. Saber saw blades will wobble quite a bit when doing this.
Using the T-bevel, recorded angles and your favorite tool for the job
adjust the bevel all along the curve till it's right. I like low
angle block planes and spoke shaves for this. Lots of trial fits
against the hull are called for as you fair the bevel. If you plan
on gluing with thickened epoxy perfection is not required.
This is a variation of one method of making patterns for traditional
carvel planked boats. It takes some practice to master but yields
excellent fits once mastered. I suggest for the first attempt using
throw-away quality stock.
The second method also uses pattern, T-bevel and compass, but no
batten. Here you will be directly copying the hull curve onto the
pattern.
As above get your pattern situated and stable. Now find a radius for
the compass that will work all the way along the pattern. Here's the
method, you'll hold the compass so the point rides along the hull at
the line the keel attaches keeping the pencil lead on the pattern.
Draw the curve on the pattern. The key to success is to keep the
compass point and the pencil point in the correct alignment at all
times. Imagine a straight line attaching the two points. Whatever
the angle that line makes with mother earth at the instant you start
it must not change throughout the drawing of the curve.
Think of it this way, you can even practice this before you ruin good
wood. Put a gallon can down on a piece of paper. Set the compass at
about 3" radius. Put the point of the compass against the can and
put the pencil on the paper such that the line between the points is
parallel to one edge of the paper. Move the compass along the
surface of the can about 1/3 to 1/2 of it's circumference keeping the
points parallel to the paper edge. Cut that curve with scissors and
it should fit the curve of the can bottom. If it doesn't fit it
means you let the sharp point to pencil point radius get out of
parallel as you went along.
So back to the keel. If you did it right you now have a perfect
reproduction of the curve of the hull on the pattern. Saw it out and
try it. Fiddle with it till you're happy with the fit, not worrying
about bevels. Again the advantage of door skins is cheapness.
Mistakes won't mean a second mortgage.
Now mark it at intervals and stick it all down again in place against
the hull so it doesn't move. Get the sliding T-bevel, a straight
pattern and pick up the bevels as above. Pull the pattern off the
hull, set the saw, cut and fair the bevels and try the fit.
Once you try these methods you'll understand why ply boats designed
for amature builders are so boxy in shape. Once you master these
techniques you'll be able to work with much more complex shapes.
Resist the urge to use your good stock until you've tried it a couple
of times.
Hope this helps rather than confuses.
Ray
Jeff gives a good explanation of using a tic board to pick up the
curve. If your boat's V changes along it's length you'll also need
the bevel along the curve. I'd like to give a couple of other
methods you might want to try.
The first is a series of arcs. You'll need a pattern, a batten, a
compass, a sliding T-bevel and a little practice before you cut up
good wood. The hardest part will be finding the perfect compass. It
should have for it's "pointed leg" a straight leg with a farily fine
point, not the dog leg style of the typical grade schooler's
compass. When the compass is folded closed both sides should be
parallel. The best kind has a screw for fine radius adjustment. I
found mine in an antique shop, they haven't been made for many
years. Stick a pencil in the holder and with your sharp knife
whittle the outside of the pencil down such that when the compass is
open about 1/2 way the pencil lead is the widest part of the radius,
rather than the wood of the pencil.
The pattern needs to be long enough to cover the area you from which
you want to pick up the curve and wide enough to fit the arcs.
You'll have to fiddle around with this till you get the hang of it.
I like to use thin ply or door skins for the patterns. That way my
mistakes don't break the bank.
If you are dealing with a lot of curve you can even rough out the
pattern to the approximate curve. Or cut short straight pattern
pieces and overlap and fasten to make a segmented pattern that
somewhat follows the curve.
Now you've got to use a fair amount of creativity, the object is to
get the pattern to stay in place where the bilge keel goes, stable in
all three axis. This will probably require additional hands.
Now the fun part begins. Open the compass to a radius that reaches
from the center of the pattern to the contact point on the hull.
Place the pencil lead against the hull and swing the pointed end
about till you find the top of the arc. Push the point firmly
against the pattern to make a dent and now swing the pencil leg to
make sure it exactly touches the hull. This is where the fine radius
adjustment of the antique compass comes in handy. Without moving the
sharp point swing an arc from the dent across the pattern, remove the
compass, darken the dent and sketch a line from the dent to the arc
on the pattern. The reason for this last bit is that you may have to
change the compass radius as you work your way down the pattern so
you'll need to be able to reset the compass to the correct radius.
Repeat the process till you have a series of arcs close enough
together to recreate the hull shape.
Now take out your sliding T-bevel and a straight pattern. Mark the
curve pattern at regular intervals and placing the T-bevel against
the curve pattern and hull pick up the angle between the pattern and
the hull. Place the thick part of the T-bevel against the hull and
let it find it's own resting point. Once you are happy with the
angle place the bevel against the straight pattern and record the
angle and label it. It doesn't matter which side of the pattern you
work on, but be consistent.
Remove the pattern and place it flat on your workbench blocking under
it such that it is the same height off the bench as the thickness of
the stock you'll be cutting. Fiddle with the relationship between
the pattern, the stock and the radii of the arcs to so that you'll
get the curve reasonably close to the edge of the stock. Tack
everything down with finish nails.
Get the compass out again. At each arc put the sharp point on the
dent, set the radius to the arc on the pattern matching that point
and swing an arc on the stock. Repeat this for all the arcs.
Get your batten, some finish nails and and a bit of patience.
Lightly drive a finish nail at the "top" of each arc. Spring the
batten across the nails and fair it. You'll want to find a smooth
curve that will touch all the arcs. Fiddle with the placement of the
finish nails till you're happy. Draw the line.
You now have the first part of the compound curve.
Now study the straight pattern with the bevel marks. Look out for
the "bevel monster". It can make you do all kinds of stupid things
at this point. Think about how the bilge keel will sit on the hull,
which side of the curve pattern you measured the angles, and which
side of the stock you are looking at. Pick the most severe bevel and
set your saw to that angle. Sharp curves with lots of bevel are best
cut on a band saw. Gentle curves with shallow bevels can be cut with
most any saw. Experience will teach you which is the best tool. If
you have to use a saber saw use the widest hallow ground blade it
will take, and if your saw has an adjustable orbit set is as small as
will work with your stock. Cut wide of the line and fair the cut by
hand. Saber saw blades will wobble quite a bit when doing this.
Using the T-bevel, recorded angles and your favorite tool for the job
adjust the bevel all along the curve till it's right. I like low
angle block planes and spoke shaves for this. Lots of trial fits
against the hull are called for as you fair the bevel. If you plan
on gluing with thickened epoxy perfection is not required.
This is a variation of one method of making patterns for traditional
carvel planked boats. It takes some practice to master but yields
excellent fits once mastered. I suggest for the first attempt using
throw-away quality stock.
The second method also uses pattern, T-bevel and compass, but no
batten. Here you will be directly copying the hull curve onto the
pattern.
As above get your pattern situated and stable. Now find a radius for
the compass that will work all the way along the pattern. Here's the
method, you'll hold the compass so the point rides along the hull at
the line the keel attaches keeping the pencil lead on the pattern.
Draw the curve on the pattern. The key to success is to keep the
compass point and the pencil point in the correct alignment at all
times. Imagine a straight line attaching the two points. Whatever
the angle that line makes with mother earth at the instant you start
it must not change throughout the drawing of the curve.
Think of it this way, you can even practice this before you ruin good
wood. Put a gallon can down on a piece of paper. Set the compass at
about 3" radius. Put the point of the compass against the can and
put the pencil on the paper such that the line between the points is
parallel to one edge of the paper. Move the compass along the
surface of the can about 1/3 to 1/2 of it's circumference keeping the
points parallel to the paper edge. Cut that curve with scissors and
it should fit the curve of the can bottom. If it doesn't fit it
means you let the sharp point to pencil point radius get out of
parallel as you went along.
So back to the keel. If you did it right you now have a perfect
reproduction of the curve of the hull on the pattern. Saw it out and
try it. Fiddle with it till you're happy with the fit, not worrying
about bevels. Again the advantage of door skins is cheapness.
Mistakes won't mean a second mortgage.
Now mark it at intervals and stick it all down again in place against
the hull so it doesn't move. Get the sliding T-bevel, a straight
pattern and pick up the bevels as above. Pull the pattern off the
hull, set the saw, cut and fair the bevels and try the fit.
Once you try these methods you'll understand why ply boats designed
for amature builders are so boxy in shape. Once you master these
techniques you'll be able to work with much more complex shapes.
Resist the urge to use your good stock until you've tried it a couple
of times.
Hope this helps rather than confuses.
Ray
--- In bolger@y..., Shorty@S... wrote:
> To mount a pair of bilge keels on the bottom of my hull (curved V
> bottom, not flattie), how do you measure and transfer the the
compound
> curve needed to match the keel to the hull? And then how do you
cut it?
>
> Also - after the keels are cut, what is the preferred method of
mounting
> them? Just glue and screw? Do I need large thru bolts?
>
> Thanks
> Shorty
There is a thing called a Tic Board I believe that anyone can set up to get
the curves or duplicate compound curves. Essentially, get a long board to
cover the full distance of the curve. Make sure it is set up like a
baseline on a set of plans. I.E. set it at a predetermined distance and
parallel to the curve. I've done it before and just made sure it was level.
Mark it every 3 to 6 inches (depending on the accuracy you want) with a
ruler then draw a line using a square. Using a yard stick, framing square,
T-square, etc. Check the distance between the board and the hull and write
down the distance next to each mark on the board. Once done you can lay the
board and duplicate the curve by going back over the board and making a mark
for each measurement. Then drive a small nail on each mark, and using a
batten or such to lay against the nails to mark the curve. This is the way
you can get hull offsets when duplicating a hull without the offset table
available.
This can be used anywhere to get exact bulk fittings, etc. Very useful and
completely free other than the reusable 2X4.
Jeff
the curves or duplicate compound curves. Essentially, get a long board to
cover the full distance of the curve. Make sure it is set up like a
baseline on a set of plans. I.E. set it at a predetermined distance and
parallel to the curve. I've done it before and just made sure it was level.
Mark it every 3 to 6 inches (depending on the accuracy you want) with a
ruler then draw a line using a square. Using a yard stick, framing square,
T-square, etc. Check the distance between the board and the hull and write
down the distance next to each mark on the board. Once done you can lay the
board and duplicate the curve by going back over the board and making a mark
for each measurement. Then drive a small nail on each mark, and using a
batten or such to lay against the nails to mark the curve. This is the way
you can get hull offsets when duplicating a hull without the offset table
available.
This can be used anywhere to get exact bulk fittings, etc. Very useful and
completely free other than the reusable 2X4.
Jeff
----- Original Message -----
From: <Shorty@...>
To: <bolger@yahoogroups.com>
Sent: Tuesday, September 18, 2001 1:14 PM
Subject: [bolger] Compound Cut - Match Curve
> To mount a pair of bilge keels on the bottom of my hull (curved V
> bottom, not flattie), how do you measure and transfer the the compound
> curve needed to match the keel to the hull? And then how do you cut it?
>
> Also - after the keels are cut, what is the preferred method of mounting
> them? Just glue and screw? Do I need large thru bolts?
>
> Thanks
> Shorty
>
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
> - pls take "personals" off-list, stay on topic, and punctuate
> - add your comments at the TOP and SIGN your posts, snip all you like
> - To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA,
01930, Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject tohttp://docs.yahoo.com/info/terms/
>
>
To mount a pair of bilge keels on the bottom of my hull (curved V
bottom, not flattie), how do you measure and transfer the the compound
curve needed to match the keel to the hull? And then how do you cut it?
Also - after the keels are cut, what is the preferred method of mounting
them? Just glue and screw? Do I need large thru bolts?
Thanks
Shorty
bottom, not flattie), how do you measure and transfer the the compound
curve needed to match the keel to the hull? And then how do you cut it?
Also - after the keels are cut, what is the preferred method of mounting
them? Just glue and screw? Do I need large thru bolts?
Thanks
Shorty