1/2 Model help urgent

[MarcusH]

I have been requested to build half models for a class of year 10 students. Later to include complete models of small to large craft. Dinghy build has been shelved due to cost. a. Can I use old plans that have line drawings? How to get to the first stage? Any good books available? I would like to do a half model of my own boat as an example. 40' timber schooner designed by C.D.Mower in 1926. Any help would be very much appreciated.

[b.o.a.t.]

Never made a half model, but from what I've read, I think you need either the table of off-sets,
or have sufficiently detailed drawings to be able to measure them at each station point.
Here's an example from Philip Bolger's "Boats With An Open Mind"
scan0001.jpg

Make up horizontal "slices" of timber using these numbers.
Glue them together in a stack, & plane off the excess to a smooth finish.

If that sounds too complicated or time consuming, another possibility might be building a model boat.
A book like Boat Modeling with "Dynamite" Payson might offer ideas suitable for a classroom?

HTH
Alan J

[MarcusH]

Thanks very much boat. I'll look at the designs I have. There are a few that have lines and I may be able to transfer them to a scale set of drawings. Regards
Marcus

[piquet]

The info that you have been given so far is correct.


I made quite a few doing my apprenticeship but haven't made one for years.

In print this is a very difficult thing to explain but I will give it a go.

The table of offsets is the best way to go but you also need the sheer plan to be able to measure where each frame station is and also to get the profile of the boat along the centreline.

The way that I was taught was to make a number of profiles of the boat at probably half the frame stations on the drawings. These were made from 1/8" plywood.

The blank is made up from a number of pieces of timber glued together as waterline slices of the boat being modelled. We used two different types of timber. Usually a dark timber for below the water line of the boat and a light coloured timber above the waterline.
For example it could be cedar below the waterline and a timber like kauri above. I wouldn't use Oregon above the waterline due to the harder part of the grain which is harder to carve and to get smooth next to the softer part of the timber.

The blank of the model needs to be screwed to a rectangular piece of timber about 200mm long with an agle cut on the top end where the model blank is screwed so that the whole thing can be clamped in the woodworking vice. This will allow access to the rear of the model to line up the fame station templates and the model to be angled around to find a comfortable working position for all the fiddly stuff of shaping the model.

Being in Tasmania there would be good stocks of Huon Pine for the above the waterline part of the model.

The frame station templates need to have the waterline marked on them, the centreline of the boat at the bottom and thetop and the sheer or top edge of the model clearly marked on them. These are the reference points that make up the points for the carving of each frame station on the model.
On the back flat section of the model the frame stations need to be marked, so that when the frame station templates are being fitted to the outside of the model they can be lined up. Then the outside of the model needs to be carved so that the frame station template fits over the station being carved with the waterline mark lining up with the waterline, the bottom centreline mark lining up with the centreline of the model and the sheer mark lining up with the sheer and the top centreline lining up with the centreline of the model.

After you have one go on to the next frame station and do the same. I would think that if it is a model of a small rowing boat then there would not be the number of templates as would be needed for a yacht similar to for example an Americas cup yacht that has a large change of shape from bow to mid ships to the area around the rudder.

The frame stations need to be carved with chisels and gouges to get the templates to fit. After all the frame stations have been fitted reasonably closely to the correct profile the the shape between the carved sections need to be " faired " in with other tools such as flat and curved spoke shaves. The shape needs to be checked frequently with the profile templates to ensure that not too much material is taken off

When the shape is close with the spoke shaves it is time to start sanding of the model to
a get the surface smooth
b ensure that the shape is fair with no high spots

The sanding will need to be with various grades of sandpaper. Sometimes the sandpaper may need to be wrapped around some different sizes of dowelling to get the sandpaper into the hollow/ concave parts of the model so that it fits the profile templates.

After all this work comes the time to put some varnish on the model? I would probably use satin varnish. The model can then be mounted on a backing board which should also be varnished.

Gosh after all that I just hope that I agent either put you off or totally confused you

Cheers
Peter

[MarcusH]

The info that you have been given so far is correct.


I made quite a few doing my apprenticeship but haven't made one for years.

In print this is a very difficult thing to explain but I will give it a go.

The table of offsets is the best way to go but you also need the sheer plan to be able to measure where each frame station is and also to get the profile of the boat along the centreline.

The way that I was taught was to make a number of profiles of the boat at probably half the frame stations on the drawings. These were made from 1/8" plywood.

The blank is made up from a number of pieces of timber glued together as waterline slices of the boat being modelled. We used two different types of timber. Usually a dark timber for below the water line of the boat and a light coloured timber above the waterline.
For example it could be cedar below the waterline and a timber like kauri above. I wouldn't use Oregon above the waterline due to the harder part of the grain which is harder to carve and to get smooth next to the softer part of the timber.

The blank of the model needs to be screwed to a rectangular piece of timber about 200mm long with an agle cut on the top end where the model blank is screwed so that the whole thing can be clamped in the woodworking vice. This will allow access to the rear of the model to line up the fame station templates and the model to be angled around to find a comfortable working position for all the fiddly stuff of shaping the model.

Being in Tasmania there would be good stocks of Huon Pine for the above the waterline part of the model.

The frame station templates need to have the waterline marked on them, the centreline of the boat at the bottom and thetop and the sheer or top edge of the model clearly marked on them. These are the reference points that make up the points for the carving of each frame station on the model.
On the back flat section of the model the frame stations need to be marked, so that when the frame station templates are being fitted to the outside of the model they can be lined up. Then the outside of the model needs to be carved so that the frame station template fits over the station being carved with the waterline mark lining up with the waterline, the bottom centreline mark lining up with the centreline of the model and the sheer mark lining up with the sheer and the top centreline lining up with the centreline of the model.

After you have one go on to the next frame station and do the same. I would think that if it is a model of a small rowing boat then there would not be the number of templates as would be needed for a yacht similar to for example an Americas cup yacht that has a large change of shape from bow to mid ships to the area around the rudder.

The frame stations need to be carved with chisels and gouges to get the templates to fit. After all the frame stations have been fitted reasonably closely to the correct profile the the shape between the carved sections need to be " faired " in with other tools such as flat and curved spoke shaves. The shape needs to be checked frequently with the profile templates to ensure that not too much material is taken off

When the shape is close with the spoke shaves it is time to start sanding of the model to
a get the surface smooth
b ensure that the shape is fair with no high spots

The sanding will need to be with various grades of sandpaper. Sometimes the sandpaper may need to be wrapped around some different sizes of dowelling to get the sandpaper into the hollow/ concave parts of the model so that it fits the profile templates.

After all this work comes the time to put some varnish on the model? I would probably use satin varnish. The model can then be mounted on a backing board which should also be varnished.

Gosh after all that I just hope that I agent either put you off or totally confused you

Cheers
Peter

Thanks very much Peter. What you have described is what I thought I would need to do. I do have a couple of plans that have lines and profiles and some with offsets. It would be amazing to see how the students go. I'll keep you informed on how they turn out and I'll post a few pictures as a record.
Regards
marcus

[bloggs1968]

Hi Marcus,

Send me an email and I'll send through some info.

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