craftsmen

I'm being asked to repair this shell, a 70s model wood stampfli.

I've got to wait until summer to be back at my house again where I can set up proper shop.

There are half dozen splits like this on the hull, though the cockpit and interior structure look to be in fine shape. It's not easy to see, but the skin has lost it's shape and has flattened out.
https://photos.google.com/photo/AF1QipM8FLNSYpBQgjr9Xpikj8mU38Iw4nOKZ7VTy35K email sul at slac dot stanford dot edu if you can't see this and want to help. I THINK I have public access to these.

To repair this I'll open up the decking, and make a mold of the inside hull on the opposite hemisphere of the split. Briefly, I'll strip the varnish down to the wood, steam the area around the split and tape the skin down over the mold clamped on
the inside. After the moisture dries, I'll glue the split, remove the clamp after during and reinforce with fiberglass on inside hull, then refinish.

Am open to criticism of this method, I've used this before successfully but I' an amateur.

Now the problem. There are similar splits under the seat platform. On many wood hulls, the seat platform is set down on the stringers in various ways depending on builders. I can remove screws or pry up seat platform to get inside. the Stampfli
looks like the stringers are above the seat platform (screwed in upside down perhaps?)

Is there a trick to repairing this sort of radical check from the outside and not have to go into the inside? I can't imagine one.

Doesn't look simple to me, and I dare not go exploring willy nilly as I do with my old boats I usually return to working order.

thanks

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Hi Mike,
I'm not a craftsman. I assisted a Stampfli pair-builder repairing a shell once and he described the construction method - first there are forms on a strongback, and the stringers are laid out end to end, and the boat is built as a skeleton and keel first,
and then the skin (a 2 mm thick piece of "ayuz" (that's what Werner called it)) is carried over (very carefully) clamped to the stringers, and then hot-water-heat-gun bent to the forms at that point anything that doesn't look like the boat is shaved off
with razor sharp block planes. The inner surface of the boats made in the 1980s was "varnished" with a thin layer of silk - it was a 2--part synthetic varnish that cured, more than it dried. While the ayuz was being carried and steam-bent the silk was
almost all that held the wood together, and it was a major effort to get the wood formed in place without cracking. Werner let me help with some aspects of the repair but mostly it was "hold this, carefully, and don't talk, I need to hear the wood"

Might not be much help but yes, the boat is assembled upside down, first, and a bunch of layers of the 2-part 'varnish' are applied.. The joints Werner made were all VERY tight - no gaps between parts filled by epoxy - just very tight joinery and "
varnish" as the glue.

Cheers,
Walter

On Thursday, 18 March 2021 at 21:33:41 UTC-6, sully wrote:

craftsmen

I'm being asked to repair this shell, a 70s model wood stampfli.

I've got to wait until summer to be back at my house again where I can set up proper shop.

There are half dozen splits like this on the hull, though the cockpit and interior structure look to be in fine shape. It's not easy to see, but the skin has lost it's shape and has flattened out.
https://photos.google.com/photo/AF1QipM8FLNSYpBQgjr9Xpikj8mU38Iw4nOKZ7VTy35K email sul at slac dot stanford dot edu if you can't see this and want to help. I THINK I have public access to these.

To repair this I'll open up the decking, and make a mold of the inside hull on the opposite hemisphere of the split. Briefly, I'll strip the varnish down to the wood, steam the area around the split and tape the skin down over the mold clamped on the

inside. After the moisture dries, I'll glue the split, remove the clamp after during and reinforce with fiberglass on inside hull, then refinish.

Am open to criticism of this method, I've used this before successfully but I' an amateur.

Now the problem. There are similar splits under the seat platform. On many wood hulls, the seat platform is set down on the stringers in various ways depending on builders. I can remove screws or pry up seat platform to get inside. the Stampfli looks

like the stringers are above the seat platform (screwed in upside down perhaps?)

Is there a trick to repairing this sort of radical check from the outside and not have to go into the inside? I can't imagine one.

Doesn't look simple to me, and I dare not go exploring willy nilly as I do with my old boats I usually return to working order.

thanks

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 19/03/2021 03:33, sully wrote:

craftsmen

I'm being asked to repair this shell, a 70s model wood stampfli.

I've got to wait until summer to be back at my house again where I can set up proper shop.

There are half dozen splits like this on the hull, though the cockpit and interior structure look to be in fine shape. It's not easy to see, but the skin has lost it's shape and has flattened out.
https://photos.google.com/photo/AF1QipM8FLNSYpBQgjr9Xpikj8mU38Iw4nOKZ7VTy35K email sul at slac dot stanford dot edu if you can't see this and want to help. I THINK I have public access to these.

To repair this I'll open up the decking, and make a mold of the inside hull on the opposite hemisphere of the split. Briefly, I'll strip the varnish down to the wood, steam the area around the split and tape the skin down over the mold clamped on

the inside. After the moisture dries, I'll glue the split, remove the clamp after during and reinforce with fiberglass on inside hull, then refinish.

Am open to criticism of this method, I've used this before successfully but I' an amateur.

Now the problem. There are similar splits under the seat platform. On many wood hulls, the seat platform is set down on the stringers in various ways depending on builders. I can remove screws or pry up seat platform to get inside. the

Stampfli looks like the stringers are above the seat platform (screwed in upside down perhaps?)

Is there a trick to repairing this sort of radical check from the outside and not have to go into the inside? I can't imagine one.

Doesn't look simple to me, and I dare not go exploring willy nilly as I do with my old boats I usually return to working order.

thanks

I meant to post the following on RSR yesterday but sent it only to
Sully. Here it is:

Mike -
It ain't simple. The skin consists of a single wood veneer, formed over
frames & then stiffened/reinforced by applying a layer of fine Dacron
cloth over the outside & lacquering that in place. This was an
improvement on the previous way of building shells, which omitted the
cloth layer

The loss of the cloth & the presence of splits encourages the veneer to
return to its original flatness.

The old way of repairing such splits was to apply a thin piece of wood
to the inside of the hull, bed it in shellac & then fix it with thin
copper rivets. In the UK these patches, visible as 2 rows of copper
heads, were called "tingles". Some boats acquired quite a lot of them.

Another problem with this form of construction was the ease with which
the cloth peeled away from any split.

A first step towards repairing these splits would be to inject epoxy
resin into the split, then push the split line back inwards by applying
a narrow, square-section stick (released with scotch tape) along the
crack & judiciously pulling the split back into shape with transverse
bands of tape. If that does it, you then have the problem of what to do
to reinforce the hull, given that the cloth is lifting and the hull has
been impregnated with a lacquer that won't help resin adhesion.

We do things better these days, although I do recall one UK builder who
thought that a unidirectional carbon cloth mono-layer skin was a good
idea - until they started splitting & going angular, just like pre-WW2
boats.

Cheers -
Carl


--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write: Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find: tinyurl.com/2tqujf
Email: carl@carldouglasrowing.com Tel: +44(0)1932-570946 Fax: -563682
URLs: carldouglasrowing.com & now on Facebook @ CarlDouglasRacingShells

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