Wedging Stretchers

[Stray Feathers]

Another thread raised questions for me about strainers and stretchers. We use (contrary to lots of opinions here) strainers to stretch odd-size canvasses. It would be nice to have the flexibility of wedges but we are too small to stock much in the way of sizes, and in any case sizes are often custom. Is it possible to buy larger stretcher bars, cut them down on one end each and join them, so that there are two diagonally opposed corners joined, and two diagonally opposed with wedges?

 

[Artrageous]

Wouldn't the stretcher/strainer go out of square if you only adjusted opposing corners?

 

[Jeff Rodier]

Is it possible to buy larger stretcher bars, cut them down on one end each and join them, so that there are two diagonally opposed corners joined, and two diagonally opposed with wedges?

That is not that unusual but does not solve all problems. Joined bars can be expanded with turnbuckles and Best Stretcher Bars sells a very easy to use version of them. Even if you glue and v-nail they will pop the joint after the fact if needed. Buy a small quantity and if anything comes back loose you can install them at that point.

Always slip a scrap of mat board in the corner where you are working on the back of an oil painting while installing or adjusting corner keys. I made a little oops on a $10k painting while installing keys on a piece that had just completed a restoration. Customer said no big deal just let me know when it is restored again. Could have gone badly though.

 

[wpfay]

Strainer stock can be used to make stretchers. All you need is a slot cutter (router table), a thickness plane, and some turnbuckles. The joint can also be made with aluminum dowels and knock-down cabnetry hardware in the fashion of the late Jimmy Lebron.
Alternately using manufactured stretcher bars, you can scarf join lengths (with reinforcement) that have a section removed from the middle to reduce its length to the desired measurement.

 

[Prospero]

In the UK there is a moulding available that is basically a strainer with a groove cut lengthwise. Some have two grooves so you can use it deep or shallow. The idea is that you cut plywood triangles and bang them into the grooves to form an expandable corner. Not as good as proper stretchers, but they do work quite well and for odd sizes they are great. You can make your own if you have a table saw.
I've found the trick is to make bigger corner triangles for bigger canvases. They are quite strong once put together.

If you can quite visualise it from my weird description I got some pictures somewhere.....

 

[GrumbleMike2]

I order all our stretchers custom from (local to me) fotiou or ucs, the answer is in your signature

here's a great source for stretcher corner info maybe some hardware ideas could be adapted as in fig 35b

http://www.conservation-wiki.com/wiki/PSG_Stretchers_and_Strainers_-_III._Materials_and_Equipment

 

[Less]

I use strainers when cost is more important than quality, which is often. Since I am not set up as a wood shop, I find just as easy to order custom sizes. You just need to explain the options, and factor is the cost.

 

[Prospero]

Strainer bar with groove cut with table saw.

Staples are just to hold the corners in place while stretching.

Once tensioned, tiny screws in the groove stop the ply triangles from slipping back.

 

[Stray Feathers]

Strainer bar with groove cut with table saw.

Staples are just to hold the corners in place while stretching.

Once tensioned, tiny screws in the groove stop the ply triangles from slipping back.

This idea looks really workable. It looks like there could be enough material to drive screws through the stainer and plywood from the side. I'll look into other suggestions too - thanks.