Kyle Hamilton makes custom covers at reasonable prices.  She has done several for CLC boats including her own Skerry:  [email protected]

   You might try The Sailors' Tailor.  They make many different small boat covers in several different types of canvas.  You might find something in nearly the correct dimensions "off the shelf" for one of the commercial boats they already have measured - even though they make most of the standard covers once the order is placed.  They don't keep too many other than the most common actually in stock on the shelf.  They will also make covers to custom measurements.  Not cheap, but good quality.

But then again, you might go just a step or two up from a blue tarp - the cheap blue tarps never seem to last me for half a season - thus I don't buy them anymore.  However, with some carefull searching of local stores (truck supply or farm supply) you can find some very heary duty silver/black poly tarps.  Even these come in several thicknesses.  I recommend the thickest you can find.  Silver side out helps reduce heat in summer, black side out helps de-icing/de-snowing in winter (if you have that problem). They are stiff enough that they don't flap in the breeze so much as blue poly tarps, either.  Still very cheap compared to canvas, and last a season or two or three, location dependent.

   Oh, another thought. On my NE Dory (3 sets of oarlocks) I got some of the flexible plumbing tubing (PEX) and rigged it with a couple of hollow aluminum pins, put through the PEX pipe and an angle that poked down into the oarlocks, creating a "conestoga wagon" type set of arched hoops.  Left about 3 inches long on each end to creat an "eave" that sticks out wider that the gunwale of the boat, and put a tennis ball on the end of each pipe. I tied a line to the center-top of each arch that runs from stem to stern like a backbone, so that the arches can't move fore or aft.  The bow-end of this line is finished in a loop that fits over the bow and the line remains permanently  attached to the hoops.  This thing is very quick to install - plug the pins in the oarlocks to set up the hoops, throw the loop over the bow, leaving only the stern end of the line to pull tight and knot.  Then the cover goes over this.  Plenty of ventilation.  No chance of water pooling on the cover and therefore pulling the cover off/putting water in the boat.  Whether you put one, two or three oarlock positions on your Chester Yawl, the "Conestoga Cover" support sytem is, I think, a good idea - whatever type of cover material you use.  

   Thank you for the input. 

Yes, I was aware of Sailor's Tailor, they made me a sail cover several years ago. Appreciate the details for your "wagon cover". I had seen many boats with semi-custom covers made of t h e silver and black fabric.

DaveJ

I've been using heavy white polypro tarps to cover my catboat for the winter.  Much better'n the common blue ones.  Plus, which, the white won't beat blue color onto your boat.

Last bought a 12x24 from Tarps Plus for about $50 plus shipping.  Good stuff.

http://www.tarpsplus.com

They have a wide selection.

.....Michael