from “Rovings,” Professional BoatBuilder No. 153
Compiled by Dan Spurr
In the Rovings column in PBB No. 151, page 16, we published photos of reader Michael Robertson’s 1978 Fuji 40 (12.2m) rudder, which he had opened up to investigate why it was dripping water. From one side he cut out a 12″ x 18″ (305mm x 457mm) panel and was surprised to find no metal webbing, just foam and epoxy. At the end of the write-up we asked, Is this observable method of construction sound? And, How common is this construction method?
We received a fairly detailed response from Phil Locker at Competition Composites Inc. (CCI) in Ottawa, Ontario, Canada:
“We take apart quite a few rudders per year in order to build a new blade around the existing rudderpost, to save the customer the costs involved from total replacement. Rarely do we actually see stainless steel inside the rudder. Generally, the post is stainless, and any additional metal structure is (rusty) mild steel. This is nearly universal on older cruising boats with spade rudders. The rest of the OEM blade would be pour-in-place urethane foam, and heavy fiberglass skins of chop and/or roving in polyester resin. These will be waterlogged, crumbling, and moldy by the time they come to us.
“The rudder as described in the article had only a fiberglass web on center forward of the rudderpost, and no observed metal plates or other structure. Was this a sound method of construction? Judging from the length of time that the rudder was in service, it seems to have been fine. There will have been no internal rust issues. One hopes that the fiberglass web included wraps around the post at the time of fabrication. Often on skeg-hung rudders we’ll see the internal structure dogleg around the lower bearing location, and have minimal support below. Skeg-hung rudders typically being of lower aspect ratio exert less of a bending load on the support system.
“We build a lot of new rudders to current designs, and the metal structure inside the rudder is going the way of the dodo bird. Carbon posts are frequently trapezoidal in cross section, and make direct contact with the rudder skins. There is no need for additional internal structure to prevent the blade from rotating around the post. When a round carbon post is used, before the halves of the foam core are bonded to it, a few wraps of fiberglass around the post and leading back into the body of the rudder (on the parting line) are sufficient.”
On further discussion with Robertson, he said he believes his rudderpost was machined with flat sides inside the rudder for more contact surface area with the wraps Locker describes above.
Competition Composites Inc., 168 Wescar Ln., Unit #3, Ottawa, Ontario, Canada, tel. 613–599–6951, website www.fastcomposites.ca.