17' square back Grumman S with fins at the stern along the waterline

I’ve had many canoes over the years. Cedar Geislers, Fiberglass Old Town and a Detroit Boat Works canvas that dates to 1910. A few years back I bought a 17’ Grumman with two factory installed wings at the water line. It has a square back for a motor. It is heavy! I have spoken to Marathon boats in New York state but they have no records of ever making this kind canoe. I even spoke to an employee that worked there back in the Grumman days. He said he kind of remembered some experimentation that was going on in the 1950’s or 1960’s with this type of craft. It rides well and is very stable. I sure wish I could find out more about it. It’s an attention getter and my outing always take extra time to show folks this unique craft.

Could the fins have been meant as trim tabs for use with a motor? They might be to keep the stern from dropping down in the water.

Hi Craig- Yes I believe this is why they were installed. I have heard this canoe is referred to as a whale tail. All the mounting structure is consistent with the way Grumman built boats. The bending of the aluminum fins from extruded materials make me think it was original the manufacturing of this craft. This is only a guess in my quest to find out more about my canoe. Thanks for responding.