I did use the standard backing plates. But you couldn't go wrong using bigger ones of aluminum or G-10 cut to fit the space available below deck.
When Atlantic Towers talks about "pre-loading" they are talking about putting stress into the system to stabilize it. The way this is done is set up the legs of the arch so they are significantly further apart than the mounting points. The width of the arch is adjustable by design, so this isn't hard. I used a Spanish windlass to pull the legs together to get them to fit. This "loads" the arch so it is under tension and it doesn't have as much freedom to move.
My recollection is that I pulled them together about 6 inches, but talk to them to get the right distance--don't count on my memory! More is better... up to a critical point of course! I don't think they emphasize the importance of this part of the process enough in their instructions.
We mounted ours with the aft arch feet just clear of the back of the stern cleats. That way the arch clears the mizzen boom, we didn't have to fuss with reinforcements to the transom, and access to the underside of both feet for bolting is inside the lazarette.
Holes in the deck were drilled oversize through the top skin, core removed, and then filled with thickened epoxy before drilling to final size for the bolts.
---In amelyachtowners@..., <jamessterling88@...> wrote :
Can you explain a little bit more about the process of pre-loading and bracing the Atlantic Towers Arch? Also, did you use standard backing plates?
S/V Longbow SM2K #418