Classic Sport 13 or 15 Raising Rear Thwart Seat

[BlueSmoke]

Classic Sport 13 or 15 Raising Rear Thwart Seat

I would like to raise the aft thwart seat for comfort and to give me some room in the future to mount a backrest under the seat. As it sits now as original from the factory on the hull rail, there is no clearance above the gas tank. In the picture [now inseted below--jmh] you can see how I would like it to sit, however, the side risers are bowed out and there is about 1/4-inch gap on each side. I am trying to decide what to do to get thwart sit right.



Does fixing the seat to the riser do anything negative to the hull?

For instance, will this keep the hull from flexing and put pressure on the wood and screws into the hull creating problems down the road? Or is the hull solid and doesn't flex?

How should I attach the seat as it is about 1/2-inch to short to sit squarely?

I was thinking I could add rails underneath one side to support it, and leave the other side lined up.
Or, trim the seat down shorter length wise so it fits flush between the side risers and mount with two rails underneath on each side so that the top of the seat it level with top of riser. This may be more work, but look nicer.

[BlueSmoke]

image1 (1).PNG (110.42 KiB) Viewed 4398 times

[NOTE: I added this image to your initial posting--jimh]

[jimh]

...I am trying to decide what to do to get thwart sit right.

I don't quite understand this comment. Are you asking about getting the thwart seat to sit properly on the riser? Please clarify.

...Does fixing the seat to the riser do anything negative to the hull?

No.

...For instance, will this keep the hull from flexing and put pressure on the wood and screws into the hull creating problems down the road?

Boston Whaler themselves moved the location of the thwart seat to sit atop the riser board instead of being captivated under the riser board, so it would seem quite reasonable to infer that Boston Whaler did not think doing this would cause hull damage. See the image below:


CENTER CONSOLE 15 with thwart seat mounted atop rise and with backrest added.

...is the hull solid and doesn't flex?

All hulls flex somewhat. Exactly how much your hull will flex will probably be a function of its condition. If your hull still has its original structural strength it won't be flexing very much, if any.

How should I attach the seat as it is about 1/2-inch [too] short to sit squarely?

Replace the board for the seat with a longer board. Or, attach a gusset to the riser.

[ConB]

Or loosen the rail screws, tip the top in, screw seat down and retighten rail screws.

Con

[padrefigure]

Or put a cushion on the thwart seat to raise the sitting position. We often use standard boat cushions that raise the sitting position by about 2". Or go to a canoe and kayak store and find one of the fit over seats with a back rest. You get a little more height and back support at the same time. Or finally, find a stadium chair that fits over the thwart. For these simple boats, low tech can often be the best solution.