Aluminum boat hull flexing/twisting

[QuinnRooney]

Hello everybody. I recently turned a runabout closed bow in to a “fishing” style boat with bench seats. I have found that the sides of the hull flexes when i shake the boat. The floor and bow is nice and sturdy. I know i am just shaking it when its on the ground but is this amount of flex okay? I have a video below.

Thanks for any input

 

[DaleH]

Simple ... while OK, whereas you already have bolt holes holding the seats, some 1" wide by 1/8" thick aluminum (most hardware stores carry such stock) would make nice brackets. Bend 1" flat on an end and determine how much 'span' you need to get up near the gunnel and then bend a 1" flat on that end too.

A simple carboard model would help you size them correctly. You'd be done in 1 beer-time +/-.

If using SS hardware, use nylon washers underneath SS bolt head and SS washers, or tape the 1" flat end with duct tape ... anything to insulate the aluminum from the SS hardware. These simple brackets would add strength and rigidity back into your hull, if crossing a lot of boat wakes or in any chop and they are actually copied from other tin hulls! Many open skiffs use similar brackets.

With some creativity, one can also mount oar, paddle or rod holders to them, etc. Have fun!

 

[DaleH]

Hey ... I'm near you ... if you need a hand, bring the skiff by ... but in the Spring, LOL!

Need a motor?????

 

[QuinnRooney]

Simple ... while OK, whereas you already have bolt holes holding the seats, some 1" wide by 1/8" thick aluminum (most hardware stores carry such stock) would make nice brackets. Bend 1" flat on an end and determine how much 'span' you need to get up near the gunnel and then bend a 1" flat on that end too.

A simple carboard model would help you size them correctly. You'd be done in 1 beer-time +/-.

If using SS hardware, use nylon washers underneath SS bolt head and SS washers, or tape the 1" flat end with duct tape ... anything to insulate the aluminum from the SS hardware. These simple brackets would add strength and rigidity back into your hull, if crossing a lot of boat wakes or in any chop and they are actually copied from other tin hulls! Many open skiffs use similar brackets.

With some creativity, one can also mount oar, paddle or rod holders to them, etc. Have fun!View attachment 113098

Simple ... while OK, whereas you already have bolt holes holding the seats, some 1" wide by 1/8" thick aluminum (most hardware stores carry such stock) would make nice brackets. Bend 1" flat on an end and determine how much 'span' you need to get up near the gunnel and then bend a 1" flat on that end too.

A simple carboard model would help you size them correctly. You'd be done in 1 beer-time +/-.

If using SS hardware, use nylon washers underneath SS bolt head and SS washers, or tape the 1" flat end with duct tape ... anything to insulate the aluminum from the SS hardware. These simple brackets would add strength and rigidity back into your hull, if crossing a lot of boat wakes or in any chop and they are actually copied from other tin hulls! Many open skiffs use similar brackets.

With some creativity, one can also mount oar, paddle or rod holders to them, etc. Have fun!View attachment 113098

Thanks a lot for the input dale! Ill definitely keep this in mind for next spring. Too cold to work at the boat now lol

 

[airshot]

Your boat doesnt have the substructure where flotation is normally held. That structure adds rigidity to the sides. If that boat has no flotation, I wouldn't use it!! Fabricate some alum sheet to create some stiffeners for under thosebench seats...just look at pics of other boats and you will see.

 

[LDUBS]

Your boat doesnt have the substructure where flotation is normally held. That structure adds rigidity to the sides. If that boat has no flotation, I wouldn't use it!! Fabricate some alum sheet to create some stiffeners for under thosebench seats...just look at pics of other boats and you will see.

A lot of older boats did not have floors/floor structures. Many of that style/era had floatation in the bench seat boxes. Those 2x benches look pretty robust. Im not sure stiffeners are needed, but adding some floatation boxes wouldn't be a bad idea.

 

[airshot]

A lot of older boats did not have floors/floor structures. Many of that style/era had floatation in the bench seat boxes. Those 2x benches look pretty robust. Im not sure stiffeners are needed, but adding some floatation boxes wouldn't be a bad idea.

That it what I wascthinking of, sorry my description wasn't better. Building a box to hold flotation would add some stiffness to those sides if the box is attached to those sides!!