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Ken

  • Karma: +16/-0
Well, I haven't been on lately, as we have had some unexpected medical issues with my little girl, but I need to keep busy, to keep my mind "occupied" during this time, so I'm working on the jet between Dr. Visits and my job.

 So, anyways, when replacing the stringer or stringers, has anyone used aluminum? I work at a place that uses aluminum for almost everything we make, and I have virtually an unlimited access to any 5052/6061/T6, and just about any size up to 20X15 foot sheets.
I was wondering about making a hollow 2X4 out of .125 sheet, or using a wood 2X4 and capping it with a "U" channel out of .125, or using a .375 piece of aluminum from front to back, or any other option and glassing it in.
Is there a reason to use the "normal" 2X4 wooden stud stringer, versus my aluminum theory, such as the aluminum is TOO rigid and the hull will crack around it, as the wooden stringers have some flex in them, or is it just a cost issue.
Thanks, Ken
« Last Edit: May 15, 2014, 09:40:06 pm by Ken »
  • Boat #1: '77 Marlin
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ka0tyk

  • Karma: +30/-0
Re: Using aluminum as an option for replacing the stringers.
« Reply #1 on: May 14, 2014, 10:20:35 pm »
hulls need to flex.  if you toss something in that rigid you're jsut gonna get cracks wherever the weakest point is at. 
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jyeager

  • Karma: +62/-0
Re: Using aluminum as an option for replacing the stringers.
« Reply #2 on: May 14, 2014, 10:49:47 pm »

hulls need to flex.  if you toss something in that rigid you're jsut gonna get cracks wherever the weakest point is at.
Exactly. Fiberglass needs to flex, the aluminum won't. If your just looking to do something different, I've been hearing a lot of talk about all carbon fiber stringers or composit stringers. Cool thing about the carbon is it will never rot. But it's stupid expensive last time I checked.


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  • Boat #1: Southwind Tunnel Dragster 19
  • Boat #2: DiMarco18 V-Bottom
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Ken

  • Karma: +16/-0
Re: Using aluminum as an option for replacing the stringers.
« Reply #3 on: May 15, 2014, 04:44:18 am »
Yeah, that's what I thought, but wasn't sure. Not necessarily looking to do "something different" just for the sake of being different. For me, the aluminum route is actually cheaper than using wood. Definitely not trying to be a cheap ass either, but wanted opinions on my thoughts. I'll do it the wooden traditional way. Thanks.
  • Boat #1: '77 Marlin
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Ken

  • Karma: +16/-0
Re: Using aluminum as an option for replacing the stringers.
« Reply #4 on: May 15, 2014, 09:06:48 pm »
BTTT, for a few more questions. Been searching all I can on stringer repairs, and getting some conflicting thoughts and ways of doing it.
I see some people stand firmly by "marine grade" wood only, and some say regular wood that's layed up and saturated with 'glass. Saw another post on the internet about using pressure treated, to prevent future rot, and also redwood, which is a natural (for the most part) rot proof wood, layed up in 'glass.

Next is the way of attaching the stringer to the hull. Thick consistency of resin and cabosil, subfloor construction  adhesive (NOT sold on that one!!), or marine grade adhesive? I kinda like the marine adhesive, as I've heard that it is almost impossible to separate the items after they are attached, it's waterproof, flexible, and once the stringer is 'glassed in and marine adhered, it seems like it is a permanent repair. Seems like the cabbed, resin will set up solid and hard and like has already happened, it could crack/separate after some use since there is little flex?
Thoughts, experiences??!
  • Boat #1: '77 Marlin
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jyeager

  • Karma: +62/-0
Re: Using aluminum as an option for replacing the stringers.
« Reply #5 on: May 15, 2014, 09:39:24 pm »
BTTT, for a few more questions. Been searching all I can on stringer repairs, and getting some conflicting thoughts and ways of doing it.
I see some people stand firmly by "marine grade" wood only, and some say regular wood that's layed up and saturated with 'glass. Saw another post on the internet about using pressure treated, to prevent future rot, and also redwood, which is a natural (for the most part) rot proof wood, layed up in 'glass.

Next is the way of attaching the stringer to the hull. Thick consistency of resin and cabosil, subfloor construction  adhesive (NOT sold on that one!!), or marine grade adhesive? I kinda like the marine adhesive, as I've heard that it is almost impossible to separate the items after they are attached, it's waterproof, flexible, and once the stringer is 'glassed in and marine adhered, it seems like it is a permanent repair. Seems like the cabbed, resin will set up solid and hard and like has already happened, it could crack/separate after some use since there is little flex?
Thoughts, experiences??!

They way i lay up all my stringers is first start with kiln dryed 1X4 or 2X4, i use dougless fur or a hardwood of some kind. Make a Jig to hold the stringers and lay them down on a layer or 2 of 3oz cloth and apply as much weight as you can down on them.

After its cured, i lay down cabosil along the bottom of the stringer and the floor to make a nice curved transition. Fiberglass doesn't like to lay down at a 90 degree angle.

I layup stringers with anywhere from 18 to 24 oz of glass. so it's up to you how you want to go about that. i use alternating layers of 10 oz mat and 3 oz cloth till i get what iam looking for. hope this helps

Check out my stringer redo here
http://www.socaljetboats.com/projects/southwind-tunnel-project-continued/msg197195/#msg197195
  • Boat #1: Southwind Tunnel Dragster 19
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Ken

  • Karma: +16/-0
Re: Different material options for replacing the stringers.
« Reply #6 on: May 15, 2014, 09:44:26 pm »
Thanks for the link. I searched and that's one of the posts I was learning from, but had to go check on something, and lost the post on this iPad, and couldn't figure out how I stumbled crossed it in the first place. Looks really good.

I edited the title, since I've stopped thinking about using the aluminum stringer design.
« Last Edit: May 15, 2014, 09:47:15 pm by Ken »
  • Boat #1: '77 Marlin
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jrork

  • Karma: +4/-0
Re: Different material options for replacing the stringers.
« Reply #7 on: May 24, 2014, 06:43:04 am »
X2 on what Jake did other than I did something a bit different in I used epoxy resin and made a thick paste of West Systems epoxy resin and 404 high density filler.   Put that down and then set the stringers in place doing exactly what Jake described.   The excess paste squeezed out enough to make a nice smooth curved transition.   When that was fully cured, you could hit it with a hammer or walk on top of the stringers and they didn't budge.    We then layed the glass over the top of the stringers fully encapsulating them and further bonding to the rest of the boat.   
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