Wooden stringers

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Jul 14, 2022
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I am getting ready to put new stringers in a little 16’ Eldocraft with a 40 horse Mercury on it. I had read where Douglas Fir was a good wood to use for stringers. I got some and as I was cutting it I noticed how soft it was between each growth ring. I’m just wondering if that’s pretty much the normal for this type wood and I was also reading where you don’t want the boards with the pith (heart) in the board. The boards I looked at in the store that had the pith in them seemed to have the growth rings a lot closer together and were not as soft between the rings as the ones that were spaced out more. I had also read that the boards with the growth rings closer together were better boards. Just asking for someone’s opinion on the subject that’s knows more than me about it. (which is not a lot.)
 

matt167

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Stringers are generally plywood but some older boats did use dimensional lumber. It will probably work fine but plywood might be better and cheaper
 
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Stringers are generally plywood but some older boats did use dimensional lumber. It will probably work fine but plywood might be better and cheaper
Thanks for the reply. Yes, this is an older boat. 1975 model It has dimensional lumber for the stringers. There is a 2x4 12’ long board for the stringer in the center of the boat running long ways. Right in the keel. There are 2x2’s one on each side of the long 2x4 about 14” up the hull towards the sides of the boat. There are no bulkheads.
 

Scott Danforth

Grumpy old guy who plays with boats
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remember, wood harvested in 1975 was probably 75 year-old trees that had good grain structure

wood harvested in 2022 is probably a 3 year old tree with bad grain structure

I would use white oak if using dimensional lumber, or go with ply
 

Chris1956

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Sounds like your Doug Fir was actually pine. A lot depends on where you are in the country/world.

I would use dry pressure treated pine for your stringers. Plywood is stronger, however, if it gets wet, it falls apart. The PT stuff will still last a very long time if it gets wet.

If you can go up a size in the height of the stringers, it will add a lot of strength. 12 foot 2x4s are not real strong. 2X2s are really only good for nailers. They have real low strength.
 

matt167

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Douglas fir is a species of pine tree. Home Depot has been selling it for years near me. Id never recommend pressure treat for stringers. It needs to be bone dry to tab with fiberglass and you won’t ever get it that dry from a yard. It also twists as it dries.
 

Grub54891

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Use plywood, saturate with epoxy and glass over. I laminate it to the correct width/height. If glassed properly, it's sealed inside there and should never get wet.
 
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Thanks for the reply guys. If using dimensional lumber in order to get my 12 foot lengths, I was going to have to put sister boards on each side of my dimensional lumber. But with using plywood I’m assuming it would be OK to put two pieces of three-quarter inch thick plywood together to get my inch and a half thickness and instead of using sister boards on either side I could just stagger my laps as I am sandwiching my two pieces of three-quarter inch thick plywood together and then do away with sister boards. Am I correct in thinking this way?
And could I use Titebond 3 to sandwich them together or do I need to use epoxy?
 
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Grub54891

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I used epoxy and clamped them together. Rounded the top edges so the glass would wrap well. I suppose tightbond three would be ok as you are wrapping them anyway.
 

JASinIL2006

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Thanks for the reply guys. If using dimensional lumber in order to get my 12 foot lengths, I was going to have to put sister boards on each side of my dimensional lumber. But with using plywood I’m assuming it would be OK to put two pieces of three-quarter inch thick plywood together to get my inch and a half thickness and instead of using sister boards on either side I could just stagger my laps as I am sandwiching my two pieces of three-quarter inch thick plywood together and then do away with sister boards. Am I correct in thinking this way?
And could I use Titebond 3 to sandwich them together or do I need to use epoxy?

You can use either Titebond 3 or epoxy. Titebond 3 has the same or greater resistance to water than the glue used to make exterior plywood, so if you use Titebond 3, you will be fine. As long as you stagger the joints, the plywood stringers will be fine and plenty strong.
 
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I used marine plywood. More layers and no voids.
Believe me I have looked high and low for marine grade plywood here. I am from Shreveport Louisiana and there is no one absolutely no one here that sells marine grade plywood. The closest dealer I could find was in Lafayette Louisiana, close to 200 miles away.
 

JASinIL2006

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You will be fine with BCX. If you're really worried about strength, just give it a extra layer of fiberglass.

I'd hazard a guess that the major of us who have rebuilt our boats used regular exterior plywood rather than marine plywood. Exterior plywood seems to work fine.
 
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Thanks gor
You will be fine with BCX. If you're really worried about strength, just give it a extra layer of fiberglass.

I'd hazard a guess that the major of us who have rebuilt our boats used regular exterior plywood rather than marine plywood. Exterior plywood seems to work fine.
Thanks for the reply. That’s exactly what I’m gonna do. BCX glued together with staggered joints.
 

kcassells

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When coating edges I can use just straight poly. No glass, until I get ready to tab it in?
That is correct no glass at this time. That being said it is also a great time to wet out both sides completely and let dry.
I call this "flat work". Just set up a work spot with screws or nails in some wood so when you flip it over to do the other side the ply will rest on the tips of the screws/nails.
Once dry then I glass the sides full height 2x, let dry and then set in pb, then after that is set up I run the tabbing. Saves alot of time and glue doing it on the flat and easier to work out air.
Not all can be done this way but will help you get a feel for glassing in the easiest position.
Good luck!
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