2x4 or 1x4 stringers

[Prkranger2]

I have a 1982 MARC I Runabout boat that I am restoring. The strigers that were rotten were 1x4 is this normal for stringers to be 1x4 for should I used 2x4?

 

[ColdFire]

Re: 2x4 or 1x4 stringers

If you can find good clean knot free douglas fir 1x4's then use them... I had a mixture of 1x2, 1x4 and 1x6's, I figured the 1X material held up for almost 20 years and would've lasted longer if the boat was kept up, besides why add the extra weight. The Hardest part with the 1X material was trying to keep it square while epoxying it to the hull.

 

[prockvoan]

Re: 2x4 or 1x4 stringers

2x4 for sure!

 

[Realgun]

Re: 2x4 or 1x4 stringers

As stated by Coldfire the weigh is not worth the extra strength you get.

 

[SuzukiChopper]

Re: 2x4 or 1x4 stringers

If you're building a speedboat then the 1x4 but the few extra ounces of weight added by a 2x4 isn't going to make much of a difference. If you do a good enough job glassing though you aren't going to really gain any strength using a 2x4, maybe just some extra width to put screws into to hold the floor down.<br /><br />Like Coldfire said, if it lasted as long as it did with what it had, then go with it.

 

[crab bait]

Re: 2x4 or 1x4 stringers

the bad thing about 1x stock is that it's only 3/4 inch.. if'n it was truly one inch thick,, it be great..<br /><br />i'd go with 1x ( 3/4 ) doug fir an sandwich it with 3/8 ab exterior doug fir ply ..or 1/4 marine ply.. use epoxy with thickeners added to a loose slurry an ss steel deck/drywall screws.. <br /><br />now that's a stringer..

 

[Moody Blue]

Re: 2x4 or 1x4 stringers

You really gain the strenght in a stringer by the long dimension, not the width. The only advantage of using the 2x as stated above is a bigger footprint to screw the floor to.

 

[SuzukiChopper]

Re: 2x4 or 1x4 stringers

depends on how you apply the force. If the force is along the 1" edge (board across two garbage cans so that the 1" edge is up, and weights applied to the middle) then there is no difference between a 1x4 and 2x4. If the weight however is applied to the 4" side (laid flat instead of stood up), then the 2x4 will definately be stronger. Of course it all depends on the type of wood too, but generally speaking

 

[agitator]

Re: 2x4 or 1x4 stringers

Wow! No wonder I had a hard time in Physics. I always thought that a 2X4 was stronger than a 1X4.

 

[fendersfender]

Re: 2x4 or 1x4 stringers

i was taught by a boat repairman to use plywood as it is much stronger than pine..he said pine will crush and splinter where plywood will not

 

[cc lancer]

Re: 2x4 or 1x4 stringers

So if I take the 1X4 which is really 3/4 by 3 1/2<br />and ripe it till I have a 3/8 X 3 1/2".<br /><br />Then I take a 2" X 4" which is 2 1/2 X 3 1/2 inches. Then ripe it to have a 1 1/4 X 3 1/2. <br /><br />So if this were true, the 3/8 X 3 1/2 will have the same compression strength as the 1 1/2 X 3 1/2???? <br /> The boat bottom is trying to be shoved in if it hits a hard wake.<br /><br />The 1 1/2 will have more vertical strength, and horizontal strength. Because of density.<br /><br />The sandwich technique mentioned by crab bait would yield a very strong stringers.

 

[SuzukiChopper]

Re: 2x4 or 1x4 stringers

The sandwidch tecnique would be the best. <br /><br />But no matter which way you dice it, if you have a 3 1/2 x whatever, vertically (on edge laying on the floor) the strength will be same. Horizontally though the strength will be determined by the thickness of the material. Of course torsional strength of the two will not be comparible. Maybe I'm way off base though.

 

[one more cast]

Re: 2x4 or 1x4 stringers

I'm not sure I'm buying this, if that were true then why is a carrier beam in a house not just a single 2X wide? However as far as the boat goes I think I would use what was there originally.

 

[Mark42]

Re: 2x4 or 1x4 stringers

How about skipping the dimensional lumber and using foam as a form to lay the glass over? A few layers to build up 3/8" thick will be mega strong in that size boat. And you never have to worry about rot again. And there is a weight savings too over pressure treated lumber. <br /><br />If I was going with lumber, I would use a high grade pressure treated lumber (yes they come in different grades - different woods and strengths) or marine plywood. No 1x or 2x.

 

[Terry H]

Re: 2x4 or 1x4 stringers

I didn't particularly read all this thread, but of you if this is a f/g boat and you want to use wood stringers that will be glassed, use plywood. Marine ply would be best, but if you're doing a proper job with the glass just about any solid wood ply will do(I don't care for the treated plywood). Solid lumber will shrink and swell and end up causing more grief than than you wants. Now, if you wants to use kiln dried Honduras mahogany for stringers you may have a little better luck. My first choice would be 1/2" marine plywood laminated to 1". Chief

 

[Mark42]

Re: 2x4 or 1x4 stringers

How about skipping the dimensional lumber and using foam as a form to lay the glass over? A few layers to build up 3/8" thick will be mega strong in that size boat. And you never have to worry about rot again. And there is a weight savings too over pressure treated lumber. <br /><br />If I was going with lumber, I would use a high grade pressure treated lumber (yes they come in different grades - different woods and strengths) or marine plywood. No 1x or 2x.

 

[SuzukiChopper]

Re: 2x4 or 1x4 stringers

Sorry, I should clarify my posts. I wasn't debating whether or not that lamination technique is comparable to a 1x4 or 2x4. I was talking to the fact that a 1x4 and 2x4 vertically are practically the same strength so if the 1x4 is being used vertically (on edge) you won't gain any strength by switching to a 2x4. Specifically to this quote:<br /><br />

Wow! No wonder I had a hard time in Physics. I always thought that a 2X4 was stronger than a 1X4.

Sorry if I created any confusion in this thread (which I'm sure I did), don't listen to me, but definately take crab bait's, Mark's or Chief's advice.

 

[Mark42]

Re: 2x4 or 1x4 stringers

Now how the heck did I double post around Chief?

 

[Terry H]

Re: 2x4 or 1x4 stringers

I don't have a clue about that Mark, if you look at the posting time there's over an hour diference. This computer stuff blows me away anyhow. <br />On another note, I would tend to agree with your ideas about stringers and foam. I don't have the engineering background to design foam stringers but I do think if done right it would last a very long time. Chief

 

[BillP]

Re: 2x4 or 1x4 stringers

If the original 1x4 stringers didn't break since 1982 that pretty much says they work. If it makes you feel better, some high end 25'cc ocean runner types with twin 200hp outboards use 1/2" exterior ply for stringers. Many production boats use 1/2" ply stringers and it works fine. The glass job has to be as strong as the stringer so don't skimp on it.