Someone with knowledge in stringer wood PLEASE help.

[Homerr]

I had to custom order the wood for my stringers.<br /><br />I ordered some 2x12x24ft. #1 Kiln-dried Doug fir.<br />They called it FOHC (free of heart center) Suppose to be the 'cream of the crop' in this line/grade of wood. I paid dearly to get them too!<br /><br />Ok, the problem: <br />I received the wood today.<br />One of them has splits almost the length of the board, and the other has some knots on the top and bottom directly across from each other. These knots are also split. These knots are in a place I cannot cut out.<br /><br />Obviously I'm not accepting either one of these boards, but I am curious if a person could safely use these? Once the glass is in place, and the wood sealed, would it matter?<br /><br />I also realize that a piece of wood this long is going to have knots and such, but splits all the way down? How does this happen? If it's kiln dried, shouldn't the inspector see this?<br />If this is #1 grade wood, than I'd hate to see their lesser grades!<br /><br />Compared to what originally came out of the boat, an old snarled up piece of madrone would probably look better!<br /><br />Thanks,<br /><br />Rob

 

[blifsey]

Re: Someone with knowledge in stringer wood PLEASE help.

Not that this has anything to do with boats, but I live in a 100+ year old house in Georgia. My roof rafters are true 2X4 (not 1-1/2X3-1/2) heart pine 24 to 30 ft long with no knots. Running up beside each door and window is a 24' 4X6 that is also knot free heart pine. If I cut or drill into it, it still smells of fresh cut pine. Probably wouldn't do for boat building though as it weighs as much as concrete .<br /><br />BL...

 

[SCO]

Re: Someone with knowledge in stringer wood PLEASE help.

The top and bottom of the beam are the worst places for knots, and if you had a knot on the top of a beam it would be better to put the knot on the bottom when you install the stringer. When pounding through waves the bottom of the beam will be in compression and the top in tension. Were there a big knot on the top of the stringer, the best load bearing meat would be gone and the beam would flex more at that one spot. On the bottom, the compression load would be transmitted through the knot. Wrt the glass, I think the purpose of the glass is simply to hold the stringer to the hull, and the actual stringer strength is mainly from the wood. I think this because the stringers on my boat were completely rotted out and the fiberglass shell could not do the job at all. I floated the boat and ran it in no waves to check for leaks prior to committing to stringer replacement, and the hull undulated like a snake. I didn't do this , butmight next time build up stringers from plywood ...taller and thinner and as long as you want by overlapping layers.

 

[suzukidave]

Re: Someone with knowledge in stringer wood PLEASE help.

They grow and cut lots of douglas fir around here and I've worked with it some. You just can't get the really good grade stuff anymore unless you know the mill owner, or are prepared to go through a pile of lumber to cherry pick. I think you can use them, but if you are really dissatisfied with the lumber you bought, I would forget ordering 24' pieces and go pick through a pile of 12' or 14' pieces for the best ones and then lap them together. <br /><br />For what you are doing you ideally want tight grain fir. The real old growth premium tight grain doug fir that they used to build fish boats out here repels salt water fifty years and more even when its not glassed in. You won't get that stuff, but you can get relatively tight grain across the board with face grain (wavy) on the sides. It should be a more or less uniform grain that is predominantly less than 1/4 inch apart. That tells you that part of the board is not recent growth.<br /><br />You ideally want clear grade but it's pretty hard these days to find a tree from which to cut a 24' 2 x12 with no knots in it. If you have some small knots (less than 1.5 inch diameter)I wouldn't sweat it. They will not have much impact on strength.<br /><br />I agree that it's surprising they'd give you a custom ordered kiln dried board that had a big split but, unless the check runs right through the board, I wouldn't be that concerned strength-wise. You just want to make sure the board ends are coated so the check is contained, and also coat the split with something before you glass it.<br /><br />I'd be more concerned that it split because they didn't dry it properly. Are the boards straight and true on all four sides? Do they have a big crown? On a board that size I'd be worried they are twisted like a pretzel when you try to lay them flat

 

[oldboat1]

Re: Someone with knowledge in stringer wood PLEASE help.

I like SCO's suggestion about plywood stringers. I've replaced transoms using laminated plywood, but haven't done stringers. I'm no engineer, but I would think that the stresses SCO desribes would be handled real well by laminated/epoxied plywood set in vertically (plys standing on end) -- probably would flex less vertically than a similar sized piece of fir.

 

[suzukidave]

Re: Someone with knowledge in stringer wood PLEASE help.

Oldboat I disagree. If plywood were the answer, boat makers wouldn't waste money on fir and oak stringers. Unfortunately, plywood is not so strong when it gets wet. The other advantage of natural wood is that it naturally flexes and so absorbs some of the shock from pounding. A certain amount of flex is a good thing.

 

[DJ]

Re: Someone with knowledge in stringer wood PLEASE help.

Homerr,<br /><br />Why don't you check out fiberglass stringers? West Marine carries them.<br /><br />www.westmarine.com

 

[Homerr]

Re: Someone with knowledge in stringer wood PLEASE help.

Thanks for the info, guys. I can always count on this forum!<br /><br />The lumber company came out and looked at the wood. They basically said it was normal to have the 'checks' in this sized wood, and it's almost impossible to get a board with no checks and knots this size. They said the other board I got that didn't have the checks may not be as dry as the one that did.<br /><br />If the checks went all the way through he said, then it would be a problem. He suggested to fill it with resin, as I am going to anyways.<br /><br />Yes, the boards are straight as an arrow. I've never seen a board this big straight! They are nice when you look at it that way. I'm also told when the grade the lumber, they only check one side? Is this true? Because the other sides look fantastic.<br /><br />The one board that has the knots I'm concerend about, runs about 1/3 up the board. I figure I'll put it towards the back of the boat where it doesn't get pounded as much, and towards the bottom as you've suggested. <br /> <br />I intend to completely glass these in. The originals were not. The glass only ran about half way up the stringer. The engine bay was completely covered however.<br />Why the factory didn't do the whole thing? Who knows. Cheap **stards!<br /><br />It's not like I'm going racing it it anyways, since it's just a fishing boat. <br /><br />Thanks again,<br /><br />H.

 

[oldboat1]

Re: Someone with knowledge in stringer wood PLEASE help.

It's an interesting issue, particularly for do-it-your-selfers who are restoring (or maybe just patching up) old hulls. Suzukidave has a good point about flexing, but I'm guessing a 10 or 12 foot span of laminated plywood would have some flex -- but would indeed have to be very thoroughly soaked and glassed or it would delaminate. In terms of flexing, fiberglass stringers are obviously not going to rate very high, but all-glass (or at least no wood) is apparently the direction builders are going. So maybe water intrusion is the big bugaboo that drives some engineering decisions about flexibility and such -- issues that wood boat enthusiasts always emphasize. There is also the recycled plastic "lumber" now being used in park benches and picnic tables. I wonder if that stuff would be a good material for stringers (with the amateur in mind)?

 

[Homerr]

Re: Someone with knowledge in stringer wood PLEASE help.

Interesting question. I wonder if it would hold up?<br /><br />I'm not real worried about water intrusion. This is a real tall ocean boat. Of course,you'll always get water, but not like my little runabout.<br /><br />I'm gonna give everything at least 2 coats of resin before they go in.<br /><br />H.

 

[cvlngineer]

Re: Someone with knowledge in stringer wood PLEASE help.

You don't need the most expensive wood on the market to make your stringers from. I would either go to the lumber yard and buy two straight, 16 foot 2 x 6's or 2 x 12's (not sure how tall you need them to be) with as few flaws as possible and cut them to the desired shape and curvature, or, as mentioned above, build your stringers from laminated plywood. Either choice will result in strong supports, and if coated in at least 3 layers of epoxy resin, will be waterproof. Just my 2 cents worth.<br /><br />cvlngineer

 

[SCO]

Re: Someone with knowledge in stringer wood PLEASE help.

Homerr, I think you are on the right track w the clear fir and keeping the knot aft where it wont see bending stress. It isa better option in your case. My ply idea I think would be valid but not tested and hard to make. I agree some with suzukiDave's logic but thinkyou could seal it and glue it first w epoxy then glass it w epoxy resin to make it waterproof. I wouldnt drill anything to it. you could glue strips to it and fasten to those strips. I think it would do fine but is an unknown and sea trials might surprize me. Go with tried and true and easy.Fir is traditional because the trees are big and straight w good grain. Cant beat that. Some of my fun is figguring out new ways to do things with the materials at hand.

 

[Franki]

Re: Someone with knowledge in stringer wood PLEASE help.

In Australian repair shops, its pretty standard to use 2 or 3 layers of ply glassed together.. <br /><br />Its the standard practise.. and it works well enough, just be sure to glass the whole works in, properly.. In fact most of the guys I know that do it, glass the wood entirely BEFORE putting it in the boat and glassing it down.. <br /><br />That way you are assured that it is waterproof.<br /><br />Also, you only want a tiny bit of flex anyway. more then that and you will have gelcoat cracks and other potential problems.. gelcoated fiberglass is not designed to flex alot.<br /><br />They have been using ply in strings for along time here, so its a perfectly acceptable solution.<br /><br />I don't like wood, (unless the whole boat is made from it.) but have yet to find a better solution. still waiting to try seacast for everything. <br /><br />rgds<br /><br />frank

 

[suzukidave]

Re: Someone with knowledge in stringer wood PLEASE help.

I think I prefer wood because I'm a pessimist. I think no matter how well you glass in a stringer someday water may find its way in in that environment and you won't know about it. Wet lumber with some water repelling caharcterstics will still have some strength -- plywood just falls apart.<br /><br />Franki, I bet you would use wood in Australia if you had any trees! Seems to me the Koalas ate 'em all.

 

[Franki]

Re: Someone with knowledge in stringer wood PLEASE help.

Well, if you read my seacast posts, you know my preference for wood free boats anyway.. but with the ply, the reason they glass the three together, is so all three are "water tight" containers.. so if one gets wet, there are still two others..<br /><br />but your certainly right, If it came to brute strength, there are two things I'd use..<br /><br />one is a piece of railway line.. and the other is a bloody big piece of jarrah. <br /><br />rgds<br /><br />Frank