Replacing stringers????

[Jerry Eisele]

I'm replacing the wood in my stringers. 1986, 18". What type of wood was used? What do you recommend?
Thanks in advance!!

[Walt. H.]

Jerry,
I'm doing the same job currently!
Doug Fir "select grade" and I just picked some up for myself from "Lowes". Or you can laminate some ACX plywood which is also made from Douglas Fir.

Doug Fir bonds best with every type of fiberglas resin, doesn't warp and does not contain oils that resist the needed adhesion that some other woods produce.It also last the longest in a damp environment. Before glassing coat your wood with a 50/50% thinned mixture of resin and Actone with hardener mixed in. Coat-1-hr before installion to treat the wood. This will also help stop moisture from rotting your new wood in the future.Just stand it in a clean 5 gal joint compound can and brush it on letting the excess run off.
Put down a layer of 3/4oz to 1-oz Matting first followed by a layer of 24oz roving and woven cloth. Any drilled holes should also be treated with the resin actone mix. You will have this mix anyway because it is a by product you make when you are cleaning your rollers, brushes and tools. :) Now you don't have to throw the cleaning stuff away recycled and no waste.

"And you just wanted to know what type of wood to use."
I felt if you were asking about wood you might also need this other info.
I've seen guys go through all this work only to glass it with plain cloth or roving and woven without first laying down the needed matt glass first and have delamination in a very short period of time. Also always put a layer of matt down between your next lay up of roving or cloth and work out all the air bubbles the best you can.

I could go on with more, But this should cover what you need to know. :rolleyes:

Good luck and measure twice,

Walt.......

[Jerry Eisele]

Thanks walt, I'm leaving for the weekend, but would like to ask some questions, if you don't mind. Please give me your number and I'll contact you when I get in the job a little further. Email= djeisele@netzero.com
Thanks again, JERRY

[harbormaster]

Why wouldn't you want to use one of the new high tech foams instead (i.e nicore)? They are lighter, don't rot and are just as strong when glasssed in correctly. I am not an expert on this.

[Donzigo]

Jerry & Walt,

I'd appreciate your keeping this post going, if there is more information. I'm very interested in learning exactly how to do fiberglass work. There's a couple of spots on my 1989 Donzi that need repair. I've wathced it done many times; but, your explanations are great to get my learning curve going.

I had over $14,000 of fiberglassing done on my Z-25 a few years ago. It was good to watch this fiberglass master at work. He used PT wood, after cutting it and drying it in the shade for 2 weeks, every piece. the guy is best in this area. Douglas Fir ........ sounds like good reasoning, and much better not to breath the toxic wood shavings from the PT.

Thanks again.

[Walt. H.]

Donzigo,

Real Expert's Never never use Pressure treated wood. The chemical's used to treat the wood is an oil substance, and like in my previous post will reject a good bond with the glass and resin mix, Plus it will start to warp & twist as it dries before you can get it secured for your installation.
Coat your Doug,Fir with the "resin actone mix" and you'll have a fiberglass treated wood made especially for Boat repairs.

Hello Harbor Master,
Scott,
Nidacore is great stuff, and can be used and it is used in all-out racing application and aircraft build up too i'm told. It comes in many forms and styles depending where and how it is used.
There's alway's a "But" and here it is "price" I had inquired about Nidacore last year, I considered it for the floor replacement instead of using plywood that was used by Glastron on my Carlson.I would be saving mucho weight!
I would need 2- 4'X 8'sheet's for the job do to the width I need. "Before shipping cost" to me I had a qoate of over $500.00 i'm not sure of the exact price since it was last year and I re-acted as one would reading a hospital bill.
I sure wouldn't want to make a cutting mistake on that stuff on my salary plus wait for another month for the distributor to place an order.
So unless you have a brother-inlaw or a good friend with access for this stuff. Well you know the rest, back to the tried and true.
Doug Fir is very =>"lite" compared to other wood anyway! And Remember "The Strength is in the Glass" when it's done correctly. In theory If the lay-up is matt roving-woven,matt,roving-w. you could remove the wood and the created structure would be strong enough. This is why some use "Foam" for constuction. But this can lead to one of those "Opinion Debates".O'My God what did I say. eek!

Hopefully "Lenny our resident Boat builder" can add more to this. I value his knowlege.I've never built/created what he showed us recently.

Gotta go and grind some more before I leave for my regular job that pay's the bill's!

Ps. Jerry, Yes you can e-mail me at walriengineering@aol.com If I can't answer what you need to know by typing, we can figure out the best time to phone and talk it through. I'm off in the mornings and work till almost midnight.

Yours in Boating, wink

Walt

[MOP]

I'm with the HM on cored stringers, if done right they will last well past any type of wood. Having done a few to me there is no weight savings just reliability and a bit more work. Wood is a lot easier and if kept dry does a good job. Wood stringers did not pose a problem till they started encapsulating the wood.

[Walt. H.]

Here is the Link for "Nida-Core"
www.nida-core.com (http://www.nida-core.com)

If only money and availability was of no object!
Or it was something Hi-tech like the Bat Boat!

If the wood job is performed correctly (no future delamination) you'll never have to do it again! At least in my life time. I'm installing floor vents that can be openned, to air out the double bottom to prevent condensation. The major cause of "mildew rot".(Trapped water) :mad:

Choices are good but can be confusing, :confused:

Walt.......

[Forrest]

The only thing that I would probabaly do differently is rather than use ACX douglas fir, would be to use marine grade plywood. Marine plywood is AA or AB douglass fir with no worse than "B" internal laminates. 3/4" marine plywood has seven plys where as the best 3/4" AC plywood has five, or maybe six plys. Marine plywood has better glue than the best exterior-grade plywood and has no internal voids to trap water. Also, marine grade plywood is not pressure treated, but there are some marine plywoods that are, but kiln dried after treatment. The downfall of marine plywood? About $80 retail for one 4x8 sheet!

[Tom Davis]

I agree with Forrest, having done allot of structural glass work, marine ply is good as well as many of the structural closed cell foams. There is also a cool kevlar/tungston/foam composite that I have found but have never used due to the cost. Those guys at NASA come up with some pretty cool stuff....

[oldLenny]

I agree with Forrest. The "XL Marine plywood" is used in many (Cobalt etc) expensive boats. It does stand up and is void free with select cross grains. I used Air-Lite and other glass/polyester "carve-able" products in my 18 projects to create the monoque stringer situation, all glass, no foam, no wood. (NOT FOAM BUT POLYESTER SATURATED GLASS, big difference) Many newer boats are done this way now that the "bugs" have been worked out. Is is "Isocyanate" bonded to the hull inside with a caulking gun. Plexus is the product and all the big boys use it. For simplicity, you can't beat the plywood. I machined up some clear 20' edge grain fir (cut to 3/8" for use as backing for the hull/deck shoebox joint and screw acceptability. It is "flipped" so the edge grain is up and the screws pass through about 8-10 (old growth) rays of grain. Should be a good bond. That is the only wood in the boats now.

As I said, the ply would be what I would use to keep it simple. As Walt said, you can NEVER apply heavy knits without a mat down first, and roven CANNOT go on top of Roven. A mat (saturated resin barrier) has to be between these ALWAYS. A typical hull lay-up shcedule is Gel, Mat, Mat, Roven, Mat, Roven, etc. (Mat and Roven is one schedule in most cases but high tech fabrics modify this principle a bit.)

Some of the fancier products, (Knytex being one, the product I used in the 18's) has a .9 OZ mat interlaced on the backside of the glass. This speeds up and eliminates the need to lay down a mat again between the heavy weaves. Saves time, but the barrier and resin diaper is still there. The best product for bonding (tabbing) your stringers in is Knytex. Buy it in 38" or 12" widths, the -45,+45 bends best, not the 0-90, and a mat, Knytex, Knytex, (#1708 or #1808 the product)and maybe one more will do the job. Keep in mind the mat is on the back side of it already so it eliminates one step between schedules. Start with a mat tho. 1OZ or 1 1/2 OZ. Not cloth.It would pay to putty your seam where the stringer meets the hull as well to help "ease" the angle for the heavy knits and eliminate air.

Remember to run the glass out (without a join in it) about 12" on the first pass on both sides of the stringer, I am referring to the heavy knits and then apply the rule of thumb to decrease the overlap by 2" each pass getting closer to the stringers. Don't put any "wax" or air dryers in the mix. Try to do it all in one day. NEVER go below 1% catalyst to resin ratio, don't let the sun even see what you are doing, and if it isn't too hot (70-ish) maybe go 1 1/4% Catalyst to resin ratio. I use 1 1/4% but I am working in 65 degrees and inside, no sun or outside warmth. If the resin starts to "kick" , gel, throw it away and make up some more. Do not re-use it or think you are thinning it by adding more resin and catalyst to it. Start fresh. Pour the wasted resin into a plastic bucket outside as it will heat up tremendously and the exotherm can ignite or at least smoke you to death.

All industry standards for cross-linking, flexural, tensile and modulus strength are based on 1 1/2% catalyst to resin mix. I find this a bit fast for me and eliminates the "playing" I like to have the time to do.

What did I forget?
:D

oh yeah, here is my original stringer system in my X-18. It has been modified now somewhat to accept the new deck configuration and longer engine compartment but it is essentially still the same. The beauty of this is the "finished gelcoat" that becomes the engine compartment liner, no glasswork to look at or ply/wood stringers, and much stronger. It tapers 3 times to disperse/absorb the loads. Engine mounts go between the "well" at back and tie to steel plates on the "unseen" side of the finished motor compartment. Access doors let you play with the nuts and bolts. Transom assembly area is solid glass, no rot. Also, you can hit a log at 50 and still have a good chance of a dry hull under you. Gas tank is moved back a bit into that "opening" and can come out with deck on... This whole liner gets "welded" to the hull everywhere. Locks up the hull for twist etc. That and the fabrics used to lay-up the hull in the first place. It is a full MATRIX. All of this is 100% (or my best ability) bonded to the hull.It does not move. The engine compartment sides and bottom as well as all the 3" tabs are part of the hull structurally and "welded" in.

http://www.donzi.net/photos/ACFFEF.jpg

[Walt. H.]

Well there you have it, various way's to do a stringer job!
Like buying Wine: Red,White,Ros'e,chablis
Cost: Cork,twist or box.

I think i'll stick with Beer! :)

I use to use only "Marine ply" But do to the cost and availability I found it only better suited when repairing all wood boats.

When it comes to "regular" fiberglass boat repair using acx is just fine because of the strength that is added with the layer's of fiberglass and the glue is too, it's enhanced with the "resin".If it makes you feel better that you used marine grade, fine go ahead it's your money.
If you think that major quality boat builders only use "marine grade" wood I have a bridge in B'klyn that I would like to show you that is forsale. When it comes to profits and availability (there's that word again)or when they just can't get a delivery fast enough, you can even find lower then "CDX" grade used! Sorry but maybe that's the answer why one 15 yr old boat is in need of work and the 20 yr old is still solid, same brand and model.

Please remember; Someone asking a "what to use" or "how to do" question, usually has limited experience otherwise they wouldn't be asking.
Let's not scare them off with to many way's to perform the same repair or rebuild.They'll take it slow and ask questions as they go.If I was first starting out i'd be overwhelmed now.

Let's not reinvent the wheel, when only the tire needed changing.

I just wanted to keep this low tech for the fellow that was asking what kind of wood should I use.
Now when he comes back from his week end away and see's all this, they'll be another boat forsale listed down below. eek!

What's that phrase about "too many cook's in the kitchen" :rolleyes:

Keep it safe this week end!

Walt.

[Jerry Eisele]

Thanks for the information. Now its time to make a decision.

[oldLenny]

Jerry, I spent a half day today at a "premium builders" boat shop and got every question out of the way that I had "questions" about. Here's the scoop. The XL treated plywood from Greenwood in Oregon is the best (most bang for the buck) stuff around short of going my route or into polyester products such as "CORECELL".

http://www.greenwoodproducts.com/moreproducts.htm

They have a treatment procedure that DEFINATELY lets glasswork bond to it. It is guaranteed by the manufacturer, and if you give them a call, they will either help and direct you, or OK your method of bonding and warranty the work if you follow their directions. It comes in 1 1/2" thick (13 ply) dimensions as well as 3/4". It apparently is great stuff, and the guys I was with today know what is going on. The "wood treatment process" has been modified to allow for the UTMOST ADHESION for glasswork. Give them a call....

:D