Another Stringer Topic

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Mac32
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Another Stringer Topic

Post by Mac32 »

Hello gang, Newbie here to the forum but 10 yr owner of a 1976 F32. Floor was flexing under the dinette when cresting over waves so I suspected rotted stringers. After opening up the bilge and sticking a screw driver through the wood on every limber hole I came to sad fact I had rot. So after reading many posts on stringer repair and purchasing the West system book I decided to tackle the project. first I completly dismantled the interior (head wall, headliner, dinette, floor ect) so I would not get anything on the teak and also opened up for a complete interior update when I am done. Then I cut the tops off one by one and vacuumed out the rotted wood that crumbled like soft cork. FYI a high speed dremel with a carbide cutting wheel with a shop vac hose end taped to the side of cutter (rotation side) made quick easy clean work of stringer DE-Topping. Sooooo now I have a clean bilge with side walls where the stringers (and cross members) used to be but no good wood from the bow (vbirth floor) to the engine room bulkhead. I was planning on cutting new wood and filling it in with west system then glassing over the tops. SO HERE IS WHERE I AM STUCK. What kind of wood should I replace it with . The original stringers are 2-1/2 wide and need to be about 10' long. Should I laminate solid white oak, PT Ply, and where can I get the new wood (I live in michigan).......Any ideas?
Thankyou in advance.
Fred
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Paul
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Stringer

Post by Paul »

Hi Fred,

When doing this type of replacement, I prefer to use layers of marine ply wood standing on edge and laminated together. The chances of this fitting snugly into your existing fiberglass pocket however are slim.

When installing this type of laminated stringer, I usually remove "all" existing glass from the section to be replaced (Sawzall). Then rough up the area, create lap joints where it join's into the existing stringer and bond it into place with West System epoxy mixed with silica thickener. Once this is done, add a couple layers of heavy woven roving and resin over the whole thing including a generous overlap at the hull and existing stringer.

Oh yeah, don't forget to seal up those limber holes.

Hope this helps
Paul Cruise Control
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awesome.

Post by JuiceClark »

Way to go...not that bad once you decide to dig in...right?!

I used marine plywood in my last boat...but I don't know why. Now that I think about it, that's the last thing I'll use next time. Since you know the approx. size, you could put any good, solid wood in there and not have to worry if it was good plywood.

The English navy took over the world using oak. Down here we get some of that Brazilian stuff that never rots...called Ipe or Ironwood or Pau Lope. I have it around the cockpit and it's very hard but also very heavy and rather expensive.
Mac32
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Post by Mac32 »

Thanks for confirming my plywood research on this one, at first I was nervous since I pulled out solid wood but this is the direction I am going.

I happen to be lucky on this one since the stringers are just under 2-1/2 wide so (2) 3/4 and (2) 1/2 layers seem to fit snug between the existing fiberglass and my local lumber supply had marine ply for around $76/sheet for 3/4 thick and $58 for 1/2 so I am on my way and will let you know next week how it goes.

Also another question, When laminating the pieces together did you use screws or just clamp it when the resin was setting. Also can I do it while down in the boat? This is how i am thinking of doing it because It will be hard to sneak the port stringer in under the head while in one piece.

And last but not least, when I removed the stringer (rot) there was a piece of laminate or something between the old stringer and the hull. Is this needed to keep from bonding the stringer directly to the hull? Or can I bond the stringer directly to the hull? It seems to be pretty flat at the bottom.

Regards
Fred
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Paul
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Post by Paul »

Hi Fred

When laminating the ply wood togeather, I use a combination of screws and clamps. Using West System with silica as the adhesive, clamp the layers of ply wood togeather snugly but not so tight that it squeezes out all of the glue, then add brass screws. If the stringer is long enough to require butt joints, be sure to stagger them. Also be sure to use lap joints where the new stringer meets the old.

What you found at the bottom of your old stringer was fiberglass matting that was laminated to the bottom of the stringer to prevent rot. (worked well didn't it :roll: ) Instead of this, I usually use a thick mix of West System to bed the stringer right to the hull with a fillet along each side. This keeps the bottom of the stringer sealed and makes it easier to apply the roving.

Hope This Helps
Paul
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Mac32
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When does it stop

Post by Mac32 »

I have purchased All the wood and west system to complete the stringer repair but I cant seem to stop tearing things apart. I just found the rot extended into the engine room on the Starboard side all the way under the forward engine mount. So I rigged a 4x4 post jetting through the forward salon windows and hanging from the roof trusses in order to support the side of the engine while removing the rotted stringer section. So now that I am into the engine bedding, can I still use plywood for the stringer? Or do I need to cap it off with something solid to screw the engine mount to? If so what?

My penny seems to be getting to be more than a pound. Although I must admit there has not been really difficult yet, My biggest challenge is to keep my work area clean and organized, when i get that down things seem to go smooth.

Fred
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Paul
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Post by Paul »

Hi Fred,

There's a couple of options for you to choose from at your engine and trans mount locations.

First, and the way I like to do this, is to choose a piece of hardwood such as oak or somthing similar and notch it into the plywood stringer. You have to keep in mind that this is the point where the thrust from the drive system pushes the boat so a solid mounting point is important. If you only cap the stringer at this point, you're relying on the bonding agent (epoxy) to hold the hardwood in place. (not including the mount bolts) However if you take the piece of hardwood, for example a piece of oak that is 1" thick x 10" long and the width of the stringer, and you cut a notch in the stringer 10" long and 1" deep for the oak to be bonded into, you now have this piece mechanically locked in place as well as bonded. Be sure the grain of the hardwood runs in line with the stringer. Then when you drill the pilot holes for the lag bolts, be sure that the bolts thread thru the oak and well into the plywood stringer. The oak being bonded to the edge of the plywood will keep the plys from seperating when the bolt is driven into place.

The second way is to drill a a hole Ø1" - Ø1 1/4" into the top of the stringer where the lag bolts will be, then epoxy in hardwood dowels. Then drill the pilot holes in these dowels for your lag bolts.

A third way, that I've never seen done, would be a combination of the two.

Hope this helps
Paul
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Last edited by Paul on Thu Mar 22, 2007 2:02 pm, edited 1 time in total.
Mac32
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Post by Mac32 »

Thanks for all the good info. I feel like I am getting sound advice for doing a quality repair job, and things would not be as easy with out this forum, THANKS everyone!!
I am going to take the hardwood cap and notch aproach. :D

Hopefully I can help to give back in some way.

Fred
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since you asked !!

Post by Beachouse »

How about coming to Grand Island, NY and help Allen and I repair our stringers? Or better yet, we could watch you do it after your completely experienced with the job !! LOL
I'm just kiddin!! Allen and I haven't tackled our stringer problems yet. We have the marina that we bought the boat from supplying us with their fiberglass repair expert to do the job (pray for us).
At this point we think that all is needed is holes drilled and then filled with epoxy. I know I need to get pictures to you guys so you can confirm the right track for the repair.
Fred, Allen and I are really glad that your stringer repair/replacement is going well for you.
By the way, how does one post pics on this forum?
Linda and Allen
Mac32
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Post by Mac32 »

Ok here is a link to a few photos of the stringer rebuild (about 30 hours into it so far). Please dont hesitate to offer helpful advice. I am trying to do a top notch job on this.

And I have to say it is really going smoothly so far I just need to keep remembering to stay calm, plan ahead, and keep area clear and organized so I never have to look for tools and such. and do a little a lot.....Oh yeah the minute I stop having fun, I go home.....



Main cabin
Image
Engine room rot removed
Image
Initial replacement fitting (like a glove)
Image
Last edited by Mac32 on Mon Nov 26, 2007 10:13 pm, edited 4 times in total.
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Paul
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Post by Paul »

Looks Good Fred,

When you're finished with the glass work, we'll talk about engine & shaft alignment.

Paul
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Mac32
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A Little Further Along

Post by Mac32 »

Well , I took the summer off on the stringer replacement and spent time on other peoples boats (it was a cost savings implementation)..... :lol:

But here is the start of this winters project......Get ready for the questions to start pouring in again!!!!!!

Engine Room Stringers installed Ribs Rough in
Image

MAIN CABIN
Image

NEW FLOOR LAYOUT IN V-BERTH AREA (Wanted standing room without stepping on raised floor and hitting head when new door is installed)
Image

STARBOARD ENGINE STRINGER (notice the splice 10 to 1 slope)
Image

THE IMFAMOUS HIDDEN FLOOR COMPARTMENT (will be putting bilge pickup down in the hole)
Image

NEW DINETTE SUPPORT KNEES
Image

STARBOARD STRINGER OVERLAP (step joint from engine section to main)
Image
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Paul
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Post by Paul »

Hi Fred,

What did you use to bond the new wood into the existing fiberglass troughs that the old stringers sat in?
Paul
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"No Control" 2012 9' Grand RIB
Mac32
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Post by Mac32 »

Hey Paul,
Was I supposed to bond the stringers to the boat????? :D

Just kiding, I used West system epoxy for laminating the boards together and for bonding to the existing fiberglass (with filler for gaps) after I ground down the insides of the mating surfaces. I also completly soaked the stringers with west system and let it soak in before bedding them to the boat. You can also see epoxy with filler on the splice in the engine room picture. I have probably used more than required (4 gallons so far) to get the job done. The job is getting increasingly more expensive.$$$$$ but it should still come in under 2k.

Being my first time I was afraid to cut out t all the stringer and risk re-shaping the hull. But next time (if there ever is) I would recomend just completly cutting the old stringers down to the hull and do it in half the time and probably less cost.
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Post by Paul »

Hi Fred,

Bedding the stringers in with West System is exactly how I do these repairs. It makes for a solid hull even before you cover it up with roving. And your right about cutting the old stringers down to the hull. It's a real time saver.

When you do a job like this your self, you tend to pay attention to details that the average shop would'nt spend time on. That being said it looks like you did a really nice job on this build.
Paul
"Cruise Control" 1978 F-26HT
"No Control" 2012 9' Grand RIB
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