Yet another Stringer Post!

Discussion in 'Fiberglass and Composite Boat Building' started by merrile, Jul 13, 2009.

  1. merrile
    Joined: Jul 2009
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    Location: Oregon

    merrile Junior Member

    Yet another Stringer Post!

    All right, I have been searching around the site and given how far I have come with this boat, I owe it all to you guys. Thanks for the itchy nights! LOL J and endless money pit!

    I need to replace the floor (sole), transom and stringers. The stringers do not appear to be in too bad of shape but they are wet, which makes it likely worth my time to just replace them now.

    What scares me about the stringers is flex and making sure its done right. I am not that great with wood but my neighbor has offered to help me cut them out when I am ready. He builds furniture for fun so he’s going to save me time and money on wood yah know! I plan to encapsulate the new stringers before installation as suggested here on the site but how do I make a template to cut new ones and can I just cut them out in one piece.

    I thought I heard someone say in here just to cut the top off and dig out the wood leaving the original fiberglass intact the putting a layer overt the top. Once the new wood has been installed.

    I was also wondering if they need to be glued to the hull at installation. And what’s the best wood to use for this application. I can post pictures when my camera gets charged here today or tomorrow.

    Thanks,
    Merrile
     
  2. mongo75
    Joined: Aug 2007
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    Location: Orange County California

    mongo75 Senior Member

    I used a cutting wheel to cut my stringers from the hull right at the joint where the glass hits the hull. THat left me with a pefectly shaped template to use on my new wood. As far as bonding the stringers to the hull, some say don't cause it'll casue hard spots, but I glued the hell outta mine with thickened epoxy before laminating them to the hull with 1708.
     
  3. tunnels

    tunnels Previous Member

    replacing stringers

    Replace means just that you need to get as much of the old glass out as well
    Trying to glass over the top of the old layup is bad news . Its been wet for who knows how long its possibly short on resin and not stuck properly so whats the point trying to put new over old .
    Splitting the top of the stringer glass is just another short cut for what . Do the job properly and dont have to worry any more !!:) .
     
  4. missinginaction
    Joined: Aug 2007
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    Location: New York

    missinginaction Senior Member

    I just thought I'd share how I approached replacing my engine stringers.

    PAR gave me the idea some time ago of using a Sawsall (reciprocating saw) with a long blade to remove the old stringers. You bend the blade so that you can run the blade along the inside bottom of the hull and the old stringer will come right out.

    SInce I was removing engine stringers I needed to make some kind of a jig so that I could install the new engine mounts in the same loccation that the old ones were in. I made up a jig out of scrap plywood and some straight pressure treated 2X4's. I designed the jig to ride on the outside stringers and installed 4 pieces of plywood that would indicate where to place the new engine mounts after the new engine stringers were made and installed. See the first photo and you'll get the idea.

    The second photo shows the 2" foam that I used to make up the stringers. This was just Owens Corning Formular 2000 from Home Depot. Doesn't absorb water.

    The third photo shows the new stringers being installed. I used a piece of 8 oz fiberglass cloth to hold the wood clamping blocks to the stringer and give the assembly a little strength so that I could handle it. Once in the boat I used 4 layers of 1708 biaxle stitch mat to make up the stringers.

    I don't have a photo of the completed stringers so I posted a final picture of one of the floors that I installed forward of the stringers using the same 1708 mat.

    I have the mounts in and the entire assembly finished. I used 3/8 inch aluminum angle with 3/8 inch backing plates. The mounts install in the area where the wooden blocks can be seen in photo 2. You need something substantial to clamp to since the glass and foam isn't strong enough in compression.

    If you'd like to see the completed stringers let me know and I'll snap a photo.

    Regards,

    MIA
     

    Attached Files:

  5. tunnels

    tunnels Previous Member

    LOOKING AT THE GLASSING ITS NOT THE GREATES BUT THERE IS VERY LITTLE STICKING THE STRINGER TO THE HULL ALONG THE SIDES .
    BONDING TO THE HULL IS MOST IMPORTANT AND NEEDS TO BE AT LEAST 100MM WIDE PREFIRABLY 120MM ONTO THE HULL AS THE STRINGER COULD SIMPLY POP OFF AND BECOME COMPLETELY USELESS !! :confused:
     
  6. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    That's a good point tunnels and one that I thought about when I did this.

    I replaced that floor following the lead of the people at Silverton who built the boat. They did not attach the floors to the topsides at all! I felt that they must have had a reason for doing this since the boat had held up well in that area for the past 35 years. I replaced that floor due to issues with the aft cabin wall (I felt it needed more support and determined a wider floor would provide it) but there were no issues that I could see with the floor itself. You may well be correct and perhaps I should have glassed that floor into the inside of the topsides. To late now, since the cabin interior and sole is installed.

    BTW the glass laminate is between 1/4" and 3/8" thick solid fiberglass over that foam when finished. I've never used 1708 mat before and am amazed at the strength of the assembly. Rock solid. The mat held so much resin that even with a medium speed hardener I could only apply 2 layers at a time. I could feel the laminate getting warm and didn't want to risk the laminate failing due to excessive heat during the curing process.

    Thanks for bringing that up.

    MIA
     
  7. bigdawg10132009
    Joined: Jul 2009
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    bigdawg10132009 Junior Member

    show the finished stringers
     
  8. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    OK I will. I'm taking a day off tommorrow, but I'll be in the yard on Wednesday. I'll bring my camera and take a couple of pics.

    MIA
     
  9. bigdawg10132009
    Joined: Jul 2009
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    Location: georgia

    bigdawg10132009 Junior Member

    thanks a million! i am just starting my project....1984 ebbtide......bought it for 350.00 with a running 150 evinrude.......
     
  10. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    Remember bigdawg, I'm not an expert , but I did my homework and tried to ask all the right questions. I used System 3 epoxy, 1708 biaxle stitch mat and 3/8" aluminum stock for the engine beds.
     

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  11. bigdawg10132009
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    bigdawg10132009 Junior Member

    thats some pretty sharp looking work my man! i was just wondering what cloth to go with.....i was thinking about a 6 ounce weave or better but didnt know.....the biaxle was used for transom and stringers correct?
     
  12. bigdawg10132009
    Joined: Jul 2009
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    bigdawg10132009 Junior Member

    more pics......
     

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  13. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    You asked about transom repair. I didn't need to repair the transom on this boat. This is a v-drive inboard and there is little stresss on the transom. The transom on my boat is actually just a sheet of 1/4" solid fiberglass laid up, it is not especially strong, but it doesn't need to be. Your boat on the other hand will need a strong transom as that outboard will be pushing on it all the time. Search this sight for threads on transom repair and you'll find some good advice. You could also look at this site...............

    http://boatbuildercentral.com/howto/repair.php

    The biaxle cloth was recommended to fabricate my stringers, but there might be another option in your case. '

    Good Luck,

    MIA
     
  14. piperca
    Joined: Mar 2008
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    Location: Southern California

    piperca Junior Member

    MIA, I am a complete novice and am trying to learn a bit for a project of my own. I am about to ask a stupid question or two, so humor me!

    The stringers you installed are foam, is that correct? Is this foam, once fiberglassed, sufficient to support the weight of an engine?

    I need to do something similar, but the stringers will be supporting a Yanmar 6LP diesel engine.
     

  15. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    I found it interesting how many different opinions there regarding the construction of stringers. Look at this and other internet sites and the questions keep appearing over and over again. So it seems that there is a lot of confusion. I read most of what I could find and frankly, I was confused.

    So I did what I usually do and looked for a reputable source of information. I'd read a book by Dave Gerr called The Nature of Boats and enjoyed it. Dave had written a somewhat more technical book called The Elements of Boat Strength. In that book Mr. Gerr goes into detail regarding scantling rules for all kinds of boats, metal, wood, glass and more, he covers way more than I'll ever need to know. As far as I could see Mr. Gerr has a great reputation so I decided to follow his recommendations. You can find detailed instructions in his book regarding stringer construction and engine mount fabrication. Those 3/8" aluminum mounts in the photo's (and the thickness of the fiberglass laminate) are what he recommends based on the weight of my engine package (it's just a small block Ford with a Borg Warner trans and a V-drive) and overall size of the boat. Keep in mind that even Dave Gerr acknowledges that there are numerous materials that could be used for stringer cores. I decided to try the Owens Corning Formular Foam because it 1. Didn't absorb water, 2. Came in the size I wanted 3. Was easy to work with. I didn't use it because it was cheap, heck I've spent thousands on parts and supplies for my boat already. I could have spent a lot more on some fancy marine grade foam or composite for the stringer cores but based on what I read in Mr. Gerrs book I could see no sense in it.

    I'd suggest getting a copy of The Elements of Boat Strength and doing the calculations that Mr. Gerr suggests for your boat. I'm planning on taking my old Silverton out to the Atlantic in a few years (we'll have to escape from New York anyway due to politics, but that's another story). I'm confident that following Mr. Gerr's recommendations I'll be safe out there.

    So, now that I've said all that I can sum up in a couple of words:

    They're strong as hell.

    BTW, Mr. Gerrs recommendations seem to be backed up my many of the senior members here who make reasonable recommendations. Par, Alan, Apex1, and others.....I thank you too.
     
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