stringer issues

Discussion in 'Fiberglass and Composite Boat Building' started by boatboy21, Mar 17, 2013.

  1. boatboy21
    Joined: Mar 2013
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    boatboy21 Junior Member

    I have removed the floor and old stringers in a i/o conversion and have hit a snag. I have ground down the hull and replaced the two main stringers with ease but the issue is with the outside stringers. From the looks of it these have been replaced several times before due to the amount of build up and mangled mess of fiberglass. Instead of having to grind out 2" of old resin and fiberglass to get back down to the bare hull I was thinking of using cross braces instead. I would take 2"x12" fir and tie them in every 2' along the main stringers at 90deg. These would be tapered to match the dead rise and glassed in. Yes, this will add more weight which is not a huge concern for this project but will this take too much flex out of my hull? And will this be enough support to the hull if glassed to the dead rise and tied into the main stringers at 90deg? All answers are much appreciated
     
  2. tunnels

    tunnels Previous Member

    Please post some pictures !!

    Please post a few pictures of what you have !! wide shots and some with close up detail we can give you a much better and straightforward answer of we see what you have already !!
    EASY TO POST PICTURES !!I found it easy to make a folder on you desk top and reduce the size of the photos you want to send (i use photo razor program )so get more loaded really fast ! I use the paper clip on the menue and load as many as you like .simple fast and all done and dusted in no time !!:D

    If you get a chisel and get the strips of glass up and rip it out in strips instead of grinding wih dust every where! then just finish off with the grinder !! Only one way to do the jobs is properly and do it once and never have to worry again !!
     
  3. boatbuilder41
    Joined: Feb 2013
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    Location: panama city florida

    boatbuilder41 Senior Member

    Flush mount arbour and diamond blade will help a lot. Typically used for cutting granite just lay it flush on the hull and cut under all the rubbish
     
  4. tunnels

    tunnels Previous Member

    yeah right and if you want to cut holes in the hull skin go for it . a big grinder would be my first choice and a 16 grit disc !!!! But in so many cases where the glass hasnt been bonded well it will probably just rip off without to much problem and save all the hassles But still need some pictures please :D
     
  5. boatbuilder41
    Joined: Feb 2013
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    boatbuilder41 Senior Member

    Dont knock it till you try it.........no disrespect intended. Diamond blades dont have teeth... i learn new things every day.......never be afraid to learn from another.....im not .......my favorite guote......LIFES MOST VALUEABLE LESSONS LEARNED ARE LEARNED FROM FAILURE......NOT SUCESS.....I WOULD NOT LEAD ANYBODY IN THE WRONG DIRECTION.......Like i said......no disrespect intended....i am on this site to share and learn from others as well.....you never get to old to learn
     
  6. boatboy21
    Joined: Mar 2013
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    boatboy21 Junior Member

    pics

    here are a few pics of what I was talking about. In the one picture it shows glass nearly an inch thick with gaps all through it. I have cut down even with the hull as much as I possibly could but stopped due to the fear of grinding through the hull. The one picture with the cardboard cutout is a template of the idea i had in the first post to run 2x12 fir at 90 degree to the stringers glassed in at every two feet. Thanks again for all the great input. Also the 2x4's between the main stringers are only temporary and will be removed after tabbing. To this point I have only used an epoxy/wood flour fillet to hold them in place and round the corners for tabbing.
     

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  7. tunnels

    tunnels Previous Member

    Yeah its a mess and like i said id sure as hell have a go at trying to get under it and rip it out if possible .sometimes if the glassing was never done very good it comes off surprisingly easy and if you just keep glassing over the top of the old then its pretty much a forgone conclussion its wont last to long !
    Even a sharpened spade is a leathel weapon and can be used to great advantage !! just be carefull WHAT you doing !!

    Whats your glassing scheduall for the stringers ?
    what kind of glass you going to use ??
    and how much ??
    are the stringers bedded down on bog or just sat in place and the corners coved ??
    you are going to cove the corners arnt you !!
    needs a 15 mm radius 30mm dia pipe size both sides . the problem with athwartships bulkheads is it creates stiff patchs and the panels cant flex like they used to so harder riding and more prone to getting stress marks in the gel coated surface on the hull bottom !! if its to support the floors inside then make the top level and keep the bottom 30mm away from the hull so dosent touch
    :confused:
     
  8. boatboy21
    Joined: Mar 2013
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    boatboy21 Junior Member

    The main stringers are bedded down in the old stringer channels and glued in. I still have some more radius work to do as you mentioned above. I was planning on using two layers of 6oz tape for tabbing then two layers of 1808 overlapping the hull and stringers by about 10in then 12oz biax to finish before flow coating and painting the bilge. I hope that will be enough glass? If I can't get the mess under control and do the bulkheads to support the floor as you say and then just tie my 3/4" floor into the sides of the hull with tabbing and a finish layer will that be enough strength. My plan is to put a bracket on the back and run a 200hp outboard. If the two main stringers are enough to support bulkheads as you mentioned and a floor then I will just glass the hell out of the main stringers and go that route.
     
  9. tunnels

    tunnels Previous Member

    Ok i just done a crued drawing of what i would suggest but i think youll get the idea .
    The glass from each side overlaps on the top !! this gives good strength where its needed . double bias and triaxle is best for the vertical sides of the stringer and lays nice with a 15mm radius and out at least 100 mm onto the hull all way bothsides !! Yes theres csm first and betweem layers and last . if you bury good glass its much stronger . do all the stringer glassing first before you add any framing as its the stringers that will be doing 9/10th of the work not the frames !! they are almost only there for the ride !! :D
     

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  10. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    I use diamond blades or carbide to cut off most of the buildup. You can then grind the rest flat. I suppose it takes some experience and a steady hand, but you can start cutting far from the hull to get the hang of it and then go lower.
     
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I agree on the diamond blades. They can't hurt you, are much easier to life with on the job and are neat and fast, though I use a 16 grit 10" wheel an awful lot.

    On your transverse support idea, yeah it might help (and add a good bit of weight), but you still need longitudinal stiffness, which is why the stringers are arranged the way they were. If you do use the bridging, you'll still want longitudinal members too. Ideally, they would be continuous from the transom, as far forward as they can go. If tabbed in well, they don't have to be continuous, but it will require a heavier tabbing schedule.

    Tunnels schedule seems pretty stout with about 70 ounces of laminate over the stringer. Most manufactures would skip the 22 ounce triax and just use a roving, but I like the triax idea better - much it's stronger.
     
  12. tunnels

    tunnels Previous Member

    There are 2 triaxles ! one i 0/45/45 and another 90/45/45 If you can find this one in a tape form its heaven and joining it on top makes it easy to lay as you can work from one side then the other and is much quicker to get rolled down with no air bubbles . used it a lot with pvc foam stringers on 90 foot boats in conjunction with Uni tape along the tip of the stringer !! :D
     
  13. boatboy21
    Joined: Mar 2013
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    boatboy21 Junior Member

    Awesome thanks for the help. Looks like I will go grab a diamond blade and start from there. The glass schedule seems very straight forward and very strong. As PAR mentioned most manufacturers skip the triax and use roving. To get the same strength would i be able to use two layers of 24oz roving with csm between them and then the biax. I have plenty of the roving laying around and the cost savings of not buying triax. would more than pay for the extra resin needed. Again thank you for all the great advice and help with this
     
  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    You can make a huge mistake by not having enough laminate, but with this sort of repair, not much harm in a little extra, so yep, two units of roving will be fine. Orient the weave pattern on each layer of roving, so they cross each other. A cheap way of getting a little more strength.
     

  15. boatboy21
    Joined: Mar 2013
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    Location: Maryland

    boatboy21 Junior Member

    Sounds good thanks again! I will post some pics as I go but this is a slow moving project due to funds. Thank you all!
     
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