Stringer replacement...noob, please discuss options with me...been reading alot

Discussion in 'Boat Design' started by Sprint18, Apr 28, 2009.

  1. Sprint18
    Joined: Apr 2009
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    Location: Roc City, NY

    Sprint18 Mind-full Appetite!!!

    Stringer replacement...need input about materials

    Hi guys.

    I have a scarab 18' that spent lots of time in the water. I pulled the 3.0l for a 4.3 build I'm doing. Now its turned into a complete resto.

    First I found some cracks fiberglass at the top of the transom wood. when I opened it a bit I found it was pretty wet, but sounded solid. So I'm going to take the top of the transom off and see if I can get away with just replacing that.

    Then when I pulled the floor because I had some rotten decking I found rotten plywood stringers and water in every compartment I have opened so far.

    I was standing there thinking while I was starring at it, and I noticed it was dripping water out of the drain hole. The boat has NO water in it. It is clean and dry. vacuumed all the water and particles out of all the compartments under the deck. So WHAT does that mean? rotten core? Again... no water anywhere by the drain hole or where the engine was.

    Questions:

    You can use foam board as a stringer? I thought it would need to be strong. I figured the glass was there just to hold it all together as one piece and add strength.

    What is the easiest way to remove the rotten plywood stringers? angle grinder and cutoff wheel, sawzall??? Dare I say a hammer? lol

    How many can I remove at once? I will be putting the boat on a 6'x5' dolly made from huge timbers scored from a huge machine pallet (big german roughcut)...must be 8x10" or so.

    stringers can not be mated right to the hull? I have read that foam strips are needed between the stringer and hull to prevent stress points and allow the hull to flex a bit under the stringer grid. true?

    most common question.... What material is the best bang for the buck for stringers? marine plywood? dried and pressure treated lumber? Foam? miss anything?

    Obviously I will need to wrap anything I use with a few layers of glass then glass it in with big weave cloth. I'm sold on using epoxy.

    can someone clear up some of this....Or even a summerized list of what to do from here, just to piont me in the right direction. I have noone to ask locally



    Any help would be very awesome!!! I will post pics asap
     
    Last edited: May 1, 2009
  2. thudpucker
    Joined: Jul 2007
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    Location: Al.

    thudpucker Senior Member

    I dont know your boat, photos are always nice for us old guy's who like to look.
    I have a friend who just finished a 25' boat that had the wet wood inside the F/glass. Transome and all.
    You plan this out right, and it wont take near as long as it seems like it will be.

    Why'd it all get wet?
    You better do some looking all over the boat. Top and bottom. Around the Cap seal. Inside the bilges and down in the cuddy.
    Where'd all that water come into the wood from? You gotta find that out.

    You have to cut the glass off the wood stringers. Same with the transome.
    Do the transome from the inside so you dont mess up the good looks of the boat.

    Now you know what lengths and sizes of wood you need, you can go shopping for the right stuff.
     
  3. Sprint18
    Joined: Apr 2009
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    Sprint18 Mind-full Appetite!!!

    the boat sat in the water for years in jersey (brick city) and I used it for 2 seasons before the bellows and such rotted out. I have the entire transom assy sand blasted. It was so rotted from the salt water that the cavity where the tiller arm is busted right through while blasting. Water was coming in from everywhere after this past season.

    The mechanical part is no problem. I am a metal guy. But as far as fiberglass and wood.....yeah. Not so much...


    So... all the wood is crap basically. I might be able to get away with the transom because is is pretty solid still...but no gaurentees.

    How do I pull the transom glass off the wood without breaking it all up?
     
  4. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    I clean all the rotten wood and glass out with an air chisel.....brilliant ....kango hammer drill style with 1 inch chisel...great on rotted transoms.....use the hammer action
     
  5. thudpucker
    Joined: Jul 2007
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    Location: Al.

    thudpucker Senior Member

    LOL, great PB. I shouldnt laugh at anything said. I've never done that, just known of other guys who did it.

    When I did do some fiberglass work, (one time in my life) I wore a suit made of a bed sheet. I had been pre-warned about the tiny little F/Glass needles that invade your skin and make you miserable for days afterward.

    Good large Eye glass covers were duct taped into my suit cap.
    I had a breating mask that had two filters.
    Still, I got that stuff all over me. I'm sure it might have made it into my lungs as well.

    I used a Sawzall to do a lot of the cutting. PistnBrokes Chisel is probably good too.
    Dont trust the Transome wood. Take the skin off the inside and replace the wood. It aint gonna be real easy, but you can do it.
     
  6. Sprint18
    Joined: Apr 2009
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    Sprint18 Mind-full Appetite!!!

    I have a bit more faith in doing it now that i have you guys to help me along. I have a brand new air chisel too...lol

    I plan on just doing all the fiberglass new anyways so I'm not too worried about keeping sections of it to replace when i'm done woodworking.

    Would 2x8 DF be a good chioce for a stringer? Do i need to look for a certain brand of style..."kiln-dried" or such??? please advise.

    I have 2 9.5' beams to use as hull supports to keep it squared while removing the wood. I was also told that supporting it in a triangle shape will keep it straight.

    Should I do both transom and bulkheads/stringers at the same time? I'm scared to completely gut it all at once.

    I found another guy who was doing the same to a baja force 265 and he seperated the top from the bottom. All it is, is just a bunch of SS screws and some silicne holding it together. Should I pull the top off? It looks like it makes life a whole lot easier....especially with a closed bow like mine. Pics in a few minutes.... I'll go do that now.
     
  7. Sprint18
    Joined: Apr 2009
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    Sprint18 Mind-full Appetite!!!

    pics:p

    #1 is a shot from the front

    #2 is the crack in the fiberglass on the top of the transom that started this journey

    #3 is the leftside on the hull where transom meets sidewall. cracked about 7" down

    #4 shot looking down from the swindeck

    #5 front right corner of engine comp.

    #6 rightside bulkhead middle of engine comp.

    #7 front left corner of engine comp.

    #8 another crack in the fiberglass on the top of the transom about 10" from the drive hole to the right looking rearward

    #9 AHHhhh... the compartment vents next to the swim deck that let water plunge in from the back. did my best to stop it form happening. but with a heavy load it just washed in regardless. those will be patched and glassed shut
     

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  8. Sprint18
    Joined: Apr 2009
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    Sprint18 Mind-full Appetite!!!

    I am putting a 280-300hp v6 in this boat. i need it strong and durable for the pounding in store for it.
     
  9. Sprint18
    Joined: Apr 2009
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    Sprint18 Mind-full Appetite!!!

    scratch te top splitting... the adhesive they used looks tough and it's all the way around
     
  10. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Yeouch. That is a lot of rotted plywood.
    Although.... it's nothing we don't see on this forum at least twice a month. Welcome aboard, Sprint :)

    Well, it sounds like you like the boat and are convinced you want to keep it. The first step is to go buy yourself a nice face mask and safety goggles, because cutting the old stringers and floors out is going to send a lot of nasty dust and chips flying all over the place, including right at your face. And glassing the new ones in will get you very much acquainted with the wonderful fumes of curing epoxy.

    The hull will have to be well supported from the outside, since it can't hold its shape while the stringers are out. The trailer won't be enough- it needs continuous, uniform support in as many places as you can.

    Decks are supposed to be very well secured to the hull. Unfortunately this makes it very hard to do a rebuild like you're planning. If you can't get the deck off, the job will take a lot longer and your chiropractor bill will soar.

    If you search "stringer replacement" on this forum, you'll find a few dozen other folks who are in essentially the same situation as you are. Lots of good advice out there, if you have a few hours to sit down with your computer and a cup of coffee. Another worthwhile read is Dave Gerr's book "Elements of Boat Strength", $30 or so from Amazon and definitely worth it. The book includes a fairly conservative method for calculating the size and shape of the new stringers, as well as lots of diagrams showing how everything is supposed to be joined together.
     
  11. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    If you rip all the wood out and take the top off you need to be able to walk around inside it to work on it so it comes down to how strong the shell is ..I just left mine on the trailer but you could sit it on lots of tyres or get some sand delivered and put it on that ..take the top off and rip everything out ..I also used a shovel and block hammer ...replace the stringers with similar size to original ...kiln dried pine or plywood depends on depth and contour but encase it in fibre glass and make sure water can get from everywhere to the transome drains...do the transom first then the stringers ( finish just before the transome for drainage) and then the floor in 1/2 in ply...start at the transom and work forward in 4 ft wide strips ..screw the floor down to the stringers and dont forget to coat the underside with resin..you can use 20% acetone it makes it sink in ....cut out floor in card first if the fit is difficult . Clean up all areas where new and old resin meet with angle grinder and wipe with acetone to soften the old a bit .... I add paint to the polyresin about 5% to get the colour I want
     
  12. Sprint18
    Joined: Apr 2009
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    Sprint18 Mind-full Appetite!!!

    marshmat, thudpucker and pistn...... thanks for the .02!!

    I've been reading the tookis off! lol

    Lots of good info, but still had a few topic to cover more addiquately enough to restore confidence in myself.

    Man I just came down with the sickness going around last night. I feel like a steamy pile of .... right now. lots of virus going around right now. cough cough... hopefully I'll feel better by the next nice day

    you think it will be ok if i just do half the cockpit at a time? I can support the hull, but maybe not good enough to do all of it at once. I have a couple 10' beams to use as the main supports along the outer strakes(chines)

    i decided not to take the top off since it has been epoxied so well to the bottom. not just silicone like the other guys baja.

    i will have some more pics of progress when I feel better. time to get the boat up off the trailer and on the ground real nice like with plenty of support.

    Thanks so far guys!!!
     
    Last edited: May 1, 2009
  13. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    my experience is that you want to get all the rotten wood out of it then brush and vac the inside ...anyway its longitudinal stringers you are fitting so at least the centre ones will be full length....some people cut part of the rear beck structure away and glass it back on later ..some cut away the transom from outside if the inner glass sheeting is good .. Others just add about 1 1/2 -2 in ply to the outside ( glass bolts etc) and then glass over the whole lot ...lots of filler and sanding and spraying on others I have seen a fancy cut 1/2 in aluminium plate fitted but usually thats for a power upgrade..
    after all no one is going to inspect it . I have found resin to be a lot cheaper on ebay and 500gram matt works better and is quicker than the thin stuff..

    Most of the boats I make are runabout style when I get them ..I then cut the top off to make and open boat tidy it up and sell it on at a good profit
     
  14. Sprint18
    Joined: Apr 2009
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    Sprint18 Mind-full Appetite!!!

    ok... stage is set... garage is cleared for boat room. made a new work bench form my old counter tops to mix and cut stuff. Buying some wood tomorrow to drop it on the garage floor. nice level cement ;)

    All I have to do is take some measurements and rip some 2x10"s to lay under the chines. I'm going to notch them all on the bottoms to lay them on some 2x4 cross beams.....just like linkin' logs...lol

    I'll take some pics during playtime and post-up. thanks again so far.
     

  15. Sprint18
    Joined: Apr 2009
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    Sprint18 Mind-full Appetite!!!

    http://www.noahsboatbuilding.com/noahusa/itemdesc.asp?ic=OKO108815%2E&eq=&Tp=

    is this the stuff I need for transom and bulkheads?

    I'm not a cheapo...But if anyone knows where I can get a better price than that somewhere within 100miles of rochester,ny I'll be wearing a nice smile for a day or 2 :D :D

    Was thinking of using 12oz or heavier carbon fiber. I have a way to get it at cost. saw it in the marine supplies on that link. Didn't realize it's prevalent in boat construction. Not that it isn't really a no brainer.:idea:

    Also I noticed alot of fiberglass is treated for poly resin....Y? Isn't epoxy the way to go? I've tooled around with CF and we always use epoxy because it is much stronger, doesn't yellow and also is better for chemical applications (fuel,oil.. etc)

    input?
     
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