Rebuilding only half the boat, okay for the time being?

Discussion in 'Fiberglass and Composite Boat Building' started by sikpupy, Jun 6, 2008.

  1. sikpupy
    Joined: Jun 2008
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    sikpupy Junior Member

    I have a cris craft that needs repairs. In this boat it has a stringer setup sort of like multiple tic tac toe patterns but in a stright line something like ## with an extra outter set of long stringers going front to back. It had a V-6 in her but I want to put a 470 in it, so, will need to do make a motor mount pad for it, but, thats for another thread. Anyhow... I have all of the old transome wood out. I was very lucky(?) as it basically all fell out :rolleyes: . The wood in the stringers is all but mush as of now, but, the stringers themselves (the main ones going front to back) are very solid. I was thinking I would like to put back in the transome and replace the stringers in the engine bay area ONLY with nice strong epoxy (only for now guys, only for now!!!). I would do up to, and including, the first (counting from the back towards front) port to starbord stringer, which is were the gas tank starts. So, basically, I would have my first squared area done.

    editors comment: Yea yea, I know its best to do a nice long one peice stern to bow stringer and just do it all at one time.........

    This leaves me with a two part question. If i replaced the portion of the boat I am talking about, would it be basically safe enough to use out on the water as long as I am not jumping waves? The rest of the stringer system, besides the wood inside it looks strong. I know it does not give me full structural integrity at this time, but, as long as my engine is not going to fall through the boat and the stern is not going to get ripped off.... Secondly, if I have a new 4ft piece of stringer wood (tied to the stern towards bow) all wrapped/layered water tight in epoxy and glass, how much loss of structural integrity would I lose trying to graft a second 14ft (its a 18ft boat) peice of wood to the fresh peice, already in there, at a later date as opposed to a full 18ft length?

    I have 2 boats now and I need to get rid of one like yesterday. Summer is here, so, if I sell the one thats running now (which couldbe of iffy question....I am afraid to look), I will not have a boat. I have waited 3 years to get one running and cant afford to lose another summer, lol. If it is feasable to do what I am saying, along with and tied into a new stern of course, that would be great. I can get the back floor in where the engine is too and have my boat to use until I find ANOTHER boat i want, which is a cuddy, so I can start that project, lol. Yea, I am going for the $500 cuddy and tearing her from stern to stem. Build her up and have a boat for life? Dont want to spend $5000 and get dupped. I would rather KNOW what I have, all fresh....mmm hmm...
     
  2. sikpupy
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    sikpupy Junior Member

    Guess no one wants to touch that with a ten foot pole, lol??? But still, I would think that rebuilding half would be okay as long as you could tie into the new stuff later. I want to sell my older boat and put this one on the water but I dont want it to be a 2 year affair, thats why I am wondering if it is not that far fetched of an idea.
     
  3. charmc
    Joined: Jan 2007
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    charmc Senior Member

    To answer your question of safety with a stringer partial replacement is impossible without a thorough inspection (survey) by a knowledeable professional, IMHO. A stringer repair by replacing a section is best done by cutting back at least a foot or more into solid wood. The way to maximize strength of the joint between new wood and existing good wood is by cutting a scarf (angle) at least 8:1 , in other words, if the longest width or height of the stringer is 6", the scarf length must be at least 48" for maximum strength. Yes it's a lot of work, and worth it only if you know from a qualified and objective report that the balance of the hull is sound. If not, your repair will have created a new stress point where good and rotted wood meet.

    There are many builders and restorers here who will have opinions backed by more and better experience than mine. My advice, for what its worth, is to get a qualified survey before attempting a partial repair.
     
  4. Herman
    Joined: Oct 2004
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    Herman Senior Member

    To keep it short:

    You have a V6 powered boat, that fell apart.
    You like to replace the V6 with a V8 (more power) and...
    Do only half of the repairs you should do to get the boat safe and sound for the V6 that is was designed for...

    And you expect us our on the Internet to tell this is OK, without being able to examine the boat.

    My best guess is that all replies that will follow will talk you out of this idea.

    Please don't mess with safety.
     
  5. sikpupy
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    sikpupy Junior Member

    No, I dont want anyone to talk me out of anything, actually, all I want is opinions. If its downright dangerous, then thats what I will take into account. If its possible, slightly plauseable and somewhat feesable, then I would like YOU all to be honest and let me know. The ONLY thing I dont want to hear form is a purist. I am a perfectionist myself and cant think of anything but redoing the whole boat all at one time, but, conditions are squeezing me left and right, but, I will NOT jepordize saftey. Now, if on the other hand doing stringers like I suggested would be like putting a bald tire on a car (analyticly speaking), then, thats what I want to know.

    Just for the record, I am going to put a merc 170 3.7L 4 banger in her. I dont want a speed boat, just a little ol cruiser.
     
  6. Herman
    Joined: Oct 2004
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    Herman Senior Member

    OK, get the point. Well, if you are downgrading the engine, it is up to you to assess the damege done to the boat, and decide whether it is still safe to use her. As we have no idea, as we are remote, I would not put too much value in any advice (positive or negative) being given.
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Yes, you can make repairs and upgrades, but it does create more work for yourself. This is a common approach, budget and time restraints often dictate how much can be done at once.

    This said a little more info about your boat and it's equipment is necessary, plus the general condition and results of the most recent survey would be very helpful in accessing your issues.

    You can "scab" into pieces to return their strength, but this often is as much trouble as a full replacement, not to mention the cobbled together look and potential for increased stress risers and joint failures.

    The issue I see is you may be getting into a weight distribution and point loading problems. Imagine an assembly of parts that are scaled to absorb specific loads. Now imagine these parts with more weight and more load. Typically something gives, deforms, distorts or just plane isn't up to the tasks asked for very long and breaks.

    How much of an increase in weight and power is the new drive assembly going to place on the structure? What is the condition of the other structural elements under and surrounding the pieces you plan on repairing/replacing? Can you post some photos of the affected areas?
     
  8. sikpupy
    Joined: Jun 2008
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    sikpupy Junior Member

    Thanks PAR for the open minded comment. I truly would like t do it all at once, but, there was a few points that made me consider the latter. One is that they say the fiberglass in the stringers is the main structural part of the boat that gives it its rigidity and that the wood is kind of like insurance from extra pounding. I get Munches coke can analogy.... Second is that the fiberglass in the stringers is very this and being a boat with two sets of stringers running stern to bow in parallel, and, at least three sets of bulkheads (I belive is what they are running from port to starrbord side) all in good solid condition, minus the wood inside (mush), I feel fairly comfortable with it. Again, i am no boat expert, so, to make sure my eyes are bigger than my fiberglass, thats why I am asking here. Third would be that I was thinking, just thinking for now, if I boxed my engine compartment up to, and, a little past the first bulkhead (counting from the stern to the front) and replacing the first bulkhead along with the stern, I would not have to worry about the back part of the boat at least. Lastly, I would run the new wood (stringer section's) past the first repaired bulkhead. This way, when I went to repair All I would have to do is cut into the fresh, new (well, it would be 3 months old now) epoxy/fiberglass and but the new wood up to the wood layed down and whala, good as gold??? I also heard that fiberglass to fiberglass is very strong. Maybe not a chemical bond, but, a few more layers to compensate for the cut?

    This leads to structural loading that everyone talks about. Well, could not be worse than what I was going to do before I got curious to ask, and, just lay down a new floor and go, even with the old transome! I took my other boat out this past weekend and it has the same engine/outdrive setup I am going to transfer over. Though I had a too small propellor on her, I think I got to about 20knots at most. She cruised me good enough, no hard wave pounding, even when running through them at speed and was nice and smooth. The boat I am working on is a little longer and wider, so, not sure there would be much stress on her if I used the same setup. Like I said, not looking for a speed boat or a wave jumper, so......

    Anyhow, thanks for all the replys guys so far and I will try to get some pics. Thought there was a way you could insert small ones in chat rooms, but, never learned how, lol.
     
  9. the1much
    Joined: Jul 2007
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    the1much hippie dreams

    i think he's making fun of my "coke can" analogy ,,hehe ;) ,,,charm. and Par will send ya in the right direction :) ;)
     
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  10. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The wooden elements of your 'glass boat may be structural elements with a 'glass coating to protect them or the wood may be used as a core, which isn't providing the strength (in the usual way folks look at things), but acting to keep the separated 'glass skins apart. In both cases the wood needs to be there and in firm contact with the 'glass. This includes stringers, bulkheads, etc.

    An reasonably easy way to tell which type of engineering was employed on your boat is to look at the thickness of the 'glass over the stringers. If it appears to be a moderately thin layer of fabric and resin, then the wooden element is the bulk of the strength and the 'glass work was done to waterproof the part. If the 'glass skins appear thicker, then the wood is a core and possibly could be replaced with another material of similar compressive quality.

    Knowing the year of the boat would narrow down the engineering possibilities. What model Chris Craft too . . .

    Loads can rise exponentially with just a very small change in length and beam. Don't be fooled by another boat's arrangement, it may be using different engineering principles to get similar end results (a boat).
     

  11. sikpupy
    Joined: Jun 2008
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    sikpupy Junior Member

    I have uploaded a few images to my photo gallery (they are on pending approval as of 9:00am). The are random pics I took a while back. I do not have any good ones that would be definitive help as of now. Can get the year later also. I dont "think" it is a thin layer, except in the bulkhead areas, as the stringers seemed hard as a rock and then some. Its been a while since I looked at them, so, for now, I will use that term loosly. Will get some more info by the weekend though.

    I was not using my little red boat as the benchmark of stress points and such, but, more to the fact of how fast I want to go/need to go, how I would handle playing in wakes, how they feel (have not been out on my own boat much) floating in them when a big boat comes by, deliberatly driving through them after a boat comes by, trying to judge where and if stress is placed on the boat trailering her, putting her on/off (uhm, not really much there, lol).... ALL the variables taken into account as best as possible.

    I have the floor loosly on, so, this weekend, if not sooner, I will pull up the floor and take a picture of the stringer setup and get real close on the stringers for you all.

    Thanks again for the help, I really appreciate the input.
     
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