Transom & Stringer replacement

Discussion in 'Fiberglass and Composite Boat Building' started by blaze_125, Apr 2, 2009.

  1. blaze_125
    Joined: Mar 2009
    Posts: 87
    Likes: 1, Points: 0, Legacy Rep: 14
    Location: Canada

    blaze_125 I see the light!

    Call me nuts, or set the record straight. I just add an idea :confused:

    I need to replace the transom and stringers on my boat.

    The transom seems like a b**ch to get to because of it's configuration and the pit that's in front of it. I figured removing the wood should be fairly easy. It's putting new one in that'd be a pain in the neck. So here's my idea... tell me if I'm lunatic or if I missed something.

    The transom layout looks like this.

    |*|
    |*|
    |*|

    | being a layer of fiberglass
    * being a sheet of wood

    So what if I was to do this:

    |~|
    |~|
    |~|

    | being a layer of fiberglass
    ~ being poured in resin

    So basically, I'd remove all the wood and fill the void with resin(and vertical rebars). I'd end up with a (approx.) 1" think resin transom.

    And what if I was to do the same with the stringers? Remove the rotten wood, create channels, pour resin in the chanels and voila!

    Pros:
    It will never rot again
    It's easy to make it happen

    Cons:
    Probably mad expensive to make such a thick plate of resin

    Stronger than wood? The transom is currently holding a 45hp motor, I may upgrade sooner or later to a 50hp motor. It's a relatively small boat, so by law, I can't go crazy on HP ratings... Would a poured slated of resin crack over time? If it did crack, it'd be easy to patch. So my question should probably be... Will it shatter when it gets stressed?

    My other concern is weight... How heavy is that going to be compared to wood? On the other hand, my uncle used thick steel plate to replace his transom when he installed a 200hp motor... I can't image resin being heavier than steel.

    ???
     
  2. blaze_125
    Joined: Mar 2009
    Posts: 87
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    Location: Canada

    blaze_125 I see the light!

    All I can say now is "Holy *@$%&#@"
    I just did the math with approx. measurments.

    Assuming the transom was this size: 1" thick, 48" wide, 40" high
    It would hold a volume of 8.3 gallons. 8.3gal@100$/gal = 830$ to pour a transom :eek:

    Now the stringers... 8' long, 2" high, 1.5" wide X 2 maybe 3
    A volume of 1.24 gallon each. 1.24gal@100$/gal = 124$ per stringer :eek:

    I knew it'd be expensive, just not THAT expensive lol. I'd still like to know if it would be solid enough though. I don't really plan on going that route anymore, but I'd like to know.
     
  3. PAR
    Joined: Nov 2003
    Posts: 19,133
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Resin by itself is way too brittle, this is why we use reinforcements in it and attempt to control the resin/fabric ratio.

    Secondly, it'll weigh a lot more then the plywood core that's in there. Now you can use a pour in transom repair, but if you've checked the previous threads here about transom repairs, you might have seen my opinion about these types of repairs.

    Plywood is used, because it is pound for pound stronger then steel, very stable, can take repeated flexing, easily accepts fasteners, is easy to cut to shape, cheap, etc.
     
  4. blaze_125
    Joined: Mar 2009
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    Location: Canada

    blaze_125 I see the light!

    I was introduced a few minutes ago to "pourable transoms" such as Nida-Core. Being a Canadian resident shipping would most likely be killing me on prices... so yeah, plywood is most likely my better option at the moment.

    I'll keep reading threads on here and wherever they are available to gather a better understanding. Meanwhile here's my new theory. You see, I'm good with when it comes to the rough stuff, but finition and making things pretty isn't my strongest ability. I'd like to avoid removing the well that's in front of the motor and then have to glass it back in when the new plywood has been inserted.

    Could I simply cutout the circled portion, slide a new wood sheet in, then glass the top to seal it?

    [​IMG]

    Or will I have to cutout the whole rear end(the fiberglass layer the motor lays against) and start fresh?
    If that's what I have to do... let me know if I have the steps right:

    Cut the outside layer of fiberglass
    Use that as a template to cut the shape of the new plywood
    Cover the plywood with 2-3 layers of fiberglass woven frabic
    Insert the new transom in the currently empty spot
    Glass the new transom to the boat using 2-3 layers of fiberglass woven fabric
    Lay new stringers against the transom and glass the stringers in place

    Does that sound right?
    What I hate about that is I'll have to paint the back. Or can I reuse the fiberglass layer I cutout? Cause I mean, once the rotten wood is removed from the fiberglass, that fiberglass panel is still good right? So I could laminate the new plywood with the old fiberglass panel, then glass the whole thing back in place? I'd still have to sand and paint a bit, but that would be limited to maybe 2-3 inches on each side of the cut. How far do I have to glass from the cut to make sure the transom is properly secured to the rest of the boat?
     
  5. blaze_125
    Joined: Mar 2009
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    Location: Canada

    blaze_125 I see the light!

    When I take the motor off the boat, can I lay it on the ground on its side? Or does it HAVE to be standing up?
     
  6. blaze_125
    Joined: Mar 2009
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    Location: Canada

    blaze_125 I see the light!

    I'll try to keep this thread updated as the project goes...

    Here you can see the current rotten floor. The fiberglass is cracked all over the place. No wonder water got in. And what you don't see, is a small hole near the front of the whole. The hole is most likely you main cause of all this mess.

    [​IMG] [​IMG] [​IMG]

    Tonight I got pretty much all the floor out. I still have to do some grinding/sanding to remove the remaining fiberglass that covered the floor along the sides of the hull.

    [​IMG] [​IMG]

    This is god damn discuting... [​IMG]

    Just how much water can foam hold? This boat hasn't seen the lake for months. I just got out of storage where it sat for nearly 6months. Yeah it was sitting outsite, but it was covered with a hole free tarp.
    [​IMG] [​IMG]

    Btw, I still need answers on my previous two posts.
     
  7. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Unfortunately, you can't just cut in a repair, because typically the rot extends down and sideways well into the multiple veneers of the plywood. Gravity has an obnoxious habit of always pulling in the same direction, meaning the moisture will collect at the bottom of the transom, then work it's way up. By the time you notice a soft transom, the whole central portion is rotted away.

    The foam can hold moisture for years after it's removed, if not baked dry. It's not worth the trouble of cooking the moisture out, so it's removed and replaced if desired.

    I don't bother replacing foam, I just provide a drain and weeps to permit the moisture to move aft and run out the transom plug. The sealed under sole compartments serve as buoyancy just as well as foam.

    There are two approaches to your transom, inside or outside skin removal. I prefer outside, as it's a whole lot easier. Many like the inside because you have the hull shell intact on the outside when you're done.

    My logic is simple. When a transom is shot, the gel coat is likely also near death too, so the boat needs to be painted anyway, so I hack the outer skin off, remove the plywood, install more in lots of goo, then re-bond the outer skin. If you're neat about it, you just paint the transom and call it a done deal.

    Judging by your pictures, you have a lot more then just a transom to worry about. I'd stop farting around trying to save stuff and gut the inside of the boat. The sole, the stringers, the lot of it. At least the back half of the boat if this has a large percentage of rot.

    This will expose the inside of the transom. You also appear to be trying to do this with everything still attached. Forget about it, strip the boat of the engine, the equipment, everything in the way. It'll make life a lot easier on you.

    The deck cap is a pain in the butt, though often times you can remove the screws (in the rub rail) say about half way up the sides of the boat, then jack it up enough to clear and provide working room.

    If not, it has to come off or have the back section cut (splash well and side decks) away to gain access. This all can be bonded back in place, but you'll have to paint things up to make it pretty again.
     
  8. blaze_125
    Joined: Mar 2009
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    Location: Canada

    blaze_125 I see the light!

    Outside is the way to go for as I want to avoid playing with the well. As far as I know, the well is fiberglass only. I'll dig the foam that surrounds it to ensure it is though.
    I won't be keeping alot. I'm actually going down to bare fiberglass. The stringers, foam, and transom are all going to the garbage.

    I have yet to take the engine off. It's an old and bulky engine that weighs a ton and a half... can I lay it on the ground on its side, or does it HAVE to be standing up? Once the engine is off, I'll cut out the outer skin of the transom, do some more cleanup and and put it back together with some fresh plywood. I'm not in a hurry to remove the foam as it allows me to freely walk in the boat right now. Once the foam is out, I'll have to rig something up so I don't step right through the fiberglass hull. I need something that does the weight distribution when I walk in there.

    That will remain off the current boat is the following... Fiberglass hull, front deck(which is fiberglass molded to the rest of the boat and has no wood) and the dashboard. Everything else goes out the door as far as structural stuff is concerned.

    It's a much bigger project than I first thaught it would be... but in the end I know I'll be proud of all the work and all the new things I will have learned along the process. Knowledge is power, and that's just 1 more thing to had to my list.

    So hopefully, I should have the engine off of there saturday and the transom should be out by sunday.

    This is the most important question at the moment: "can I lay the engine on the ground on its side, or does it HAVE to be standing up".
     
  9. PAR
    Joined: Nov 2003
    Posts: 19,133
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Both two and four stroke engines can be placed on their sides, though four strokes usually have to be laid on one specific side, which will have nubs sticking out of the covers to receive the weight.

    The bare 'glass will support your weight, you will not put a foot through it.

    Leave a 3" flange of transom 'glass around the perimeter of the transom, don't cut it right at the corner of the boat. This area is heavily reinforced and molded into the hull shell when it was laid up. You'll need this flange to help hold and tie everything in when you re-install the skin.

    I use a reciprocating saw with a metal cutting blade. It steers well, the fine tooth blade leaves much less mess and you can plunge cut or angle it around stuff.

    Of course this will leave an area (plywood) along the edges of the transom that you'll have to hack out with a chisel and grinder, but the flange is worth saving, trust me.

    I also usually cut right through the side deck and transom cap too., It makes it easier to drop in the new plywood.

    Grind all the cut edges to feather them back. A big taper is what you're looking for, so the old material has a place for new materials to live without bulges. Along the flange I grind back to right about the corners of the transom. The inside edge is 1/3 the thickness of the hull shell (after feathering), which gradually thickens to the full thickness at the corner. Do the same thing with the removed skin (feather the edges). When the two are re-married, you'll have a shallow depression that you will fill with fabric and thickened goo. This bonds the edges and provides a lot more surface area for the epoxy.

    Again, check out the other treads on this subject on this site. I cover the feather edges thingy and a few other tricks for increased strength, etc.
     
  10. blaze_125
    Joined: Mar 2009
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    Location: Canada

    blaze_125 I see the light!

    You just made my day. Now I know I can move forward with this project :D
    After reading your post I remembered a site where some guy described how he did his transom.

    http://www.hydrostream.org/ArticleArchives/Transom.htm

    It seems very similar to the process you described above. And his technic to laminate the new transom might just be the best option for me since I don't want to remove the splash well.

    Using his "technic", I'd cut out a portion of the transom, leaving a few inches all around(like you suggested). Once the rotten wood is cleaned out, I could insert the new transom and laminate it inside the boat. Once laminated, I could then laminate the wood to the skin that was removed in the first step using the feather/taper technic you talked about.

    Look at the thumbnail for my lamination process. I think the most important part in doing it that way is to ensure joints aren't becoming weak spots. So the transom has to be layered sort of like bricks would be layed down to build a wall.

    That technic would make my life a whole lot easier(I think). It would be easy to get the wood between the splash well and the outer skin
     

    Attached Files:

  11. blaze_125
    Joined: Mar 2009
    Posts: 87
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    Location: Canada

    blaze_125 I see the light!

    So basically... it'd go something like this...

    - Cut the back leaving 3-4 inches all around the edges
    - Get all the wood out
    - Paint resin over the back side(facing the inside of the boat) of the first transom layer, and paint the edges of all the transom layers
    - Insert first layer of transom, cover it with resin
    - Insert second layer of transom, lightly screw layer 1 and 2 together to get enough pressure to laminate
    - Paint resin over the second layer
    - Paint resin within 3-4 inches of the edge of the third layer(the portion that comes in contact the outer skin still molded to the boat)
    - Insert the third layer and lightly screw it against the second layer to get enough pressure to laminate
    - Clamp the transom laminated plywood against the outer skin to ensure good lamination between the plywood and outer skin
    - Laminate the outer skin that was previously removed to the new transom, and make it all pretty again.

    I just had some fun with Fireworks making a little demo of the process
     

    Attached Files:

  12. blaze_125
    Joined: Mar 2009
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    Location: Canada

    blaze_125 I see the light!

    I think I just figured out what you meant. I think the top portion(deck) is molded to the rest of the boat, but when I think of it more deeply, it doesn't really make sense. Unless they glassed it onto afterwards. I know there is foam under the side deck, so I'll dig in and look for bolts, joints, or any thing that could show be the hull and deck are 2 seperate piece that can be taken appart. If it's the case, if I understand your statement properly, it would mean that the splash well would actually come along with the top deck.

    Thanks for all the input so far.
     
  13. blaze_125
    Joined: Mar 2009
    Posts: 87
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    Location: Canada

    blaze_125 I see the light!

    The plywood I purchased for the floor is 3/8" thick. I want to mount 2 seats using pedestrals like this:

    [​IMG]
    The pedestral height will be in the range of 9 to 12". And the pedestral will be bolted in t-nuts.

    Is my floorboard thick enough or will I need to add some thickness where the pedestrals will be mounted?

    I used to seats like this. But I hated them
    [​IMG]
     
  14. blaze_125
    Joined: Mar 2009
    Posts: 87
    Likes: 1, Points: 0, Legacy Rep: 14
    Location: Canada

    blaze_125 I see the light!

    Here's the latest update.
    This weekend I got the motor off, and got most of the transom out.

    This is how it looked from the top looking down at the transom.
    [​IMG] [​IMG] [​IMG]

    I started the day by marking my cut
    [​IMG] [​IMG] [​IMG]

    9 Mastercrap blades later, the skin finally dropped on the floor
    [​IMG] [​IMG] [​IMG] [​IMG]

    A 3 hours later it looked like this
    [​IMG] [​IMG] [​IMG] [​IMG]

    So yeah... I got some more rotten wood to remove from 1 side, and also the inside fiberglass layer on both sides. Once that is out, it will be time to start making the new transom.

    I'm sorry I can't get pictures that show the whole back of the boat. My garage is 20' long and I had to park the trailer at an angle to be able to close the garage door and still be able to work on the back. I only got about 2' of room between the transom and the back wall of my garage, which isn't enough to capture the whole rear end.
     

  15. blaze_125
    Joined: Mar 2009
    Posts: 87
    Likes: 1, Points: 0, Legacy Rep: 14
    Location: Canada

    blaze_125 I see the light!

    Call me cheap... but can I use a lower quality resin with a higher quality glass cloth?

    I'd be using:
    6oz West System cloth for the transom
    West System 4" tape for the stringers
    Bondo resin?
     
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