20ft Fibreglass boat repairs help & advice needed

Discussion in 'Fiberglass and Composite Boat Building' started by stuee, Aug 27, 2012.

  1. tunnels

    tunnels Previous Member

    So what are you doing with those stringers ?? you rebuilding ?? with big thick stringers like those its better to tapper the hight off as they go forward . the panels get narrower so stress is less plus cuts some of the weight down . they get heavy when they are wet !!. . Me i like all glass no wood any where specially under and including floors . Its a part of the boat gets wet and stays wet vertually forever or untill the floor gets ripped out to replace rotten and wet wood . No wood no worries !!simple !!:D:p
     
  2. wooky30014
    Joined: Jun 2012
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    Location: East of Atlanta Ga

    wooky30014 Junior Member

    That is what was there from the factory, 2X8's I think, and I AM open to suggestion, another (larger but basically scrap) boat I had was 3/4 ply stringers with a block of oak glassed in for the twin engine mounts, mine will have a single Volvo drive
     
  3. tunnels

    tunnels Previous Member

    Ok give me a rundown on the boat !! what size is it ?? what is the motor a 6 cylinder volvo sterndrive ?? is /was it a open boat and whats the plans for the inside ??
    if it what i think you have id be in for foam stringers and glass over every where . its a bit of work but easy to do and makes a really nice job . With glass stringers they will last the life time of the boat and never have to ever do them again !!
    This can be done on smaller boats as well just a lot more fiddly work !!
    We just done a 90 foot boat with total foam stringers and frames in the hull bottom . but i cut down on some of the frames and got rid of 50% of then by adding a couple of layers of heavy unimatt to the inside of the hull and frames on top of that !! . its all new so was just a part of the build !!. send a good collection of picture with lots detail and see what can come up with !!:D:p
    Foam stringers distribute load better over a wider area so with the right glass layup you get a stiffer bottom with less movement ! still moves but its the glass in the stringers that determins how much it moves !!.
     
  4. wooky30014
    Joined: Jun 2012
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    Location: East of Atlanta Ga

    wooky30014 Junior Member

    It's a 19 ft SeaBird open runabout, a step down walkway between the seats in the cockpit helm, Volvo 270 drive with a Chrysler Slant 6, I was thinking of changing the motor to either an inline Volvo 4 cyl, also with a 270 drive, that a friend of mine has or look for a V6 that would fit it. Recently I got ahold of another boat for the hardtop and windshield and cut the entire cuddy cabin off of it, the rest of it was rotten so it was scrapped. After looking at your sketch I'd probably be better off putting 4 stringers instead of just the 2 to support the floor. I'll attach pics of what it looked like before and the rough sketches I have so far. Like I said I'm open to suggestion on this project and just in the planning stages right now, I've done a little bit of glass work but nothing major like this before. The 'Bird will be used mainly on local lakes for fishing and riding around. Thanks for your help with this, want to do it right as I can ONCE ;) I'll get a pic of the cuddy in the morning, measurements I've taken say it should fit and I have not cut any on the 'Bird's deck cap yet. The inside will have 2 helm seats with storage boxes below (which I have) and in the cuddy will be a place to stretch out

    Oh, the drawings are not to scale and the dark areas in the smaller ones are the bilge drains
     

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  5. tunnels

    tunnels Previous Member

    why dont you consider a out board on a bracket outside and gain some more floor space and its lighter and the boat is going to go faster and be much more usable . The volvo motor along is heavyer then an outboard on a bracket :D
     
  6. wooky30014
    Joined: Jun 2012
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    Location: East of Atlanta Ga

    wooky30014 Junior Member

    Tunnels, an outboard is a possibility and would allow more walking room, only reason I haven't given it much thought is already having the Volvo, I'll have to look into that, would changing over have any effect on the rated HP of the hull I think max is 165
     
  7. tunnels

    tunnels Previous Member

    The best bracket to get would be the one that also incorperates a boarding plateform as well will bring it really up to date and really much more usable and distrubute the loads over the whole transom not just in the middle . Its worth a serious look at !!. specially if you vertually rebuilding the whole boat from the ground up so to speak !! the most popular hp is in the 150 hp plus Merc, yamaha , suzuki or omc !:D:p
     
  8. wooky30014
    Joined: Jun 2012
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    Location: East of Atlanta Ga

    wooky30014 Junior Member

    Yea, a total rebuild is what it will end up as and I've seen the full width bracket/platforms on other boats just not up close, with it's installation knee braces will need to be added as well (I think I read that here somewhere) from transom to the stringers correct ?
     
  9. tunnels

    tunnels Previous Member

    Its just a thought that all !! its completely your choice what you end up doing !!:)
     
  10. wooky30014
    Joined: Jun 2012
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    Location: East of Atlanta Ga

    wooky30014 Junior Member

    True but it gives me another avenue to check into as far as the power plant, Back to the hull, putting 4 stringers as in your drawing might work better as well for floor support, let me get something straight, other than the stringers nothing else should be glassed to the hull ? I'm mainly wondering about the bulkheads containing the belly tank and the helm walkway up to the inside of the cuddy, I got the pics and will post em here
     

    Attached Files:

  11. tunnels

    tunnels Previous Member

    Needs to be done in a sequance and in the right order !!
    stringers longtudinal then hull bracing and bulkheads and the back ends of your stringers can be come engine beds ,Still foam glassed over but with some steel plate inside to drill and tap and bolt the motor mounts to !!
    just need to make sure you get all your measurments rigtht before you start . !
    You could need to be in the hull for a few hours grinding so its 99% clean and clear of crap so the glass witll stick properly !! Is best to put down a wide glass pad to help stiffen the hull bottom and for the new stringers to be glassed on top of the new glass with a wide pad all the new framing is on new glass so adhession shouldnt be a problem .old inboards have oil and diesel spills and getting glass to stick is a major and its usually from end to end where its been in the bilge sloshing about for years so clean up is the most important thing other than you breathing .:D;):p
     
  12. wooky30014
    Joined: Jun 2012
    Posts: 25
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    Location: East of Atlanta Ga

    wooky30014 Junior Member

    Yea, I tend to measure everything twice then again just before cutting ;) what kind of foam are you talking about vs 2X8 or laminated ply ? The old stringers were the engine mounts using a bracket bolted to the front of the block with ears (with the rubber parts) extending out to brackets bolted through the stringers, stringer pad is about 2 inches wide, I left the old channel up for the time being (see pic), I've scrubbed the crap out of the inside with degreaser but know also that isn't quite enough, the grinding/sanding I was planning on using an orbital on slow speed with 40 or 60 grit with a shop vac hooked to it instead of the dust bag to carry away most of the dust with dust mask on as well, it will be under cover in a portable garage to keep it dry, it's sitting firmly on the trailer with new bunks under where the old stringers were all the way up to where the bow starts curving upward, wide rollers on the keel every 2 or 3 feet front to back (it's not going anywhere), like I said before it'll be after the first of the year before I can get started back in earnest on this just prepping and learning now and studying options (like the OB bracket)
     

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  13. stuee
    Joined: Aug 2012
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    Location: Australia

    stuee Junior Member

    Tunnels.
    Just a couple of q's
    (i need a break from the hammer and chisel getting the old bog out..... im surprised i cna type with my smashed knuckles)

    1. For the keel stringer you have mentioned s 50x75, can you recommend any wood for that as or would i just use 3 pieces of marine ply sandwiched? 1 piece of wood would make life easier :)

    2. Under the stringer in the strake you have extra glass sheet. would i glass a strip down and let it dry or just glass the strip down and while wet put the bog on that and let it set.

    3. Would it make sense to prepare the stringers and a couple of bulkheads then get them all setup and sealed, then temp screw them and glass strip tack them all together so i can lift out after then bog etc and place it all on top. this way everything stays straight and in place.

    4. from the look of your drawings you have the tank with supports on the top of the 2 side stringers connected to the top of the tank, is this ok to do?
    i was thinking of making a stainless frame strips to hold the tank in shape from stringer to stringer then then the floor is in place cut the hole out the floor and make a fibre box build into the floor resting on the frame strips for extra support, this way i can access the tank if needs be and its also a sealed box holding the tank from under the floor.

    5. i still need to know the best way to join 2 pieces of stringers together as there is a mixed opinion on the net and im guessing from experience you would know better.


    Hi Wooky,
    it ok, the more heads the better, its pointless making 2 posts about the same thing, one of us will be working faster than the other so can give the other advice too.
    Im happy to see the pic of your boat as it makes me feel im not the only one in this situation.

    Cheers
    Stu
     
  14. tunnels

    tunnels Previous Member

    ]Tunnels.
    Just a couple of q's
    (i need a break from the hammer and chisel getting the old bog out..... im surprised i cna type with my smashed knuckles)

    1. For the keel stringer you have mentioned s 50x75, can you recommend any wood for that as or would i just use 3 pieces of marine ply sandwiched? 1 piece of wood would make life easier :) [nothing in particular just the size wtih the corners rounded so you can glass over easy and not get air bubbles aling the edges > radus about the size of a 5 cent coin .

    2. Under the stringer in the strake you have extra glass sheet. would i glass a strip down and let it dry or just glass the strip down and while wet put the bog on that and let it set.Have a look at the glass lay up it 2x 450 gram chopped strand with a 800 gram double bias and a 450chopped strand over the top if you keep you catalyst to 1% or there abouts you willl or should have plenty time to do it all one layer after the other , make the first and secon csm wet then put the double bias in and roll it then cover with the last 450 csm and lest go hard !!! this goes under all the stringed and under the keel as well . because the boat is old dont know what the layup is so better to be sure than sorry when all those horses are working
    3. Would it make sense to prepare the stringers and a couple of bulkheads then get them all setup and sealed, then temp screw them and glass strip tack them all together so i can lift out after then bog etc and place it all on top. this way everything stays straight and in place.
    You can use a couple of the bits going across to hold the stringers upright yes !! but the stringers need to sit in wet catalysed bog enough so its squashes out from under and then immediatly cove the sides and let it all go hard ,You might need to sand with 40 grit and then check the glass lay up i gave also and how it needs to go over the top . All his glassing is really important and is supporting the whole of the bottom of the boat front to back side to side you will appreciate all this when you hit a wave and the boat goies flying into the air and comes back down with a thud . what you doing is holding the boat together !! any joining of glass you need 50mm as a minimum over lap bigger is better but never smaller





    4. from the look of your drawings you have the tank with supports on the top of the 2 side stringers connected to the top of the tank, is this ok to do?
    i was thinking of making a stainless frame strips to hold the tank in shape from stringer to stringer then then the floor is in place cut the hole out the floor and make a fibre box build into the floor resting on the frame strips for extra support, this way i can access the tank if needs be and its also a sealed box holding the tank from under the floor.
    You can mount the tank how ever you want ,who ever makes the tank just weld some heavy straps to the top and screw directly to the top of the glassed over stringers and recess the back of the floor ply so it all ends up level !! how ever you decide dont let the tank sit any closer then 25 mm from everything . it need spaceall round bottom ends and specially the bottom where the hull will move up and down !! just need to cut a thin plywood shape of the hole and take 25mm off it and hang it in place so the person making the tank has a actual shape of the tank then its what ever length you need . front and back could be differant shapes slightly so check


    5. i still need to know the best way to join 2 pieces of stringers together as there is a mixed opinion on the net and im guessing from experience you would know better.
    I have a favorite scalf join i do its strong and when glued and a couple of srews is as strong as the rest of the stringer . its a japanese design we used doing old building will draw and give you a picture theres is a sort of a formular which i will write as well .


    Hi Wooky,
    it ok, the more heads the better, its pointless making 2 posts about the same thing, one of us will be working faster than the other so can give the other advice too.
    Im happy to see the pic of your boat as it makes me feel im not the only one in this situation.

    Cheers
     

  15. tunnels

    tunnels Previous Member

    Hope you can read it ok !!

    This is a really good join for any size of timber specially when the size gets up . 150x50 , 200x50 , and even 300x50 were the sizes of beams i used on my deck at home just pinned the ends with 100 mm flat headed nail each end !! As a decorative measure i did left and right scalf joins where they were seen . The inspector was amazed he could not believe what he was seeing , like no one does these kinds a things !! he even took pictures . as i say it was you for more than 10 years and was perfect still . When i sold the house the land agent wanted me to come and do her deck same way . Posts and panels all checked in and no nails any where to be seen, the odd one or two were hidden behind and under things !

    For yours better to screw the ends and epoxy the joins . done to that formular never breaks ever !!


    Some of the buldings i was able to work on in Japan were close to 600 years old The old houses are called Minka and they are works of art how they are held together !!
     

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