efficient 10m displacement powercat (build thread)

Discussion in 'Boatbuilding' started by groper, Apr 15, 2012.

  1. groper
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    groper Senior Member

    Well im using the fishbone pattern for a few reasons... it also could have been done sequentially with 3 parralell lines and pulled sideways to each edge - so open the middle line, then the next 2 when the front reaches them...

    I choose NOT to use the sequential method because i prefer to mix the entire amount of resin upfront. I prefer to mix it all like this, as i can let the weighed resin (uncatalysed) sit for a long time to let the air bubbles rise up before adding the hardener. If you use the seqential method, a large amount of resin is in the bucket for a long time before the second 2 lines are opened and things start to move quickly again, and ive had an episode where the resin started to kick off whilst i was waiting to open the second 2 lines on a different job a while back. The fishbone pattern empties the bulk of the resin quite quickly and so this isnt a problem. I dont like adding more resin to the bucket mid infusion, as again this airates the resin in the process of pouring it into the feed bucket.

    I stop the flow media 2 inches from all panel edges, this allow the underside to catch upto the topside (the lag) and also allows the fishbone resin front to even itself out when it reaches the panel edge.

    The core thickness in this boats bridgedeck is 20mm, however this thickness is determined by the stiffener locations and thus the unsupported panel length and width between stiffeners. This will vary for every different kind of boat. It really is a stiffness issue, not a strength issue. Im running 1 longitudinal stiffener down the guts over the top of the join between bridgedeck halves. Also the furniture locations in the cabin reduce the unsupported spans aswell, then there is the beams running athwarthships in 4 locations aswell, so the floor shouldnt be springy at all in most places. There is one area on the back deck where the panel spans 1.3m. I may need to add another stringer if it feels springy there, ill wait and see how it goes. Simple to bond them on afterwards.

    The resin inlet connections i use are the Airtech RIC`s... these do not make any appreciable indent in the laminate. The resin lines however, do leave a thick resin rich hump on the panel. I grind these down afterwards.

    This is what the panel looks like after infusion and then straight to paint, will lift it into place tomorro - gotta wait for the damn paint to cure :(
    Note the recessed edges for tape joins, and also the imprint of the packing tape i used to help vacuum seal the table between sheets of melamine. These fair out with one extra strip of high build paint where the imprint is. The core is a mixture of divinycell (grey) and airex (green) -using up offcuts thus the different colors you can see...

    [​IMG]

    [​IMG]
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Groper, did you say 1500kg "splashed" for this ? Even if that is sans engines, surely this will plane off with ease ? I'd have thought it would be difficult to keep under 3 tons.
     
  3. waikikin
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    waikikin Senior Member

    Some great info there Groper, those panels look pretty good, what's the go with some whitening presumably in the pattern of the feed lines?

    Regards from Jeff.
     
  4. groper
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    groper Senior Member

    yes the slight whitening is directly below the feed lines on/around each perforation... i put this down to needing to mix an additional 2kgs of resin when it was clear i didnt have enough near the end of the infusion... so i mixed up the extra 2kgs and then poured it into the feed bucket near the end of the infusion, the resin was probably quite airated as i didnt leave it to settle out... im not concerned by it tho, its only very slight - its so noticeable because the rest of the laminate is perfectly transparent. The quality you get with infusion has to be seen to be believed...

    Yes Mr efficiency, without any fitout junk, the boat should come in around 1,5tonnes... im keeping a spreadsheet that adds each panel weight as im going... so far im upto 540kgs and most of the big heavy panels are already in that...
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Should fly with the twin 90's, how will she handle with just one engine in the water, do you think ? Maybe more fuel efficient in flat conditions than both engines in use ? I'm thinking with the sort of resistance curve this type of boat has, it might not labour the engine too much running solo ? But in choppy water holding course could be a problem.
     
  6. groper
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    groper Senior Member

    Don't know until i splash it.... If the weight comes in at around1500kg i think ill go for the yamaha F70's instead of the 90's... Otherwise it will just be overkill...
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    'Twill be interesting ! I guess the wide spacing of the engines makes single engine running a bit hard. On planing cats sustained single engine running is usually impractical because the resistance hump kills them.
     
  8. groper
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    groper Senior Member

    The floor is up, i was surprised at how flat it ended up... i thought for sure there would be something out of plane, but it came out within 2mm all over... happy about that!

    looking aft;
    [​IMG]

    Looking forward;
    [​IMG]

    The next peices are infusing on the table as i type, more in a couple days...
     
  9. groper
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    groper Senior Member

    Heres the last piece of the bridgedeck, will tidy it up and offer it up to the leading edge of the bridgedeck when next i get a chance.

    It was built in 2 halves split down the middle, by infusing them on the table - it was too big to fit on the table in 1 peice. The complete bottom laminate was infused along with only the straight section of the top laminate so i got the shiny side off the table (face down). I made kerf cuts at 50mm spacings in the topside and bent the panel into shape with a template. Underneath the ratchet straps is a series of straight edges to hold the panel in plane whilst it was joined and glassed. Completed the inside laminate and joined the 2 halves all wet on wet by hand laying it all. Now its beer o-clock...

    [​IMG]
     
  10. jorgepease
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    jorgepease Senior Member

    Just read the entire thread thanks for sharing it, this is super!! Can't believe how light she is going to be LOL!!
     
  11. jorgepease
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    jorgepease Senior Member

    Groper, thanks a ton for all your input on mine, if you are ever in the keys I will hook you up at ele-shack.

    I have a few questions about this picture
    ---------------------------------------------
    1. Do you have two, maybe more, inlets into the same main feed and is that main feed a larger diameter than the branches?

    2. Are you using cross T's or regular T's to make the fishbone .. or no T's somehow?

    3.is that spiral wrap (resin feeds) below the flow media, on top of the release film?

    Thanks! Love the boat you are building. It's what I need for offshore, a nice big boat driven with smaller efficient motors!! What will be the draft on her?
     
  12. groper
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    groper Senior Member

    Im using 2 * 5/8in feeds into 1/2in spiral wrap. The spiral wrap just meshes together for the branches, no tee`s or anything like that, just pull the spiral apart and wrap them into one another. I have also done an identical panel with 2 * 1/2in feeds and it was still ok, but i did notice it was a bit slower to fill in the beginning of the infusion. This infusion was around 20kgs of resin in total, and i think with only 2 feeds, this is about the limit i would want to do with 1/2in feed line diameter. So either add more feeds, or go up in diameter to 5/8in when the job gets bigger than 10kg per feed etc.

    The flow media is on top of the spiral, so i lay out my resin lines on top of the release film, then lay the flow media over the resin lines, place the inlets on the media, then bag it.
     
  13. jorgepease
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    jorgepease Senior Member

  14. groper
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    groper Senior Member

    Well the last peice of the bridgedeck in now in place, just some cove and tabbing left to do...

    [​IMG]


    I guess ill have to start the interior work now, putting in a few more bulkheads, the fuel tanks, the rear transom steps, frame up the rear beam and turn it into a big long seat, soooo many things to do, its looking a bit dauting at this point...
     

  15. jorgepease
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    jorgepease Senior Member

    Looks great, one bite at a time! :)
     
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