Tips on Dagger Board Trunk Construction?

Discussion in 'Boatbuilding' started by CatBuilder, Dec 21, 2011.

  1. AndrewK
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    AndrewK Senior Member

    Infusion is the way to do it, but you need to use perforated core (drill holes into your foam) so that you only need the mesh on the outside.
    You only need peel ply at either end where you will glass it in, also add en extra 2-3mm spacer here to allow for the glass tape.
    If you are going to infuse let me know so I can expand on how I would do it if you like.
     
  2. Charly
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    Charly Senior Member

    I didn't taper mine, but a little bit, when I went over the splintery edges of the ply with a grinder. I don't know if it was appropriate or not. the bog went on the inside to fair everything out before the glass cloth went in. I rolled up dry strips of varying widths and unrolled them in place, then wet them out with a brush, squeegeed and lapped on the next.
     
  3. CatBuilder

    CatBuilder Previous Member

    Please!! YES!! I would love to infuse this, so I come out with a high quality part without voids.

    I was hoping you'd find your way in here. I nearly put a little hint in the infusion thread to ask you to stop by here. :D

    I have perforated core that's already tapered and ready to go.

    I had planned to put flow media on the inside as well as peel ply. Force of habit maybe?

    I guess that makes sense to leave it alone and just let it be rougher glass in there. Don't want to do any sanding deep in there though. :D

    So, yes, if you could please expand on how to infuse a trunk, it would be most appreciated. I could really use input here from someone with your experience, having already infused a dagger board trunk or two on a cat.

    The main problem here is I can't seem to figure out how to hold all these layers in place, since I have a bag inside the trunk that can be damaged by my Raptor staples. Also, there are so very many layers to keep still before infusing.

    Thank you, Andrew.
     
  4. Silver Raven
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    Silver Raven Senior Member

    G'day C-B aka Andrew. Wish I could help. Am sure I could have. Problem with new-type-guys, that very unfortunately think they know the definitive answer -which they - ADSOLUTELY DO NOT - I'm available @ - jamesaviculture@hotmail.com - I live in Far North Queensland,
    Australia. I've worked with several designers & have spent the last 50 + years building boats, designing wing-masts, rudder & c/b foils again with several designers that whilst - very humble - did manage to win the "America's Cup", the 'Little America's Cup, etc, etc, etc.

    I don't wish - will not get into a futile arguement or discussion with others aboaut - structural shapes & strengths - of FRP composite laminates - that have worked - very successfully since at least 1964, cause I in all honestly - don't think they have sufficient experience - - sorry Richard (Kurt) & to others that are - - "X-purts" (we all know that joke - which is in fact the truth).

    To the 'guy' that claims to have expotential kknowledge of Aeronautical engineeing, Richard & others - I suggest that you do one hell of a lot of homework - long before - you get your feet stuck in you very wide open mouth.Very embarrassing, especially at this time of the year when we should all be enjoying "tom & jerry's' - 'hot-toddy's' & several 'sundowners'. R. Woods - Sir - with great respect - (& you do have mine) the way you describe - your thoughts is not as clear as it might be. There have been a few multis designed & built - that might show another side to your - 'statement' which I DO NOT agree with. Said multi's were designed & built in the 60's, 70's & 80's & succeeded. Your continued presence in this forum is a wonderful asset to all of us & I truely thank you - VERY MUCH. I have no desire to argue with anyone in here or anywhere else but the continued use of - categoric statement - when they just don't stack-up is very misleading to all of those in here seeking honest - impartial advice. Suggest y'all think more carefully - in the future - before - expounding - non correct - principles.

    Enjoy Christmas - I'm sure I will. Ciao, james

    PS> - C-B - The answer to your - how to do it is right in front of you - think you have mentioned it - but missed - what you, yourself - have said.

    We've had 1200 lightening strikes - in 3 hours - this afternoon (said as 'avo' here in Oz land) so I'm off air until tomorrow. Just stole this time between - more 'strikes' - sorry about that - but it's life. Ciao, jj
     
  5. Silver Raven
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    Silver Raven Senior Member

    Plywood IS NOT a correct boat building material - over time. Period. james.
     
  6. Silver Raven
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    Silver Raven Senior Member

    You can do that. You've mentioned how - I think you just missed - what you said. james
     
  7. Silver Raven
    Joined: Oct 2011
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    Location: Far North Queensland, Australia

    Silver Raven Senior Member

    'C-B' Andrew - Why not buy the "rope"????? If you buy the right 'rope' you are going to use 300 times that amount - when you go sailing - so it's not wasted - just a - pre-investment (at less cost than when you want it to go sailing). Just make sure you wrap it up very well - - glad-wrap & waxed paper. Then lay - a laid-up laminate on-to-it & then the rest of the construction & vac-it. Easy as, me thinks. - Afet only 50 + years of doing it - what the hell would I know??? NOT MUCH, eh. Whatever you call it over there - these days. I've been AWOL for 50 + years - so don't remember what/how you call thing - these days. Ooooops, darn,. Ciao, james
     
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  8. hoytedow
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    hoytedow Wood Butcher

    1152 feet? How long is that centerboard, again?
     
  9. CatBuilder

    CatBuilder Previous Member

    8 ft x 12 inches per foot x 2 half inch rope loops per inch x 7' distance around the trunk.

    Silver raven: that's a lot of posting to not say how to do it.

    Andrew, where did you go?
     
  10. hoytedow
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    hoytedow Wood Butcher

    That's a lot of rope. You would probably use a lot over time. The wax wouldn't hurt it.
     
  11. rberrey
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    rberrey Senior Member

    Check the price of foam backer rod. It may be strong enough, cheep enough, and if you cant pull your board out a little gas will eat the foam backer out. Rick
     
  12. AndrewK
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    AndrewK Senior Member

    Hi CatBuilder; I just scanned through the thread and see that your diagram shows a parallel sided case with shaped crush foam in the aft section, this is not what I was thinking.
    If you want to build a parallel sided case like that it would be easies to do on a flat vacuuming table. The inner laminate first on the table, then your 2 pieces of perforated core spaced at the appropriate distance apart then the top laminate/peel ply/perforated release film/infusion mesh. Feed the resin in the middle with vacuum lines at each long edge. When the laminate has cured you heat the laminate between the foam past its HDT (electric blankets are best) then drape over the board to form the U section.

    But if you dont have a big enough table then make use of the board, this is how most one off builds are done. But most do a full shaped case and also with no crush foam.
    My suggestion is a blend of the two, you end up with full shape case with crush foam (not including the aft D section) incorporated with the infusion. But I suspect your tapering of the case foam may not suit, my suggestion requires an undercut taper at the aft end 45 deg. And a 45 deg matching reverse taper for the side crush foam.

    1.First put two bands of masking tape on the board where you plan to seal the bag onto later on.
    2. between the tape put release agent on the board I prefer pva rather than wax.
    3. build some stands so the boards leading edge is up.
    4. drape plastic sheeting over this section, over size.
    5. spacer material, if your board is true with no high spots 6mm spacing is enough common ways to achieve this is to use the pvc plastic signboard (coreflute), cardboard, lino flooring or short nap carpet, nap facing down.
    6. at either end of the case put a 100mm band of 3mm packing material if you want a rebate so that tapes from the outside into the the case can be accommodated without creating a high spot.
    7. drape another sheet of plastic over this.
    8. position your two pieces of foam the right distance apart ( length of solid laminate at the leading edge) place your inner laminates over this and staple to the foam.
    put a long stick in the middle fold the cloth and laminate over and use the stick to pickup.
    9. drape this over the board, position in place and then clamp to the board.
    10. for the crush foam either side of the board trailing section (with the above taper) you slip this under the bottom laminate and position with staples so that the bottom laminate is sandwiched between the two foams along the taper.
    11. drape and staple the top laminate in place
    12. then peel ply and infusion stuff.

    All the laminates and release plastic covering the board and spacer material to be oversize so there is excess hanging down, spacer material to be only a bit oversize.

    13. trim this excess to a neat line but still leaving an inch or two more than you need.
    14. grab a 200mm or so wide scrap light weight glass that is the length of the infusion job and place vacuum spiral in the middle, fold in half and staple close to the spiral.
    15. attach this to the bottom of the infusion job so that the glass is on both sides of the mesh and staple or tape in place.
    16. place the resin feed line at the leading edge.
    17. pull the masking tape bands off, drape your bag film over and seal to the board and itself at the bottom.
    18. bring on the vacuum slowly while pulling along the bottom of the laminate to make sure there are no creases formed in the leading edge.
    19. when you have full vacuum you can flip the board over so that the vacuum line is on top if you prefer.

    Hope this makes sense, it would be nice if I learned how to do sketches.

    I did not mention a rebate for control line above, but you can incorporate this into it if the above description is acceptable to you, at least something to think about.

    Andrew
     
  13. CatBuilder

    CatBuilder Previous Member

    Andrew, first, thank you very much for responding with how to do this laminate. Some great ideas.

    I don't have the full size glass table set up due to backordered foam. I could set it up early though, if needed for this. I need a glassing table the size of my cross beams, so plenty of room for a tiny board lamination. :)

    I think you are misunderstanding my foam crash block though. It is not part of the laminate. It is an insert you slide into the aft, "D" section. The trunk is done without the foam, leaving space to slide it in later. I have set up a PVC pipe on the aft trailing edge of the board to account for this "D" section.

    I actually did understand all of that without diagrams. The "stick" part was a little fuzzy, but I get the picture.

    I was not trying to use the board as a mold itself. That was the major problem. I had set it up in the following order, from outside, in:

    *Bag
    *Enka channels
    *green flow
    *peel ply
    *glass/foam/rebates/whatever
    *peel ply
    *green flow
    *bag
    *spacers (bubble wrap, rope, etc...)
    *board

    So, I was planning to bag the part to itself, via a back on the inside.

    Doing it your way makes much more sense, provided I can find a suitable material to give me a large gap between the board and the materials. Also, I need to pick up some PVA. I don't have any yet. I will try setting it up your way after I locate some disposable spacer material that will stand up to vacuum - and some PVA release.

    The beauty of doing this by bagging right to the board is that I can staple all that glass into place without danger of the staples compromising my inner bag, since there will only be an outer bag. That's really where I was having problems with an infusion... keeping all that stuff in place and not piercing the inner bag with staples through the foam. With no air tight area to worry about below the foam (just spacer and the board), I can staple to my heart's content.
     
  14. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    You could use styrofoam to fill the gap. After the epoxy cures a few drops of acetone will dissolve the styrofoam and shrink it out of the way. You could make the whole male plug out of styrofoam and glass over it and dissolve the whole thing.
     

  15. CatBuilder

    CatBuilder Previous Member

    Hoyt, I'm not sure styrofoam would hold up to the vacuum. A full vacuum is pretty intense. I think it would crush styrofoam to a little sliver. I need something more "beefy" to hold it. Maybe I would use both... foam and something beefy, knowing the foam will crush?

    It would be nice to have something that will get out of the way after the infusion though. I can see it being nearly impossible to pull the trunk off later unless there is a way to get that material off.

    I would do the entire trunk (front, sides and D section) in one shot if I can find the right way to release it.

    I need more of a 1/2" gap around my trunk to account for bog and bottom paint still to go on the trunk, plus bogging in the exit points around the hull and deck areas, one of which will have a slot in the bog for control lines. Rick's idea about bogging those areas was really good, since it also give something to wear down instead of the glass.
     
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