Trimaran

Discussion in 'Boat Design' started by remora, Jul 15, 2019.

  1. remora
    Joined: Jul 2019
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    Location: Philippines

    remora Junior Member

    Hello All,

    I am not an expert on composite but will be taking some class and seminars as the subject interests me.
    I have seen trimaran design in Philippines using solid fiberglass (flat panel) as stringers/frame. It is designed the same concept and structural as wooden hull motor bancas.
    Is flat panel stringers any good? What about buckling issues, compared to foam cored or hollow fiberglass stringer?
    Any input is appreciated.
     

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    Last edited: Jul 15, 2019
  2. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    Hi Remora and welcome, I use recycled fibreglass so your photos are of interest to me. If each stringer has a brace glassed in, the same distance apart as the stringers are, a very strong and light frame can be made. the braces will stop the stringers from twisting. When you look at the centre deck on the first picture you can see what it would look like. This allows two skins an inner and an outer to be laid., it is very hard to lay fibreglass matt when you are under it so panels with tags would be made up to fit for the cabin roof. and glassed into place before the deck itself. It would be very time consuming fitting and glassing all of the braces but small batches of glass and matt can be continuously produced which suits fibreglassing ,especially in warm weather ,and with a team of workers. All the stress points will need to be doubled or tripled up, and triangular/ diagonal braces within the box shapes you make will help reinforce stress areas also It's a nice frame , very stick insect/praying mantis.
    It will be interesting to read what all the people with more experience than me think. Good luck
    Good luck
     
  3. remora
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    Location: Philippines

    remora Junior Member

    Hello Fandango,
    You are very correct, layup will be time consuming and tedious.
    Excuse my terminology if mistaken but This is how we build frame on our wooden boat motor banka. I have 5 100’ wooden boats with converted automotive engines. Mitsu 6d14 and top speed at 14.8 knots (gps clocked), varies a little on each boats.
    Longitudinal frame (2x4’s) are 16” spaced apart from hull bottom to gunwale (2x6) and transverse frame (2x2’s) are 12” spaced apart, 1/2” marine plywood for hull side shell. Hull is 12” thick x 42” wide hardwood.
    We are planning to build fiberglass motor banka. Specs as followed:
    LOA 80’
    Breadth 13’
    Hull width 42”
    Hence we will use plywood mold for hull, I see 2 options. instead of flat panel for frames and laminate per squares, we use fabricated frp channel from 2x2 (transverse) and 2x4 (longitude) wood mold. We glue the transverse channel to skin and do continues laminate. After we achieve 4 layers, glue the 2x4 channels and laminate in sections overlapping each laminate. Second option, instead of fabricated channel, we can use rigid polyurethane foam (save time fabricating) but I think needs more than 4 layers.
    FYI, I seek design plans from companies abroad but their prices are enormous. Local naval architects are a lot cheaper not very experience with composites, if any, very limited in numbers and I have not met one. But I have seen these boats built and ride on them. They seem very sturdy and perhaps very heavy.
    Deck will be prefab with honeycomb and stiffeners. Attach to main hull (gunwale) by means of glue, screws like speedboats and laminate from inside with bulkheads.
    Sorry, I am writing a novel, LoL. I really appreciate advises from forum members. This will educate myself to right direction and have some knowledge when discussing with naval architects and during building process.
    Thank you all.
     
  4. remora
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    remora Junior Member

    Here’s a finish boat and it cruise about 14 knots on a 4 hour voyage. It has 3 engines.
    I also wonder how they reinforce the lateral beams. Previously I said I have seen them built. However, only partially and not the whole process as it is far from where I live.
     

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  5. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    The transverse ribs would be strongest if they don't overlap but are glassed in flush with the beams/stringers, like how honeycomb works, this will save weight and be easier to finish internally, bulkheads would be built in also. If you read Old Multi's thread on Trimarans you will get a really good feel for what is required. Everyone is working on the equation,. low weight + price = speed
     
    Last edited: Jul 17, 2019 at 3:03 AM
  6. remora
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    remora Junior Member

    Thank you Fandango
     
  7. rxcomposite
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    Location: Philippines

    rxcomposite Senior Member

    remora-
    From the pictures provided, the crossbeams is most likely to fail if not given a very thick skin. It looks like the arrangement was copied from a catamaran with a full deck.

    Outrigger beams are cantelever loads and are designed to handle the tension and compression on the caps (top and bottom) element and the web (sides) to handle the shear. It is usually a box beam for simplicity. The top and bottom caps are usually built up of unidirectional fibers because of its longititudinal strength and the webs of biax fabrics which are stronger in shear. Two simultaneous computations are used here, the tension/compression of the caps and the shear of the web dictated by the geometry of the section.

    Besides the primary cantelever loads, the beams are further analyzed for the dynamic load it will encounter in head seas, diagonal or quartering waves, and transverse waves, each of which present loads more complex as it is a combined load.

    In head seas, the front part of the float will rotate up from its axis introducing torsion to the beam.

    In quartering seas, The front part of the beam/float will rotate opposite of each other (port and starboard). The twisting effect.

    In transversal wave, one float will rise higher first, increasing the load. In the case of trimaran, it will not be lifting only its displaced volume but a part of the center hull. This is further complicated when the transversal wave length is longer than the beam/float spacing. If the wave is equal to the spacing, one float is lifted, the opposite float goes down in synch. If the wave is longer, the opposite float will experience a sudden change in momentum and send a shock wave along the beam opposite of the incoming wave. This is known in the local parlance as "pitik" and this phenomenon occurs also in large ships. It can break a large ship in half or break the outrigger beam which is so common in Philippine bancas.

    Now to change from wooden construction to FRP or hybrid, it is not a simple scaling down of the geometry of the wooden design. Wood is solid and limber, FRP is much stiffer and the stiffeners hollow. So things like 2"x 2" and 2"x 4" will not only introduce weight gain but errors in stresses calculations.
     
    Last edited: Jul 18, 2019 at 5:17 AM
  8. rxcomposite
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    rxcomposite Senior Member

    P.S. If you want to study, better obtain a copy of NK (Japan) rules on FRP construction. I heard this is the foundation from which the local (MARINA) is basing its rule design on FRP construction. Then we can talk much better in technical terms.
     
  9. rob denney
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    rob denney Senior Member

    Remora,
    Not only is hand layup tedious, it uses a lot more material which adds weight and cost. You might want to check out another 80' option, the harryproa cargo ferry http://harryproa.com/?p=2561 The hulls, beams and masts are infused in simple flat sheet moulds with bulkhead etc landings, joins, rebates and openings included in the infusion. There is no wet laminating, grinding or cutting off cured laminates.

    If this is of interest, we are looking for builders around the Pacific. Please contact me at harryproa@gmail.com

    rob
     
  10. remora
    Joined: Jul 2019
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    remora Junior Member

    Hello rxcomposite,
    I am more a marine bio and electronics. But observing how it behaves and experiences on these wooden motor banca, I understand your thorough explanation on various loads and good point on what weave to use on laminate.
    With the picture posted, what I have in mind is add a horizontal in the middle to make it H beams and of course laminate top and bottom to become a box. I will post another picture of this boat. It is operating south of Philippines.
    Anyway, are a naval architect base in the Philippines?
    I will check on NK rules. Thank you.
     
  11. rxcomposite
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    rxcomposite Senior Member

    I assume you mean me. Yes I am in the Philippines especializing in composites.

    I suggested NK because if you are going to build/manufacture in the Philippines, you will need the approval of the local body MARINA.
     
    Last edited: Jul 18, 2019 at 5:18 AM
  12. remora
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    Location: Philippines

    remora Junior Member

    Of course, we need MARINA approval for the plans prior building and after for licensing and permits.
    Yes, I was asking if you are a naval architect?
    We hired a naval architect but not very specialize with composites.
    How much for your services?
    You can email me at indopacjoe@aol.com and perhaps I can call you
     
  13. remora
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    remora Junior Member

    Here’s another picture on lateral beam

    picture on lateral beam.jpg
     
  14. trip the light fandango
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    A nice efficient design, with built in inflatable tubes on the wings that could be triggered in case of imminent disaster and air tight bulkheads forward and aft, this would be a very safe feeling fast boat, I hope the build goes well Remora, cheers
     

  15. remora
    Joined: Jul 2019
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    Location: Philippines

    remora Junior Member

    Thank you fandango. That is a good safety feature to have, inflatable tubes on the side under the wings. Like the ones they use to launch ships ( a smaller diameter).
    That will be like a rib boat.
     
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