Possible contract for Composites Engineer

Discussion in 'Services & Employment' started by rwatson, Jun 18, 2010.

  1. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    I am just in the process of having a 28ft trailer/sailer hull design completed by an NA.

    I would be interested to know an approximate cost for preparing a detailed layup schedule for a foam/fg construction.

    All suggestions or offers of professional help would be appreciated.
     
  2. chrismcg
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    chrismcg Junior Member

    Is the designer not specifying this as part of the total design? correct me if i'm wrong but i always thought that the designer gave details of the laminate schedule as part of the design package?
    Or am I mis-understanding what you are looking for? I apologise if I am.
     
  3. waikikin
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    waikikin Senior Member

    The NA Doing the design so far would be the best as they would already have some idea of the weights targeted for the design & your application. From what I've seen a spreadsheet of all panels/bulkheads including tabbing in etc etc have their weights & moments calced for the hull/deck/rig/engine/steering/deck gear etc to determine trim/LCG etc. Get the NA to supply the info otherwise they're just drawing a picture of the boat- I'm sure even if they don't like doing it, the laminate schedule could be outsourced by them from SP or FGI or similar. All the best from Jeff.
     
  4. rwatson
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    rwatson Senior Member

    The design isnt one that the NA developed, but rather one I specified based on similar designs. The weight table for the boat incorporates all the gear, with an allowance for hull weight based on those boats of similar size and construction.

    I may or may not be able to get a detailed layup schedule from the NA due to his time constraints. The hull design has already taken three years part time, and I am only up to the stage where the final hull sections have been produced. The design is remarkably good, and I have no problems with it, but I have reached a stage where I am ready to start a prototype - and I cant wait another 12 months if he is unable to complete the project.

    Also, even if he is able to produce detailed layup specs, I would also like them viewed, and maybe even improved by an experienced composite person as I dont think the NA has had a lot of hands on experience with the materials.

    I know that even amongst boatbuilder there can be considerable variance of opinion on building methods, scantling requirements and material suitability, and I would want to get as many opinions as possible before starting a prototype, let alone production.

    Also, at this stage, I won't be looking at complex vacuum bagging techniques, as I am hoping the methods used will suit fairly "mainstream" builders for ease of production. I have been keeping an eye on the Kelsal method of production, which has some basic vacuum bagging involved - which I would consider. I am also keen on the "joined flat panel" techniques he uses.

    Your suggestion of getting Sp or FGI to do the layouts is a good one W - I may contact them next week to get more info. There are probably a number of FG suppliers who can provide professional construction advice, especially with their own products.

    Thanks for the suggestion.
     
  5. rxcomposite
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    rxcomposite Senior Member

    rwatson,

    Marine engineering companies charge about usd 300 per sheet. You need about 3 sheets minimum covering hull layup schedules, deck layup schedules, and stiffeners proportions and schedules. Each sheet would specify the materials to be used, the properties, glass to resin ratio, and the fiber direction.

    Should you need more details, extra sheets cost about $250. This covers reinforcing details, hull to deck joints, and any other details that the shop floor cannot fill in.

    Material take off, or rough estimates of the materials can be had for free as part of the bargain. It is usually in excell format.

    If you ask for validation of the design, that is a different story. Most refutable companies or freelancers have numerus proven design to show. Other professionals would be able to show validated softwares and the resulting design output.

    Prices are indicative only as I work in a marine engineering firm. Others may vary but should be close.

    Bear in mind that designers and boatbuilders must be balanced in terms of experience. Some boatbuilders are not exposed to class rules and may deviate where it is most critical. Details are quite important.

    Rx
     
  6. Alik
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    Alik Senior Member

    Get Your NA/designer to supply structural design, otherwise he is not a NA but 'artist'. The original designer of boat has better ideas of weights and loads, if he is in business he would have enough experience to specify structural details.

    I have seen structural designs developed for some boats by third parties (mainly for US boat designers as most of them do not have engineering degree), most of them were lacking of details and some were overweight.
     
  7. tunnels

    tunnels Previous Member

    Send me some details of your boat hull and deck lay out etc and i will give you what had to use for the 8 ,36ft match racing yachts .
    Was glass inside and out plus all the internal frame work , used vinylester resin throughout the whole boat and H80 and H60 foam core in differant places with H 200 foam under winchpads etc etc .
    Just need to see what you have . Was light strong and easy to lay up . The same lay up is used on the irc cruising verssion of the same boat with a differant designed deck with interior head room . Will need details of the centrecase as well and the pivoting /lifting mechanizium for the keel !.
    For a crusing t/sailer i would ues it as it is but if you are into racing you could save a little weight by swapping the 600 gram glass for 400 gram Wont save much but will be a little !
    stuartwrcom@gmail.com is my email address :p
     
  8. rwatson
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    rwatson Senior Member

    Hi all - many thanks for the input. I am expecting final drawings *and* material specs version 1, in the next week or so, so I am close to being able to share full details very soon.


    Re comments on replies ...

    a) The info on the prices and number of sheets was interesting, though I have no idea what I should expect to see on a "sheet". Do they actually print out the patterns of the pieces like a developed surface of a plywood boat ?
    I know I have seen automated cutting machines producing pre-drawn cloth panels, but I had always assumed that that sort of planning level would only be worthwhile on large production runs. Maybe not ?

    b) The mention of H80 and H60 was also interesting, because up to now I had only considered up to H40 foam. I cant believe the price differentials of the stages of density.
     
  9. waikikin
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    waikikin Senior Member

    RW, I would only consider H40 foam for furniture or canoes/or the like- for a trailer sailer esp' in the bottom the roller point loading must be carefully taken into consideration unless you plan to float on/ float off with molded bunks/cradle to support the hull I'de steer well clear of the 40kg foam. All the best from Jeff.
     
  10. tunnels

    tunnels Previous Member

    One of the biggest problems with foams is people using the wrong densities .
    H80 in impact areas and places where there is stress involved an the rest is H60 but you need to use Vinylester resin in combination . The for we used was 20mm but 18 mm in the lower part of the hull and 15 mm for the topsides would be ok for a 28 footer . All the ring frames were 15 mm x H60 foam plys all the longtudinal stringers that had a flange and unidirectional glass along the flang . But neet to see what you have to say where the differant foams should be placed and places where there should be no foams just solid glass plus extra layers .All the sheets were cut in a special way so they could be bent and conformed to the hull shape with no print through and sheet marks on the outsdie of the boat . Hope you are able to vac bag !!
    :D:p :)
    Find out about CORE SHEAR !!! then you will understand why you should use the more dense foams !!:p
     
  11. rwatson
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    rwatson Senior Member

    Many thanks for all the hints so far. I went back over emails from the NA, and he does indeed specify "at least H80 for the sides". I have no idea why H40 was stuck in my mind. (Probably lost 50% of memory over the last 12 months)

    The bottom section (wetted area) is to be made out of solid fibreglass. This is mainly to maximise weight. It needs 100kilos of permanent ballast (the rest is water ballast), and as much of this will be structural as possible. No point in weight saving at that location in the hull.

    I am trying to avoid vacuum bagging if I can.

    The two material types/methods I have been considering are Vinylester, using the special "putty" to ensure adhesion to the foam without vacuum bagging.

    The other is Epoxy, which is reputed to adhere to foam well enough to not need putty or vacuum bagging. I understand that I need to use special Glass with Epoxy - without the coating normally applied to the fibres.

    Cost will be the biggest factor here.

    I will be interesting to compare the specs from various sources.
     
  12. tunnels

    tunnels Previous Member

    So you want to carry all that water all the time ?? You can dump it and sail down wind and go like stink !!
    Vac bagging is really easy and the putty is call core bond , And even using that you still need to bag it into place .
    A solid glass bottom is stepping back into the dim dark ages .:D
    yeah you gotta be an Australian !!!
     
  13. rwatson
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    rwatson Senior Member

    Tunnels - you seem to be out to create unecessary angst in my post.

    a) What makes you think I cannot dump my waters ballast ???? Why on earth would that be the case ?

    b) A solid glass bottom is wrong ? There are thousands of boats being built this minute entirely of solid fibreglass. Why would I need foam on the bottom ?

    c) What has being a new zealander got to do with knowing what you are talking about ? :)
     
  14. raw
    Joined: Jul 2006
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    raw Senior Member

    If your NA cannot do it (which he should btw)....

    then try either of these guys in Australia. I have worked with both these groups in the past.

    EMP composites (Sydney)
    ATL composites (Gold coast)
     

  15. rxcomposite
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    rxcomposite Senior Member

    rwatson,

    a) Usually, the patterns are not included. Fglass comes in rolls and you need to cut whenever necessary but it is minimal. the shop floor takes care of this. Only series production levels do pre cutting or "kitting". As for the hull lines, the NA should provide you with this. A typical hull lines drawing should include the table of offsets.

    b) Different densities of foam are used due to varying stress levels, otherwise if you design with one density, you will have varying core thickness. Hatch openings requires high density foam around. Anything that's bolted or screwed to the laminate should have a higher density foam beneath, sometimes up to H200. Tightening the bolt alone would crush the core.

    Rx
     
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