longboarding plug

Discussion in 'Fiberglass and Composite Boat Building' started by nevilleh, Oct 8, 2010.

  1. nevilleh
    Joined: Sep 2008
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    Location: scotland

    nevilleh Junior Member

    Well guys, we are still surfacing this 35' plug. I guess I jumped the gun asking about which gelcoat to use earlier !

    It seems to be going on forever. Slowly getting there taking off the high spots .

    Question : We have been using longboards up to 120 grit. (for approx 3 weeks ) between 3 people.

    We have since started on a flatbed sander which seems to get the results quicker, however I am worried that the finished product wont be 100% perfectly straight.

    Can anyone advise when the best time is to stop manually longboarding and to start on the machine sanding?

    We are still applying small amounts of filler & spray polyester filler, not quite at the duratec stage yet.

    I dont want to waste any time on the manual longboards if we can use machine, but atthe same time i dont want to jump the gun and spoil the plug.

    Any comments welcome - its costing me a fortune.

    F.y.i. Im going with tooling gel , but most likely not tooling resin.

    Cheers

    Neville (Scotland)
     
  2. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    ...not sure where you are up to as it is only a description and a picture tells a thousand words....so.....you are using a dust coat of alternative colour to sand off to I hope....otherwise how are you telling when it is fair. You only need to fair to 120 before using Duratec, but still do the dust coat thingy after the duratec first coat anyhow, this time with 180. (or if you wet it use 240).

    ...three weeks three people is not right for a 35 footer...it must have been pretty crappy before this fairing deal.
     
  3. GG
    Joined: Jan 2008
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    Location: MICH

    GG offshore artie

    I agree and pics would really help and i always use a product called guide coat and the general rule of thumb is...... when fairing anything thing in if it is to high sand and if it is to low fill, and to tell you the truth you can spray duratec up to 120 mills at one time depending on what type of there primer you are using and is it there 707-051, and the longer the board the straighter the surface and to tell you the truth you would be jumping the gun if you were to move on to a machined surface because doing a plug and making it right ............takes time . http://www.expresscomposites.com/duratec1.html
     
  4. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    dust coat/guide coat, same thing just different names.....
     
  5. nevilleh
    Joined: Sep 2008
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    Location: scotland

    nevilleh Junior Member

    thanks guys, unfortunately im nowhere near the project at present. i will get a couple of photos up on monday. my question was more about when the best time is to change from long boards to machine. i have bought an 18" long flat bed sander which is doing better than the tedious process of manual longboarding but im just paranoid its not going to be 100% straight. The boat is quite hard chine with some inverted chines on it so there ae alot of flat panels. I mistakenly thought that these would be easier than the curvy bits but it appears not !
     
  6. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    It's just car body work so I just always used car body repair materials. First a plug and then fiberglass, then bondo, fairing putty, hi-build sanding primer, a gloss black enamel, 3 coats wax and 1 coat PVA, then a light buff to the finished plug. Lots of fluorescent lights showed up any waviness or imperfections in the plug. Here's a site with a few homemade powered longboards, the air file one looks best...

    http://www.rutuonline.com/html/long_boards.html

    One thing you have to watch out for is when you fill a dip, you have to make sure you sand off all that is not needed. Otherwise every dip filled ends up creating a very, very slight hump and pretty soon a good surface becomes a wavy, lumpy surface. It almost seems like you are sanding too much but you have to fair and blend in the edges of the new fill to the old surface. That's why the final sanding surface should be a very easily sanded material, so as to not need much pressure. Then the plug fairness is a product of the fairness of the sanding apparatus and hardly subject to the vagaries of human touch and feel. The human eye, aided by reflected lights, is the final test for a quality surface.
     
  7. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    That sounds like quite some time for a plug. However, I don't know if it is a complicated, full of edges, shape. 120 should be as fine as you need to go with longboards. At that point it should be fair and only needs to be smoothed. DAs can be used.
     
  8. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    One thing that jumps my mind:

    In the first stage, you can determine high spots by sliding something light and straight over the surface. (for instance an old fluorescent light). When you hold it just in the middle, you feel it canting as you go over a high spot. take a pencil and mark that area. After checking the hull, give the marked areas a treatment with grit 36 on a random orbital. This at least gives you a headstart.

    3 weeks for 3 people is WAY too long. Are these guys experienced? I guess not. Get a pro to at least show them, and train them.
     
  9. GG
    Joined: Jan 2008
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    GG offshore artie

    Hey guy's you are really killing me and the reason being is i have assisted in the build of many plugs while working at Skater 28 ,36 ,40 , and 46 and after doing all the lofting they all took many months to build from sanding (long boarding )to dialing in the bottom making sure everything was straight and true and not to mention all the man hours & materials that were used in the whole process just to pull one part or (mold)and when i was employed at S2-YACHTS it was pretty much the same thing when building plugs for hulls and decks because most of you on this thread make it sound like everything happens overnite unless everything you have done in the past was just slapped together with no care in the world on workmenship and how straight something really is, and like i said you guys are really killing me :p ha ha ha But then again i am just a dummy down the trail of life who has been in this business for over 39 years and once again just my 2 cents .Landlubber point taken yes dust coat is a 3M product that is in dry form but Guide Coat is sprayable and comes in a spray bomb which is wet !!!
     
  10. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    Dust coat/guide coat, call em what you like...all they are is a light spray of something contrasting over the job that has to be all sanded off to prove the job is flat and smooth, simple as that, call it what you like.....I do not recommend any brand as anything will do the job.
     
  11. waikikin
    Joined: Jan 2006
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    Location: Australia

    waikikin Senior Member


    At the least, your guys will learn to respect the mold surface they are creating, longboarding is the fairing process, be carefull of the machine it can easily undo good work. fairing starts with lofting then carefull plug construction, any more than 2-3mm of filler is getting rough.
    Its nearly 10 years :) since I've done much of this, in the past my approach has been to define the surface to be faired with battens, make note in pencil on the surface, apply filler with a batten (25 x 12 x3mm aluminium channel) to significant longtitudinal locations such as sheer, boot top line, centerline etc- this really helps on flattish surfaces- these I board fair & guide coat in red, screed a 2.5-3mm layer between & slightly over them- guide coat a light spray of black- long board with 40-60- anything high hit lightly with a soft pad 8" sander- light black guide- longboard & plane(trying, jack , smoother these work well on most fillcoats Q cells probable the toughest so sharpen more often)- any low areas top up & plane in (the plane cuts high areas off & avoids "halo" sanding of area around the top up filler)-guidecoat-longboard- fill again but now hopfully to smallish areas to 6-8" dia & plane in with smoother or block plane- guidecoat & long board with 80-120- spotfill, hand sand & shoot primer/duratech grey- chase up any pinholes & board with 180-240- tack down & shoot with duratech black gloss- here any slight irregularities can be chased out into the grey if nessesary & fine sand & buff to lovelyness PS the red guide coat on the early batten work is like a warning on sanding deeper than is nessesary, the alu battens get waxed & pva then filler aplied as live a really long gable roof shape will contact a lightly resin primed surface middle first for least bubble entrainment- temparary hotmelt glued shelves support the batten to position.
    this has worked for me about 6-7 days by one man & some occassional help to get the battens on & to 2 man board for a 13 x 1.4m surface(flattish catamaran topsides) fron 6 oz fabric to full black gloss using Q cells, polyester,grey duratech primer & black duratech gloss, some automotive glazing putty used on minor pinholes & skimcoats.
    Hope that makes sence as I'm kinda thinking out loud from memory;)
    all the best from Jeff.

    PPS:with duratech be careful of your shop temp & curing-too low & it don't go, also once you've got the black on don't rush to make the mold, take head of the "surface energy" as quoted by the manufacturer- some have ended in a big stick up thru impatience(thankfully not me-I couldn't afford it!)
     
  12. tunnels

    tunnels Previous Member

    Long boarding with 120 is slave labor If you haven't got to a painting stage yet !! all your filling should have been done and roughed off and long boarded with 60 and 80 then into multi coats of hi build with q cells added and a different color each coat so you never go through the first coat to the bare plug and then your 120 long boarding !! If you want to keep it fair no machine sanding at any of these stages . Long boards 8 foot long with 4 guys and keep the beers flowing . Fair as like a gorgeous lady !!
    Machine sanding will always give flat spots !! Dont care how good or how careful you think you are ! dont do it Then dura tech 2 or 3 generous coats and long board with 120 to start and get to 180 then wet and dry sand .
    Have done my share of hard hours on long boards over the while . :p:D:p:);):eek:

    Tooling gel for sure but a couple of layers done with Vinylester resin and finish with Poly for the rest ,Vinyl has a bit less shrinkage and more stable and harder than poly !!
     
  13. GG
    Joined: Jan 2008
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    Location: MICH

    GG offshore artie

    Who cares ...... Mr Brisbaneeeeeeeeee......and with that in mind .... quit making a mountain out of a mole hill .........because i could really give a $hit what you want to call it, and do you have to special order that product considering you do not live in the good ole USA .....& once again might i mention... the good Ole USA..... and yes it could be a can of Kraylon Spray Bomb at any color you might prefer including white if that is your color of choice ha ha ha ha .:p
     
  14. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Just a reminder to everyone of the possible neurological damage that one can be exposed to with long time or even short time use of chemical products.
     

  15. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    ....oooohhhh sensitive little fella GG, sorry if I twitched your nose mate, did not mean to do so. Genuinely thought that there may have been a misunderstanding....I will leave it alone. Off to have my red pills, they seem to work.....
     
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