Newbie asking for advice

Discussion in 'Multihulls' started by jmoropeza, Oct 17, 2021.

  1. rberrey
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    rberrey Senior Member

    fallguy , build treads I have looked at using foam post 40% to 60% which would be about the same as your 100 oz glass 110 epoxy , so a person can get close to bagging with hand layup , we are saying the same thing . I bought material bulk for a 33' trimaran build , all said and done foam -v- ply was very little more when shipping was factored in , if I had bought 1/2" H80 instead of opting for 5/8" price would have been even closer . Epoxy and glass are another matter , but I bought glass by the roll and 75 gl. of silvertip epoxy from the same supplier , so my price was much cheaper than buying 5 gl at the time , or buying by the yard . Forming is not an issue , you strip it with battens , or pvc pipe with masonite strip,s to stiffen it and keep down fairing . I have not built a boat out of foam , I have done some work on a couple using C flex , so I know how to grind .
     
  2. redreuben
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    redreuben redreuben

    By using epoxy you can trim a bit of weight but for the most part you are spending a lot of money and putting up with longer gel and cure times for boasting rights.
    Vinylester resin is way cheaper, far easier to use with much quicker turn over times.
    Structural strength and chemical resilience are more than adequate. And whilst it may have a bit of nuisance odour from the styrene, it has nowhere near the potential for allergy reactions and health issues as working with epoxy.
    No brainer.
     
  3. rberrey
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    rberrey Senior Member

    redreuben , in one of Ed Horstmans books he has Vinylester listed at 69.8 lb a cubic ft and epoxy at 74.2 to 77.3 lb per cubic ft , so Vinylester is a little lighter as well as cheaper . With all that being said one of the designers I follow pushes for Silvertip epoxy in a foam build , so for me a little more money in the structural area of the boat is the way to go .
     
  4. redreuben
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    redreuben redreuben

    @rberry; Depends what you call little money I guess, epoxy is without doubt better, and for a race boat or best possible outcome it is essential, however, for the average cruiser - home builder I do not consider it good value for money.
    The savings of going to vinyl ester on a 9 meter boat would go a long way towards buying a mainsail.
     
  5. fallguy
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    fallguy Senior Member

    Another factor is if you are building at home in an attached garage. Did like two polyester projects and luckily, my build space is 3 rooms away from the house or it would have been trouble. A typical house cannot use esters. And even my place would not have worked for the panels and everyday. The stink is really bad.
     
  6. guzzis3
    Joined: Nov 2009
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    guzzis3 Senior Member

    Perhaps the OP can do some reading, consider which boat if any to build and then later get into the minutia of building options.

    I'd never vacuum bag, it's just too hard. Infusion doesn't add that much expense and you can take your time. The resin savings are just a bonus.
     
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  7. rob denney
    Joined: Feb 2005
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    rob denney Senior Member

    Richard's advice to "buy/build the smallest you need" is spot on, but does not apply to length, which should be maximised, IF the boat weight does not increase significantly, you can resist the temptation to fill it with stuff and you can afford the extra to keep it in a marina. Longer multis are more comfortable, less likely to pitchpole and draw less. They are faster, giving more options re avoiding storms and reaching safe locations. Most importantly, especially for a beginner, they feel safer in big winds/waves.

    Apart from a dramatic increase in cost relative to foam and a general decline in quality, building with ply has barely changed in 50+ years ( I built my first ply multi in 1979, my latest ones last year) , and it still results in boats that need to be carefully looked after if they are to survive. There has been a lot of boat building development in that time.

    Vacuum infusing is clean, non stressful, uses far less resin and has less waste, some of which is reusable. Flat panels or dory half hulls infused on an mdf table can have the following included in the layup, all added accurately and at your leisure before mixing any resin: both skins, core, window rebates, joins, local reinforcing and holes for beams, rudders and masts, landings for the bulkheads, shelves and furniture, cut outs for windows and doors, the doors themselves, decorative surfaces, different thicknesses of foam and weights of resin.
    When cured the components are glued together, with little or no cutting, grinding, fairing, bulkhead shaping, edge treatment, or tedious 3 dimension lining up and levelling. On the 24m prototype mentioned above, 2 people were prepping, infusing and removing a 12m/40' x 1.2m/4' panel in 3 days. No gloves, dust masks or overalls were required.

    Apart from build techniques, some other things that have been developed since the 70's:

    Unstayed carbon masts are all about stress reduction, which makes cruising a much more pleasant experience:
    They allow you to sail dead down wind without the sail rubbing on the shrouds, less fear of an accidental gybe and no headsail flapping unless it is poled out.
    They flex in gusts, automatically depowering. Consequently, they can often be large enough not to require extras.
    There is very little to break or maintain, no need to climb them or remove them to check for corrosion, wear or damage, nothing to tune and none of the anxiety stayed rigs create.
    The main can be totally depowered, hoisted, reefed or lowered on any point of sail
    Gybing in big wind/waves is no longer a white knuckle experience. Either release the sheet and let the sail go round the front of the mast or gybe and let the boom swing across until it weathercocks as there are no shrouds for it to crash into. With a self vanging rig (fixed boom, ballestron or wishbone), there is no traveller to pay for, maintain and trap unwary fingers.
    A simple, near idiot proof anticapsize device can be fitted which works on any point of sail when a given angle of pitch or heel is reached.
    You can build them yourself cheaper than buying a new alloy rig.

    Many cruiser's reduce sail at dusk due to the possibility of a squall at night and the accompanying dramas reefing/furling/running downwind . With an unstayed rig you have 2 options. 1) release the sheet. The rig weathercocks, the boat sits quietly until the squall passes or you reef at your leisure with the boat slowly drifting and no flogging sheets or sails. 2) release the sheet, then sheet on just enough to keep you moving at your desired speed.

    Unstayed masts may not perform as well as a race rig with race crew, but to quote Richard (about a ballestron rig, but it applies equally without the jib): "The sails are always working correctly, whatever point of sail. Maybe it would be better to say the rig works to 95% efficiency all the time. A conventional rig may work to 100% if you're an expert, but only 70% if you're not."

    Collision safety. There is a lot more stuff in the water to hit. Vertical and near vertical stems, daggerboards and rudders are an accident looking for a rock, log, whale or debris to happen. Making them crash proof and kick up is not trivial, but should be a requirement on any reasonably fast cruising boat.

    Shunting as an alternative to tacking. The classic fear scenario is being caught on a lee shore with big wind and waves at 3 am.
    On a tacking boat, you need to raise enough sail (deep reefs are usually half the main, plus a headsail) to give you speed to tack. This will usually be more than is safe while sailing so you constantly trim the sails. You then have to lift the anchor and get the boat sailing, which invariably requires sailing backwards and steering in reverse, which is scary with the beach behind you.
    If you tack and a wave slows the boat, it will be caught in irons and blown backwards. Backing the headsail and steering in reverse are required, see above. The flogging headsail then needs to be sheeted back in. Motoring is far safer, as long as you don't pick up a crab pot, mooring line or loose sheet and you have a motor capable of working in steep waves, which rules out many outboard solutions.

    On a shunting boat, it is much less of a problem. Raise just enough sail to give you steerage. This may be as little as a metre or so. Lift the anchor, then sail away 'in reverse'. To shunt, you luff, release the sheet, the boat stops head to wind, the rudders automatically reverse and you luff and sail off in the new direction at a speed you choose. The difference is a huge reduction in stress.

    Alternatively, if the beach is sand and the boat draws less than 300mm/12" you can simply raise the rudders/boards, and let out enough anchor rode to wash up on the beach, in shallow enough water that the waves will not be a problem. Snub the anchor just before high tide and you will be able to haul and sail off on the next one, after a good night's sleep.

    This is some of the development that went into Harryproas, which the OP might want to consider as an alternative to a cat. Maybe check out the EX40 and compare it with the cats. Any questions, either ask here, or email me at harryproa@gmail.com.

    Regardless of your boat choice, I can organise for you to get materials from Utek in China if you decide to do this. We have bought several tonnes from them in the last 18 months. Their prices, service and quality are excellent.

    Your usage says more about your build technique and/or the laminate specified than it does about the merits of foam construction. 300 US gallons is 1.1 tons of epoxy! We used less than that on a 24m/80' workboat, including a 28' flax (uses more resin than glass) catamaran tender, 2 unstayed masts, wing sails and a heap of experiments and test panels.

    As was described to you at the time, your vacuum technique was poor, which is why you got 65% resin instead of 50% and had to suck so much out.

    re your Oct 17 post: 20 oz/800 gsm of glass either side of foam does not equate to 6mm ply with 8 oz glass on one side in any practical boat building sense. If you left the stringers and frames in, 6mm foam with 400 gsm/12 oz each side would be lighter and cheaper than the ply, stiffer and sufficiently strong. If you left the stringers and frames out, 12mm/0.5" foam with 400 gsm either side would be lighter, quicker to build, stiffer and sufficiently strong.

    I think you posted that you used cabosil for fillets, then glassed over them with mat backed knitted fabric? Few fillets need glass, none need mat. Those that need glass, and many that don't, should be made with Qcell/microballoon filled epoxy. The resin and weight savings are significant.

    In Australia, epoxy is $Aus12/kg which is $US36/gallon. You could import it from Aus for about half what you paid. Or a third if you get it from China.

    However, you are correct that vac bagging is stressful and wasteful. I have no idea why anyone would do it (or build a minimum cost/time/weight multihull from ply) instead of infusing foam and glass.
     
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  8. fallguy
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    fallguy Senior Member

    A few points of clarity are in order.

    My glass and resin rates I miswrote. They are close or at ideals. 65% glass to total iirc or about 35/65% resin to glass which is 54%. I am suffering with a back injury; so needing a break here.

    The problem with my method is wet bagging. Start off over 100% resin in a hurry to bag and end up woth all of it in the media is worse than infusion pot losses by a long mile.

    I followed specified tabbing, but I erred adding the mat to help with moving tapes. The weight penalty is severe and I should have not. Perhaps 150# per hull severe.. I really should have spent more time discussing it with Richard..my mistake, not his..

    As for me equating foam and plywood, I was only trying to get to a ratio as a generalization. If you feel 12 oz glass each side is comparable to a 6 oz one side ply layup; you are saying the ratio of glass and epoxy ply to foam is 4x and I said 40oz vs 8 ounce which is 5x. I was not trying to equate, but rather approximate the delta between foam and ply methods use of epoxy (and glass). I did NOT at anytime equate the layups and was only trying to make a very quick comparison which is 25% greater than yours unless I am misreading. A lot of people forget that epoxy use is higher in foam and good foam work drives wastes. It would be more edifying to hear your waste rates for infusion because wet bagging for me had super high waste rates to the bag and some in trimmings, and I used bleeder to reduce it after early panels seemed starved...etc..
     
  9. guzzis3
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    guzzis3 Senior Member


    Just out of curiosity how much do you pay for vinylester ?

    I just bought epoxy and thin hardener for infusion and it works out about $13.85 (AU) a liter including shipping. The infusion hardener is dearer than the general purpose stuff. Not sure how much difference it makes.
     
  10. redreuben
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    redreuben redreuben

    You would have to check with the suppliers.
     
  11. rob denney
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    rob denney Senior Member

    You also erred with the cab-o-sil.

    No idea what you were trying to convey, but:
    6mm okoume ply weighs 3,100 gsm (grammes per sq m). Plus 200 gsm glass, plus 200 gsm to wet the glass, 200 gsm to fill the weave/wet the timber and another 200gsm to coat the inside (2 coats). 3.9 kgs per sq m.
    6mm H80 foam weighs 500 gsm . Plus 400 glass each side, plus 200gsm resin each side to wet the foam and another 200 to wet the glass. 2.1 kgs, which is close to half the weight and stiffer.
    1 kg =2.2 lbs, 200 glass is 6 oz, 400 is 12 oz, 1 sqm =10.75 sq'

    Remove the stringers and frames that are supplying the panel stiffness for the 6mm and use 12mm foam and the skin weight increases to 2.6 kgs per sq m. 500 gsm added weight is usually way less than the stringers, frames, glue and fillets removed. It is also far quicker, cleaner and less cluttered.

    The ply requires scarffing/butt blocking, edge treatment, dressing up like a spaceman to avoid getting poisoned by the dust and epoxy and significant wastage from applying by hand.
    The foam and glass are cut dry, laid out on a full length table, bagged and infused (no dressing up, sticky or dusty) and are ready to join. Plus the options for tailoring I mentioned in my other post.

    Infused foam/glass is a no brainer in terms of weight, ease of build (if infused) and cost (in Aus, or anywhere else that material can be sourced from China).

    Intelligent Infusers routinely get 2:1 fibre to resin. Wastage varies depending on whether distribution medium or slots in the core are used, but is seldom more than a kg or so.

    Guzzi,
    Infusion resin also allows more powder to be mixed, making for easier to sand bog and faster wetting out of cloth and tow. The hardeners are the same price. I have not bought vinylester for 5 years, but it was $10/kg in a drum, plus catalyst. AFAIK, styrene (in VE) rots your brain, epoxy destroys your skin. This is by far the best reason to infuse rather than hand lay up or vacuum.
     
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  12. jmoropeza
    Joined: Oct 2021
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    Location: Mexico city

    jmoropeza Junior Member

    I saw a Florida store selling it before the virus plus some seller in ebay. The ebay seller dissapeared and the FL Store kyrocketed it's prices and it's no longer online, maybe because the virus.
    Thanks for the answer!
     
  13. jmoropeza
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    jmoropeza Junior Member

    Thanks for your answer and warmth welcome Will!
    I have checked with some Boatwork shops and all of them work with glass, no marine plywood available, only under special order ant the quotes are around $170-$180 per 9mm sheet. About going to Houston, I would have to add the travel expenses to the costs of materials and yes, we have to pay import taxes over prime materials, 16% tax. Gypsy list of materials ask for more or less 50 sheets of 9mm, plus other smaller numbers for different mm sizes wich makes a van insuficient for the task (I think), so I should have to renk a truck wich adds to the final costs. Sadly I'm trapped with foam core unless I can afford to build in FL or Tx but it doesn't look like a realistic possibility at the moment. Crazy how some milles make things so different right?
     
  14. jmoropeza
    Joined: Oct 2021
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    jmoropeza Junior Member

    Thans for the tip rberry!
    I just quoted Strucell P80 (Chinese version of Divinycell tested by guzzis3) and they quoted me $25.92 per 1080*1000mm shteet, sea SHIPPING COST INCLUDED wich in my opinion is a great price. Gypsy's plans ask for 600/300g biaxial glass as far as i have seen, wich still is affordable in my opinion. If i go with epoxy instead of vinyl i won't need mat as far as i understand but i have to check it with Mr. Woods.
     

  15. jmoropeza
    Joined: Oct 2021
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    jmoropeza Junior Member

    Thank you again guzzis, i have been reading a lot and i think i'll go for gypsy. I think the sensible option is the flat panel even tho i would love to have the round version because the speed. I'll have to build it only with foam core since wood is not an option for me.
    In that case i will go for strucell p80 with vaccum infusion because i want to be in the water ASAP, and it looks like the most reliable, cheaper (saving resin) and effortless method (no big time expended fairing and sanding in the end).
    Not sure yet what to do under the water line. I read that US costguard don't accept boats with foam core under the water line but maybe is not the case anymore, i have to research more about it.
    Cheers!
     
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