switching from hand layup to infusion, what am i forgeting

Discussion in 'Fiberglass and Composite Boat Building' started by scphantm, Dec 12, 2010.

  1. scphantm
    Joined: May 2009
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    Location: St Augustine, FL

    scphantm Junior Member

    my buddy and i started with a 41 foot hull literally about 10 years ago it was popped out of the mold and thrown in a storage yard for 10 years. we bought it, cut the stringers out, designed a whole new lower deck, put the stringers in, extended the walls of the hull, etc, etc, etc. we have been working on it for about two years now.

    up until now we have been doing all hand layup. since we are doing structure, our primary glass has been a 24X15 biaxial mat and we have been using a basic hand layup vinylester resin.

    we are now moving into more detailed parts, the bow, with major contours, the exterior walls, etc. stuff where weight and quality become more of an issue so we decided to try switching to an infusion method for the rest of the build. i have been doing a lot of research and this is what i have figured out. and i have a few questions at the end. please look my plan over and let me know what im missing and what i appear to be clueless on.

    equipment:
    resin catch tank. i found some really good ideas on making cheap catch tanks with PVC pipe and fittings. only problem ive found with the idea is i can't see the volume of resin in the bucket. i figure until we start doing stuff frequently to justify the cost of a true catch tank i will build two of the cheap PVC tanks with 4 inch pipe and put them in series. or just one very large one and one small one and go by weight.

    vacuum pump. i read the vacuum pump size thread here and i pretty much got if it can't pull 29 inches mercury with a continuous duty cycle don't bother with it. then comes down to CFM. i found a guy on ebay that sells 3 CFM 29 inch pumps remanufactured for $175. i figured i will get one, start with small stuff like hatch doors and test panels and such and when i get to bigger stuff i will simply buy more pumps.

    consumables,
    peel ply. use is optional. required if the surface is going to have a secondary bond

    perforated release film. required. always cover the glass with release film. if the bag surface is to be smooth, use this.

    vacuum lines inside the bag. small stuff, i can use the nylon vacuum channel. big stuff use the spiral tubing.

    resin flow. seen posts were people use the sun shade cloth for patio furniture for a fraction of the cost of the airflow stuff. try it and see what happens.

    bag material. small stuff you can use polyethaline drop cloths from home depot. big stuff use the real deal to get away from porosity of the drop cloth bags.

    sealing tape. don't mess around, use the real stuff.

    thats all i can think of tonight. now the questions

    1 - how do i calculate the amount of resin that should be used for the glass. i know it varies by glass type and such but how about some math. i see other threads here where you are talking ounces. is that by weight or volume? im completely clueless here, i need a lot of help

    2 - if im putting up thick panels, say 1/2 inch. how do i know when the resin has reached all the way down to the mold?

    i need a lot of help here. i know. but im getting the research part out of the way

    thanks guys
     
  2. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    Better ask one of these guys like Herman.
    Do remember that the most important boat building tool is the simple ...coffee maker...for all methods of construction, the coffee maker is always the most used tool in the shop. Drip or espresso.... better get both, in case of a breakdown
     
  3. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    The first thing you will get is a heavier boat.
     
  4. scphantm
    Joined: May 2009
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    Location: St Augustine, FL

    scphantm Junior Member

    we want a heavy boat. this is a live aboard. if we can get the thing to 10 knots we will be thrilled. the marine architect thinks even with the extra boyancy provided by what we are doing in the back that we will have to fill the bow stringers up with concrete. he's getting back with us after he runs the numbers but he thinks its a good idea.

    i havn't even gotten into the part where we cut the transom off the boat and extend the lower hull 9 additional feet and add a sea drive to mount 3 or 4 honda 225's on it. thats a discussion for later. this thread is about am i on the right track to start infusing hatch covers and stuff so that i can get the correct experience to start doing some more of our bigger more complex parts. the final two being the 1 1/4 inch thick sea drive and the 20 foot by 14 foot foam composite wheel house roof.
     
  5. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member

    Their might be some good threads on resin infusion buried in Boat design net. If not , have patience , a few guys who work with it are on the forum. Also surf the net for home boat builders using infusion...I see a few. Try " resin infusion boatbuilding blog" on google
     
  6. Coen
    Joined: Aug 2004
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    Location: The Netherlands

    Coen Junior Member

    Scphantm,

    As a rule of thumb, I usually say that I want the same amount of resin, as I have glass. Since vinylester is approx. 10% heavier than epoxies (which I'm used to), I would say that you add 10%.
    Please note that this is the amount which I have 'ready to go'. So everything is mixed in (if necessary), except for the hardener. I always like to have some more to have something to fall back on.
    Please note that infusion lines, mesh and so on, are quite 'greedy'. So when using a lot of lines, or thicker (or doubled) meshes, have some extra resin ready.

    For bagging materials, I would always use new bags of high quality (this realy pays itself back in my opinion). Please don't forget to do a small test to check the compatibility of your transport and bagging materials, and your resin.

    I can't say anything about the pumps. I am used to using several pumps on 1 infusion projects. We created certain rules of thumb about the vacume, but those were based on those pumps so I can't help you there.
    The only thing I can say; a big diameter vacuum line between your pump and your project helps putting the project under a quick vac. The smaller the line, the longer it will take and thus it will be harder to note leaks.

    Hope to have helped you a bit.
     
  7. Herman
    Joined: Oct 2004
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    Herman Senior Member

    I wished I had more time to respond, but I do not have (still some loose ends to arrange before my new kid is born. (within a week...)

    About question 1: Coen answered that. Although 1:1 is quite conservative, also I like to have plenty of resin at hand.

    Keeping in mind a Vf of 50%, you can say that you need only 1/2 of the weight of glass in resin (resin is half the weight of glass, approx). But that does not take into account any overhead at all.

    Question 2: It will. Unless the fibers are so tight together, the whole stack will infuse. To reduce problems, pull as much vacuum as you can get, and get resin in slowly, not utterly fast.
     
  8. War Whoop
    Joined: Jun 2003
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    War Whoop Senior Member

    I would spring for the proper bag material,that polyethylene film is a disaster waiting to happen, tacky tape is a given, the flow medium as well, the peel ply gives a nice finish instead of a ugly wrinkly shiny look ,as for the pump avoid these toys when a real pump can be had,you need to have the reserve capicity and can sell it when finished.

    Do some test on a small panel with your laminate to get a idea of the infusion rate,that will help setup the feed system.

    The Dow VE I used to use was @ 8.1# a gallon Herman is right weigh the glass.

    Remember the more you experiment,the more likely disaster, there are reasons for these materials Bag Films and Etc.
     
  9. rxcomposite
    Joined: Jan 2005
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    Location: Philippines

    rxcomposite Senior Member

    Laminate Properties

    I had to cut my post short because I was goofing off and was called.

    You will get a heavier boat because you are switching to resin infusion.

    Based on what you have stated;
    1. You have started building the boat with hand layup
    2. You are now working on the bow area.
    3. You are switching to resin infusion.

    Builders who switch to infusion, especially in the middle of the process should be wary of the consequences. . This is important as you will be working in the bow area, subject to slamming forces. You started with hand lay up, the parts are thicker because of heavy resin content. The frame spacing is designed to handle thick panels.

    Resin infusion is a process whose main objective is to reduce the amount of resin and consequently make the laminate “stronger” and lighter. Stronger in the sense that the laminate is denser, hence the material property (psi) increases. Consequently, the laminate also becomes thinner, losing a lot of flexular strength.

    When you lose flexular strength, the laminate flexes and cracks at the point where it is supported. To gain back the flexular strength, you add more fiber to regain original thickness, thus making the part heavier. Fiber is more than twice as heavy as resin (2.56 density versus 1.2 for resin). Another approach would require closer stiffener spacing to reduce flex to accommodate the thinner laminate. Obviously, you cannot do it anymore as the boat has started with pre determined stiffener spacing. The only way to go is with intralaminar infusion such as enkaflow or other method where the mid part of the laminate is where the resin is flowed. Resin and mat is a bulking material.

    Infusion is great but should be used with care. Thin panels with closer frame spacing or thin skins with cored layup is the engineering method suited with infusion. You just don’t switch to infusion because it is the “cool” way to go.

    Attached is an excel spreadsheet I am using to determine glass/resin ratios. Note that Fiver Volume (Fv) is the packing density or efficiency (volume) of the fiber while Glass Content (Gc) is the ratio in weight (expressed in decimal) of the glass to resin. Gc is the more accepted method as Fv is more complex and varies heavily if the fiber is Uni, stitched, woven, ect as shown on the next sheet of the spreadsheet.
     

    Attached Files:

  10. scphantm
    Joined: May 2009
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    scphantm Junior Member

    we want to start switching over definatly not because its a cool thing to do. we bought the hull premolded. the bottom of it is nearly an inch and a half thick of solid glass. i talked to some guys that built it 10 years ago and it was one of two prototypes that was built and abandoned because of money problems at the time. all of our glass work so far has been extending the walls of the hull 18 inches. putting in header boards across the top edge so we can mount our deck, tabbing bulkheads in, tabbing in stringers, all pretty easy stuff. we are now in the process of getting the upper deck and wheel house on and getting everything weather tight and we are getting to the part where we start making some molds and such. my research and talking to guys that build these things and customs for a living have all told me that hand layup is not the way to go with the parts we are planning on building. its been recommended many times already to switch to infusion when we started showing pictures and sketches of what we want to do. that is the reason we are doing this.

    and i think im going to get the tinker toy pump to play with and get my feet wet. and when we get to the part of doing larger parts like the bow and sides i will spring for a big pump.
     
  11. scphantm
    Joined: May 2009
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    scphantm Junior Member

    and on the resin estimates, rule of thumb, if i have 10 pounds of glass, i weigh out 10 pounds of resin to start with and have a bit set aside just in case, am i hearing you correctly on that? does the weave of the glass change that rule of thumb?
     
  12. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    That is called a 1: 1 ratio or 0.5 glass content by weight. That is correct.

    It applies mostly to Woven Rovings, hand laminated. As the name implies, it is woven so the fibers goes up and down causing undulations and the fiber packing is not efficient. In Uni the fibers are closely nested together side by side so the packing density or fiber efficiency is much higher (less resin content).

    The resin fills up whatever is void thus the Uni's have less resin content than the WR's. If you apply pressure during manufacturing as in VARTM, the fibers are compressed so it does not need that much resin.

    Well I guess, (I am only guessing as I do not know your panel size) you have no problem. For a 41 foot boat with 1 1/2" thick bottom, your boat is overbuilt. You can build two boats out of the materials used.
     
  13. scphantm
    Joined: May 2009
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    scphantm Junior Member

    yea, it starts at an inch and a half at the keel and gradually tapers up to about 1/4 by the time it gets to the top of the hull. ive been told by the guy that designed it that it was way overbuilt because it was intended as a test prototype so they planned on gutting it and reusing it several times to test different power combinations and such. thats why they only made two like this. the other one is long gone. but it worked out for us because since the hull is so thick, we could reduce the height of the stringers by over half and still be strong enough and put in a lower deck on a boat that was never intended to have one. big win for us. when we are done we will have a little over 900 square feet of living space. not bad for a boat.

    we bought the hull for 3,000 so im not complaining.

    so far we have been using 24X15 bilateral mat for our primary glass. we have been judging strength by thickness (my partner is a cabinet maker, its the only way he knows and i got tired of arguing with him)

    i know im going to have to switch glass once i start infusing panels and making composite panels, but is there a pseudo-easy way to calculate how strong a shape is going to be? and for the biggest part i have trouble with, how do i translate that to real world. sure something may be able to handle X of pressure in the middle, but how does that compare to 6 naked chicks dancing on it? tomorrow when i get to work i will draw a cross section of one piece in particular that im curious how to build. i know the shape i want, just not how to build it so it will be strong enough.
     
  14. rxcomposite
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    rxcomposite Senior Member

    It seems overbuilt allright. The most I need for a keel is less than 3/4" thick and that is running at 28 knots.Bottom about 5/8".

    Pressure points in the hull varies according to location. Generally greatest at the bottom/keel and diminishes towards the waterline. the only exception is the bow/forward area but that is if the boat is running fast greater that S/L of 1 where it receives a lot of slamming. The lesser ones are the sides and the deck because the pressures to be considered is the occasional lapping of the waves or as you said, naked chicks dancing on the deck. (I appreciate naked chicks dancing on my boat but not wearing high heels;))

    Give me particulars like length, breadth, draught, displacement. speed, area of operation, panel size (the area bounded by the frames or stiffeners) and I will try to crunch some numbers for you.

    What is a 24 x 15 biax? what is the density or make/type number?
     

  15. scphantm
    Joined: May 2009
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    scphantm Junior Member

    24X15 is what the yard said to use. its 24 ounce roven woven with 15 ounce cut strand stitched to it with a nylon thread. i should have kept the box top but i didn't so i don't have any part numbers for ya. its only intended for ester resins because the cut strand is held together with styrene. we decided to use vinylester resin thru the whole boat so it worked well. 4 layers will give you a good 1/4 inch thick panel.
     
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