S2 6.7 Junk Rig Conversion

  • 27 Aug 2019 00:37
    Reply # 7850704 on 6872873

    Sometimes it pays not to think and worry too much. I have this problem - a fellow junkie described it as "analysis paralysis". Your trailer worries turned out to be no problem at all. I am sure your rig will be the same - an awful lot just depends on the hull itself anyway and your little boat is going to scoot along just fine.

  • 26 Aug 2019 13:44
    Reply # 7849288 on 6872873
    I have been reading the topic titled A Question of Balance. It seems I made a bad assumption about the rig I am building. I thought adding long batten parrels, and a running tack parrel, to one of Arne's master sails would allow me to cant the sail fore and aft and set the sail with more balance when running down wind.

    Arne said, "My Johanna-style sail can hardly be set with much more than 17% balance."

    I thought I would be be able to move the yard sling point forward of the center to adjust how much the foot of the sail 'wants' to move forward as I ease out the running tack parrel. Is this wrong?

    Also: I went sailing. I like sailing.

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    Last modified: 26 Aug 2019 22:37 | Anonymous member
  • 11 Aug 2019 23:28
    Reply # 7823043 on 6872873

    The time is here. Tomorrow starts the week I set aside to start sailing my newly converted junk rigged trailer sailer! Back on February 10th when I ordered the WeatherMax 6.5 it seemed like a reasonable plan.

    In reality I was able to construct what I think is a functional sail and about half of a mast step. This is a long way off from 'ready to sail'.

    After so much time invested I find it difficult to explain to my friends and neighbors how all this nonsense I am doing in the driveway adds up to 'easier' sailing. They say things like, 'If the sail you made is so much better, then why wasn't the boat built that way in the first place?'

    I remain committed! I think summer 2020 sometime is still likely. I really hope it does not slip all the way to 2021.

    Scott.

  • 07 Aug 2019 13:25
    Reply # 7815917 on 7815096
    Annie wrote:Sorry, I wasn't very clear.  Normally, when I glue some wood down on top of another piece of wood, there is some spillage, glue 'squodging out' or some type of mess that needs cleaning up before I can put down the next layer.  If I don't clean it up, there will be cured glue that may stop both faces lying smoothly together.  I always clean this up first.

    Thank you for the response. I understand now.

    I am using the fast hardener and yes the pieces are greasy and oily after it cures. I can see why you like to do it all in 'one shot' with un-thickened epoxy first and then a layer of thickened glue mix while the first layer is still in the 'pot life' time.

    Maybe I will try this technique for other parts of my project. Right now the boat is back in storage and I am coating plywood pieces in the garage at home.

    I am amazed at how much epoxy this plywood soaks up.

  • 06 Aug 2019 22:24
    Reply # 7815096 on 7813090
    Scott wrote:
    Annie wrote:

    [...] My own method would be to clear up epoxy on the top layer down to a smooth base, and then coat the bare wood of both faces before mixing up the glue mix.  [...]

    Annie,

    I am not able to understand your method. You say to 'clear up the epoxy on the top layer' and then also to 'coat the bare wood of both faces'.

    If both faces are bare wood then where is the top layer that needs epoxy cleared up?


    Sorry, I wasn't very clear.  Normally, when I glue some wood down on top of another piece of wood, there is some spillage, glue 'squodging out' or some type of mess that needs cleaning up before I can put down the next layer.  If I don't clean it up, there will be cured glue that may stop both faces lying smoothly together.  I always clean this up first.
  • 06 Aug 2019 18:06
    Reply # 7814648 on 7813090

    Robert,

    You said here that 'your target group of US-based aluminum flagpole or lightpole buyers the commercial vendors still specify metal strengths, bending moments, etc. in English units of pounds-per-square-inch, foot-pounds'

    I have not been able to find any specifications regarding strength from any of the vendors. The datasheets specify the material but not the material properties. I attached a screenshot as an example.

    US-based vendors of 6063-T6 products. For example:

    https://www.metalsdepot.com/aluminum-products/aluminum-round-tube

    https://www.onlinemetals.com/en/product-guide/alloy/6063

    The pole vendors used to specify the strength in psi when specifying the alloy (always 6063-T6). These days you've got to do more digging to get the mechanical properties.

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  • 05 Aug 2019 22:56
    Reply # 7813333 on 6872873
    Anonymous member (Administrator)

    Scott

    I think your spreadsheet looks neat, and makes sense.

    As for getting access to mechanical data of 6063-t6 or 6082-t6 alloy, just google it, and you soon have it.

    Wikipedia looks to be good on this,
    and as I said in that Kittiwake thread:

    1MPa (=Newton/mm2)=145psi

    and 1ft-lb=1.356Newton-meter
    (=1.356/9.807kilopond-meter=0.1383kpm)

    Arne

    My use of kilopond (=kilogram force) may look illogical as forces are measured in Newton in the SI system. However, although Newton is essential when mechanical power and energy is dealt with, kilopond and kilopond-meter (kpm) is quite practical when working with static forces like righting- and bending-moment of boats and rigs.

    Anyway, since 1kp =9.80665N, one misses with less tan 2% by simply saying that 

    1kp = 10N  -  roughly.




    Last modified: 06 Aug 2019 08:51 | Anonymous member (Administrator)
  • 05 Aug 2019 20:06
    Reply # 7813090 on 7800621
    Annie wrote:

    [...] My own method would be to clear up epoxy on the top layer down to a smooth base, and then coat the bare wood of both faces before mixing up the glue mix.  [...]

    Annie,

    I am not able to understand your method. You say to 'clear up the epoxy on the top layer' and then also to 'coat the bare wood of both faces'.

    If both faces are bare wood then where is the top layer that needs epoxy cleared up?

    Thank you to everyone for the help and advice. I think I have a good plan now. I will be sure to seal up the edges of the ply very well. It looks like I will need to buy much more epoxy than I expected.

    I also wanted to invite Arne and Robert to discuss my excel sheet here so that we avoid taking over Janine's Kittiwake topic.

    Robert,

    You said here that 'your target group of US-based aluminum flagpole or lightpole buyers the commercial vendors still specify metal strengths, bending moments, etc. in English units of pounds-per-square-inch, foot-pounds'

    I have not been able to find any specifications regarding strength from any of the vendors. The datasheets specify the material but not the material properties. I attached a screenshot as an example.

    I have been using sites like this to get the 'Tensile Yield Strength' in MPa and then following Arne's equations. I think this is valid. Please tell me if I got something wrong.

    Scott.

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    Last modified: 05 Aug 2019 20:12 | Anonymous member
  • 28 Jul 2019 23:05
    Reply # 7800664 on 6872873
    Anonymous member (Administrator)

    I see no reason for turning this into rocket science.

    The mast steps (all from plywood) of my first three boats were just primed with West epoxy resin, and then glued together after the coating had set. I never worried about that waxy ‘blush’. None of those mast steps has come unstuck yet. I guess the very big glue surface makes it strong enough, even if the strength of the glue joint should turn out to be only 30% of that of a correct joint.

    When making Ingeborg’s mast step, I ‘moved up’ a little: After the coating resin had hardened, but before gluing the whole lot together, I wiped the surfaces off with water with some household ammonia ( known as Salmiakk here) in it. That got rid of the waxy feeling, for sure. I guess a light sanding after that cleaning, would not hurt, but I can’t remember I did that. Even Ingeborg’s mast still stands upright.

    My main focus has been on avoiding water penetration anywhere at the mast step.


    Last modified: 28 Jul 2019 23:06 | Anonymous member (Administrator)
  • 28 Jul 2019 22:20
    Reply # 7800621 on 7798242
    Scott wrote:

    I will be using small paper cups and never putting more than two pumps in at a time (using West System 300 mini pumps). As Annie says it is not so bad to run out of epoxy in the pot and need to mix more. It is much worse to have the whole thing become a hot and urgent situation.

    I am not sure how thick I need to make these sealing coats of epoxy on the mast step layers. Do I need to have it thick enough that the piece looks like it is encased in smooth glass? Or is it OK to end up with a thin coat that is still a little rough?

    I believe the purpose of this sealing coat is to prevent starving the joint when I bond the mast step layers to the hull and layers below. Is a thin, rough, sealing coat enough to ensure that the wood will not soak up too much epoxy when I glue it into the boat?

    I tend to use containers with a wide base - I have an everlasting supply of yoghurt pots from which the set glue breaks out easily - because the smaller the cup, the more likely the epoxy is to warm up while you are mixing it.

    I wouldn't put a sealing coat between each layer and let it partially cure.  My own method would be to clear up epoxy on the top layer down to a smooth base, and then coat the bare wood of both faces before mixing up the glue mix.  That way you don't need to worry about amine bloom, sanding or how far the epoxy has cured.  My rule of thumb is never, never to put the glue mix directly onto the wood unless it's a really runny mix; and then I make sure there are plenty of microfibres to wick the epoxy to dry places.

    I rarely have a problem with amine bloom from slow - 206 - hardener.  It's the 205 that causes the problems and sometimes the coating is positively slimy.  I try to avoid using fast hardener.  But washing with fresh water with a drop of ammonia in it sorts the problem.

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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