S2 6.7 Junk Rig Conversion

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  • 18 Nov 2019 13:46
    Reply # 8127143 on 6872873

    In case anyone is interested -- I am trying to keep my rig conversion moving along. There was some unusually cold weather here last week and I was not able to do any epoxy work. The photo attached is from two weeks ago when the temperature, according to my cooking thermometer, was just above 40 Deg F. Epoxy seemed to cure without any issues overnight using the West System fast hardener.

    Yesterday I went out in the snow and did some sanding and grinding with the angle grinder. I think I now have the closest thing to a 'good fit' between the sides and center that my skills will allow.

    I am trying to follow the JRA article and the work documented on Voyaging with Annie Hill.

    Does anyone have a suggestion on when I should use fiberglass? I was planning to just use thickened epoxy to join the sides to the center section. Then I noticed that Annie put glass on the top of the middle section and also on the lower part of the sides and let it cure before doing the final assembly.

    I do not completely understand how fiberglass and wood composites work to make stronger materials. I suspect that there should be almost zero gap between the wood pieces for it to be effective. Should I use both glass and thickened epoxy? I wonder if that will make a weaker joint compared to glass alone.

    I am seeing some highs up above 40 in the forecast this week. I hope to keep everything inside and warm (~66 Deg F) and then move it outside to mix the epoxy, clamp it and screw it together.

    Just to be clear -- the photo showing professional quality wood work done in a proper boat shed is from Annie's blog. The photo with misaligned pieces featuring a cooler in the background is mine. I hope it is OK I borrowed your photo here, Annie. Please let me know if you want me to take it down.

    Last modified: 18 Nov 2019 13:52 | Anonymous member
  • 20 Oct 2019 19:11
    Reply # 8067399 on 6872873

    I decided clamps are necessary. I think I got it to bend without doing any damage. I hope to get it glued together before it is too cold for the fast epoxy!


    Last modified: 22 Oct 2019 15:50 | Anonymous member
  • 19 Oct 2019 23:49
    Reply # 8066477 on 6872873

    Thanks for the replies. I plan to use tapered pole. The boat came with a gin pole setup that makes it relatively easy to raise the original mast. I hope to re-purpose it for raising the freestanding mast.

    I decided that I would somehow find a 7" pole and then started building a Tabernacle. I learned the hard way that west system slow hardener must be used at 60 deg F or higher. I thought 50 deg F was the minimum. I was wrong!

    I used 2x dimensional lumber which is actually 1.5 inches thick. The article in JRA magazine issue 61 article recommends 2" lumber. I hope 1.5" actual is close enough for my small boat. If anyone thinks this is too lightly built please let me know.

    I am stuck now because I can't think of a way to make the sides of the tablernacle bend for the taper. Do I need to buy something like 10 big clamps to make it bend? I attached a photo.

    Any advice is appreciated as always!


    Last modified: 20 Oct 2019 00:43 | Anonymous member
  • 26 Sep 2019 03:50
    Reply # 7901363 on 6872873

    Wouldn't the 8" tapered pole you were looking at before, cut down to 24', be better than one of the four straight tubes you are looking at now?

    I am staying away from the mathematics, but just a direct comparison between that and the 7" straight pole (no. 3 on your list that Dave refers to) it would come out slightly lighter, and with a lower c. of g.  The wall thickness is slightly less, but the outside diameter at the base is greater. And its tapered.

    Its actually not that hard to make a mast from two parts. But if you can get a tapered pole which is a little longer than you need, and at a good price - well, I wish I could be that lucky.

    The tabernacle will be an inch wider, but if that is a problem then you can make an aluminium tabernacle (from folded sheet aluminium) which may help.

    With a proper tabernacle I think raising and lowering the mast is still a practical proposition even if the weight ends up around 35 kg. If it is too heavy for you to walk up into position (it possibly would be for me, these days) there are still ways, with or without a strut (sometimes called a gin pole), to apply a little bit of mechanical advantage and get the job done. Here are some examples of raising the mast on a 22' boat, using various forms of mechanical advantage (trailer winch, block and tackle - not shown here but a small electric anchor capstan will also do the job) - and using - and not using a gin pole. 

    https://www.youtube.com/watch?v=Ve8lzTy-7JQ   no gin pole

    https://www.youtube.com/watch?v=C5WdqdlB8Nc  no gin pole

    https://www.youtube.com/watch?v=w0Sc1e3MXyA  gin pole

    https://www.youtube.com/watch?v=l81rwc6-8SM  gin pole part 2

    Not one of these guys has a proper tabernacle. A proper tabernacle is an advantage.

    The junk rig is at a distinct disadvantage here, because of the mast position being a lot closer to the stem head where a turning block would be. If that turns out to be a problem you just have to figure out a  way around it - in one of the examples above, the person pulled from the trailer winch instead of the stem head. There's always a way.

    I think that whatever mast section you choose, provided you decide it is going to be strong enough, you can just stop worrying too much about other issues and push on, confident that you will find your own solutions to the other problems as they arise (and they will arise.)


  • 25 Sep 2019 23:32
    Reply # 7901138 on 6872873

    Hi Scott,

    my suggestion would be not to compromise on the strength. This eliminates the first and last option. The wall thickness is not too important, this requirement is more related to the ease of damaging the section and as long as it is more than about 3.5 mm thick then this should not be a problem. I would go with the third item on the list as the weight is closer to your aim than the second.

    All the best with the project.

    David.

  • 25 Sep 2019 20:12
    Reply # 7900142 on 6872873

    Next on my 'bottom up' build plan is a tabernacle. I am a little stuck on that until I can decide on the diameter of the mast. I would very much like to use a tapered pole and avoid having a two-part mast that will need assembly. I looked at the 8" pole available at a great price nearby -- to me it is clearly bigger than what I want.

    I am trying to find something that meets all the calculations and rules of thumb I have read. So far nothing meets the criteria.

    I will need to fall short of one, or more, of the goals I typed up:

    1. Mb_yield greater than 1753 kpm

    2. Wall thickness between 2.5% and 5% of the outer diameter

    3. Mass somewhat under 30kg

    If anyone is willing to look at the summary I attached and provide feedback I would appreciate it. At the moment I think going with 'too heavy' might be OK. I am not sure how literally I should take the 'between 2.5% and 5% of OD' rule.

    Last modified: 25 Sep 2019 20:18 | Anonymous member
  • 23 Sep 2019 00:24
    Reply # 7893598 on 6872873

    Thanks to everyone who took the time to give advice on the mast.

    I now have 6 layers of 1/2" fir plywood glued into the hull. I also have 4 more layers laminated together for the top of the mast step.

    I am sure I would do it better on the second try ... But I guess I have to learn somehow. I am not terribly proud of the crooked base and I only really got the top two layers glued in the way I would like them all to be. I should have used much more epoxy, I think.

    On the other hand if needed to remove it I have no idea how I could get it out without first chipping all the wood into little pieces and then grinding the epoxy off the hull. Thinking about how difficult it would be to remove intentionally gives me some confidence that it is strong enough.

    I am pretty happy with how the top section turned out.

    It seems that considering epoxy a recurring expense like boat storage makes more sense than thinking of it as a one time expense like buying a boat.

    Last modified: 25 Sep 2019 13:31 | Anonymous member
  • 12 Sep 2019 16:12
    Reply # 7877707 on 6872873

    My 7in mast is 36kg bare tube weight, around 40kg after completion and with rigging added. I can just about lift it, but transporting it single handed needs some wheels strapped to one end. Imagining it to be in a tabernacle, I think I could live with raising and lowering it once a season, but doing that every weekend would be a deal breaker for me. It would be sad to have to pass on a bargain, but in this case, it does seem more sensible to hold out for a 6in or 7in mast, somewhat under 30kg.

  • 12 Sep 2019 14:41
    Reply # 7877514 on 6872873

    Its not easy to weigh a mast so I have only an estimate of the  weight of mine - 25 kg at least, and maybe getting towards 30kg. It ended up much heavier than I wanted, and much much heavier than the mast plus rigging it replaced. The boat is only 1700 lb and has no ballasted keel, only a centre board. (There may be a little bit of ballast in the stub.) Anyway, for what that is worth, surprisingly to me, the mast does not seem too heavy, she stands up quite well in a breeze - though it is about the limit for me these days, for stepping. [edit: I can do it though - I have a good tabernacle. For a younger person 30kg would be "up there", but OK I think provided it is being raised in a tabernacle.]

    If your 28' lamp post weighs 35 kg then by simple proportion cutting it down to 24' will bring it to something like (24/28)*35 = 30 kg. (Maybe a little under that, since you will be cutting off the heavy end.)

    James G is carrying a 37kg mast on his 19' (1200 lb) River Rat and says it is too heavy, though he is sailing with it.

    I agree with Arne, but would go further: don't cut the mast at all until you have made the sail and hoisted it high enough to be out of the lifts and lazy jacks. Then you can take the mast down and cut off what you don't need, from the bottom end allowing a little extra, as Arne suggests. Don't cut it too short, is the lesson I learned.

    Last modified: 12 Sep 2019 21:41 | Anonymous member
  • 12 Sep 2019 14:12
    Reply # 7877467 on 6872873
    Anonymous member (Administrator)

    Scott,

    if the price is good and if the boat were mine, I might still jump at it. There are three reasons for it:

    • The boat is not to be crossing oceans or win races.
    • The boat is so light that body weight will have a significant effect on keeping it upright.
    • This mast will still be much lighter related to the boat than the wooden masts of my Malena (her about 85kg mast was 6.1% and her hollow 70kg mast was 5%)

    The solid mast really was too heavy, for sure. The 70kg mast (1400kg boat) was still not ideal, but I could live with it in lack of anything better.

    I would therefore not call a 35kg mast a show-stopper. However, you are to raise and lower that mast before and after each sail, right? Then I guess 35kg would feel on the heavy side.

    Arne

    PS: When cutting down the lamp post to fit your rig, I think you can safely cut from the thick end. Leave a mast about 1-2 feet longer than you think you need, and then trim it down after having gone for a few sails. It's easier to subtract length from a mast than adding more to it...

    Last modified: 13 Sep 2019 14:11 | Anonymous member (Administrator)
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