How to convert a 18ft bare hull w/60HP outboard to JR?

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  • 23 Jul 2017 06:51
    Reply # 4990220 on 4976050
    Deleted user

    Thank Graeme, I hear you, and although I don't agree with some of the the points I will definitely take your recommendation into consideration. Thanks again for your help. 

    Last modified: 23 Jul 2017 06:54 | Deleted user
  • 22 Jul 2017 03:01
    Reply # 4989056 on 4976050
    Anonymous member (Administrator)

    Just before you go....

    Your last post concerned me a bit and I’m 100% with David now. 

    I made a mistake in my last post too. We are totally rained-out here and stuck inside a small cabin with a few hours to kill – it was not very clever of me and I regret being a little flippant. I still say that hull is not too extreme, it could be made to tootle along quite nicely at displacement speed, and for that reason, while not ideal, it could be made to carry some sail. I have had the fun of doing that sort of thing and wanted to share that. But here’s the problem. There is no harm in chopping into an old boat which nobody wanted, changing things around a bit and being a bit creative – which is what I was going on about. But I completely forgot, that is not your case. Even though you are a long way from it and still in the dream stage, at some point you will have to get your power tools out and prepare to start doing some drilling, cutting and grinding – and if you are wise you will stop at that point.

    Your boat has integrity the way it is, it would be a shame to lose that.

    Its probably just you and me on this thread now, and I have already dug a hole for myself, and it is still persisting down with rain here, so I will carry on a bit.

    This has nothing to do with winning regattas or trying to get from A to B a bit quicker. The extra weight, 115 kg, placed where it is on your boat, most certainly represents a “big deal”. This is not “mitigated” by the helmsman shifting forward a couple of metres to that unsuitably high central steering position. That might improve the fore-and-aft trim a little, but much more than that is at issue. In fact there is nothing you can do by shifting weights (or worse, adding weight) to mitigate against the effect of that motor being placed where it is. The designer has already done that, in the best way possible, by shaping the aft sections so as to provide the extra buoyancy needed, and providing that long flat bottom at the back, which allows you to utilise all that power, and plane at 25 knots. And in the process, made the hull less suitable for sail, though I must say he has done it gently and rather well – I suspect that probably a bit less than 65hp was in his mind – and the result is nothing too extreme, which is why a bit of sail would still not have been out of the question. (And that gorgeous fore-body that makes her look like a whaler when viewed from the front – damn, that’s a lovely motor boat!)

    You have got the idea of twin kick-up rudders, which I think does allow the existing steering gear to remain in place, and of course lifting the motor reduces the drag of the propeller (not much probably, at the speed you will be sailing at but every little bit counts.) But who is going to want to drill the holes in the transom, necessary to fit them? And that’s only the start of it. I think that central steering pod would need to go, for a start, and then where would you hang the hydraulic steering? And are those buoyancy compartments up the front there, where a mast will have to be fitted?

    By the way, I am not the one to advise on junk rigs, but to answer your question, if you draw or copy a nice picture of a junk sail that you like the look of and then super-impose a scale on it so the mast is 4m, then you will quickly be able to calculate the sail area for yourself. I don’t think any rig will give you enough area if boat and rig has to go under a 3.8m bridge. You will probably need to have a longer mast, and put it up after you have gone under the bridge, or maybe consider two masts. But I have gone off the idea, personally. Listen to David, his advice was good.

    Don’t do it.

    Lets step back and have a complete fresh look at the problem. You want to have a junk rig – but what type of rig to have is actually way down on the list of decisions that need to be made (and a junk IS a type of balanced lug, by the way, or I stand to be corrected.) OK, OK, if having a junk rig is the uppermost requirement, then next you need to find a suitable hull to put it on. I would suggest not your motor boat because it now becomes evident that you (quite rightly) don’t want to part with any those things which make it the excellent little vessel it currently is.

    But you can’t have your cake and eat it too, that’s the reality.

    My approach, in New Zealand, would be to look at the second-hand market and find some run-down specimen that needs a bit of love and care and make it a test bed for your ideas, don’t spend too much. So I had an online trawl through the brokers’ columns for Mauritius, and now I appreciate what you are up against. I was surprised, considering the sailing conditions I imagined must exist in Mauritius, to find there was nothing, absolutely nothing in the least bit appealing or suitable. Actually, there was one exception – there was one rather nice-looking hull that caught my eye, and would you believe, on closer inspection, it turned out to be an Aclin 18 – exactly like yours, only it had a 30hp motor.

    It surprises me there are no old trailer yachts or car-top sailboats for sale. That would have been your easiest solution, quickest result.

    So that leads to one remaining suggestion. Can you get sheet plywood etc in  Mauritius? How about a winter project, build a little plywood boat especially for your children to use in the lagoon – make it light so you can carry it on your car top – if not too big you might even be able to sling it across your foredeck and take it away with you on the Aclin on fine days – but better I think, for three sons, to be a little bigger and made for sailing in the lagoon, with a junk rig, on the days when you don’t want to go out in the Aclin.

    It does not need to be too flash or expensive. A perfect example is right before your eyes, in the current edition (Issue 74) of JRA Magazine – Freebie, by Marcus Ramon. (And a bit more detail was given on this website as Freebie was last month’s “Boat of the Month” – if you missed it, maybe the webmaster can dig it out for you.) That should inspire you. You don’t need to copy Freebie either – Freebie might be a bit too big for you to build at home or carry on your car top, though great if you could manage it.  But a little smaller (and a little more wholesome!) would be OK. It’s the idea of it, the spirit of it that Marcus has captured so brilliantly.

    I am sorry, I don’t know why I did not think of that before.

    I bet if you started a new thread, with the quest for a suitable plywood dinghy junk, you would get a flood of suggestions. As a matter of fact, some of the technical experts have recently been considering just such a boat, as a test bed for comparison trials, on one of the other threads. The cost of building a simple plywood boat would be less than the total cost of modifying your existing boat, if you include in the costings the reduction in its resale value after it has been modified.

    Build a simple little plywood sailboat you can keep at home. Have two boats.


    Last modified: 22 Jul 2017 04:14 | Anonymous member (Administrator)
  • 21 Jul 2017 16:43
    Reply # 4988108 on 4976050
    Deleted user

    Further to my own comments below, and after some basic lookup into the physics of sails, I cant see that this exercice, no matter how theoretical it gets, will inevitably boil down to gradual real-life experimentation. From what I gather,and nonwithstanding its many advantages, the lateen sail is not the most efficient design for lift. In addition, my self imposed constraint of reducing the mast size would further affect the sail plan and its lift-to-drag ratio. This may or may not be a problem given that I intend to sail in 8-to-15kt winds.  And so after openly throwing all these questions on this forum, and getting some interesting answers, I have decided, for now, to withdraw from the JRA platform. That means I will continue to assemble the elements that I think are necessary to realize this project, and execute it by steps in the coming weeks. Hat tips to Graeme and David. Thanks to all.

    Last modified: 21 Jul 2017 16:49 | Deleted user
  • 21 Jul 2017 07:30
    Reply # 4987489 on 4976050
    Deleted user
    This is an edit from a version which did not take into account important considerations I overlooked in Graeme's comments. [New comments are in brackets]
    -----------------------------------------------------------------------------------
    Thanks Graeme for your insightful comments. I can understand that when someone is in a regatta or in a hurry to get from A to B, additional weight such as a 115kg outboard engine might be an issue. BUT, what's the big deal here? People on board a sailboat of comparable size would affect both the weight and the center of gravity of said boat to a much greater extent than a 115kg outboard. From a weight distribution point of view, the fact that these 115Kg are at the stern would be mitigated by the displaced forward position of the skipper due to its ability to stir using the existing hydraulics. I can already think of a very simple design to translate the vertical rotation of the engine body to a couple of removable rudders. Sure the immerse engine would create some drag, to a degree. [Having re-read your comments, I can see that you already had in mind a system by which you could operate the twin rudders with the hydraulics via the engine lifted. That's great and even better than what I was considering doing. This will decrease the engine/prop drag while sailing]. I would only be interested in sailing with prevailing SE trade winds between 8 and 18kts anyway. Below 8 is family fun activity weather in the lagoon. Above 18, breaking crests and intimidating swells are definitely not enjoyable especially with the kids. The bottom line might be that with the luxury of choosing your weather, I might go for a smaller size rig which means smaller mast. With a smaller mast up to 4m may come the advantage of not having to hinge it as it will just clear the bridge at MSL. Now comes the next question: what is the largest batten sail area I can mount on a 4m mast? I am only interested in experimenting with a JR for now. I know that I can toy around with a balanced lug, but don't want to resign myself to it just yet. Thanks!
    Last modified: 22 Jul 2017 11:49 | Anonymous
  • 20 Jul 2017 14:32
    Reply # 4986212 on 4984068
    Anonymous member (Administrator)
    Dom Lang wrote:

    I know that I cant make a race horse out of a donkey. 

    My concern is rather that you might very well succeed in making a donkey out of a race horse.

    If your heart is really set on this, I will offer one more little suggestion. A few years ago I was in a similar position to you, I had a 6m boat with a decent outboard motor and a forward-facing steering position. It was actually a sailboat hull which I had modified, and fitted a high-thrust Yamaha permanently mounted at the centre of the transom. I trialled two different motors on that boat, but that’s a whole ‘nother story.  I successfully used it at displacement speed, or occasionally slightly more, for a lengthy historical exploration of a major river here, with nightly stopovers at long-forgotten battle-sites from the colonial war. The river was moderately swift-running in places…..damn! Getting side-tracked. Anyway, after completion of the project I had planned to add a junk rig to this little “launch” – but after I had finished the river trip I got sick and had to sell the little boat and give up on the junk idea.

    My goal had been to learn about, and enjoy, the junk rig – but also to continue carrying the motor, which I really liked, and to be able to convert between sailing and motoring within a minute or so. Admittedly my motor was a lot smaller than yours, (9.9 hp) and the hull was actually that of a trailer yacht which still had its centreboard – which I was in two minds about removing….by the way, in your situation a swinging centreboard would be more suitable than a dagger board in my opinion, for a couple of reasons, but I am guessing you have no intention of fitting a case, and rightly so at this point in time so.… anyway, this put me with a similar wish list to you - just a little ahead of where you are, but not too different in some ways.

    Having no rudder was the problem, as it will be with you. Eventually I realised I could have excellent steering while under sail, yet be able to switch almost seamlessly to power – by mounting two kick-up rudders on the transom, set fairly well out, one each side of the motor. I had cable steering so it was going to be possible to have the rudders and outboard all hooked up to the same steering system. When motoring the rudder blades would be lifted up (180 degrees from vertically down to vertically up.) When sailing the blades would be pulled to vertically down, and the motor (it was a delight) had a power tilting arrangement which allowed it to be raised at the press of a button. I loved that motor, it was smooth, quiet and actually did the job better than the 15hp Honda I first tried, which went a little faster, but not much faster, in a straight line at full throttle but would ventilate and over-rev like all getout when going into a turn……anyway, all three tillers could remain linked, so that part needed no attention and I could still use the wheel steering while sailing. Or, a quick flip of the attachment when the motor was up and I could optionally steer by tiller too…… although unlike a lot of junkies I actually quite like facing forward and steering with a wheel. Anyway, at any one time, either the propeller would be in the water, or the twin rudders – but not all three.

    If you look at the folding rudders of most sailing dinghies, you can make two rudders something like that, but make them so the blades don’t just lift, but lift right up until they are vertical. Gets them right out of harm’s way when motoring - and would look pretty cool at 25 knots too, I should think – you might even be able to persuade a gullible bystander that they help with the steering at that speed. The swing-to-vertical blade on a Noelex I once owned looked cool in the up position too – and served as a mast crutch when towing…. anyway, being two rudders instead of one, the blades can be a bit smaller. Apart from the question of cost and complication, there can be advantages to having twin rudders and they are quite the thing to have these days.

    Regarding the rig as merely an auxiliary to the motor -  to be available “at the drop of a hat” when conditions are ideal - there are a number of simple small-boat rigs that would be cheaper and simpler to make than the junk rig and would probably do just as well – since the only requirement is to be able to set it or hand it, instantly and with ease. And I mention this as an aside, because some of these rigs don’t need such a long spar as a junk, and I imagine might take a little less time to set up or dismantle. But a little junk rig would certainly be suitable, and I just wanted to try it anyway (same as you.) I wish I had been able to complete that project, but another one has replaced it now and the opportunity probably will not come back.

    So now you can see why half of me sort of wants to see you have a go at this – but the other half of me says be careful. Your proposal is a bit more extreme than mine was – David knows what he is talking about and the weight of that big motor will limit your sailing and in the end, if you get the least bit serious about sailing, you will eventually want to either do away with that motor – or start again with a different sort of boat, with a hull (and deck) perhaps a little bit better adapted for sailing.

    On the other hand if you are not expecting too much more from the sailing than a bit of good fun and variety at times, and the learning therefrom, then I have to put this non-technical argument alongside David’s wise comments:  if you keep the rig fairly modest, and the spars light and stowable when not in use, keep it as simple as possible and don’t invest any time and money chasing anything more than very modest performance - then you will have a pleasant surprise when conditions are right. And with the suggestions you have been given, you will not have degraded your power boat to any irreversible degree if you do decide you prefer the race horse after all. And I might add this - unless conditions are ideal and the wind is coming from the right direction, more and more sailboat owners these days don’t seem to do much more than just motor about the place anyway – at about one fifth the speed your boat can do.

    I just hope you have good fun and stay safe. I think David might be proven right in the end, but no harm will have been done. The image of a junk going by on a calm day, at 25 knots, makes me feel slightly ill, and I just hope the idea doesn’t catch on - but that might be just me.



  • 20 Jul 2017 13:54
    Reply # 4986162 on 4976050
    Deleted user

    Thanks David for your reply. I appreciate the candidness. I am planning to give it a shot though. If nothing else, this might motivate me get another (sail) boat after all.

  • 20 Jul 2017 07:38
    Reply # 4985802 on 4976050

    Dom,

    Look for an aluminium alloy tube of 100mm diameter, 3mm wall thickness. This size has been used on daysailers of this size. A sail of 10 - 12 sq m is about the right size. 

    But I have to be pessimistic about the performance you're going to get. You'll be able to go downwind, but if you retain the large motor, I doubt whether there's anything that will get her to sail with the wind forward of the beam. If you take that motor off, add a rudder and dagger board, and a motor of say 8HP on a bracket off to one side, as a get-you-home motor, then things are looking a bit more hopeful. Overall, though, I'd say not to persevere with the idea of putting a sailing rig on this boat. I think you're going to fall between two stools. Either keep her as a motor boat, or sell her and get a sailing boat, is my advice. 

  • 20 Jul 2017 07:24
    Reply # 4985797 on 4976050
    Deleted user

    Bamboo is an interesting thougth . The issue is that, paradoxally, virtually nothing is grown in Mauritius besides sugar cannes, and with all the kitesurfing/windsurfing activity, it is easier to find a carbon composite mast than a long bamboo stick. The problems with these windsurfing carbon masts are that (a) they are relatively short, and (2) are designed for totally different physical constraints. I cant imagine that they can be used for my project, but I can be wrong.
    What kind of material did the ancient chinese junk use anyway, bamboo?

  • 19 Jul 2017 23:32
    Reply # 4985418 on 4976050

    Have you thought of bamboo?  I'm sure there's plenty in Mauritius.

  • 19 Jul 2017 16:22
    Reply # 4984525 on 4976050
    Deleted user

    In case you are wondering, I am not trying to keep this topic on top, I just have lots of questions and not so many answers...
    Finding a tapered aluminum pole in Mauritius appears to be a challenge especially if you don't know exactly what to look for, which I must admit, is my predicament. So, I was wondering if among the JRA experts, someone could suggest an OD, wall thickness and height of the aluminum pole I intend to order as an unstayed mast? I am thinking about 10-to-12 sqm sail max. Anyone? Thanks!

    Last modified: 19 Jul 2017 16:23 | Deleted user
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