JIF 65

[carl brothertonParticipant @carlbrotherton75833]

Is that how it is really done?

[carl brothertonParticipant @carlbrotherton75833]

I am starting the build of a JIF 65 Yacht, and I apparently know nothing.

Looking at the plan of the hull, it is a chine type build. I expect to find stringers at the hull/deck, the chines themselves and a keel stringer, to allow the bonding of the ply skins to have a reasonable gluing area. What I have found is that the ply skins seem to be butt joints.

Is the usual or just an omission from the plan, for convenance?

Has anyone built one or similar, or perhaps there is a thread on this site which shows how to do things?

[Ray Wood 3Participant @raywood3]

Hi Carl,

Yes I just printed off the plan, without the build article it's difficult to see an easy way of building it !!

It is obviously built inverted on the board by magic with the deck flat ? If it were the old stitch and glue method like the mirror dinghy you would have the shapes of the side and bottom panels on the plan ! tape them together and glass tape the internal joints. but no sign on the drawing.

You can of course cut notches in the bulkheads and fit conventional stringers to fix your skins too.

Perhaps Maximo Lange had a cunning plan ??

This is a traditional approach I use, not a racer this one but similar

Regards Ray

[Chris FellowsParticipant @chrisfellows72943]

Just Googled the yacht and indeed it doesn't have any stringers. Those who have built it may say that they are not required and it may be that they aren't used due to the curvature which would require another bulkhead.

If I was building it I would shape and fit some fillets where you'd expect stringers as you say to give more gluing area and strength.

So you do know something!

Chris

Edited By Chris Fellows on 28/01/2021 19:35:07

[timgParticipant @timg12590]

Hi Chris

I'm no expert , I would imagine that it is to save weight, but if your not racing then Ray's suggestion to add the stringers is what I would do.

Good luck with the build

Tim g

Edited By timg on 29/01/2021 08:45:22

[Chris FellowsParticipant @chrisfellows72943]

Hi Tim

It's Carl that's building it but your assumption about weight is probably right. I tend to over-engineer my own builds and like nice positive connections. It won't add much weight anyway and can be clawed back by taking the centres out of the other bulkheads.

Chris

[Malcolm FraryParticipant @malcolmfrary95515]

One practice is to butt join the two edges, tacking with cyano, then reinforce the join with a strip of glass cloth and epoxy. The cloth/epoxy becomes the stringer, and gives a much larger surface area for the join. Probably simpler than shaping stringers.

[Ray Wood 3Participant @raywood3]

Hi Carl,

If you put "RG65 Alpha" in the search box, you will find a thread with photos of John Goodyear's design Alpha a single chine RG65 a very nice race boat, he also designed Omega a balsa planked hull round bilge also a good looking boat and he makes his own sails

Regards Ray

[Tim RoweParticipant @timrowe83142]

Posted by Chris Fellows on 29/01/2021 10:44:21:

Hi Tim

It's Carl that's building it but your assumption about weight is probably right. I tend to over-engineer my own builds and like nice positive connections. It won't add much weight anyway and can be clawed back by taking the centres out of the other bulkheads.

Chris

Hi Carl

Suggestions flying. Chris is right. Stringers won't add that much weight but I would caution taking the centre out of the middle bulkheads too quickly as it might be required for supporting the keel box. Haven't got the plan so can't be sure.

Tim R

[carl brothertonParticipant @carlbrotherton75833]

Here is the plan I have.

I see that it is sheet 1 of 2, I do not have sheet 2. The reason being the friend who gave me the plan, gave me the one,sadly he has since died.

Looking carefully at the plan, I find with respect to the hull, there are no details of the materials to be used, such as thickness. I assume that the skins are ply, measuring where I can, the skins seem to be 2mm, the formers 3mm.

For ease of bending and working I would prefer 1.6mm. I guess this should be birch ply, whatever thickness? As for the formers, I have some 3mm light ply, would this be OK, or does this need to be std, or birch ply?

The stringers (or whatever they should be called) appear to be quite chunky on the pictures and threads I have been pointed at. I had been thinking of using 1/8"*1/4" spruce, is this a little light. Even if I laminate two pieces, with the aim to keeping the bending easy?

My lack od experience is most obvious in that I have a lot of indecision. This goes down to the timber balk, to attach the bulkheads/formers. If I keep it relatively narrow, it should be easier to work around the lower skin(actually the top, when sailing). A wider piece keeps it more stable on the work top.

I have only just worked out that the formers need to be deeper, to allow the lower skins to be attached. Although the plan came with templates to the drawing.

If my friend was still alive a lot of these questions would have been answered by him. He certainly was very concerned about weight. In my case not a pressing issue, as i will not be competing. My challenge is initially, maybe long term getting it to go where I want. Only then maximising the speed that the boat can achieve, although this is not anything like a priority.

I expected to finish the hull in a finishing cloth, using either Finishing Resin or Water Based Varnish (WBV) (Ronseal Hardglase). Is this a good idea?

Any thoughts on materials, sizes will be appreciated, as hopefully I can avoid pitfalls, and understand the limitations of any options.

Also can any one point me to an image of a JIF plan with more information than my plan, particularly sheet 2, what is on it?

I will probably purchase if possible the sails, as I cannot sew, and often the small items required cost more than a comprehensive purchased item.

I have only just realised I have no idea on servo arrangements or rigging, although this is probably an issue far into the future. Although I would like to have some knowledge of where I will be heading.

[Tim RoweParticipant @timrowe83142]

Hi Carl

I suspect that the second sheet has the developed shapes of the hull panels.

If you follow this link JIF 65 you can see that Sarik Hobbies have the complete set.

If so Malcom's technique of "stitching" with cyano will work very well.

Tim R

[Chris FellowsParticipant @chrisfellows72943]

Tim – good point about the bulkheads.

Carl – blimey you don't make it easy for yourself do you only having one of the plan sheets! I'd do as Tim suggests and get the full set which should answer most of your questions. If not ask away. They are also available from Cornwall Model Boats.

Chris

[Ray Wood 3Participant @raywood3]

Hi All,

This is a good one everybody getting involved

Carl the skins only need to be 1/32" ply if your glass clothing and epoxying the hull in my opinion.

Getting the drawings for the skin shapes is a good idea.

1/16" ply is hard to bend on a small hull like this, trust me I've been there.

Liteply will be fine but never mention it on this forum as some people love it and some don't

Regards Ray

 

Edited By Ray Wood 2 on 29/01/2021 16:56:16

[Tim RoweParticipant @timrowe83142]

I am in the love it camp.

Strong enough for most purposes especially if properly braced. Sometimes I laminate 2 to make 6mm. Absolutely fine if it is well sealed. What's more it's light

+ one with Ray. The thin ply will be much better and achieves amazing strength simply by being curved. I don't know about your supplier but here in Mallorca the thin and thinnest ply is more expensive but so much easier to use. My go-to tool for cutting thin ply is a pair of good scissors and a scalpel for the fiddly bits.

Tim R

[carl brothertonParticipant @carlbrotherton75833]

I will buy the ply from SLEC, also the Spruce and cut it down with a cheap HK model circular saw, which just about copes.

I will be going the base plank method. The main two reasons are, no plan, more importantly, any slight error, with the edge method will result in a hull that is not symmetrical. In my case, both skill and accuracy are in short supply.

The old method may be slightly heavier, as I am not racing or competing in any way, absolute weight reduction is not the most important issue. Not knowing what I am doing is a major issue though.

[carl brothertonParticipant @carlbrotherton75833]

I have ben considering how to make progress building this model.

Given my lack of experience, I have decided my model will not be built as light as possible, the emphasis will not be building as light as possible. It will be on towards the robust and weight end of the spectrum.

The plan indicates a truly light weight build. The formers and transom are 1/8" balsa.and so on.. An example of how light weight everything is, is that the rudder is made of 1/16" balsa sheet, the rudder post CF rod, also the fin is shown as 1/16 aluminum sheet.

I decided that I would build from a jigging beam, with stringers, which will then be covered with ply.

My next task is to write a materials list, then order what I need

[carl brothertonParticipant @carlbrotherton75833]

I have now produced the various bulkheads.

Placing them on my jig, I realised that the jig needed modifying. So far it has taken two further attempt at modifying to hopefully make it viable.

My package of materials has arrived from SLEC. As can be seen not yet opened.

There was however a surprise, whilst going around the workshop I found this pretty large sheet of ply, nice and flexible.

The good bit it is better have options, than non at all.

Not knowing much, with even less experience, requires me to think for longer, plus a bit more. Even them get various options, from others experience.

I will next consider how wide the stringers can be, from 1/8" spruce, to make the stringers'

I am also wrestling with the aluminum keel, how thick should it be for both performance and normal, rough and tumble use.

[Malcolm FraryParticipant @malcolmfrary95515]

I am also wrestling with the aluminum keel, how thick should it be for both performance and normal, rough and tumble use.

If the plan suggests 1/16", 1/16" it should be. Or 2mm.

The really important parameter is that it should be rigid. Clamp one end, put your weight on the other, Any flex should be minimal. At a Laser meet a few years back, we tried two stock Laser fins against each other using a step and the ground as mount and reference. One drooped considerably more than the other. Use of the more rigid one gave a faster boat. The same applies with any other fin.

Even if not racing, with any sailboat you need to get the best performance you can. It can make the difference between getting the boat back and sailing again, or not. I expect that "real" RG65s would use carbon fibre to get the thinnest profile combined with the stiffness needed.

[Tim RoweParticipant @timrowe83142]

Hello Carl

I know the plan says 2mm aluminium but that is a bit like saying 2mm cheese. It could be parmesan or it could be a mature brie, Ordinary aluminium at 2mm is not going to be much use unless you can be certain of its grade. Ideally it should be in the 3 series or the 5 series.

For this reason and anyway, if I was building this boat for rough and tumble I would go to 3mm or 1/8" (3.12mm)

If you want, you have a bit more meat to file an aerofoil profile with a slightly rounded leading edge and a sharpish trailing edge. For good efficiency it is important that keel and rudder surfaces are very smooth. More important than the hull and lead bulb although it helps here too.

Tim R

[carl brothertonParticipant @carlbrotherton75833]

Malcolm & Steve

I hear what you written. I certainly can appreciate the issues are significant and of importance.

Like many people who have materials as old stock, I cannot be as sure what they are , specifically.

In the case of the Aluminum, I would guess that they are Silicon grades, as these are the cheapest and most prolific in use in the 70s. The types we were taught about, the precipitation hardening, or those with alloying elements blocking slip planes or distorting the lattice structure, were of academic interest, or of use in specific sections of industry.

As one who has been a victim of their own incompetence, I am weary of aluminum. A badge bar (for car) that suffered badly from pitting corrosion (road salt). A cooling fan bracket that suffered from stress cracking, after bending (a few days later).

I am tempted to go with the approx. 1/8" sheet, which has a oven baked finish. It is strong, straight/flat. It does enable me to produce a well rounded LE and a good tapered TE. I could then slightly abrade the painted surface and then clear lacquer the whole thing. Being thicker it makes it a lot easier (I think) to bond in a top end retaining bolt.

Not knowing generally accept conventions, or practical knowledge does make decision making prolonged, with potential pit falls avoided by the experienced. Plus I often will be asking what appear to be stupid questions. The other end of the spectrum, I am not as encumbered by preconceived answers or practices. Just my own prejudices.

[Chris FellowsParticipant @chrisfellows72943]

Hi Carl

Another solution, and one I'm probably going to use on a future build, is that you can buy the keel and bulb for the Dragonforce 65 yacht and it strong and smooth.

Last time I looked they were a reasonable price. I suppose it depends on how much you want to build yourself? For me, who generally likes to build as much as I can, I'm not precious about the keel and would be happy to use something much better than I could manage!

Chris

Edit: Just had a look at the RC Yachts web-site and the fin is £6.50 and the weight is £22.20 which might preclude that option.

 

 

 

Edited By Chris Fellows on 07/03/2021 17:03:46

[Malcolm FraryParticipant @malcolmfrary95515]

A pre-made fin will likely be easier to mount than a home build. It will* come with a moulded in fixing rod that goes far enough down the length of the blade to spread its load, and long enough to go through the deck of its DF65, again, spreading the load. With home made, either there is the problem of fixing the rod down the inside of the blade, or extending the blade upwards into a fin box far enough.

I have been tempted in the past to try a helicopter blade, since some have spoken well of them, but haven't plucked up the will to try. Not knowing if they are, or are not, symmetrical or if they vary between types, is one off-put. Understanding the strange techno-babble of heli-folk is another.

* just looked on the ripmax spares page – the fin says "complete with screws" but I take that to mean the ones that fit the weight to the bottom end. No way can a fin just bolt to the boat bottom, it needs more support, either a rod going far enough down the inside of the fin and up through the deck, or a substantial tab at the top sitting in a fin box, with a screw bolt holding it in place from above.

[carl brothertonParticipant @carlbrotherton75833]

Malcolm

I have not seen any model helicopter blades wide enough to come anywhere near to the width stipulated on the plan. I am not sure about the stiffness of a helicopter blade. The set I have are pretty flexible, relying to a degree on  centrifugal forces to Iimit coning.

I guess it is more than co-incidental that I have considered and undertaken a limited search for suitable printed circuit board or Carbon Fibre board/sheet that could be suitable.

I have found I have a lot more aluminum sheet than I was aware of. The smaller pieces requiring a lot less work to cut to size. At 1/8" the sheet I have is pretty stiff. It would take a pretty sever force to cause a permanent bend (Yield).

Using aluminum the Keel bolt (?) will not impart any substantial strengthening role.

An advantage of a removable fin is that it can be replaced, if it comes to "hey lads hey".

You probably will gathered I have never sailed a yacht (model or full size), other than probably occasional trips to the nearly local model boat pond, as a 5-10 year old. The boat never went where I intended. I had no idea as to how or why it sailed, beyond the wind played a part. What has changed, not a lot.

Perhaps I do recognise that the fin, the wetted side area, and where the combined forces generated by the sails can be considered to act, in some way. All of this is not understood by myself beyond thinking this is probably what is happening. Although the sails are said to be an aerofoil, it is not as a aircraft wing, I am guessing. as the wind seems to be often at such an angle, to suggest it should be stalled. Yet looking at a sail in operation indicates I am wrong.

Al of this re-enforces the notion, this is not a model for racing, it is about the fun of learning, and do better against myself. That is the model going roughly where I want it to go.

 

Edited By carl brotherton on 08/03/2021 12:30:28

Edited By carl brotherton on 08/03/2021 12:33:43

[Ray Wood 3Participant @raywood3]

Hi Carl,

It's not that complicated really the fin just stops the the boat being blown sideways by the wind and the weight on the bottom counteracts the wind trying to blow the boat over, and the sails are tensioned in such away that they do make an aerofoil wing section and they create lift which drives the boat forward. The aluminium keel 1/8" thick will be fine and I guess around 2" wide to fit into the plywood keel box as shown on your drawing, with a pin through the box and keel to stop it dropping out.

Regards Ray

[Chris FellowsParticipant @chrisfellows72943]

Posted by Malcolm Frary on 08/03/2021 11:12:46:

A pre-made fin will likely be easier to mount than a home build. It will* come with a moulded in fixing rod that goes far enough down the length of the blade to spread its load, and long enough to go through the deck of its DF65, again, spreading the load. With home made, either there is the problem of fixing the rod down the inside of the blade, or extending the blade upwards into a fin box far enough.

I have been tempted in the past to try a helicopter blade, since some have spoken well of them, but haven't plucked up the will to try. Not knowing if they are, or are not, symmetrical or if they vary between types, is one off-put. Understanding the strange techno-babble of heli-folk is another.

* just looked on the ripmax spares page – the fin says "complete with screws" but I take that to mean the ones that fit the weight to the bottom end. No way can a fin just bolt to the boat bottom, it needs more support, either a rod going far enough down the inside of the fin and up through the deck, or a substantial tab at the top sitting in a fin box, with a screw bolt holding it in place from above.

Hi Malcolm

The method that the Dragonforce uses is that the fin is taken up to deck level and is bolted to a combined mast and fin box so the fixing screws are only short.

Chris

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