can it be done in steel?

I have other photos I can send you, the attached is an alloy CAT build but principle is same for steel, just make up a pile of weld cleats to anchor and pull. Combination of chain blocks to pull plates to frames, stringers and keel is easiest method then clamp for welding.

I've used builders Acro jacks, fender repair porta power pumps with extensions or whatever I can get my hands on to position plate.

 

radius chine

tugboat, your image file shows easily developable surfaces that could be edited if needed to insure they will cut from flat stock. That work, plating with these panels will not require any 'forming' just a bit of pulling/dogging the edges and tacking; and that's been discussed.

There are several designers who specialize in radius chine, Dudley Dix is one I think? If you were to find some of his plans, or those from others' boards, you'd be able to learn to adjust your model stations to allow a constant radius at the turn of your tug's bilge.

Of course, you've likely already figured out that this radius needs to adjust in depth (profile) as the stations chine angles (in plan) change along the hull.

This will allow you to use a plate rolls to perform the chine region forming and avoid having to find someone do this work with an English wheeling machine. In case you intend to gear up yourself, with these tools, the rolls is more easily acquired and learned compared to the E'wheel; given the steel capacity implied by your design.

After you frame up, and have the two adjoining developable hull plates, bottom and topsides, tacked on to the frame; the radius chine can be fit from lengths of rolled plate between the outer edge of the bottom and the lower edge of the topsides, bow to stern.

While I have not seen the full lines plan it seems the radius chine design relies on the designer's ability to use the forefoot curve in conjunction with the chosen radius so the oblique cut of the radius material at the bow stem is a clean/even/exact function of that cylindrical section?

I've only experimented with this occasionally in lines I've drawn but it does seem to me the crux of that design process? Construction wise, all the plates are shapes from two fixed original forms- flat and cylindrical, steel is easily available in both forms.

Cheers,
Kevin Morin
Kenai, AK

 

build technique?

Hi Kevin...I've just posted the contours for the framing to give an idea of what I'm dealing with...

my thinking was- that if I plated all the easy places -i.e. the bottom sections- i.e. form keel to the beginning of the radius turn, then the topsides down to the radius turn at the bilge, then once that was done. used short sections layed diagonally, and pulled the plate into shape using the methods described- i.e. com e along, clips, clamps etc. etc.. would not that make it quite easy? or would it steel need to have rolled sections? I CAN take the difficult area's to a machine shop and have them rolled?? I cant imagine it costing too much- I think the labour rate here is 55.00 per hour...

 

radius chine

tugboat,

I suggest that you spend more time with the model, perhaps make an 'object' in Rhino that is the radius/constant cylindrical section you intend to use.

Draw the hull hard chine, and fit the curve object to each station as a 'fillet' so the topsides frame element and the bottom frame element are tangent to the radius object.

This should help you draw the fore and aft taper (an intersections at the transom and forefoot) that seems to me- pretty elusive to the non-full time marine designer! The tangent points of the curve will be less distance vertically as the angle changes fore and aft, and that will give a set of points to 'fair' in the Profile View of the lines.

Question; to roll OR to cold form with winch, cable, come-a-long and wedge&dog?

Test: can you bend the plate you propose over a radius fixture you build? If so, then use the cold pull methods if not- roll the plate.

Build a small set of frames of the radius you propose, take some of the thickness plate in your build and cold bend it- if the material won't cold bend the you can roll it, and at 55 an hour (seems very reasonable to me!) you can roll lots of it; a hundred times easier than you can cold bend one piece with a come-a-long!

Just my take. When someone asks to see the lines, it is customary to publish the traditional views (Plan,Profile,Body). Perspective is only useful when you can refer to the lines in the three views to make the perspective meaningful, without the Lines, perspective distorts information, like the body plan chine intersection and especially the forefoot in Profile.

Cheers,
Kevin Morin

 

Hi Kevin- I was forced to do just that- now it should be developable. or if not much much more easily plated up. I just used a simple hard chine. It was compromise for me, but it kept the true "look" of the tug...
comments?

 

A rounded chine of constant radius can be created in Rhino using FilletEdge (if the bottom and side are joined as a polysurface) or FilletSrf (if the bottom and side are separate surfaces). Quick and generally easy to see what a rounded chine looks like, and you can backup and change the radius.

 

Is there a way to stop the radius from wrapping around the stern?
that is what usually happens when I try FilletEdge?

My guess is, if there was a knuckle at the stern the radius would stop at the knuckle. there would be a fairing point...

Anyway- the hard chine makes it easy to plate so- I think(hope) I've solved the problem...it will reduce roll too.. and it actually increased the beam slightly at the waterline.

 

You can use VariableFilletBlend to vary the radius of the fillet but then you'll have to roll conical rather than cylindrical plates for the chine. Also, I've found the setting the radius on a handle to exactly zero doesn't always work so I set it to something like 0.001 instead.

There is another method to have a constant radius round chine taper out at the rounded stern but it's more complicated than a single command. Send me a note if you're interested.

 

A very simple and effecient method of bending plate for either cylindical or conical radius is done using a brake press.
All you need do is mark in the radii centre line then chalk line in each pre calculated press line incroments either side to guide each fold movement to achieve the desired radius.
This method was used very sucessfiully to acheive a 60mt long fair curved form in both sides of a supersructure with each 3mt long 10mm plate tapering to match its fore/aft partners.

 

10 gauge steel is just a touch more than 1/8", wouldn't that be easy enough to beat to shape by hand with a hammer?

 

SamSam, hard work to hand form a fruit bowl from 10g or guards for swamp buggy using hand hammer, easier with power hammer and swages but forming 5mm plate or heavier needs serious heavy machinery.

Electric/hydraulic power press, triple pinch rollers, brake press, power hammer with formers or 10tonne plate worker English wheel

 

this is why I gave up on the variable radius design...would be nice to have that in steel. But its too complicated...everyone here has been great in offering advice. most of it I took.

 

Well, it isn't a fruit bowl shape except vaguely on the corners. If it's a fairly constant radius, a trough roughly gouged into the end of a chunk of log and a sledge hammer could turn it out without anyone dieing. Why talk about how hard it would be to form 5mm plate when the material is 10 gauge?

All these scenarios are run through to death. It's not going to do any good asking here how much trouble or how much it will cost to do stuff, go to the people who will be doing it and ask them.

 

From what I can tell in the renderings in post #1, that skinny 'chine' strip is not the one with any serious rolling needed and it almost looks to be un-needfully separated from the bottom. The metal forming is needed at the bottom of the sides, separating a strip from there would make the forming easier as you wouldn't be dealing with a huge plate. The way it's drawn up, first you'd have to bend the develop-able surface and then roll in the compound surface onto that. I'm not even sure that's possible, much less practical.

The strip needing forming doesn't need to be full length. If cut to shorter lengths like 3', it would be much easier to deal with.

http://www.youtube.com/watch?v=8N7auIRvzLQ

http://www.instructables.com/id/Power-hammer/





I'll bet she could even mash 5mm stuff...

 

There's also trip hammers...



http://www.google.com/search?hl=en&...fp=53f6f487ea26e51e&biw=1067&bih=557&imgdii=_



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