Model tug boat plans

I've been looking on e-bay for a set of model tug plans and have found one I quite like, as I haven't seen a boat plan before a question I need to ask. With engineering drawings there is no need for or I haven't come across the need to use the drawing as a pattern. The important part of the tug drawing is the shape of the hull but the drawing shows the profiles but not at the scale as the tug, which is 27 inches long and a 8 inch beam. The drawing looks half that size, how do you convert the drawing profile to the full size, is a drawing set needed to double the size. I've made model glider in the past and used the drawing as the pattern for the wings etc.

Thanks Bob

In the olden days (when I used to make model boats) I would transfer the lines onto graph paper by tracing or carbon paper then scale that by hand to whatever size I needed (drawing out a custom grid if it wasn't a straightforward multiple).

The full lines got transferred to templates using more carbon paper.

These days, you could probably do it all with a photocopier.

At that length it is probably about 1:30 if a small harbour tug (picking the figure off a plan I happen to have by my chair) but if the prototype was an ocean going one it could be up to 1:48 which is another popular scale.

To scale the plans without a photocopier you can try a photo, enlarge in the computer and print out, if you have a printer. I fact if you can get it into the computer it makes it much easier to print the cross sections, cut out, glue to the wood frames, saw as per wing ribs in a 'plane.
Can you mention the plan so we can take a look?
You can also, being an engineer, knock up a quick pantograph with a few bits of wood to trace round and scale the drawings.
BTW with a boat plan you need the side view to get the keel shape but then build up the shape with the frames. The other side view lines aren't too impprtant. The plan view gives you the deck shape but the other lines on that view aren't too necessary. (the designer draws them as they help derive the cross sections but that will be on the plan after he's done the work).

Have a nose around the beginners sections on Model boat forum (link at the very bottom of this forum page) and Modelboatmayhem.

I had a quick look on ebay and there are loads so couldn't pick out which one you were thinking about. You might not want to mention the actual one in case someone bids against you but you can PM me the detail. I promise not to bid on it as I have two in progress and at leat two plans in the queue already.

.

Could you please give us a ‘Code of Conduct friendly’ hint, by naming the model, Bob

... I have a screenful of ebay offerings before me.

MichaelG.

When I built my tug I scaled off critical dimensions using proportional dividers but that can take a long time if wishing to transfer all hull lines.

I would now scan the plan and then vary the scale as I print it. Slight distortion errors creep in but only matter if you are pedantic over accuracy.

With electronic calculators now available I often take a proportion of the hull length on the drawing to the finished hull length I desire and then apply that multiplier to each dimension I require, measuring using a digital caliper.

However the easiest method for you (if you are prepared to pay) is to take the drawing to a decent architectural copy shop who will scan it ('digitize' and then print at any scale you desire using their plotter onto roll fed paper. It hlps if you draw a 'scale 10m length' on the drawing to enable a quick check of the final size and scale.

The first copy will be dear but if you need more than one copy their price starts to drop significantly.

If you know someone who works in a decent sized surveying or architectural practice they may be able to do the same for you at a cheaper rate.

You can scan the lines into a computer, file format not critical could be pdf. Then print to a scale, just increase scale until you get what you want. You only need to print one side to get it on A4, then mirror for the other side. I use this to get a near true full size when I need it.

Scan could be photo from your phone or camera, before we start with not having a scanner.

This might help:

https://woodgears.ca/bigprint/

Old skool methods include Proportional Dividers and Scale Rules, both of which can be home-made.

Proportional dividers are set to swivel at the required scale, and from then on the pointers at one end are scaled to the other. Dividers can transfer dimensions from one plan to another or direct from plan to object.

Scale rules are slightly slower. The scale on one edge is a multiple of the scale on another, so measurements can be read on one and transferred from the other.

Both methods above are limited by the physical size of the plans and of the real object. When dividers and rules become impractical, list the measurements in a notebook and scale the values with mental arithmetic, or a slide-rule, calculator, spreadsheet or database. Hard work, but the notebook and maths method can cope with anything.

Dave

Edited By SillyOldDuffer on 29/11/2020 14:07:29

Take the plan to a copy shop and ask them to print it off twice full-size. I use our local one they are very helpful getting drawings to the sizes I want and not expensive.

Bob,

At 27 inch length and 8 inch beam a plan for a boat that size should be full size, I have built two tug boats at 42 inch in length and the plans were full size, with a tug boat there are a lot of complex lines and sections in the hull form, I wouldn't want the extra work in scaling up the drawing before I could start building.

There must be plans for tug boats that are drawn full size.

MichaelR.

If you have a vector drawing application (I use CoreDRAW!): Scan the profiles; using the 'guide lines' function, set two guides the required distance apart (somewhere off the page will do); pick up and drag the required profile and place it accurately against one guide; drag an opposite corner handle to uniformly enlarge to meet the other guide; copy to a page of its own and label accordingly with frame number.

I recently went through this exercise to enlarge a Starlet model yacht drawing from a small low resolution download. In my case, I used half-profiles and flipped a copy down the centre line.

Alan

Thanks for all the replies. ways of scaling up noted, but I think that a full size plan will be the best way to go as Michael has made a 42 inch hull with out scaling up.

Bob

I see there are two tugs 27" x 8" listed on eBay as being from free plans that were in model boats mag, maybe this is the reason the drawings are smaller? Sarik do the plans so may be worth enquiring with them what size sheet theirs are printed on

Hi Bob - usually a model boat plan will feature the drawing in profile and deck(s) elevation. Sometimes this is not to the scale the model is intended to be built. Usually however there should however be the profile stations (moulds, forms or frames - correct name evades me) of the hull drawn at the full size the model is intended. Doing it the other way round is not usual. Allowance usually has to be made from these for the thickness of the hull material. I can't think of an example I've seen where that is not the case.. Your best option is a photo copier - divide the size you have on the drawing into the size you want and scale to that percentage. That way you can make allowance for the hull thickness however you choose to build it.

It's always better though, as previously suggested, to have a full size plan and there are many different tug plans to choose from.

Although I did not finish it I did print off the drawings for the Tug 'Cruiser' from the book British Steam Tugs by PN Thomas - a book well worth looking out for if you have an interest in them - lots of ship builders drawings of full size to whet the appetite.

Regards - Tug (and no, no conection there!!)

It does look like it is full size on the plan. There are a lot of cross sections but you will not need to make frames to all of them. Start in the middle at around no 20 and go in each direction picking ones at about 3in intervals, At each end where it is changing shape faster go down to two inch spacing.
Since they are full size you can use teh normal method of tracing and pin ricks to transfer onto your ply frames. For the keel I would suggest real wood unless you can get waterproof marine ply as even if the outside is painted you never know how much water will get inside.......

Thanks all, looking forward to making it, problem is where to float it after its made. Boiler certificate needed if used in public area, how do others get on who make steam models ? not over bothered as its making it is the interest for me.

Bob