Tips for masking straight waterlines

Thanks for the lead John, I must have had a senior moment, as my nose is rarely out of the Longridge book, although I have not visited the early chapters of late.

For those interested, the subject is covered on page 56 of his book. He says in relation to his Victory model:-

"Draw a line with a scribing block around the hull 1/8" above the waterline. If you lay your copper strakes strictly to this line you will be very disappointed when you have finished the coppering, because it will appear to sag downwards at the bows and stern. This is an optical illusion produced by the curving inwards of the ship's body. To prevent this you must raise the line 1/4" at each end of the ship and then the top line of the copper will appear horizontal. Begin to raise the line at the level of the Foremast and the Mizen, which is roughly where the cant frames begin"

Of course these specific measurements relate to his 1/4" scale model.

 

I used a lasor level to get a line on my 1/35 Italeri Pt boat. I set the hull upside down on the counter to make it nice and stable. i marked with a fine tip flair pen the waterlie at the bow and stern and then adjusted the lasor line to pass through both. Once set, I made a series of very small dots along the beam. I did a few along the straight sections and more, closer ones in the curved areas.

Try a laser level, I used one for a 1:48 scale FLETCHER class DD.  Here's an example - http://www.rcgroups.com/forums/showthread.php?t=351339&highlight=laser+level .  Best of all, you don't need to make sure the models' waterline is perfectly level, since most laser levels are adjustable when shooting the laser line.

 On modern (since the mid 1960's) the boot topping stripe on USCG vessels has been tapered - higher at the bow than at the stern.  Depending on the length of the vessel, there is a formula for determining the height of the boot topping at amidships.  The boot topping height at the bow is 1.33 times the amidships height.  The boot topping at the stern is .66 times the amidships height. 

George, you're right.  The subject is discussed in Longridge's book about his model of H.M.S. Victory; he urges modelers to compensate for that optical illusion by curving the waterline upward a little bit at each end.

A few years ago I reviewed a book (whose title and author now escape me) of old drawings produced by the Harland & Wolf shipyard.  These drawings - which were quite beautiful, with watercolor washes to give them some color - were the ones the yard provided to its clients as reference material when the ships were delivered.  The typical set of plans consisted of an outboard profile (with sail plan, if appropriate), deck plans, and a body plan.  If I remember correctly, every single plan in the book showed the waterline with a slight curvature at bow and stern.  So apparently the real ships were treated that way as well.

I have not painted a waterline for a considerable number of years but I seem to recall that depending on the curvature of the hull at the bow and stern, a perfectly straight line can appear to sag at these points when viewed from the side due to an optical illusion, which needed to be countered by a marginal rise in the line towards the bow and stern.

Has anyone experienced this?

Funny how ideas pop into your head.  As soon as I saw "square" in your post it hit me.  I have a nice solid engineer's square.  It has a nice heavy flat and square base, and a wide blade at 90 degrees.  I used a heavy duty spring clamp to hold a sharp pencil in place and it worked perfectly.  Thanks for the inspiration!

Dave

I USED TAMIYA BLACK TAPE AND PAINTED IT FLAT CLEAR AS A SEALER(WHAT DO I KNOW I AM NEW TO THIS)

In the old days I'd simply tape a sharpened thick pencil lead onto a perfectly square block,and lightly run around the hull, which was mounted so that the waterline marks at the stem and stern were level. Worked every time.