Now that you have the exact scaling measurement you require I would suggest that you make your self a simple proportioning divider with the arms set to 1.66666 to one. Look at https://www.ebay.com/itm/Accurasee-Artist-Proportional-Scale-Divider-Drawing-Tool-Measurement-Accuracy/274013238062?epid=1630191377&hash=item3fcc76332e:g:MdQAAOSwOWtdfVat one of the pictures shows how to use them.

STEVE

Yep, as near as damn it!
You'll end up with 1to12.5, which'll give you a boat about 93 x 32 cm.
Plenty of room for goodies 😎

hi bud thanks for that so i multiply by 1.6 and that will give me the scale 1/12

5/3 Phil, (20/12)
=1.6666666666666666666666666666.....
Happy scaling🤞
Cheers, Doug 😎