Boat Design Forums  |  Boat Design Directory  |  Boat Design Gallery  |  Boat Design Book Store  |  Thanks to Our Site Sponsors
Old 02-27-2017, 11:36 AM
OllyP123 OllyP123 is offline
Join Date: Feb 2017
Rep: 10 Posts: 1
Location: london
Optimist with Topsail and spinnaker - Extra sail area


The optimist is the only dinghy we can take on our yacht however I have slightly grown out of it. I would like to put on a spinnaker, which has been done before. Also I would like to increase the sail area. To do I think that the best method would be to make a topsail with just over 1 meter square sail area. I thought I would attach a pole to the top of the mast and fill in the gap between the sprit and the pole but also go up a little bit higher.

I think I would have to rake the mast back massively or it would be extremely unbalanced so I will have the top sail tie of the normal sail attached around the pole or I won't fit under the boom.

Firstly will there be any issues in how the sail is balanced even when it is raked fully back? Also how would I work out the camber ratio and draft position for the topsail. Would I just make it like a normal sail except it is just a different shape or would I have to factor in other things. Also what would be an appropriate topsail size for a 60-80kg sailer?

Thanks in advance

Reply With Quote
Old 03-01-2017, 06:58 PM
messabout messabout is offline
Senior Member
Join Date: Jan 2006
Rep: 1279 Posts: 2,651
Location: Lakeland Fl USA
If you add a topsail, do you not need to increase the height of the mast? If you are going to make the mast longer, why not just have a sprit sail with a longer luff? That way the center of effort will not move much if any.

There is a practical limit to how fast you can make an Opti go. If you add power beyond that which the little boat can use..... you have not gained much, if anything, aside from the satisfaction of having exceeded the bounds of practicality.

As you say, you have outgrown the boat. If that is to be taken to mean an increase in the skippers weight, then there are some arguments that you can make about power to weight ratio which also has its limitations in a boat like the Opti.
Reply With Quote
Old 03-01-2017, 07:12 PM
Munter Munter is offline
Join Date: Jul 2007
Rep: 125 Posts: 282
Location: Australia
The Opti already has a tendency to push the nose in. Adding sail up high will accentuate that when sailing downwind. The effect on other points of sail will depend a lot on how the extra rag is set, eg the tightness of the leech, the amount of twist etc.
Also - be careful you don't overload the mast gate and mast foot - without stays to take the load these two areas will be carrying more load than usual.
Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Similar Threads
Thread Thread Starter Forum Replies Last Post
Sail Area vs Keel Area - Stability Calculation Dabrownone Hydrodynamics and Aerodynamics 39 06-09-2012
12:13 AM 
Optimist Pram with.....spinnaker! Doug Lord Sailboats 0 12-24-2010
09:59 PM 
100 sq. ft of sail area is about 2 HP? F.H.B. Sailboats 17 01-08-2010
08:02 PM 
Increasing Sail Area dm567 Sailboats 6 01-10-2007
07:36 PM 
sail area to lateral area ratios Ian Boat Design 5 04-07-2004
05:39 PM 

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.

All times are GMT -5. The time now is 03:19 PM.

Powered by: vBulletin Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Web Site Design and Content Copyright ©1999 - 2017 Boat Design Net