VG 20 or VG 23, and AD16

Sail Boats 15' and up. Please include the boat type in your question.
Post Reply
jbro5000
New Poster
New Poster
Posts: 7
Joined: Thu May 11, 2017 11:16 am
Location: Manila

VG 20 or VG 23, and AD16

Post by jbro5000 » Mon Jul 31, 2017 11:42 pm

While I am close to placing an order for the construction of an AD16, the VG20 and VG23 also appeal.

However, there is no specific information in the study plans that might assist in decisions on design selection regarding the range of positive stability for the VG vessels, although likely to be comparable with overall study plan statements regarding AD16.

Qualitative statements that are often applied to small recreational vessels like 'very stable', while reasonably valid, are not sufficiently convincing for safety regulatory and vessel registration authorities.

Although judged by most people to be not needed for amateur construction, especially when using drawn up panels and stitch and glue methods, it would be useful to prospective purchasers if lines plans or tables of offsets could be included with purchased boat plans from which stability curves etc could more easily be prepared where needed.

This would avoid uncertainty at the planning stages and the need to duplicate the original design work during construction plan approval processes.

While I appreciate the AD16 is not normally considered for use beyond sheltered coastal waters, one feature of the AD16 that I would also address is the lack of a back stay. It seems to me that in exposed or offshore locations, pitch poling could be a relative risk that would be mitigated by a back stay and therefore also a change in the sail plan.

Designer comments are requested.

Kind regards



User avatar
jacquesmm
Site Admin
Site Admin
Posts: 25851
Joined: Wed Aug 14, 2002 1:00 am
Location: Florida USA
Contact:

Re: VG 20 or VG 23, and AD16

Post by jacquesmm » Tue Aug 01, 2017 10:10 am

I somewhere have the stability curves for all those boats but if you are talking about pitchpoling, you may be looking at the wrong boats. :D
Those small boats are not designed to cross an ocean or go far offshore.
For AD's, I count very much on self righting due to the high freeboard: those boats would be very unstable upside down and if you were rolled, it means waves that will roll you back quickly.
The VG18 and 20 have a higher ballast ratio.
Until I go back in my archive and find the stability curves, please compare to similar boats, you"ll see that those designs are within the norms.
Many small boats 18' or less have rigs without a backstay.
Many large Hunters, up to 40', are also rigged without a backstay and BTW, the absence of a backstay has no influence on pitchpoling.

Lines and offsets: The lines are included, see the stations drawing. I do not show a table of offsets since we do not need it. It is an antiquated method to define a hull shape. Today, most good designers use 3D modeling and extract the values you ask for from that model.
I use Orca3D, see it here:
https://orca3d.com/modules/hydrostatics-and-stability/

I do not do conformity calculations except for professional builders and in that case, there is a fee for it. Most countries do not require it for amateur boat building.
Jacques Mertens - Designer
http://bateau.com

jbro5000
New Poster
New Poster
Posts: 7
Joined: Thu May 11, 2017 11:16 am
Location: Manila

Re: VG 20 or VG 23, and AD16

Post by jbro5000 » Fri Aug 04, 2017 6:40 am

OK thanks, noted.

Amateur boat building is illegal in the Philippines.

I would nevertheless incorporate a back stay as a mitigating measure.

Post Reply

Who is online

Users browsing this forum: No registered users and 2 guests