DN NA Class  

DN America Forums

November 27, 2021, 12:03:20 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Search Login Register  
Pages: [1]
  Print  
Author Topic: Opti Plank  (Read 8889 times)
Bob Gray
Class Member
*
Posts: 194


« on: November 03, 2010, 10:29:44 AM »

    Last night our club built a plank for our Opti. We used the materials suggested by Ken Smith  ie. 1/4" ash and 1/2" redwood for the construction. We didn't have any figures for spring back (the amount of over bend put into the plank while gluing it up to get the desired crown when out ot the jig) so I took the figures for a DN two piece ash plank that was in an old article and did some recalculations that I won't bore you with. To make a long story short for an 8ft DN plank you have to over bend it by 33% ( to get 2" of crown, prebend it to 2.66"). To get a 2" crown in an Opti plank over bend it by  62% or 3.24" to get 2" of crown. It actually worked out to be 59% with the redwood/ash plank but I believe an all ash 2 piece plank would be closer to 62%.
Logged
dnus4925
Newbie

Posts: 35


« Reply #1 on: November 03, 2010, 11:31:49 AM »

I think Paul Goodwin might have a computer progam that will calculate plank crown or spring back.
Logged
Geoff Sobering
Class Officer
***
Posts: 461



WWW
« Reply #2 on: November 03, 2010, 12:44:12 PM »

I think Paul Goodwin might have a computer progam that will calculate plank crown or spring back.

The spreadsheet is at: http://idniyra.org/articles/plank_design.htm
« Last Edit: November 05, 2010, 01:04:43 PM by Geoff Sobering » Logged

Man Why You Even Got to Do a Thing
Bob Gray
Class Member
*
Posts: 194


« Reply #3 on: November 03, 2010, 03:01:31 PM »

   The numbers I got for the DN plank came from an article written by John Jombock back in 1991. The problem here is that it's for an 8 ft. plank. Because values are cubed when you talk about different lengths, a shorter plank will spring back considerably more and a longer plank less. When I figured this out for the Opti I used John's values and took the length difference into consideration.
                                                                      Bob
Logged
Paul Goodwin - US 46
ADMIN

Posts: 100



WWW
« Reply #4 on: November 05, 2010, 11:10:36 AM »

Both articles on the IDNIYRA website (one article by John Jombock (Demystifying Plank Stiffness), and the Plank Stiffness spreadsheet (written by John Bushey) deal only with calculating plank stiffness, not springback.

Bob --- if you have a copy of the article from John Jombock with information on plank springback I could see about adding it to the IDNIYRA articles.
Logged

Paul Goodwin
DN US-46
Bob Gray
Class Member
*
Posts: 194


« Reply #5 on: November 07, 2010, 08:01:57 AM »

  The June 1991 IDNIYRA Newsletter has the springback article by John Jombock.
Logged
Pages: [1]
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1 RC3 | SMF © 2001-2006, Lewis Media Valid XHTML 1.0! Valid CSS!