DN Specifications

A. Fuselage

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IDNIYRA OFFICIAL SPECIFICATIONS

REVISED MAY 2022
Note: Dimensions are given in inches in the English System (except as noted) and in millimeters (MM) in the metric system.

A. Fuselage English   Metric  
  Max Min Max Min
1. Length overall: 147 141 3733.0 3582.0
2. Beam: 21 ½ 17 ½ 546.0 445.0
3. Thickness of decks and cockpit floor: ¼ 0.118 6.3 3.0
4. Thickness of bottom: ¼ 0.118 6.3 3.0
5. Sides and bulkhead at front of cockpit: 1 5/8 25.4 15.9
6. Intersection of seat back and floor to pivot pin of steering runner: 110 ¼ 98 ¼ 2800.0 2496.0
7. Distance from bow to front of cockpit: 66 54 1676.0 1372.0
8. Stem block length is optional.        
9. Stem width at bow: 3 ¾ 2 95.0 51.0
10. Stern block length is optional.
11. Stern width at stern: 4 1 ¼ 101.0 31.0
12. Seat backs shall be raked aft at an angle of 45 degrees plus or minus 10 degrees. They may be hinged for access to stowage compartment.
13. Seat back shall be flat, measuring 11’’ (280. mm) in length at the center line, no maximum height, the crown on top of seat must be a minimum of 2’’ (50.8 mm) radius with minimum seat width 4’’.
14. Depth of side panel at each fuselage station shall not be less than heights in the following table:
Layout of Side Panel/Minimum Side Heights
Position along side panel starting at bow Minimum Side Panel Height
Inches mm Inches mm
2 51 2-9/16 65
12 305 3-7/8 98
24 610 5-1/16 129
36 914 6-1/16 154
48 1220 6-7/16 164
60 1524 6-5/8 168
72 1829 6-5/8 168
84 2134 6-1/2 165
96 2438 6-3/16 157
108 2743 5-9/16 141
120 3048 4-5/8 117
132 3353 3-3/8 86
Last station: 2 inches (51mm) from stern 2 51

 

 

15. Side Panels

  • a. Bottom heights of side panels shall not exceed a maximum of 1’’ (25.4 mm) above zero line and/or a maximum of 1/2’’ (12.7 mm) below zero line. Zero line shall be established by a straight line tangent to stem and stern on bottom.
  • b. Maximum height of side panels above zero line may be 8-1/2’’ (215.9 mm) including deck and bottom covering. All heights of side panels shall be proportional to height as shown in “Layout of Side Panel”. The top edge of the side panel may not be concave at any point along its length.

16. Hull outer surface cross section must be rectangular ± 2 degrees from a point 6’’ (153. mm) from the bow to a point 6’’ (153. mm) from the stern. Exclusions: Cockpit surface, seat back, knees, rails, fittings, and hardware. A maximum 1/4’’ (6.3 mm) radius is allowed on the corners of the fuselage where the deck / bottom and side panels intersect. Concavities in the deck are not permitted.

17. Cockpit floor shall be installed as shown in plans, cockpit bottom must be on top of listings. The total thickness of the cockpit floor including the bottom skin and cockpit floor skin must be a minimum of 5/8” (15.9mm). A minimum of 2 knees must be installed.

18. Structural members such as longerons, stringers, knees, listings, bulkheads, bottom, deck, etc. may be added. Deck may not protrude more than 3’’ (76mm) into the cockpit from the bulkhead at the front of the cockpit.

19. Design of the internal structure of the fuselage is optional.

20. Grab rails may be installed on the inside and/or outside vertical surface of the side panels. They may not extend beyond 8’’ (203. mm) from either end of cockpit. Rails shall not exceed 1’’ (25.4 mm) in depth or width. Rails are exempted from fuselage measurements.21. Steering post and chock may be inclined in the vertical plane of symmetry.

22. Steering shall be accomplished by means of a tiller. Tiller may be of any length or shape but may not be more than 8 inches (203 mm) wide. “ Material is optional and may include para-aramid fabric.

23. Either steering rods, cables, or a single push pull link shall be used and shall be positioned beneath the fuselage as shown on the Official Plans.

24. Ballast, if used, shall be permanently installed.

25. Fuselage shall be constructed of wood only, except as provided in specification A.31. (Sitka spruce is most popular). Fiberglass may be added for reinforcement only. See Interpretations – General.

26. Sides shall not be hollow.

27. Minimum weight shall be 46 lbs. (21 kg) with all hardware, blocks, and tiller.

28. A full bulkhead must be installed at the front of cockpit.

29. Horizontal distance from the Bow to the pivot point of the front runner:

English   Metric  
Max Min Max Min
7 3 178 76

30. National letter and sail number is optional and may be affixed to each side of the fuselage below the mast stepping point. If a national sail letter and sail number are affixed to the fuselage, the color shall contrast with the fuselage and the recommended size of each letter and number is 5.5 inches (140 mm) high and 0.79 inches (20 mm) wide. National letters and sail numbers affixed to the fuselage should match those on the sails, except for boats loaned or chartered for a regatta.

31. Foam is an allowed material for the internal construction of the fuselage, reference A.19

See Fuselage interpretations below.

INTERPRETATIONS OF THE OFFICIAL SPECIFICATIONS BY THE TECHNICAL COMMITTEE

Effective May 31, 2020

GENERAL

12/16/2017: Material – Kevlar cloth may not be used in DN constructions with the exception of the tiller, reference Spec A22.

11/24/87: All DN racing equipment must be in accordance with the DN specifications. Whether or not he reveals the structural components of his equipment, the competitor is responsible for making sure his equipment is in compliance with the DN specifications.

3/18/89: Specification A.25. specifies wood in the fuselage with fiberglass added for reinforcement only. Carbon fibers and other materials are not allowed. Specification B.7. specifies wood in the runner plank and fiberglass may be added. Carbon fibers and other materials are not allowed. Specification D.8. specifies the boom will be of wood or aluminum. Carbon fibers and other materials are not allowed.

A. Fuselage
11/24/56: Members (such as fiberglass, stringers, knees and longer stem blocks), may be added after the specifications have been complied with and providing the addition does not exceed the specifications.

11/10/73: Sides must be solid wood.

9/23/82: Fiberglass may be used between laminations of the side panels for reinforcing.

10/17/83 amended 1/19/2013: With respect to the hull side profile: the term proportional” will be defined as a “smooth curve” without reversing the line abruptly. Concave sections will not be allowed. A side profile is acceptable if there are no concavities, the maximum panel height is not exceeded, and the height at each station is not less than the specified minimum. Reference specifications A14 and A15.

3/18/89: The tiller post must be located forward of the bulkhead at the front of the cockpit. The tiller must be attached to the post at a point above the level of the deck. The sheet block that is installed on the tiller post (Specification H.17) must be attached to the tiller post at a point higher than the point of attachment of the tiller

3/26/89: Definition of deck as used in A.18: the deck is the covering on the top of the fuselage in the areas foreword and aft of the cockpit. The deck extends uninterrupted from the outside of the side panel on one side to the outside of the side panel on the other side.

4/15/91: In A.14, the depth of the side panels does not include the deck and bottom.

7/01/92: The bulkhead at the front of the cockpit must be solid wood and may not be hollow.

7/01/92: To comply with A.9, the forward most part of the stem or a portion of the stem if it is vertical, must comply with the minimum and maximum dimensions allowed.

12/15/2011: Rigging and fittings are not part of the integral structure or reinforcement of the fuselage and may be attached to the fuselage by mechanical fastenings and/or adhesives. The materials allowed in the rigging and fittings attached to the fuselage are optional providing they comply with the Specifications in sections H. and I. and the Interpretations in sections General, H., and I. The dimension and location of the rigging and fittings must comply with the Specifications in Sections A., H., and I. and the Interpretations in sections General, A., H., and I.

12/01/2012: In the side panels it is not allowed to use engineered or composite materials formed by binding particles or loose fibers of wood and fiberglass.

02/15/2013: The bow tang should not be included when measuring the length of the fuselage, specification A.1., and the distance from the bow to the front of the cockpit, specification A.7.