Scantlings

Here are all the scantlings calculations, using MacNaughton's formulas.

Items in red were imported from the design, hydrostatics calculations, stability calculations or some other external source. All other numbers, factors and rations are calculated in this page.

Particulars:

Item	Monohull	Trimaran		Units
		Folded	Open
Name	Apotheosis
Designer	Milton Miller
Latest updated on	October 26th, 2018
LOA: Length Overall	64.916			ft
LWL: Waterline Length	64.9			ft
Maximum Beam	17	21.42	36.99	ft
BWL: Waterline Beam	12.564	19.402	36.402	ft
Draft	3			ft
Depth of Hull (height at midships from sheer down to top of the keel)	10.35			ft
Flare	35.3			%
Displacement (30.73 long tons)	n/a	68835		lbs
Waterplane area	n/a	620.2		ft2
Prismatic coefficient	0.5601	0.5737	0.5488
CWP: Coefficient of Waterline Plane	0.5191	0.562	0.562
ItWP: Transverse moment of inertia of the Waterplane	4799.6	7297.6	14235	ft4
Ballast	None
Watertight compartments	3 (forepeak, accommodations, technical room)

Design ratios:

Item	Monohull	Trimaran
		Folded	Open
D/L: Displacement-Length ratio	113
Hull speed	10.79 kn
Gerr's hull speed	15.31 kn
SLR: Speed to Length Ratio	0.17
L/B: Length/Beam ratio	3.8	3	1.8
LWL/BWL: Waterline Length/Beam ratio	5.2	3.3	1.8
Waterplane loading	n/a	111
MCR: Motion Comfort Ratio	37.4	27.5	13.3
CSF: Capsize Screening Formula	1.66	2.09	3.61
Roll period	2.8	3.01	3.92
SL ratio - Displacement speed @ 145HP	1.34

Structural elements:

Scantling Number		Cube Roots = 10.25
Strip planking	Thickness	1.5 in
	Fiber and epoxi skins (unidirectional fiber cloth)	18.8 oz/yd2
Back bone	Keel	7.2 in
	Stem, sternpost	6.1 in
	Bilge stringers (just one on each side), section area	19.68 in2
Longitudinal members	Stringer core width
	Stringer core height
	Stringer laminate thickness
	Tabbing runout on hull on both sides
	Deck stringer spacing
	Clamp, section area	22.96 in2
	Carlins, section area	11.48 in2
Transversal members	Floors spacing	15.4 in
	Floors siding (thickness)	2.6 in
	Floor molding (lenght of contact along the hull side)	>= 7.7 in (minimum 3.1 in)
	Partner knees (thickness)	4.5 in length of arms >= 12.8 in
	Deck blocking	Length and width 38.4 in Thickness 2.6 in

Wood choices:

Moisture contents	Maximum 12% moisture at the time of application.
Strip planking	Cedar, fir, pine, or Honduras Mahogany or equivalent. Generally any good, strong, even grained, knot free softwood with good gluing characteristics could be used.
Longitudinal members	Longleaf yellow pine, Honduras mahogany, or other strong easily glued wood.
Transverse members	Longleaf yellow pine, Honduras mahogany, iroko, locust, or other strong easily glued wood.
Deck blocking	Longleaf yellow pine, Honduras mahogany, iroko, locust, or other easily glued wood.

Notes:

• The scantings have different formulas for metric and imperial measurements. Here the imperial system was chosen unless specifically noted.
• The keel is sided at the widest point at least twice the molded dimension.
• The bilge stringer will be made of the same sections strips as the planking and added inside of the planking inside the sheathing.
• Stringers should be placed so that they reinforce the point at the turn of the bilge which the hull will rest on if lying on its side in grounding.
• The clamp may taper to 50 percent of its section area at the ends.
• The molding shall be sufficient to allow the arms of the floors to extend along the planking for a minimum distance no less than 5 times the siding. In no case shall the molding be less than 2 times the siding.
• Use monel fasteners.
• Keep mortises to a minimum.
• All structural gluing and lamination done in 2-part epoxy.
• When laying longitudinal strips make sure to stagger the scarf joints so they don't end up next to each other. Also stagger the position of nails.
• When joining strips and planks with scarfs, the slope runs 12 times the width of the timber. The nibs at the ends must be 25% of the timber width. Always use hooked scarfs. In hull sides strips the nibs must be minimal or none at all.
• Laminated keels and other structural elements must use planks about an inch in diameter. To avoid problems with dimensional changes due to variations in moisture contents, 1.5 inches is the maximum thickness for glued planks.
• Every wood piece must be sealed with epoxy at the end of the grain upon purchase and before storage or work. That stops moisture from entering the planks, especially at the ends.
• Every time a hole is drillet through the planks, the inside of the hole must be encapsulated with epoxy resin or filler, and let dry before anything else is placed there.
• Once used in the hull every wood piece must be, sooner or later, encapsulated in epoxy from all sides. The sequence of construction may vary the timing for that procedure, but in no case must any piece of wood be left without encapsulation.
• Always use the smallest timbers that are strong enough to stand up to the required loads.
• Make frames of cold-bent narrow laminates.
• Each bulkhead must sit on a ring frame which acts as a "backing strip" to spread the loads transmitted between the hull the and bulkhead. This adds great strenght to the bulkheads and avoids creasing the hull at the point it meets the bulkhead.
• No more than twice the resin's gel time should be permitted between the application of each subsequent layer. The resin in each subsequent layer then forms cross-linked chemical bonds with the preceding layer.