2006 Schoolner Project

[RHough]

Thanks to help from the fine folk here I'm closer to a final design for my Hot Rod Schooner.

Phil Bolger's Light Schooner is the inspiration. He called it the Light Scooner when the plans were first drawn.

Since I've had to take myself to school to finalize the design I'm calling mine a Schoolner

Basic stats are:
~ 23-6 LOA (3 8ft sections)
~ 5-0 Beam (4 ft at bottom)
~ 5-6 Draft
1100 lb Empty Displacement
210 lb ballast
495 lb Crew (3)
1595 Lb Loaded Displacement
19% Ballast/Displacement (light)
64% Ballast/Displacement w/crew
~ 21-6 LWL
309 ft^2 Upwind Sail Area
46.4 SA/D (light)
51.4 L/D
SCP = 15% of loaded displacement at 10-15 degrees heel
140+ degrees range of positive stability
Self righting from masthead in water with 100 lbs at masthead.

She'll be fully powered up in about 12 knots True (at max CL) and able to carry all working sail to about 25 knots (at max L/D)

At less that 5 degrees heel she has the SCP to plane off the wind (11%).

My target is the "Rocket 22"
21-6 LWL
1600 lb Displacement
385 ft^2 Upwind Area
9-6 Beam
40 SA/D
92 D/L

I'm hoping to beat Donny Martin's re-work of Gary Mull's Pocket Rocket with my re-work of Bolger's Light Schooner. My home built $4,000 plywood boat vs his $40,000 composite sport boat.

My thanks again to the people here that have answered questions and pointed me to reference materials that have allowed me to get this far.

When I have the lines a bit more firmed up (I'm working on keeping the bow up when off the wind) I'll post them. I hope that the professionals here won't die laughing.

Looking forward to seeing this boat! It looks to me like loaded(all up) displacement is 1805lb.; is that right?
Just for clarification for those that don't know: Bethwaites formula for SCP is Righting Moment divided by Heeling Arm(CE to CLR) which comes out as a number and his ratio to determine upwind planing performance is SCP divided by Total Weight which is expressed as a percentage. 30% or above signifies upwind planing according to Mr.Bethwaite. See ilustration page178 of "High Performance Sailing". For what it's worth he goes on to talk about three ratios he considers important and say's that SCP divided by Total Weight "governs upwind breeze performance".
How are you dividing your upwind sail area? Will you use a spinnaker ?
Good luck and be sure to post pictures as you get to building and sailing!

[RHough]

Originally Posted by Lorsail

Looking forward to seeing this boat! It looks to me like loaded(all up) displacement is 1805lb.; is that right?

How are you dividing your upwind sail area? Will you use a spinnaker ?
Good luck and be sure to post pictures as you get to building and sailing!

1100 lbs hull, rig, ballast (less sails)
1595 lbs with 3 crew @ 165

Hull sides and side decks 1/4" ply, Hull bottom 1/2" (2 layers 1/4")

Foil will span 5 ft from hull, with ~ 210 lbs lead in the end, or a bulb if that doesn't bring the CG low enough (I need the VCG at -.9 ft to get the RM)

3 working upwind sails,
196 ft^2 Main
77 ft^2 Fore
36 ft^2 Jib

Once I get the rig<>foil lateral balance right, those ratios may change slightly, I have to get the main mast just forward or just aft of the foil if I want to be able to haul the foil up to get the beast on a trailer.

I have what looks like a good gaff sail proportion ratios that puts the gaffs at 45 degrees and the leech of each sail as close to the luff of the following sail as possible with no overlap. All the sails will be almost self tacking.

I'm also playing with rake to keep the main boom out of the water when the boat is powered up on a reach, the main boom is 12-6 at the moment.

I just finished getting some volume forward without killing the lines.

The 3 crew can move forward and to leeward and the boat sits on her upwind lines, when they move aft it looks like they can keep the stem out of the water.

The first off the wind sail will be a staysail off the main mast, that (crossing my fingers) shouldn't move the CE for and aft much.

If I feel the need for more speed I'll add a kite (if I haven't killed myself first).

Now I get it: you're including ballast in the empty displacement...
When do you think you'll start building?

[RHough]

Here are a GIF and a DWG of the BCSchoolner.

Upwind sail area is now 316 sqft

Main 176 ft^2 (55.6% of total)
Fore 86 ft^2 (27.3%)
Jib 54 ft^2 (17.1 %)

SA/D is 47.4

SCP/Displacement is 17% w 3 crew @ 15 deg heel

The images have both the geometric centres of lateral areas shown and the hydrodynamic neutral point and the aerodynamic centres so the relationships can be compared.

The design ends up having negative "lead" when the geo centres are used.

The aero centre is forward of the NP to compensate for the weather helm due to heel and the lateral offset of the centres due to trim. To calculate moment

At this point it looks like the boat will carry less than one degree of rudder trim at her design upwind heel of about 15 deg. The leeway angle should be between 6 and 7 deg. The hull and foils have a calculated L/D of about 16:1

If the true centre of the sail effort is the geo centre, the boat will carry about 4 deg of rudder trim, have a leeway angle of between 5 and 6 degrees and a hydro L/D of over 20:1

The downside is that it looks like the boat won't point higher than 31 deg apparent. The predicted upwind VMG is between 4.1 and 4.4 knots at about 50 deg TWA. I've traded upwind performance for sail carrying power of the wind.

Once I get the panels laid out, I plan to build a sailing model at 2" = 1ft to sort out construction details. If nothing else I'll have a pretty toy to play with.

[Windvang]

Originally Posted by RHough

When I have the lines a bit more firmed up (I'm working on keeping the bow up when off the wind) I'll post them. I hope that the professionals here won't die laughing.

Looks like a fun boat! A little more freeboard at the bow might help preventing her diving. I would recommend drawing the hull in Freeship, easy and you can devellop the plates.