Doug Lord
Flight Ready
- Joined
- May 26, 2009
- Posts
- 16,679
- Reaction score
- 354
- Location
- Cocoa, Florida
I'm bogged down in the Real World so have not been able to work much on the model-that should change before long. Here is a summary of the model so far and my thoughts about it:
A while back, I designed and built unique production RC sailboats-which I designed and built the tooling for. I'm damn good at building and finishing plugs to a high standard so that an extremely high quality mold can be built. But this is different-and I'm not good at building one offs-or should I say they have been a real pain in the past to finish cosmetically to a level I'm satisfied with while at the same time maintaining a one-off weight budget.
I played around with the numbers on this one so that I'd get a model that would give good results in testing while allowing me a weight budget that I hope I can live with while having an excellent finish by the time I'm ready for RC testing. Again, the main hull for this model is scaled down from a full size boat that is to be the Trapwing prototype(Design Challenge thread in "Sailboats") with some mods.
--------------------
Self-Righting Trimaran-Model Specifications
--
The model is scaled down to the following dimensions(reference the full size dimensions in post #1 of this thread) / weight will be carefully and precisely scaled down. Scale 1'= 3.375" :
1) LOA-5' (60.75")
2) Beam- 6'
3) SA 3077sq.in( 21.4 sq.ft.)(tested sail area will vary a lot)
Target Weights :
1) Main hull = 3.858lb
2) Amas(for both)=1.25lb
3) Mast and Sails =1.05lb
4) 2 "curved pieces"(ama extension)=1.25lb
5) 2 cross arms = .74lb 1.1" OD CST carbon
6) 2 foilsets = .74lb
7) "crew" = 3.9lb
8) Ballast = 3.9lb
All up---16.688lb
Note:
a. leeway in these targets is given by the "crew" weight which can be made up of RC equipment, battery etc as long as CG is in the right place for the "crew".
b. For both model and full size pitchpole* RM ,keel alone, is 1.6 times HM for rig,incl sail. RM including buoyancy due to dihedral at capsize is 5.87 times HM for rig including sail. Keel will not ever act alone.......Cross arm dihedral will be adjustable for testing on model.
c. The mast weight based on the Fiberform Tornado section multiplied by 1.27 to account for greater RM of the 18 tri and then scaled accordingly.
d. Main on model will not use full battens since they are very difficult to make work right in small scale. On the other hand, if my sailmaker thinks he can do it since this is, after all, a 20sq.ft. sail I'm open to change. In either case the main planform will be nearly rectangular....
updated 1/10/11---Corrected for new length of 60.75" which allows one foot to equal 3.375"
e. The ama reflects a full size ama+ curved piece* with a total buoyancy of 657lb. Boat all up=750lb.
f.** curved piece is integral to the ama and critical for the self-righting capability of the boat. The ama for the model will be a "normal" high L/B hull with the exception of the "curved piece". A planing ama may also be tested.
g. The model will be sailed using foils for foil assist and flying.
-- "self-righting" in the context of this concept means that the boat will right itself automatically with no intervention from the crew except to ease the sheets.
h. model designed to take off(lift main hull) in about a 5mph wind(as is fullsize) and will use the performance info from the F3 model I designed and built in the mid nineties-it became the worlds first production RC foiler,so:
--SRT model mainfoil area= 68 sq.in.
-- rudder foil= 34 sq.in
-- ama foil/ full flying= 11 sq.in----Foil assist approx 8 sq.in.
-- For full size reference: this foil area is about 10% more than a Rave foiler but the system is entirely different and takes off MUCH earlier than a Rave. In addition, the main foils of the Rave continue to load up as the wind increases while the mainfoil of the MPX concept unloads the faster it goes(with standard crew and ballast) The model will takeoff in about the same wind as the F3(5mph). On the MPX concept the ama foil will eventually support the max weight of the boat with main and rudder foils mostly unloaded.
*pitchpole=boat floating bow down with tip of mast touching water. It is unstable like this(theoretically) and will likely roll to one side accelerating automatic righting process.
** see last picture below for "curved piece" that connects ama for the MPX to the cross arms. Same thing will be used on this boat though the ama is entirely different.
++++++++++++++++++++++++++++++++++++++++++++++++++++
Self-Righting Trimaran (SRT)Full Size Specifications
Length: 18' / 5.49m
Beam: 22' / 6.7m (foldable for trailering)
Ama LOA: 10'
100% ama buoyancy: 337lb.
Ama attachment(curved piece ) buoyancy: 320lb
Total Buoyancy for ama + curved piece attachment: 657lb
Draft w/boards Up: 6.4"
Draft, daggerkeel down: 4' 8"
Mast Length: 28' / 8.3mm
Sail Area:
--284 sq.ft. upwind SA
--575 ft2 / 53.4 m2 downwind SA
Total Boat Weight incl. ballast and crew : 750 lbs
Crew weight: wide range-for these numbers 175lb.
Ballast: (at the juncture of the daggerboard and main foil)- 175lb.
Boat weight minus crew and ballast: 400lb
=====================
COMPARITIVE RATIOS:
Bruce Number: SRT=1.86 F18=1.66
SA/WS:
-- not flying-SRT=5.73/1 F18=4.77/1
-- flying main hull-SRT=11.14/1 F18(flying one hull)=6.03/1
SA/D: SRT=55 F18=44.16
W/SA-smaller better): SRT=2.64 F18=3.29
===============
Click on image/ patterns for model hull sections are right side up(!). Because of the hull shape it is convenient to build the model right side up and then remove it from the station extensions. See modified sections below:
-------------
A while back, I designed and built unique production RC sailboats-which I designed and built the tooling for. I'm damn good at building and finishing plugs to a high standard so that an extremely high quality mold can be built. But this is different-and I'm not good at building one offs-or should I say they have been a real pain in the past to finish cosmetically to a level I'm satisfied with while at the same time maintaining a one-off weight budget.
I played around with the numbers on this one so that I'd get a model that would give good results in testing while allowing me a weight budget that I hope I can live with while having an excellent finish by the time I'm ready for RC testing. Again, the main hull for this model is scaled down from a full size boat that is to be the Trapwing prototype(Design Challenge thread in "Sailboats") with some mods.
--------------------
Self-Righting Trimaran-Model Specifications
--
The model is scaled down to the following dimensions(reference the full size dimensions in post #1 of this thread) / weight will be carefully and precisely scaled down. Scale 1'= 3.375" :
1) LOA-5' (60.75")
2) Beam- 6'
3) SA 3077sq.in( 21.4 sq.ft.)(tested sail area will vary a lot)
Target Weights :
1) Main hull = 3.858lb
2) Amas(for both)=1.25lb
3) Mast and Sails =1.05lb
4) 2 "curved pieces"(ama extension)=1.25lb
5) 2 cross arms = .74lb 1.1" OD CST carbon
6) 2 foilsets = .74lb
7) "crew" = 3.9lb
8) Ballast = 3.9lb
All up---16.688lb
Note:
a. leeway in these targets is given by the "crew" weight which can be made up of RC equipment, battery etc as long as CG is in the right place for the "crew".
b. For both model and full size pitchpole* RM ,keel alone, is 1.6 times HM for rig,incl sail. RM including buoyancy due to dihedral at capsize is 5.87 times HM for rig including sail. Keel will not ever act alone.......Cross arm dihedral will be adjustable for testing on model.
c. The mast weight based on the Fiberform Tornado section multiplied by 1.27 to account for greater RM of the 18 tri and then scaled accordingly.
d. Main on model will not use full battens since they are very difficult to make work right in small scale. On the other hand, if my sailmaker thinks he can do it since this is, after all, a 20sq.ft. sail I'm open to change. In either case the main planform will be nearly rectangular....
updated 1/10/11---Corrected for new length of 60.75" which allows one foot to equal 3.375"
e. The ama reflects a full size ama+ curved piece* with a total buoyancy of 657lb. Boat all up=750lb.
f.** curved piece is integral to the ama and critical for the self-righting capability of the boat. The ama for the model will be a "normal" high L/B hull with the exception of the "curved piece". A planing ama may also be tested.
g. The model will be sailed using foils for foil assist and flying.
-- "self-righting" in the context of this concept means that the boat will right itself automatically with no intervention from the crew except to ease the sheets.
h. model designed to take off(lift main hull) in about a 5mph wind(as is fullsize) and will use the performance info from the F3 model I designed and built in the mid nineties-it became the worlds first production RC foiler,so:
--SRT model mainfoil area= 68 sq.in.
-- rudder foil= 34 sq.in
-- ama foil/ full flying= 11 sq.in----Foil assist approx 8 sq.in.
-- For full size reference: this foil area is about 10% more than a Rave foiler but the system is entirely different and takes off MUCH earlier than a Rave. In addition, the main foils of the Rave continue to load up as the wind increases while the mainfoil of the MPX concept unloads the faster it goes(with standard crew and ballast) The model will takeoff in about the same wind as the F3(5mph). On the MPX concept the ama foil will eventually support the max weight of the boat with main and rudder foils mostly unloaded.
*pitchpole=boat floating bow down with tip of mast touching water. It is unstable like this(theoretically) and will likely roll to one side accelerating automatic righting process.
** see last picture below for "curved piece" that connects ama for the MPX to the cross arms. Same thing will be used on this boat though the ama is entirely different.
++++++++++++++++++++++++++++++++++++++++++++++++++++
Self-Righting Trimaran (SRT)Full Size Specifications
Length: 18' / 5.49m
Beam: 22' / 6.7m (foldable for trailering)
Ama LOA: 10'
100% ama buoyancy: 337lb.
Ama attachment(curved piece ) buoyancy: 320lb
Total Buoyancy for ama + curved piece attachment: 657lb
Draft w/boards Up: 6.4"
Draft, daggerkeel down: 4' 8"
Mast Length: 28' / 8.3mm
Sail Area:
--284 sq.ft. upwind SA
--575 ft2 / 53.4 m2 downwind SA
Total Boat Weight incl. ballast and crew : 750 lbs
Crew weight: wide range-for these numbers 175lb.
Ballast: (at the juncture of the daggerboard and main foil)- 175lb.
Boat weight minus crew and ballast: 400lb
=====================
COMPARITIVE RATIOS:
Bruce Number: SRT=1.86 F18=1.66
SA/WS:
-- not flying-SRT=5.73/1 F18=4.77/1
-- flying main hull-SRT=11.14/1 F18(flying one hull)=6.03/1
SA/D: SRT=55 F18=44.16
W/SA-smaller better): SRT=2.64 F18=3.29
===============
Click on image/ patterns for model hull sections are right side up(!). Because of the hull shape it is convenient to build the model right side up and then remove it from the station extensions. See modified sections below:
-------------
Attachments
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I really want to see physical progress! I've seen the pictures a hundred times, like most folks I want to see something new, forward movement, concrete progress.
