Reply
 
Thread Tools Display Modes
 
Old 05-08-2013, 02:05 PM   #61
Senior Member
 
deckofficer's Avatar
 
City: Northern California
Country: US
Join Date: Jan 2013
Posts: 409
Tad Roberts,

Solar panels are down to $1 per watt. When I bought mine 25 years ago I paid $5 per watt and they still produce rated output. When you figure just 1500 watts of panels can push a light, efficient hull 65 nm on 5 hours of exposure in a 24 hour run with average speed of 2.7 kt, the math says it will have a quick payback on the added investment. Lets say you used every watt produced by $1500 worth of panels, stored in $5000 worth of lithium cells to power a $2000 motor and controller for propulsion, you would be ahead on savings over diesel fuel in short order. One year, 24,000 nm on solar vs 8000 gallons of diesel at 3 nmpg. I know I picked a very slow cruising speed to make my point (2.7 kt) but as you know, to double your speed in water requires and 8 fold increase in power. So at a more real speed of 5.4 kt, then 12 Kw of panels needed. The Solar 21 crossed the Atlantic with 10 Kw of panels and heavy lead acid AGM batteries with a reported 5.5 kt average.
__________________
Advertisement

__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
deckofficer is offline   Reply With Quote
Old 05-08-2013, 02:06 PM   #62
Guru
 
Join Date: Aug 2012
Posts: 741
The Greenline website uses the term "superdisplacement" for their highly advanced hull design, thereby invoking thoughts of efficiency. One of the models is listed at 22 knots with a pair of diesels. The photo above shows hard chines with flat surfaces aft. Superdisplacement, indeed.
__________________

Underway is offline   Reply With Quote
Old 05-08-2013, 02:25 PM   #63
Guru
 
City: Hotel, CA
Country: Fried
Join Date: Sep 2011
Posts: 8,328
I look forward to seeing what you come up with for that Loop project Tad.
__________________
Craig

It's easier to fool people than to convince them that they've been fooled - Mark Twain
CPseudonym is offline   Reply With Quote
Old 05-08-2013, 02:39 PM   #64
Scraping Paint
 
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
Quote:
Originally Posted by skidgear View Post
The Greenline website uses the term "superdisplacement" ...
Bottoms up!
Attached Images
 
RickB is offline   Reply With Quote
Old 05-08-2013, 02:48 PM   #65
Guru
 
Tad Roberts's Avatar
 
City: Flattop Islands
Country: Canada
Vessel Name: Blackfish
Vessel Model: custom
Join Date: Dec 2012
Posts: 707
Quote:
Originally Posted by Marin View Post
Now I'm sure the boat had to meet whatever stability requirements are set by whatever regulatory agencies set them-- the USCG, I suppose, in the US---
With the exception of pontoon boats, there were and are not currently any stability or capacity standards for pleasure boats over 26' in length in the US.
Tad Roberts is offline   Reply With Quote
Old 05-08-2013, 03:19 PM   #66
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
Quote:
Originally Posted by Tad Roberts View Post
With the exception of pontoon boats, there were and are not currently any stability or capacity standards for pleasure boats over 26' in length in the US.
Thank you for the clarification. I am amazed that there are no standards or requirements for larger boats. Perhaps I am influenced by the industry I work in where you can't change the type of fastener or wire tie used without getting approval from the FAA, JAA, and all the other aviation regulatory agencies around the world.

What is the rationale-- if there is any--- for having standards for boats under 26' feet but not over 26 feet?
Marin is offline   Reply With Quote
Old 05-08-2013, 03:21 PM   #67
Guru
 
Join Date: Aug 2012
Posts: 741
Commercial versus private applications. Careful what you wish for...
Underway is offline   Reply With Quote
Old 05-08-2013, 03:58 PM   #68
Guru
 
Tad Roberts's Avatar
 
City: Flattop Islands
Country: Canada
Vessel Name: Blackfish
Vessel Model: custom
Join Date: Dec 2012
Posts: 707
The Great Circle boat is not yet ready for the light of day. But we have another that may fit the conversation. As there are so many variables I think having a specific boat to consider might help.

This boat is under construction so all data are guesstimates at this point. She is a family weekender for Georgia Strait. Length is 40' overall and waterline. Beam is 8', displacement is 5400 pounds. Power is a 29HP Volvo MD2030 (weight 335LBS) diesel with 2.37:1 reduction turning a 16" by 16" three bladed prop. Construction is 3/4" red-cedar strips sheathed with glass inside and out, the deck and cabin top are foam cored. If the builder can maintain design weight she will manage around 11 knots top speed and cruise in the 8-9 Knot range. 20 US gallons will give her 600 miles at 7.5 knots. At a little over 9 knots she'll burn .54 usg/hr and go 345 miles on 20 usg. That's about a season's usage......

As you can see she is very, very basic to keep weight at the minimum. Her open forward cockpit is an empty well with a hatch access to the fore cabin. Her stateroom under the foredeck is a tunnel with a bunk P&S, nothing else! The deckhouse contains a settee, big dinette which makes a double, galley, helm, and private head against the aft bulkhead. The engine is in a box outside in the cockpit. Solar panels will go on the roof.

Click image for larger version

Name:	B40view01.jpg
Views:	73
Size:	98.1 KB
ID:	19100

So switching her to pure solar, how much does weight go up and range decrease? Besides the fact that here in the PNW (Periodically Not Wet) solar is questionable at best......
Tad Roberts is offline   Reply With Quote
Old 05-08-2013, 04:14 PM   #69
Senior Member
 
deckofficer's Avatar
 
City: Northern California
Country: US
Join Date: Jan 2013
Posts: 409
Tad, that is great efficiency and I agree that the PNW is not too solar suitable. Your kind of range on diesel combined with lack of sunshine for your boating area makes that design a winner. Good luck with it and can you keep us posted on it's development?

BTW since I'm new to the forum, are you THE Tad Roberts of Tad Roberts Yacht Design?
__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
deckofficer is offline   Reply With Quote
Old 05-08-2013, 04:23 PM   #70
Guru
 
Tad Roberts's Avatar
 
City: Flattop Islands
Country: Canada
Vessel Name: Blackfish
Vessel Model: custom
Join Date: Dec 2012
Posts: 707
Quote:
Originally Posted by deckofficer View Post
BTW since I'm new to the forum, are you THE Tad Roberts of Tad Roberts Yacht Design?
apparently........
Tad Roberts is offline   Reply With Quote
Old 05-08-2013, 04:24 PM   #71
Guru
 
City: Hotel, CA
Country: Fried
Join Date: Sep 2011
Posts: 8,328
Although it seems redundant to say Tad, I love the lines of that boat.

You state an 8' beam. Was trailering a consideration in that design? It certainly has the weight right for it if not.
__________________
Craig

It's easier to fool people than to convince them that they've been fooled - Mark Twain
CPseudonym is offline   Reply With Quote
Old 05-08-2013, 04:27 PM   #72
Senior Member
 
deckofficer's Avatar
 
City: Northern California
Country: US
Join Date: Jan 2013
Posts: 409
My guess would be a narrow beam for efficiency.
__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
deckofficer is offline   Reply With Quote
Old 05-08-2013, 04:29 PM   #73
Senior Member
 
deckofficer's Avatar
 
City: Northern California
Country: US
Join Date: Jan 2013
Posts: 409
Tad,

Many years ago during my CMA days I seem to have picked up that on displacement hulls if you double your speed it requires an 8 fold increase in power. Did I remember right, or had it wrong all these years?
__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
deckofficer is offline   Reply With Quote
Old 05-08-2013, 04:34 PM   #74
Guru
 
Tad Roberts's Avatar
 
City: Flattop Islands
Country: Canada
Vessel Name: Blackfish
Vessel Model: custom
Join Date: Dec 2012
Posts: 707
Quote:
Originally Posted by Marin View Post

What is the rationale-- if there is any--- for having standards for boats under 26' feet but not over 26 feet?
Probably someone from the US could answer better than I......But......I'll guess it's a combination of many issues. Smaller boats are more likely to be open (un-decked) and subject to swamping. The crew load is a larger factor in overall loading for a small boat, thus smaller boats are more likely to be overloaded (thus becoming unstable and/or unsafe). And the large boat manufacturers lobby managed to stave off regulation......

With some notable exceptions, stability or lack thereof is not a huge safety issue with US pleasure boats. Sad exceptions are horrors like last years capsize of a 34' powerboat on July 4th (at night) on Oyster Bay NY. Boat was wildly overloaded with 29 people aboard.....
Tad Roberts is offline   Reply With Quote
Old 05-08-2013, 04:42 PM   #75
Guru
 
Tad Roberts's Avatar
 
City: Flattop Islands
Country: Canada
Vessel Name: Blackfish
Vessel Model: custom
Join Date: Dec 2012
Posts: 707
Quote:
Originally Posted by CPseudonym View Post
Although it seems redundant to say Tad, I love the lines of that boat.

You state an 8' beam. Was trailering a consideration in that design? It certainly has the weight right for it if not.
Thank you for your kind encouragement, it's always welcome

Actually trailering was not a consideration at all. The beam may be 1.5" greater than 8' above waterline midships. The main criteria was to keep the molds and bulkheads (NC cut) to one sheet of plywood.......saving money.....
Tad Roberts is offline   Reply With Quote
Old 05-08-2013, 04:43 PM   #76
Senior Member
 
deckofficer's Avatar
 
City: Northern California
Country: US
Join Date: Jan 2013
Posts: 409
I remember that accident. OK to overload a bit with guests at anchor, a different story when underway. This is a 8500 lb PDQ 36 with a bit of a deck load.
__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
deckofficer is offline   Reply With Quote
Old 05-08-2013, 04:46 PM   #77
Senior Member
 
deckofficer's Avatar
 
City: Northern California
Country: US
Join Date: Jan 2013
Posts: 409
Quote:
Originally Posted by Tad Roberts View Post
Thank you for your kind encouragement, it's always welcome

Actually trailering was not a consideration at all. The beam may be 1.5" greater than 8' above waterline midships. The main criteria was to keep the molds and bulkheads (NC cut) to one sheet of plywood.......saving money.....
So long and lean wasn't part of the equation but rather maximizing material yield?
__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
deckofficer is offline   Reply With Quote
Old 05-08-2013, 04:54 PM   #78
Guru
 
Tad Roberts's Avatar
 
City: Flattop Islands
Country: Canada
Vessel Name: Blackfish
Vessel Model: custom
Join Date: Dec 2012
Posts: 707
Quote:
Originally Posted by deckofficer View Post
Tad,

Many years ago during my CMA days I seem to have picked up that on displacement hulls if you double your speed it requires an 8 fold increase in power. Did I remember right, or had it wrong all these years?
That may hold true for a particular ship type, but resistance is not a linear function. It's a curve that becomes almost vertical at some point (popularly over the S/L 1.34). So the difference will depend on where on the curve you are comparing. For instance just looking at the boat I posted above, the difference in required power between 6 and 12 knots is 13 times as much, from 1.6HP to 21HP (Theoretical).
Tad Roberts is offline   Reply With Quote
Old 05-08-2013, 05:07 PM   #79
Senior Member
 
deckofficer's Avatar
 
City: Northern California
Country: US
Join Date: Jan 2013
Posts: 409
Thanks Tad. I've always used it as a rough rule of thumb. When I come across a new hull design that is touted as efficient, I take its top speed and hp required and start reducing speed to see what speed electric would start to be viable. For example the new Aspen C90 will run 20 kt on 150 hp, so if my rough rule of thumb holds true, then 5 kt would only require 2.5 hp.
__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
deckofficer is offline   Reply With Quote
Old 05-08-2013, 05:12 PM   #80
TF Site Team
 
Larry M's Avatar
 
City: JAX, FL
Country: USA
Vessel Name: Hobo
Vessel Model: Krogen 42-120
Join Date: Nov 2008
Posts: 5,725
Quote:
Originally Posted by deckofficer View Post
... One year, 24,000 nm on solar vs 8000 gallons of diesel at 3 nmpg. I know I picked a very slow cruising speed to make my point (2.7 kt) but as you know, to double your speed in water requires and 8 fold increase in power. So at a more real speed of 5.4 kt, then 12 Kw of panels needed. The Solar 21 crossed the Atlantic with 10 Kw of panels and heavy lead acid AGM batteries with a reported 5.5 kt average.
Bob: 24,000 nm in one year at the speed you mentioned? We cruise full time and in the last 5.5 years we have covered between 2500 to 3000 miles per year. When we cruised on our sailboat (7+ years) we averaged ~6000 miles per year but we were crossing oceans then. I don't think these number are out of line with the average cruiser. I'll be the first to admit though, I'm a better travel than I am a sailor. The boat is the instrument to get us to where we want to go.
__________________

Larry M is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 09:59 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012