|
|
01-12-2014, 05:51 AM
|
#1
|
Member
City: Maidstone
Vessel Name: Teaser
Vessel Model: U.S Bertram 42 c
Join Date: Jan 2014
Posts: 5
|
Re-powering Bertram 42
Hi to all, i would be most grateful for your advice.
this boat has twin 430hp,which are dead. i,m trying to redesign the engine size to my particular needs. all i want do is 8 to 12knots for trolling and be fuel efficient at that speed. would this be possible with this hull as its a semi displacement not displacement, i need know this achievable first. this boat is 20 tons and come on the plan at 14knots with the 430,s. but i dont need that it to plan, is this possible to re -power with say 220 hp engines?
|
|
|
01-12-2014, 06:37 AM
|
#2
|
Guru
City: Annapolis
Vessel Name: Ranger
Vessel Model: 58' Sedan Bridge
Join Date: Aug 2013
Posts: 7,088
|
Might help folks answer if you say which model Bertram.
I'd have thought that would more likely be a planing hull, not even semi-displacement. Just a guess, though...
-Chris
__________________
Chesapeake Bay, USA
|
|
|
01-12-2014, 07:44 AM
|
#3
|
Scraping Paint
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
|
He did. Vessel name, vessel model ... you might be familiar with it.
|
|
|
01-12-2014, 07:57 AM
|
#4
|
Guru
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48 (sold)
Join Date: Apr 2008
Posts: 10,186
|
Andrew, two questions, assuming vessel is in UK:
What brand and model are the current engines?
If you repower are the current Euro regs restrictive as to emissions?
On boatdiesel.com there are several UK members that could offer some help also.
|
|
|
01-12-2014, 07:59 AM
|
#5
|
Enigma
City: Slicker?
Join Date: Oct 2007
Posts: 16,566
|
Greetings,
Welcome aboard. Something tells me even 220 HP engines would be to much. I vaguely recall some sort of "ideal" for what a vessel needs to achieve certain speeds. Something like 3HP per ton or 20 HP per gallon of fuel????? Can't remember at all but I'm sure some of the younger folk can enlighten you.
__________________
RTF
|
|
|
01-12-2014, 08:10 AM
|
#6
|
Guru
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48 (sold)
Join Date: Apr 2008
Posts: 10,186
|
Quote:
Originally Posted by RT Firefly
Greetings,
Welcome aboard. Something tells me even 220 HP engines would be to much. I vaguely recall some sort of "ideal" for what a vessel needs to achieve certain speeds. Something like 3HP per ton or 20 HP per gallon of fuel????? Can't remember at all but I'm sure some of the younger folk can enlighten you.
|
RTF - my guess is the 220 HP was suggested by Andrew because it matches the ubiquitous Cummins 6 cylinder reman that is cheap, simple, reliable and available. Just a guess though.
|
|
|
01-12-2014, 08:42 AM
|
#7
|
Guru
City: Fort Myers, FL... Summers in the Great Lakes
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 12,834
|
Andrew, the first thing you will need to do is determine if 20 tons is an actual weight or is the size area of the boat. Boats of this size in the USA are often listed in tons which is area and pounds which is displacement, not sure about the UK. My gut feeling is that 40,000 pounds for a 42' planning hull seams high.
While I think the Cummins 6BT 220s would work, one needs to understand that planning hulls are fuel efficient in displacement (7 to 8 knotts for a 42'), and somewhat efficient on plane (say 14 knotts for this boat), they may be really inefficient between 9 and 13 knotts. Basically most planning hulls start to push a big bow wave when they exceed hull speed and before they attain planning speed. Takes a lot of energy (fuel) to make a big bow wave.
Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
|
|
|
01-12-2014, 09:45 AM
|
#8
|
Guru
City: Miami Florida
Vessel Name: Possum
Vessel Model: Ellis 28
Join Date: Aug 2011
Posts: 5,308
|
My first thought was that you'd ruin the resale value of the boat. My guess is that there are very few people who would want a Bertram that underpowered. Bertram's are built to go fast in rough water. If you were in the US I'd tell you to consider selling the Bertram and get a boat like OC Diver or mine which are designed to travel the in the speed range you're interested in.
|
|
|
01-12-2014, 10:11 AM
|
#9
|
Enigma
City: Slicker?
Join Date: Oct 2007
Posts: 16,566
|
Greetings,
Mr. H. I would think a re-power of any vessel to a performance level not similar to original would impact on resale for sure BUT if the OP already has the vessel and is not terribly concerned about resale, the engine choices are pretty well limitless.
One could even go so far as to suggest running one engine and driving the two props. I think there are transmissions/drive trains that would allow this.
My initial comment was directed to what is the minimum HP necessary to achieve the desired results (12 knots max.) and I still think twin 220 HP is too much.
__________________
RTF
|
|
|
01-12-2014, 10:51 AM
|
#10
|
Guru
City: Sidney BC Canada
Vessel Name: RochePoint
Vessel Model: 1985 Cheer Men PT38 Sedan
Join Date: Apr 2009
Posts: 1,744
|
Quote:
Originally Posted by RT Firefly
One could even go so far as to suggest running one engine and driving the two props. I think there are transmissions/drive trains that would allow this.
|
The boat across the dock from us did exactly that..........
|
|
|
01-12-2014, 11:13 AM
|
#11
|
Guru
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48 (sold)
Join Date: Apr 2008
Posts: 10,186
|
Quote:
Originally Posted by rochepoint
The boat across the dock from us did exactly that..........
|
Is that called the Geared Up system. Philbrooks has been pushing this for a few years. BTW, nice clean install, but where is the exhaust run, RW feed line, fuel lines etc?
|
|
|
01-12-2014, 11:18 AM
|
#12
|
Senior Member
City: Florida USA and Ontario Canada
Vessel Name: anytime
Vessel Model: 2007 Chaparral 270 Signature LOA 29'
Join Date: Jan 2014
Posts: 301
|
Quote:
Originally Posted by O C Diver
While I think the Cummins 6BT 220s would work, one needs to understand that planning hulls are fuel efficient in displacement (7 to 8 knotts for a 42'), and somewhat efficient on plane (say 14 knotts for this boat), they may be really inefficient between 9 and 13 knotts. Basically most planning hulls start to push a big bow wave when they exceed hull speed and before they attain planning speed. Takes a lot of energy (fuel) to make a big bow wave.
|
Just to expand on this ... using the standard 1.34 factor, the displacement hull speed for 42' boat with LWL of 40' (just a guess) is approx. 9.5 knots. Anything more and the hull is being pushed up and over own bow wake and wastes a lot of fuel until it goes on plane (if capable).
Plan for that boat to cruise efficiently up to 9.0-9.5 knots.
__________________
Best ... Richard
|
|
|
01-12-2014, 11:25 AM
|
#13
|
Guru
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48 (sold)
Join Date: Apr 2008
Posts: 10,186
|
Quote:
Originally Posted by Richard W
Just to expand on this ... using the standard 1.34 factor, the displacement hull speed for 42' boat with LWL of 40' (just a guess) is approx. 9.5 knots.
|
I get 8.5 knots @1.34 and using a more efficient 1.2 multiplier about 7.5 knots.
|
|
|
01-12-2014, 11:29 AM
|
#14
|
Member
City: Maidstone
Vessel Name: Teaser
Vessel Model: U.S Bertram 42 c
Join Date: Jan 2014
Posts: 5
|
thanks for all the reply's,
the boat is 1986 Bertram 42c sport fisher.
info i have is 20 ton actual weight and 39,400 lbs displacement.
existing engines are detroits 6v92 tas @430hp,
re powering with big like this size is,nt an option due cost.not worried about resale just cheap reliable running cost at that trolling speed.and enough power in a rough sea!
want it to take Madeira and set up a big game fishing charter.
i know this boat was designed for high speeds cruising at 18 knot and top 30 knots.
My concern is because the hull starts deep v then goes th shallow, with a planning chins that goes down it length,with low power would be fighting to push the vessel up ! and have a strange effect on performance. if it full displacement it would be easier to work out.
|
|
|
01-12-2014, 11:39 AM
|
#15
|
Member
City: Maidstone
Vessel Name: Teaser
Vessel Model: U.S Bertram 42 c
Join Date: Jan 2014
Posts: 5
|
Ted, hit the nail on the head with my concerns
|
|
|
01-12-2014, 11:41 AM
|
#16
|
Guru
City: Sidney BC Canada
Vessel Name: RochePoint
Vessel Model: 1985 Cheer Men PT38 Sedan
Join Date: Apr 2009
Posts: 1,744
|
Quote:
Originally Posted by sunchaser
Is that called the Geared Up system. Philbrooks has been pushing this for a few years. BTW, nice clean install, but where is the exhaust run, RW feed line, fuel lines etc?
|
Yes it is the Geared Up System, the photos are just of the base mechanical installation done at Philbrooks.
|
|
|
01-12-2014, 11:44 AM
|
#17
|
Senior Member
City: Florida USA and Ontario Canada
Vessel Name: anytime
Vessel Model: 2007 Chaparral 270 Signature LOA 29'
Join Date: Jan 2014
Posts: 301
|
Quote:
Originally Posted by Andrew 72
My concern is because the hull starts deep v then goes th shallow, with a planning chins that goes down it length,with low power would be fighting to push the vessel up ! and have a strange effect on performance. if it full displacement it would be easier to work out.
|
My pocket express cruiser with modified-V planing hull and LWL of around 25' cruises efficiently up to 7 knots (exactly as the formula says).
The hull does not track well in the displacement mode as it is a modified-V hull ... or ... a modified flat bottom hull ... pick your poison ...
__________________
Best ... Richard
|
|
|
01-12-2014, 12:30 PM
|
#18
|
Guru
City: Pender Harbour, BC
Vessel Name: Gwaii Haanas
Vessel Model: Custom Aluminum 52
Join Date: Sep 2013
Posts: 3,791
|
I thought the idea behind a sport fisherman was to go like hell to the fish, spend the time fishing, not travelling, catch some fish and then zoom back to the marina to display the corpses? Isn't travelling at trawler speed a contradiction for a fishing charter?
|
|
|
01-12-2014, 12:31 PM
|
#19
|
Senior Member
Join Date: Oct 2007
Posts: 323
|
Quote:
Originally Posted by Andrew 72
thanks for all the reply's,
the boat is 1986 Bertram 42c sport fisher.
info i have is 20 ton actual weight and 39,400 lbs displacement.
existing engines are detroits 6v92 tas @430hp,
re powering with big like this size is,nt an option due cost.not worried about resale just cheap reliable running cost at that trolling speed.and enough power in a rough sea!
want it to take Madeira and set up a big game fishing charter.
i know this boat was designed for high speeds cruising at 18 knot and top 30 knots.
My concern is because the hull starts deep v then goes th shallow, with a planning chins that goes down it length,with low power would be fighting to push the vessel up ! and have a strange effect on performance. if it full displacement it would be easier to work out.
|
not many people who charter a boat don't want a slow one they want to get there to fish,not spend all day getting ther
|
|
|
01-12-2014, 01:23 PM
|
#20
|
Scraping Paint
City: Fort Lauderdale
Vessel Model: CHB 48 Zodiac YL 4.2
Join Date: Oct 2007
Posts: 3,804
|
The OP wrote: " i,m trying to redesign the engine size to my particular needs. all i want do is 8 to 12knots for trolling and be fuel efficient at that speed."
That is the bottom line and if anyone can help him obtain that objective I am sure he will be happy and glad TF could help. I can't find any request for opinions on if the idea is "good" or not.
A string of folks telling him what he wants is not what they want or would do is no help to anyone.
|
|
|
|
|
Thread Tools |
Search this Thread |
|
|
Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
» Trawler Discussions |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|