Reply
 
Thread Tools Search this Thread Display Modes
 
Old 11-19-2019, 10:33 AM   #1
Senior Member
 
Turner's Avatar
 
City: Biloxi
Join Date: Mar 2017
Posts: 160
Towing a tender

Question, we have a 30 ft Sundowner trawler with a new 50 hp Beta Marine engine, we are planning some 8hr - 12hr cruises towing a 16 ft Key West tender, approx weight 900 lbs. What concerns should we have regarding fuel consumption and speed. Will a tender that size creatate significant negative effects?
Turner is offline   Reply With Quote
Old 11-19-2019, 11:13 AM   #2
Guru
 
C lectric's Avatar
 
City: Gibsons, B.C., Canada
Vessel Name: Island Pride
Vessel Model: Palmer 32'
Join Date: Oct 2007
Posts: 4,409
I do know your boat but not your dinghy.
I doubt you will get a definitive answer on increased fuel use since the only ones who will know are those already doing EXACTLY the same using exactly the same setup.

Fuel use will go up and your boat speed down a bit at the same engine rpm, towing vs not towing, I would GUESS 10-15%.
The dingbat will add drag.
That increase in fuel use should not be a deal breaker unless you are planning to push the main boats tankage range.

I know many people who tow dinghys successfully with boat/dinghy ratios similar to what you are proposing and although the dinghy can be a problem sometimes they would not be without it.

But I cannot answer your question any more precisely.
C lectric is offline   Reply With Quote
Old 11-19-2019, 11:30 AM   #3
Senior Member
 
lipets's Avatar
 
City: FL
Vessel Model: Benneteau Swift 42
Join Date: Jun 2019
Posts: 469
You also can hold the tow line at different lengths to find the least resistance and tied it off
lipets is offline   Reply With Quote
Old 11-19-2019, 12:38 PM   #4
Valued Technical Contributor
 
DavidM's Avatar
 
City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,775
As noted above about adjusting the tow line length, dinghy towing can have very little effect on fuel usage of the towing boat. Even in the worse configuration, with the dinghy always pointed bow up into the boat's stern wave, the effect on fuel consumption is mostly unmeasurable.

Here is some physics and math: Worst I have seen is a tension of about 100 lbs on the tow rope at 7 kts. 7 kts is about 12 ft per second. So that is 100*12= 1200 ft lbs/second or about 2.2 hp. Since it takes about a gallon per hour to make 18 hp for most diesels that is 2.2/18=.12 gph of diesel. You won't begin to notice that little diesel usage and it will be much less than that if you adjust the tow rope length correctly.

David
DavidM is offline   Reply With Quote
Old 11-19-2019, 01:11 PM   #5
TF Site Team
 
Larry M's Avatar
 
City: Jacksonville
Join Date: Nov 2008
Posts: 11,670
We towed a 18.5’ Key West, center console two years ago from the Berry's to Vero Beach via Lake Worth. No problems towing. The tow line was ~75 feet plus the length of the bridle that probably added another 20'. Once in the ICW, we shortened the tow line to ~50’.

I’d think about doing it again. We’re full displacement and couldn't go fast enough to get the Key West on/out of the water and to maintain 6.5-7 knots our fuel burn went up 25-50%. It was like pulling a plow. Docking with just Lena and I was also a bit of a challenge.

It was nice in the Berry's though, the additional mobility/access to other (skinny) waters without having to move Hobo was pretty cool.
Attached Thumbnails
DD7A6503-2E6C-4571-959D-DDE2DEC66E29.jpg  
Larry M is offline   Reply With Quote
Old 11-19-2019, 01:39 PM   #6
Valued Technical Contributor
 
DavidM's Avatar
 
City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,775
An 18-1/2' center console is more than a dinghy. It will weigh 1,500-2,000 lbs which is 5-10 times more than a 10' RIB with a 10 hp O/B on it. That will increase its towing force to as much as 1,000 lbs which will definitely result in a measurable fuel consumption increase.


But I agree, having such a tender would be nice in the Bahamas and may be worth the extra fuel consumed.


David
DavidM is offline   Reply With Quote
Old 11-19-2019, 02:31 PM   #7
TF Site Team
 
Larry M's Avatar
 
City: Jacksonville
Join Date: Nov 2008
Posts: 11,670
Joe: Can you try towing the Key West locally to give it a try? What didn’t help my situation was the Key West was half full of fuel plus fishing rods, anchor, life jackets, boat toys, lines, tools, etc. The weight adds up quick.
Larry M is offline   Reply With Quote
Old 11-19-2019, 04:33 PM   #8
Guru
 
Fletcher500's Avatar
 
City: San Diego
Vessel Model: Helmsman 4304
Join Date: May 2016
Posts: 2,005
I spent the Summer towing a hard shell Bullfrog 11 ft with a 30Hp. I used a bridal for the longer runs, and a single line on a side cleat when in protected waters. I would make minor adjustments to the tow bridal length as needed, but come night fall didn’t touch it and just checked it was still back there. Largest swell we hit while towing was 4 to 5 ft on 6 seconds. I have always carried a small Dinghy before, so towing this past Summer was a new gig. Learned a lot, and got a nice cut on my finger during the process...another story. This is smaller than a center console, but my unscientific feeling was that I was losing about a .5 kn of speed when towing offshore, especially with any chop or swell.
Fletcher500 is offline   Reply With Quote
Old 12-08-2019, 08:18 AM   #9
Senior Member
 
Turner's Avatar
 
City: Biloxi
Join Date: Mar 2017
Posts: 160
An additional question on towing a tender which I asked before but posted it on a wrong thread. Anyone have issues with the inconsiderate people on large boats fly past creating huge wakes not thinking a thing about it! I'm curious if any of you have had your tender sink or damaged by large wakes? I'm thinking the shorter the line the more control we will have over the situation. Any thoughts?
Turner is offline   Reply With Quote
Old 12-08-2019, 08:22 AM   #10
Guru
 
psneeld's Avatar
 
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,119
Something to be concerned about, 14 years as an assistance tower and many a time wakes and boaters not paying attention threatened tows.
psneeld is offline   Reply With Quote
Old 12-08-2019, 09:23 AM   #11
Guru
 
City: Northport
Join Date: Aug 2015
Posts: 2,046
Quote:
Originally Posted by Turner View Post
An additional question on towing a tender which I asked before but posted it on a wrong thread. Anyone have issues with the inconsiderate people on large boats fly past creating huge wakes not thinking a thing about it! I'm curious if any of you have had your tender sink or damaged by large wakes? I'm thinking the shorter the line the more control we will have over the situation. Any thoughts?
A good question....
This is why we never towed dinghies less than about 16'.
And the ones we did tow were RIBS that had self bailing hulls and were towed with a bow up attitude.
In the same category of concerns was heavier seas and longer heavy rains.
smitty477 is offline   Reply With Quote
Old 12-08-2019, 09:35 AM   #12
Guru
 
Fletcher500's Avatar
 
City: San Diego
Vessel Model: Helmsman 4304
Join Date: May 2016
Posts: 2,005
A large boat wake was how I got the cut on my finger as noted in my earlier post. I was in the middle of the bay, close tied the tender to get inside to make an adjustment. A big boat came by and I went on a bucking bull ride. The Dink slammed on top of the swim step and took a chunk of FG out. The next wake I was aiming for the side of the boat, and thought I would take a piece of FG out off the side of the boat. Lesson, secure everything properly and don’t get inside the Dink when in the Harbor, and not in the ocean unless absolutely necessary. Pay attention to your tow line and lengths when running in congested areas in mooring fields etc. I put a little reminder note next to the helm: “Towing, close haul when needed”. Don’t rely on your Nephew to tie it off the Dinghy prior to dropping the mooring can hawsers on the bigger boat without checking he did it properly. I could go on.
Fletcher500 is offline   Reply With Quote
Old 12-08-2019, 11:07 AM   #13
Veteran Member
 
City: Arnaudville, Louisiana
Vessel Name: Anticipation
Vessel Model: Mainship 390
Join Date: Apr 2012
Posts: 33
We towed a 19 Grady behind our Mainship 390 while replacing our dinghy. There was no noticeable effect and it was nice to have it once we reached our destination.
gotfw is offline   Reply With Quote
Old 12-08-2019, 12:21 PM   #14
Senior Member
 
EngNate's Avatar
 
City: Bella Bella
Vessel Name: Tenacious
Vessel Model: Uniflite 31 FB Sedan
Join Date: Feb 2019
Posts: 312
15-20% will be right in there. That's what I observe with my rig, more like 15 I'm inclined to say. 31 towing a 17' center console, big difference is I'm 210 hp. At my standard cruising rpm it slows me down 15% with about the same fuel burn.
__________________
Experience develops good judgement, bad judgement develops experience
EngNate is offline   Reply With Quote
Old 12-08-2019, 12:45 PM   #15
Guru
 
Pete Meisinger's Avatar
 
City: Oconto, WI
Vessel Name: Best Alternative
Vessel Model: 36 Albin Aft Cabin
Join Date: Oct 2012
Posts: 3,145
I'm not a big fan of towing a tender. I had a couple poor experiences, one from trying to go to quickly, one from a poor towing bridle and once from a combination of things. Much rather go through a hassle and get the dink out of the water (Not perfect either).

But.. towing a 900 # 16 foot tender with a 50 hp main engine ? I don't think you should do it. How did you end up with a 30 foot boat with such low hp? I think the combined weight of your vessel and the tender exceeds the capacity of that engine. Not just weight but combined "drag".

I suspect some of our math experts will crunch the numbers and share the results with us.

pete
Pete Meisinger is offline   Reply With Quote
Old 12-08-2019, 01:33 PM   #16
Guru
 
psneeld's Avatar
 
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,119
50hp is plenty of hp to tow...as long speed isn't required....or sea conditions aren't survival conditions.

Everyone should be prepared to tow as sometimes ones davit (s) may not be working as advertised.
psneeld is offline   Reply With Quote
Old 12-08-2019, 01:53 PM   #17
Guru
 
caltexflanc's Avatar
 
City: North Carolina for now
Join Date: Aug 2011
Posts: 6,348
I'd be very wary about towing a lightweight inflatable boat. Besides, isn't a main point of having a lightweight dinghy to have something easy to carry on board?

We towed our 13' Boston Whaler in all kinds of natural and man-made sea conditions. It took them all with aplomb.
__________________
George

"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
caltexflanc is offline   Reply With Quote
Old 12-08-2019, 02:32 PM   #18
Guru
 
psneeld's Avatar
 
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,119
I would much rather tow an inflatable under normal conditions than a small hard skiff.

High winds and all bets are off, probably including small skiffs anyway.
psneeld is offline   Reply With Quote
Old 12-08-2019, 03:37 PM   #19
Art
Guru
 
Art's Avatar
 
City: SF Bay Area
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 12,569
We towed our 13' Boston Whaler in all kinds of natural and man-made sea conditions. It took them all with aplomb.[/QUOTE]

Summers throughout 1960's my family often traveled off shore NY to Maine, and in between. Had 13'3" Boston Whaler with 40 hp johnson either in tow aback our 38' SD sport fisher sedan... or... I'd take off in the Whaler and meet family at predetermined next port of call. During both types of phases of tender included travel, we have been in some pretty nasty seas [close duration big rollers from off shore storm with strong wind chop]; easily successful results occurred always of tender accompaniment.

Currently, in SF Delta fresh waters [usually very calm conditions], I tow a 14'8" Crestliner "Stinger" with 50 hp Johnson. The secret is to know how long the tow line should be in coordination with tow-boat's wake configuration as well as sea conditions. Always best to have fairly easy way to modify tow line length. For inner harbor tow; close to transom or side tie works well. If you go close to transom be sure you have appropriate fender [or rub rail] protections in place - so the tender does not put dents into tow boat transom and tow boat's swimstep does not damage [mark up] the tender's hull.

I would not like to do the 14'8" Crestliner in similar tow conditions as mentioned above during the 60's. Boston Whaler 13'3" was a joy to do it in all tow conditions. Off Jones beach LI, NY I had that Whaler in some really rough breakers. Yeah... I was young and a little too brave back then in my teens!

GO Whalers!!
Art is offline   Reply With Quote
Old 12-08-2019, 03:47 PM   #20
Guru
 
psneeld's Avatar
 
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,119
Mostly a name, not a fact.

They do have some strong points, but brand allegiance is way beyond reality in my professional boating experience.
psneeld is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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


» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 09:54 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012