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Conference unifix::sailing

Title:SAILING
Notice:Please read Note 2.* before participating in this conference
Moderator:UNIFIX::BERENS
Created:Wed Jul 01 1992
Last Modified:Mon Jun 02 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2299
Total number of notes:20724

556.0. "How Fast is your Dinghy" by PUNDIT::MCWILLIAMS () Wed May 13 1987 19:22

    Recently my wife hurt her back, and it looks like rowing the dink
    will be out of the question for her. We have a 7' fiberglass dinghy
    and I am interested in powering it for her this year.
    
    The question I have is how fast does the various motor sizes push
    a dinghy ?
    
    We will be in the Merrimack this year, so we have a considerable
    current to fight (about 3 kts peak in the channel, 2kts peak on the
    sides). What I concerned with is not how fast we would make it to the
    boat, but whether we will make it to the boat. The dinghy we have has a
    2 Hp limitation, and weighs in about 40-50 lbs. Typical load is two
    adults, and gear or about 350 lbs (max). 
    
    I would appreciate your experience as to how big your dinghy/engine
    is and what type of top speed you can make. From this I can decide
    what size motor we need, and whether we need a new dinghy.
    
    /jim

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556.1hmmmmm....PULSAR::BERENSAlan BerensWed May 13 1987 19:4417
Since our dinghy isn't equipped with a knotmeter (an oversight I must 
correct), I don't know how fast it is with our ancient 2 hp Johnson. 
However, the (displacement) hull speed of a 7 foot dinghy is about 3.5 
knots. 

All horsepower isn't equal (in practice). What you really want for a 
slow dinghy is thrust, which means a large, slow turning propeller (ie, 
a Seagull). I've noticed that our dinghy speed under power is about the 
same at half throttle as full throttle, which implies that increasing 
propeller speed is only creating froth, not additional dinghy speed.  
Never having owned a Seagull, I can't comment on their reliability, ease 
of starting, etc. I've heard that owners either swear at them or by 
them. It may depend on your aptitude with mechanical horses. 

Alan


556.2Mighty Merrimac messageIMBACQ::SIEGMANNWed May 13 1987 20:589
    Hi Jim. Most of us on 'the river' use 2 hp (by whatever rating).
    Johnsons, Merks etc seem to do very well, from powering Avons to
    10' pramms. I have seen a couple of 'Mighty-mites' and 'Cruise 'n
    Carrys' of 1-1.5 hp.They don't seem to stay around however. The
    Seagull is nice but heavy and rather expensive (and good target
    for 'borrowing'... The new Merks (anb possibly Johnsons etc) seem
    to have larger dia. and pitch props so perhaps their mktg folks
    have taken a look at where they are used. \R/, Ed

556.3GRAMPS::WCLARKWalt ClarkWed May 13 1987 21:0013
    I discovered several years ago the benefits of oars over iron wind
    for our old 7' Ensign. I never did buy a motor.
    
    Once a friend loaned us a 2 hp Johnson from his inflatable tender
    to make an ice run from our "raft" into Port Jefferson NY. I weigh
    about 210. When alone I was able to get the dingy on a plane and
    make something in the vicinity of 10 kts (wild guess).  I also
    loaded up the dingy to the gun'l and was able to create a BIG wake
    but not do much more than 3-3.5 kts (but, as Alan mentioned, was able
    to attain that speed at about half throttle).
    
    Walt

556.4VOTE for SeagullUSSCSL::PASCUCCIMon May 18 1987 15:3611
    I have been using a (this may be hard to believe) 3/4 hp ~1957?
    Seagull on an 8 ft dink.  It seems very comparible (can't tell the
    difference) to a 2 1/2 Mighty Might in speed on the same dink.  Very
    adaquate against a current.  The Mighty M is very loud and higher RPM. 
    The Seagull idles super slow and is quieter than the MM at throttle.  
    I must agree with .1 the larger low speed prop is the better way
    to go.
    
    Frank
              

556.5Slow but LightTALLIS::KLOTZMon May 18 1987 21:0118
    Hi Jim,
    	I have a BOBBARD 8' inflatable & a Evinrude Junior (~1.25 hp)
    that I bought right in Hudsons.
    
    	I use it to get in and out of the beach - but the kids run back
    and forth across the river at all tides & currents with no problem.
    
    	They think it's too slow as it won't really plane; however,
    my bad back loves the 24 lbs it weighs & my wife likes the easy
    ride.  It's also small & stores easy.
    
    	If you would like to try it out some day I'll swing by & you
    can put it on your dink to see.
    
         Keep your eye out for the PHANTA SEA, See ya,
                                                       Lou