Planing & Displacement

jimi

jimi

Well-Known Member
Joined
19 Dec 2001
Messages
28,660
Location
St Neots
Visit site
Out of interest, how many of you guys spot other Mobo's that are going fast but are'nt actually planing. It seems to me that there are quite a few. Is that because they do'nt know how to drive their boats properly?



<hr width=100% size=1>.. when's that again, but ..
 
Er, cant see how you can go 'fast' without planing. Depends what you mean by 'fast' I suppose. With smaller boats, its sometimes difficult to get on the plane if the boat is heavily loaded and some judicious trim adjustment and weight re-distribution may be required but, mostly, the only skill required is to whack the throttle(s) open

<hr width=100% size=1>
 
Clarification please. What do you mean by fast ? /forums/images/icons/wink.gif I've managed 9knts in a Bav 41, which felt pretty fast but I assume we were still in displacement mode. Made quite a big wash as well if I remember correctly. Arn't you on the wrong forum ?

<hr width=100% size=1>
 
Meaning 15+(??) knots with the throttles wide open. Wondered if some of these guys do'nt know about trim tabs or weight distribution?

<hr width=100% size=1>.. when's that again, but ..
 
What do these boats look like? Sure they are not semi-displacement instead of planing

<hr width=100% size=1> I asked an economist for her phone number....and she gave me an estimate
 
Nah they're proper planining boats, saw a Fairline Targa doing just that on Saturday as it dug a trench of water all the way along the Solent.

<hr width=100% size=1>.. when's that again, but ..
 
Well if it's a planing hull, with wide open throttle and only doing 15knts it's either:
1) got something wrong - mechanical or operator
2) got very small engines for the hull size
3) got a REALLY mingy bottom

<hr width=100% size=1> I asked an economist for her phone number....and she gave me an estimate
 
Ok it might have been doing 20+ knots, dinnae ken .. but it certainly was'nt properly up on the plane. I reckon a fewguys once they've got the engines flat out do'nt really know if they are properly planing or not

<hr width=100% size=1>.. when's that again, but ..
 
What do you mean ... "the wrong forum"? Are you all sinners of the dark side banished from grace?

<hr width=100% size=1>.. when's that again, but ..
 
if a 29 footer was doing 20 knots he was definitely planing. Not all of us can skippety skippety along causing hardly a ripple.

I think we should all come past you for you to check we are doing the planing thing properly.

<hr width=100% size=1>
 
There are probably a few idiots around with outdrives who have no idea what the leg trim is for! They'd probably be amazed to find they could actually do 30knts at that throttle setting using half the fuel :)

<hr width=100% size=1> I asked an economist for her phone number....and she gave me an estimate
 
If the engines are flat out and its doing 20knots plus, its planing for sure. A planing boat of, say, 35ft length would be planing at 12-14knots. Whilst the trim tabs and/or the sterndrive trim can help to get on the plane, adjusting these whilst you're on the plane wont make a huge difference to how the boat looked to you. More likely, they had reduced speed for some reason (could just be as a courtesy to you, heaven forbid!)

<hr width=100% size=1>
 
We have a Sealine that tops 28 knots, cruises nicely on the plane at 20 knots but occasionally we pull the sticks back, tuck the drives under, lower the trim tabs and chug along at 12 knots. Great on a nice day with a glass of vino in the hand and you are not in a hurry. What ever takes your fancy.

<hr width=100% size=1>Keith

boat2.jpg

<A target="_blank" HREF=http://www.mobiledit.co.uk>http://www.mobiledit.co.uk</A>
 
How do you define planing? I thought it was when you got the hull out the water and were able to throttle back? Not just exceeding the theoretical max hull speed?

<hr width=100% size=1>.. when's that again, but ..
 
Planing = exceeding the theoretical max hull speed, just as you've put it. Any skill needed thereafter is to optimise the fuel efficiency of the boat for any given speed and the attitude of the hull for the sea conditions. Rocket science, it ain't

<hr width=100% size=1>
 
Planning hulls are designed to climb up and sit on the bow wave as it moves forward through the water. When the vessel reaches planning speed it will climb on the bow wave, which appears to occur, on average, between 11 and 14 knots.


<hr width=100% size=1>Alf
 
I am sorry to disagree with you, but planing does not equate to exceeding the theoretical hull speed. /forums/images/icons/crazy.gif You are half right in that if you are planing you will be exceeding the theoretical hull speed. However, I can exceed the theoretical hull speed on my raggie (abt 6 knots) cause I have a relatively large engine, but have yet to get up onto the plane unless using my sails (abt 18 kts) /forums/images/icons/smile.gif

<hr width=100% size=1>
 
Not just sure what you mean jimi?? A displacement mobo will never plane even at full throttle - doesn't mean that the driver is poor. Then there is semi-displacement and then planing hulls. They are only poorly driven if the helmsman is going too fast in a restricted area or endangering others, or himself and/or crew. Other than that, its just different types of boat.

<hr width=100% size=1>Madoc Yacht Club
<A target="_blank" HREF=http://www.madocyachtclub.co.uk>http://www.madocyachtclub.co.uk</A>
 
Let me get this straight. You can plane at 18knots under sail (wow!) but under power you can only get 6 knots or a bit more. Sounds like an even bigger engine should do the trick then
Normally, you can exceed the theoretical hull speed in displacement mode by a small amount but thats because the equation is only an approximation but if you are doing, say, 10knots in a boat with a 6knot theoretical hull speed, then, per se, the boat is partially or fully planing, no question

<hr width=100% size=1>
 
Did not realise that all planing boats had to go "flat out all of the time". My Targa 31 will easily exceed 40kts but I very seldom push it that hard......Then again my Targa does not spurt out black clouds of fog because it hasn't spent its life being thrashed to death!!!!
If it was a Targa 48 that you saw nipping between Lymington and Yarmouth on Saturday at approx 15kts......then it was my mate and me ......and the reason for doing 15kts.............because it was crap visilbility and the pubs stay open all day in Yarmouth.......so no real rush!!!!

<hr width=100% size=1>
 
You must log in or register to reply here.

Other threads that may be of interest

D
Stern drive KAD32p - water dripping, any tips?
Replies
4
Views
252
James jameson
J
M
Galeon in the 50ft Class – Hoping to Borrow a Bit of Owner Wisdom
Replies
4
Views
372
Elessar
Elessar

Share this page

Top