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Old 18-04-2005, 12:44 PM   #1
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P21 questions

Hi Guys,
I have been out in my P21 a coulpe of times now - great fun and the grunt from the opti still impresses me!!

However she wobbles alot a 60 mph - nose up/down. I don't have any weight at the front, however i do have a manual jeckplate.
If I lower the engine on the jackplate, this puts more engine in the water and may stabilise it - however I will sacrifice some performance or??
Am I dead wrong here?

running it alone and she tends to roll from side to side - pretty scary at 65mph - should i get some trim tabs maybe??

I had a hydraulic steering kit mounted but it seems like she easier to turn right than left?!?

any help/advice apprieciated..

ps. how much fuel does a "normal" P21 with a rear tank take?? The gauge read Ĺ full, but I added 100L?!?

MPH readings all taken from the speedo :frown:
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Old 18-04-2005, 01:10 PM   #2
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Country: UK
Location: Alderholt
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Boat name: T/T D2S
Boat make: Midas 27' Cat, Argo 16 Cat. Avon Rib Thingy
Engines: Merc 280-ROS -JSRE,65Xs, 75 Stinger, Yam 60
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What sort of prop are you running that can affect the handling, chopper , clever, laser, ect.
The natural tendancy of a deep vee the faster you go the more lift, less boat in the water, hence less stability.
From what you describe I would tend to move the weight about and see what affect it has , try & get a bit more on the center line of the boat, and a little more aft (at a guess), it is very much trial and error. The easiest way is to get a spare body to crawl up the front when running see what difference that makes, then get them to move about a bit see what effects that has in various places. very easy & quick to do rather than unmounting stuff.
Dont change too much in one go as you will loose your datium.
You will always feel greater resistance on turnning that is do to the torqe effect, you might want to offset the anode a tad to try and counteract it, if you have full power steering then you dont feel it, but that is one big step up in price.

Edit: Spelling (Dolt)
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Old 18-04-2005, 01:10 PM   #3
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The steering will be more dificult to turn left than right even with hydraulic. The boat is constantly trying to turn right due to the torque from the prop. Therefore when turning right your just going with the flow where as turning left your going against it. Hydraulic steering makes things easier but you will still notice a diference.

Its anybody's guess how much fuel your boat takes as it depends what tank was fited when it was rigged. Measure the outside dimensions and work it out from that. It will most likely be somewhere in the region of 100 to 150 litres.

The chine walking, going from side to side, could be any number of things. Check for play in the steering it may need re-bleeding. What steering is it? Hydraulic steering some times requires bleeding more than once when freshly installed. Also check for the outboard midsection for any play. Not sure if your motor has solid mounts in the mid, if not it would be a good idea to fit them.
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Old 18-04-2005, 01:22 PM   #4
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BluFin - I am running a High Five without "vents/accelerationslots" in the side..

Johnny - solid mounts?? i quite sure what you mean.?
Of course the steering will be harder because of the torque - my mistake!! :frown:
The steering is from LS Pomps (Quicksilver) - http://www.ls-france.com/FR/ls-gb.htm
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Old 18-04-2005, 01:37 PM   #5
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Any high powered mono is gonna be unstable in 'roll' (chinewalking), especially a single engined one when trimmed out and going for max speed, part of the skill of driving this kind of boat fast is to 'work' the wheel & throttle to maintain roll stability, it won't 'just do it' however well set up it is.

get some seat time in the boat, hopefully it'll all come naturally with time.

jf
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Old 18-04-2005, 01:38 PM   #6
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Steering normally feels less balanaced when the engine is really trimed up if the front is that light try using a little less trim?

If you dont have someone else to come testing with you try a bags of gravel I have no trim tabs so use two bags of gravel on the starboard side (rear well) to balance the boat (lands flat then!) Only about £4 from the builders merchant and you could try them up front to see if that changes things.

I have a fuel tank in the front 22 gallon and an 18 gallon in the rear. Normally never use any of the fuel in the rear tank the other day I used all the front tank up and half of the rear (expensive days boating) the boat was a lot more flappy when there was no fuel in the front and rear half empty - short term solution was less trim.

Hope that helps.
Have a word with Taz because his was exhibiting the same sort of ride when i saw him out in it the other weekend.
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Old 18-04-2005, 02:37 PM   #7
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Thx guys..

For sure a bit more experience will do me good, used to drive a Sea Ray 280 powered by twin 350 mags totally different piece of kit..
Will have some more boating time soon and start experimenting...
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