Jack Plate Question - Page 2

John Kennett · 24 February 2003, 18:35

Isn't it just a variation on the modified V concept? This is very common in planing hull designs where the deadrise reduces aft to make planing easier -- the compromise is that you lose some of the benefit of the deep V in the rough, but you gain in efficiency.

John

Pete7 · 24 February 2003, 20:20

Osprey's XR range had Delta V hulls in the early days however they were slowly modified over the years so it is difficult to see it on the later boats, but the early ones you could actually see it quite cearly. There was a firm in Cornwall, prehaps "Vulture Ventures" who also used the same mouldings, seem to remember a bun fight and possible court action over design rights until it was all sorted out.

Pete

(1st Bn of the Rib Spotting Club)

crazyhorse · 24 February 2003, 21:35

JK I suppose everything with a deadrise of more that 23Deg is a modified Deep V.

To try and describe it is to say where the expected planing surface starts e.g aprox 2/3rds down the hull at the bottom of the Deadrise there is the start of a flat section that extends aft to the transom cutting the V into small A withought the top bit.This A/Flat piece could be aprox 6/18 inches off the bottom of the V when it arrives at the Transom and the length/height is down to different builders experience.

The concept is that providing more lift withought compromising the deep V at the criticle point it goes faster for less power and when deep V is needed it is there when it is required.

Its a balanceing act.

To achieve a efficient Delta Keel you need to do lots of testing,this can be done within a reasonable budget and the size of the delta/flat can be experimented with to find the best size/ height/length to achieve the optimum performance for the given hull length and weight.

I havnt seen the XR but I suppose even if I had I cant comment on there design as some people will get it right and some will get it wrong.

With a fibrglass hull mould this sort of experimentation can be very expensive and usualy you try and get a good all rounder first off when the hull mould is built.

Its interesting as the stepped hull concept came from the US and ended in court action in the UK I beleive.

The length width height of our Delta keel is a closely guarded secret by our builders as the cost of developments were high and the info gleaned is commercialy sensative.

The Acid test is what otheres think who know of the builders designs and there ribs, and one takes into account there established reputation within there respective market place for producing offshore ribs.

If they are respected for there achievments and quality then you give it a shot.

dgpw · 24 February 2003, 21:52

how does the performance advantage differ between that of the delta hull and the adversed chimes that Balistic ribs have. Does any one know? that is compared to a deep v

eksrae · 25 February 2003, 05:10

The delta keel is what can make or break a hull. to far forward and to wide and it will hit hard. It is more work than the standard deep v. but worth every effort. the boats can plane with less hp

John Kennett · 25 February 2003, 05:48

From Crazyhorse's description and Eskrae's picture then what is being referred to is just a "planing pad". Again, hardly revolutionary but done better by some manufacturers than others!

Quote:

Crazyhorse wrote:
The length width height of our Delta keel is a closely guarded secret by our builders as the cost of developments were high and the info gleaned is commercialy sensative.

It's not worth guarding that closely as it's only secret until the first boat gets sold!

DGPW, the hull design used by Ballistic, Crompton and a few others has a "delta keel" (or a "Delta Conic Planing Curve" as Crompton's like to call it) as well as the ragged chine design. They also have an extremely deep V at the bow. They plane easily, carry heavy loads, and have a hard ride.

RIB hulls designed for serious offshore work, such as the Ribtec for instance, have a very plain hull with a constant deep-V all the way to the transom and few spray rails. This makes for better performance in the rough, but does mean thay they aren't the fastest boats around.

There are all sorts of weird and wonderful variations on the deep-V hull, few of them truly revolutionary. They are all a compromise between offshore performance, speed and economy. Horses for courses . . .

John

crazyhorse · 25 February 2003, 07:06

Why dont you design and build boats JK?

Julian · 25 February 2003, 09:33

When I tested the Osprey which had a huge planning pad my back nearly snapped in half when the boat landed. This was the reason we did'nt buy it. They slam like mad.

I assume they got the design wrong. Got on the plane very quickly but was useless in a moderate sea.

Julian

John Kennett · 25 February 2003, 09:51

Quote:

Originally posted by crazyhorse
Why dont you design and build boats JK?

Why would I want to do that? There are plenty out there already

Julian, I know that some of the early attempts with planing pads (way back when it could possibly have been described as "revolutionary") were pretty disasterous. Things have moved in though, and Ospreys these days certainly don't suffer from this problem!

John

Julian · 25 February 2003, 10:05

Hi John

Well thats good to hear. It was about 12 years ago that we tested it. I can feel the pain just thinking about it.

Julian

crazyhorse · 25 February 2003, 18:03

You either buy into the idea that things can move on, Or buy into the idea that things dont move on. The question to ask is why produce something different when it costs more to produce it,and could as has been demonstrated above clearly be derrogetry to perfomance.

The reason for this is to try and improve on a established concept.

With todays Market Place things have to move on from a design point of view.

A Rib design brief is different today for offshore boats and whilst the Deep V concept is and was the established norm. In my oppinion you will see improvements to this Deep V design as time goes on and Fiberglass boats come onto the market and get a new hull mould to compeate efectivley in this competitive enviroment against Labour intensive Ali boats/Ribs.

There will be cock ups and there will be winners its down to your preference and the people you believe in and put your faith in.

They may not be too radical as we have a Deep V, But it is tweeked to get the best out of the hull dependant on our expected use.

The proof is in the pudding.

I have the choice of conventional deep V or Deep V with Delta keel on our boat and from the imformation I have heard and the responce from other owners commercially and leisure when using there boats Offshore with a Delta keel then I am more than happy with with my decision.

Unless somebody can demonstrate that this concept is flawed Then Im sticking to my guns.

As change doesnt worry me especially when its progress in my opinion.

John Kennett · 25 February 2003, 19:35

Nobody has suggested that the concept is flawed. I was just pointing out that it's nothing new or revolutionary . . .

John

crazyhorse · 25 February 2003, 19:42

JK the proof will be when she is on the water and we see how she goes in different conditions.

Im still a happy bunny.

Cookee · 25 March 2003, 10:19

As far as jack plates are concerned the only ones we havn't broken are the Stainless marine ones - good service direct from the USA - faster than dealing with domestic UK suppliers!

Eksrae - Tried similar items to the ones you have fitted - my advise is keep them greased and don't jump the boat to much - we were racing them with 200 hp Merc XR2 on a 24 foot RIB and they wouldn't take the pounding!

By the way I hope to be racing RIB F2 this year as well as Class III 2 litre - All the class III boats run with jack plates and I use it all the time - every race has a flat enough section for it to be of use. We expect to add 5mph to our top speed, but you need low water pick ups (XR2 have them as standard).

Manos · 30 September 2004, 10:28

I thought to bring this thread up since I've now took the plunge and ordered an aly Jack plate with the following specs:

CMC PL-65 Power Electro-Hydraulic
This unique outboard motor hydraulic lifting device works independently of your power tilt and trim to allow the boat-motor-prop combination to work at its maximum efficiency. The CMC lift gives you the ability to adjust your motor down, while underway at full speed, for better out-of-hole shots or up for more top-end speed and more prop clearance in shallow water. The Power-Lift is designed to fit V-6 and smaller outboard motors without drilling holes or making modifications in the boat or motor. Provides 5" of travel and 5 1/2" setback. The CMC Power-Lift is constructed of 1/2" 6061 T6 aluminum alloy extrusions and fastened with stainless steel fasteners for maximum strength and durability. The Power-Lift utilizes a marine hydraulic power unit operated by 12 volts DC an is totally waterproof.

65001 5 1/2" Set-Back Polished W/Gauge $691.99

The questions are:

1. if I was to change the order for a 10" set back will that make a lot of difference to the boat? or the 5 1/2" set back is OK.

2. Aslo do I need to change the prop to a 4 blades? What size - 14 x 25" or 13 1/4" x 26"? (currently I';ve got 14 1/4" x 21" SS Yamaha Pro and depending on weight 52-57 knots at 5700 what should I go for? and finaly

3. Whould I need a low water pick up set up for the 200VMax?

I know that you will say that aly ones brake and I should have got an SS but I will only use it on the recreational 700 FALCON I have and usually (most of the time) we just take it easy with family onboard. Thinking to fit one on the SCORPION if this works OK.

Dirk Diggler · 30 September 2004, 13:02

Quote:

Originally Posted by Manos

The CMC lift

I know that you will say that aly ones brake and I should have got an SS

You've bought the wrong one, the large bolts on the sides that slide up and down are the weak point, should've listened to cookee and bought a real one!

Manos · 30 September 2004, 13:14

Yes but the SS are heavier.

This one is only 28lbs where as the SS is 2-3 times that weight even more.

They make this jack plate in SS but as I said is top heavy and costs double this one with dispach costs to about $300.00 which makes very expenssive. Also with the engine, aux engine, A-frame, 2 batteries and an SS jack plate aft the boat will not stand right neither will perform correctly. The screws on the side are SS they told me.

The only choice I have as I have already paid the shop to change the order and ask for one of those. But I think they have the same operating staff on them and they are a bit more expenssive.

or

Dirk Diggler · 30 September 2004, 13:49

Quote:

Originally Posted by Manos

The screws on the side are SS they told me.

And that is the problem. Over a period of time the bolts, being a lot tougher than the ally angle that they clamp, eventually wear away the metal resulting in a very sloppy lifter.

Manos · 30 September 2004, 13:55

I get your point.

But I think for $750 in total is a good bargain. The SS would have cost me over $1,600. I will not be racing the boat any way so it will do for now. May be when we go to the Keys we get an SS jack plate for the next one.
Thanks any way.

...and the question still remains would I need a low water pick up and a 4 bladed prop?

codprawn · 30 September 2004, 14:20

Quote:

Originally Posted by Manos

I get your point.

But I think for $750 in total is a good bargain. The SS would have cost me over $1,600. I will not be racing the boat any way so it will do for now. May be when we go to the Keys we get an SS jack plate for the next one.
Thanks any way.

...and the question still remains would I need a low water pick up and a 4 bladed prop?

I have also ordered one of these Manos - time will tell I suppose!!!

The screws run through nyaltron bushes - they should wear before the guide and should be easy to replace so I don't think the stainless on alloy thing will be a problem.

As to a low water pickup it all depends on the engine - from what i have been reading some outboards need them more than others - i suppose keeping an eye on the water pressure gauge will tell you.

I have ordered the 10" setback version (mainly to give extra room in boat) - remember this will cause quite a bit of extra leverage on the transom - i am having mine built oversize to compensate!!!