Jack Plate Question

Manos · 11 February 2003, 09:56

I spoke about this with FALCON they said is best to test the boat without it first. Just set the engine one notch higher than the recreational version and trim the motor from the engine's trim swich (which is mounted on the steering wheel - you should see this steering wheel is like bloody Formula 1 racing car with all these buttons on it)
However, with a 200 bhp VMax from what I can see on other racing RIBs a Jack Plate looks like is required.
I have the BIBOA rules and there is no mention about whethere I can fit a jack plate or not (will have to ask them I guess)
But for the sake of argument do you think I sould fit one or it will wasting money (they are expenssive about $ 1,500).

Julian · 11 February 2003, 12:52

Hi Manos

I have seen a few race boats with these on mainly hard boats etc. They will help increase your speed but i'm not sure that they do the engine itself much good. Lift it too far and you may interupt the water intake etc. I have no idea if this helps to be honest,

Julian

Dirk Diggler · 11 February 2003, 18:30

Without a doubt you will need an engine jack, but not the one in the photograph. You need a Gorilla from www.stainlessmarine.com , this is the one used by most racers. As for the problem of raising the motor too high, fit a water pressure gauge.

Manos · 12 February 2003, 08:19

Thanks guys.

I have already fitted a water pressure gauge.
Right now I'm in two minds whether to fit a 150 bhp VMax and 650kgs weight or 200 VMax and 950 kgs weight.
As far as I know both engines have the same motor, gear ratio etc and the only difference is the carbs (200 VMax has bigger jets).
The boat tested already with both engines and various prop configurations and makes very marginally higher speeds with the 200 VMax. Honestly don't know if it worth’s the more money and the extra weight.
Thanks for the help

Dirk Diggler · 12 February 2003, 09:00

Manos, these weights that you are quoting, are they max weight for entire rig in F2 for given HP, or do you think that a 200 Yam is 300kgs heavier than a 150 Yam.

Also, It sounds like this rib is not even built yet, ie, tanks on deck or under floor, but you have already fitted a water pressure gauge, but you haven't decided on which size engine.

Have you been eating lots of cheese before you go to bed?

Manos · 12 February 2003, 10:02

For your info RIB is finished!!
Tanks were one issue that now is shorted.
Most gauges have been fitted. Jack Plate not necessary but considering.
Engine size is now a consideration but it looks 150VMax will be fitted. Found one for £3,000.00 NEW!!
Will post a photo of the RIB by the end of this week in the water with engine but not jack plate.
Boat shipping date to the UK 20th Feb with shipping company MCL. Do you want B/L number too?? LOL Just joking

The weights I quote are total boat weights with various engine configurations that are required for F2 i.e.

1 x 150 Merc (various types see rules) or conventional 2-stroke Yam 150 VMax boat min hull length 6.5 mtrs boat min total weight 650 kgs
1 x 200 Merc (various types see rules) boat min hull length 6.5 mtrs boat min total weight 900 kgs
1x200 Yamaha HPDI boat min hull length 6.5 mtrs min total weight 950 kgs.
To the above for extra 1 mtr hull lenght or part add extra 65 kgs

The above is a part quote from the new revised BIBOA rules.

Scotty · 13 February 2003, 18:21

Is Jack Plate any relation of Jack Schitt ?

gavin · 13 February 2003, 19:39

Manos have seen a Ballistic 7m I think with a 250 rude on the back they fitted a jack plate and ran it way up, bear in mind one other thing, when you hit big waves at speed the props leave the grip of the water, the tendancy for the motors is to rev right up or indeed over rev, you have the cooling water problem sorted, do you have a rev counter to watch the revs if the prop has insuiffecent grip or a rev limiter, just in case damage occurs due to over revving of the motor with reduced grip as the props are so near the surface, Jack plates look the part it is a cool idea gavin

Manos · 14 February 2003, 08:10

Quote:

Originally posted by Scotty
Is Jack Plate any relation of Jack Schitt ?

You are the expert Scotty you tell us
LOLOL

Manos · 14 February 2003, 08:14

Quote:

Originally posted by gavin
when you hit big waves at speed the props leave the grip of the water, the tendancy for the motors is to rev right up or indeed over rev

Thanks Gavin, I'm aware of that aspect. The boat has all rev counters, tem gauges, presure etc fitted o/b.
After having long discussions about the Jack Plate I think the general consesus is to skip it.
They look cool but do they halp in an off shore race. I think (from what I've heard) and what you also say that jack plates are good for lake/flat water racing (something I'm not doing any way - what's the point

) and not that useful for off-shore.
Thanks for the tips any way. Really appreciated

Julian · 14 February 2003, 09:23

Manos

I agree with you, Skip the Jack plate. Most of the races over here are not donein flat calm conditions so you will need the engine down to give you the grip from the prob and to keep the bow down when the going gets rough. I didn't see many race ribs with jack plates last year so save the money.

Julian

Manos · 14 February 2003, 10:48

Quote:

Originally posted by Julian
Manos
I agree with you, Skip the Jack plate. ........so save the money.

I am doing exactly that
Cheers Mate

eksrae · 19 February 2003, 04:35

I am building a 28 foot rib out of aluminium with twin 250 yamaha's. this vessel has jack plates. we had to install low water pickups to make the jack plates worth while. we r able to turn a higher pitch and larger diameter prop. the boat should be sea trialed in a week or two so i will let you know how it went.

Manos · 19 February 2003, 07:03

Quote:

Originally posted by eksrae
the boat should be sea trialed in a week or two so i will let you know how it went.

Will be very interested to know what you think of the jack plates.
Cheers

eksrae · 23 February 2003, 19:36

her is a picture "hopefully of the jackplates. they are rated to 300 horse. that is twin 250 yamaha's. the legs will be installed tomorrow.

crazyhorse · 23 February 2003, 19:43

Is that a Delta keel I spot there Eksrae? looks a good job.

eksrae · 23 February 2003, 19:56

sure is. gotta have them

crazyhorse · 23 February 2003, 20:09

Look forward to seeing a few pictures when she is done.

Im interested in Ali boats as there a very few manufactures over here who specilise in Ali ribs.

Its a specilist field and those over here who have them swear bye them,500hp on a 28ft boat Ali boat will make her fly with the Delta keel so Im interested and any imfo as it will be much appreciated.

When your ready and good luck although by the look of her you arnt going to need any.

Jelly · 24 February 2003, 14:05

HI Crazyhorse et al
Please can you explain the delta hull?
I was thinking that delta power up north made the hull, but subsiquent posts have shown (that I can't spell &) that I was wrong !
so whats a delta hull design look like ? and why is it so good?

I aggree with the comments on alu hulls as I was trying to get the offshore work boats made in alu as it was easier to weld up alu offshore that do a decent kevlar/fibre composite repair.
Jelly

crazyhorse · 24 February 2003, 17:59

Hi Jelly,The Delta keel is a design that I have only ever seen in Canada where these boats are used each day , they have become very sort after and it is something quite new to us over here.

It gives a rib lift, even though you have Deep V it is situated aproximatley 1/3 the way back and goes to the Transome.

It is the bit the boat rides on when it planes as with a very deep V you need more HP to push it as fast as you suffer from drag I.E wetted surface area when you dont want it,and you can get chine walk.But a deep V has the ride in rough weather so this enables the boat to have a deep V when needed and a Nice Delta surface when you dont. Its all about position to the waves a flat bottom will slam a deep V will not.

Its a design compromise that in concept gives more lift for less HP and consequently gives you a more stable attitude to the waves and increases speed and stability whilst achieving a deep V when required.

I can only go off my instinct and what has been confirmed in CAD testing but Eksrae can tell us more from the actual Sea trials point of view and what the costomers have found.

Hope this helps.