Help with hop / humpzone small cat

[Torben E]

Hi

I own a small cat that has a big hop / hump zone and would like to ask if there is somthing
i can do to reduce that. I am aware that it the nature of that type of hull, so i am asking if
there are some setup changes that can be done to reduce it. I am thinking of smaller setback, and lightning et
type of prop ?

I have tried to move weight around and different trim and engine heights, with little results.

I am willing to sacrifice a little topspeed if that helps.

The hop starts as early as 50 mph and stops around 80, is that not a wide unuseable zone ?
Over 80mph it is perfect, goes flat and straight, tops at over 100 with 2 persons.


The hull is light, carbon seats, light battery, small fueltank

Setup is
18 foot cat no centerpod
Bobs 8" lift
2.5 260 efi offshore
Sportmaster rh. with torque tab
30p mercury cleaver

[Torben E]

Here is the boat

[Torben E]

[Torben E]

Today i tried a ron hill 4 blade 28p hi rake cleaver. it reduced the unuseable speed zone a lot. But lost 10 mph topspeed.
So i am thinking a 30p et lightning will be a good choice.

Any input is greatly appriciated.

Torben

[eli]

a round ear will make it worse ,the hull is trying to pack air .on my 22 rapid craft twister i tried to drive it like my 23 daytona ,it did not go well it hopped after 70 to the point i had to back out , come to find out you have to trim the boat ,fly it till about 90 felt weird like you were going over then trim down once i learned this its all golden and way fun ,try higher trim than normal on a calmer day so the waves dont give false feeling

[Torben E]

I will try that. I had more seat time viith the 4 blade cleaver and getting more used to the hull. But i need a 30p again as i am on the limiter at 95-96 mph

[mjw930]

You may want to consider tunnel tabs. A pair of these, one on each side of the motor, might allow you to settle the boat, just remember to pull them up once you get past the hop zone.

http://www.lencomarine.com/index.php...abs/heavy-duty

[mjw930]

OTOH, you may be packing enough air by the time it hops to make tabs irrelevant if they are above the water. Someone with a lot more experience in small open tunnel boats would need to weigh it.

[Euroski]

My thoughts on tabs for a tunnel are, if you need them then there is a setup issue or driver needs to learn to drive it.

[Torben E]

No doubt that i am still learning to drive a cat. ��
The cat dosent feel flighty at all at speed, even with the added lift from the 4 blade hi rake cleaver. In fact it goes lower the higher the speed.
I can see the stv owners often run lightning et type props for crusing with people on board. I am thinking of buying one to try ?

[johnmiffco]

pretty much all true tunnel boats have a porpous window
3 podded boats like dcb and talons have very little to none from the center pod being there
the true tunnel hop @ 50-80 window,,,,some more some with less window
its the nature of the hulls,,,,,,even larger 40'+ have same hop
not past 70+mph to get sponsoms to ride on top
so tunnel not aired out enough to hold bow up,,,,,
if u have a drag set up for max speed,,,,set up is everything to close the hop window to be able
to drive through it,,,,
but if u try to pleasure ride,,,,,and most boats pleasure ride in that 50-80 window
from boat traffic,fuel consumption,safe riding with passengers,in poker runs,,,
tabs on larger hulls on sponsoms and tabs in the tunnel allows u to ride them speeds
so its not a set up issue for them its for ride comfort at any speed desired or needed due to water conditions/traffic

[Torben E]

Hi
I know it is the nature of a cat to have some instability in the lift zone. Just thinking it there is some things that is known to make the zone smaller.
Like i vent from a merc 3 blade cleaver to an hill 4 blade with more rake, that was much more easy to drive.
Also on my last trip out i had 40 litres of extra fuel in the front half of the boat. That made the humpzone a lot smaller, but it felt wierd at speed. Moved the fuel aft, hump back, but felt nice at speed.
Man it is sensitive
This is my first tunnel, so any advice is gold for me.
Other boats are 16 feet v bottom. 2.5 frankenmotor and 20 feet v with 300 promax

[johnmiffco]

set is everything putting any boat together to find the best combo for the application
as stated hard core drag set up
is a different set up for pure pleasure with a big load such as passengers and fuel
just as u found with the hill 4 blade with fuel up front
to the 3 blade with fuel to rear
then u havew ur all around set up,,,not fastest in speed not least handling but good all around
ur small cat is more for speed and can set it up for best speed
and put a good tab on it for the hop zone when just cruising
and as stated when going to fly ,,,,MUST be pulled up as will bite u
if hit a roller or wind pack at high speeds
I don't like hill props but if have it tuned for boat work ok
but out of box their not balanced or even blades all true to each other
so moving weight around ,,motor height to offset to prop is just taking time to dial in for best performance and safety

[eli]

if you think about it fuel tanks toward the front when heavy more fuel vs less fuel = 2 different driving styles and possibly setup's ,you can try putting ballast in rear when you have more fuel up front see if this helps .

[JPEROG]

I tend to agree with what eli said about running a little more trim then you think is needed to hold the bow up until it packs air and makes the transition. Also approaching the "hop zone" in a slight turn and being on the gas will help get you through it smoother and faster.

Joe