Asymmetrical Cat Hull Design Advice

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I had my boat mechanic move the boat motors as high as they could go and no change. Tomorrow we are going to drop them as low as they can go and test again. The fuel tanks are centrally located.
With me and 2 guys and ice and all fishing gear I would say assume 310 kilograms and the boat is definitely not level with the transom lower in the water. We even put 100 kilos of weight in the form of big water drums to counter the weight and the boat just sat below its water line. I think there is too much boat in the water and it's very sensitive to weight. If this next test doesn't fix it will be on to buy a trihull boat...

 

If you intentionally try to make the port hull dig in; how would you go about doing it? Lots of people have trouble with excess bow rise; so they modify angles with wedges, they install hydrofoils. In your case all this is the opposite, but worse! Symptom on one side.

If you trim up one motor; it is almost inconceivable that the bow dig would not go away unless the motor ends up out of water. Yet I don’t recall you mentioning.

Then if you adjust the motor tabs obscenely; can you reverse? Have you messed with them; like purposefully trying to err.

Is it possible the beam/deck bent?

Have you ever had anyone on the bow to watch the waves? It seems like the design would provide minimal interference, but not zero.

What is so significant about the 20 number?

 

This boat is extremely short. With the large engines and the load mentioned above, the boat is also extremely heavy for its waterline length and bottom area. The planing bottom area is far too small for this total weight so that the bottom can not lift into planing mode. The boat plunges through the water. At the slightest imbalance, one hull can go up in planing mode while the other drops into displacement mode.
JS

 

Thanks hjs that makes so much sense.

 

I appreciate everyone's help.

 

Def sounds like the hulls are irregular, rocker or reverse rocker in one of them. Vertical trim tabs might fit that space if you can't figure out a better way to fix the hull. Others I have seen simply affix a small ridge at the edge of the transom, you could test that before doing anything permanent.

 

Crane it off the trailer and put it on some very flat ground to find out if both hulls are lined up with each other.
Or lift it up and use a laser

 

Not much to contribute other than anecdotal evidence. Few years back had a contract for renovations at Double Island, off Palm Cove near Cairns. The resorts workboat was a hull identical to this hull. Usually about 5 or 6 tradies would be run out to the island. First trip out at high displacement speeds the boat would easily broach. After a few months using this boat (I own a 17 ft mono) I could not see any advantages to this hull in terms of handling various sea states. I agree that length to beam ratio may have something to do with it. Extending the W/Line might help.
Cheers, Gaz

 

Excellent, this would describe the antics of the one that i had been in.

 

Did you sort this out mate I have bought 1 in western australia

 

Rigoberto,

Welcome to the Forum.

Sadly, Marshall_79 hasn't visited the Forum since January 2018.