Trim Tabs and Rough water Operation

[Captain PartyMarty]

there isn't much space left or right to add more trim tab. maybe and extension would work. Maybe I should give Bennett a call and see if I can get longer tabs.....

 

[salmonkiller01]

Check engine heights. I raised mine and it made a world of difference. Can literally trim up till cavitaing and push the bow down by trimming in

 

[Pineapple Express]

there isn't much space left or right to add more trim tab. maybe and extension would work. Maybe I should give Bennett a call and see if I can get longer tabs.....

I saw a boat for sale recently that had some extensions attached to existing tabs. They were well executed by somebody with some sheetmetal experience...they had nice creases for strength.

Also, I looked back at your build thread and there no perfect photo but I'm still thinking your engines could possibly be mounted a bit low. Might be worth a double checking

 

[CIVANO]

 

[Captain PartyMarty]

I had look I can raise the engines by 1 more hole. If I wanted to go more than that I would have to take out two bolts and run with a 4 bolt installation instead of the 6 I have now. Would raising it by 3/4" really make much of a difference?

 

[brutus]

I own a 24 Wellcraft walk around with a 225 optimax with a 3 blade 19 pitch prop. Top speeds at 4200 rpm probably around 32 mph.. to be honest my hole shot sucks and low speed planning sucks even with trim tabs... fuel efficiency isn't too bad. If I went to a 4 blade would my hole shot improve dramatically and fuel efficiency? Just wondering if its worth it or not

Overprop

 

[ship happens]

I'm not disagreeing with you and your very generalized reply, but the props he is running (Enertia ECO) have huge blade area already and are considered to be a "lifting" prop.

I'm curious how the engine mounting height is? Have you got the height dialed in so the anti-ventilation plate is skimming just above the water surface when trimmed neutrally while running?

I know it's pretty vague. I can explain a bit better what I've learned. Propping a boat is challenging. It's not always about surface area although, surface area does play a part, it's also the agression of the blade pitch. 4 blades are designed a bit differently. Alot of times they have a smaller diameter and alot different rake then a 3 blade prop. The rake will give bow lift. The smaller sized blades mixed with cupping and the shape of the blade as a whole can be designed to give stern lift. Which is what 4 blades are designed for. Going down in pitch is necessary usually. 4 blades can plane easier at low speeds because of the smaller diameter and blade design. Come down to cavitation and blade shape. I'm sure its alot better explained somewhere online. Sure theres some drawings and detailed explanations. Hope this makes sense.

Some pods that have alot of flotation can also destroy the way the hull was designed to ride, and can change everything. Sometimes adding water to the pod is necessary. This is why we always rake the pod so it sits ontop of the carving the hull makes when on plane. Those trim tabs are plenty big enough. Engine height and stern flotation can be observed there. Also 4 blades would change the game 100 percent.

I'll try and touch back on this. I'm super busy lol


Ps, the cavitation plate of the motor should sit nominally 1.5 inches per foot higher than the original stern bottom V. However if the pod is hull extended, then it can be difficult to get the correct height for maximum performance. Especially when it's not a full hull extension. Ehat I mean by the is that it's not extended the width of the hull. If you change the carving of the hull, you changed the boats design completely

 

[ship happens]

Also can you take a picture with the engine down?

Is hard to see in the picture how the tab is mounted, cant see the bottom of the hull or where the reverse chine is.

 

[profisher]

I have a single 200 Yamaha 2 stroke and 9.9 kicker.

 

[profisher]

To me if your tabs are in the full down position in your photos..you don't have near the extension that I have on mine. I'll post pics

 

[profisher]

My tabs are 11 inches deep and 14 inches wide. They appear to extend downward at more angle than yours...likely the rams don't have the stroke length.

 

[profisher]

Make sure you r ram is fully retracted when the tab is parallel with the bottom of the hull. If not you should move the mount point on the tab closer to the transom...this will increase the downward angle when they are fully extended.

 

[Sharphooks]

I have been thinking more about this and comparing my boat to a brand new 2400XL Seaport. I have the same hull, same pod, same trim tabs. The only other significant difference between my seasport and new one is fuel tank location. My seasport has two tanks on both sides right to the back of the transom. A new seasport has a single tank located mid ship which is about 5ft to 6ft from the transom. This weekend I did have absolutely full tanks so maybe I am just more stern heavy due to my tank locations than a newer seasport.

As others have said I probly need more lift, either with props, or a hydrofoil.

^^^^^^^^^ THIS^^^^^

Not sure how big your tanks are but I’m guessing you have the equivalent weight of three large outboards in your stern...maybe 700 kg?

I’d bet money that if you burned off some gas and tried that rough water experiment again, you’d see an immediate change in the attitude of the bow

I have a 26 foot Seasport. I have twin 200 Suzukis on the bracket.....the large fuel tank mid-ships (680 liters!) ......it is an incredibly stable boat in all water conditions. I rarely have to use tabs at all but when I do, it’s instant response....yes, I have the ZIpWake system, but they’re still tabs and act like tabs ....I’m betting it’s a weight distribution issue in your boat

 

[Reel Gone]

Marty, it might be worth dropping an email to Sea Sport to see if they have had any others ask about similar issues once podding.

On another note I agree with Rollie, my 24" Sea Sport Explorer has tabs that have much longer stroke that the ones you have pictured

 

[Captain PartyMarty]

Interesting about the tab cylinder stroke, it definitely looks like you have more than I do. Can you measure? The Bennett bolts are specified to have 2.5" of stroke and I am getting that. I sent an Email to bennett today asking about the possibility of longer tabs. Those actuators look like the volvo ones I removed from my boat during the build. Maybe that's the issue, my stroke is too short.....

I also have to mention that if I have a couple of kids in cabin up front the boat performs better

 

[ship happens]

Sometimes you have to add weight to the bow. Sometimes to the rear. Very common

 

[Captain PartyMarty]

^^^^^^^^^ THIS^^^^^

Not sure how big your tanks are but I’m guessing you have the equivalent weight of three large outboards in your stern...maybe 700 kg?

I’d bet money that if you burned off some gas and tried that rough water experiment again, you’d see an immediate change in the attitude of the bow

I have a 26 foot Seasport. I have twin 200 Suzukis on the bracket.....the large fuel tank mid-ships (680 liters!) ......it is an incredibly stable boat in all water conditions. I rarely have to use tabs at all but when I do, it’s instant response....yes, I have the ZIpWake system, but they’re still tabs and act like tabs ....I’m betting it’s a weight distribution issue in your boat

I have 220Liters on both sides so the makes about 700Lbs which is located much further back in the boat than yours. this could easily be reason.

 

[Offshore]

Permatrims will lift the stern and not create the same kind of drag that the tabs do.

 

[profisher]

It may be more a geometry problem than stroke itself...the further away from the transom the cylinder is mounted to the tabs...the less travel resulting in a bigger angle you will get...if mounted more towards the back edge of the tabs the ram has to extend more per inch of downward angle than it would closer to transom. The ram needs to be more straight up and down in the retracted position to get maximum effect on the tab plates.

 

[Gong Show]

It may be more a geometry problem than stroke itself...the further away from the transom the cylinder is mounted to the tabs...the less travel resulting in a bigger angle you will get...if mounted more towards the back edge of the tabs the ram has to extend more per inch of downward angle than it would closer to transom. The ram needs to be more straight up and down in the retracted position to get maximum effect on the tab plates.

Put a tape to your ram and tell us how it extends per inch of downward angle.
Pics or it didn't happen.
PUI