How to reduce the bouncing/pounding of an aluminum boat

capman

Well-Known Member
I understand due to the weight, aluminum boats are more subject to bouncing. I usually add some weight to the bow of the boat and that helps. I'm also thinking of adding trim tabs to my 22' boat. Is that all I can do to help reduce the bouncing?
 
Trim tabs would help but you have to be careful adding weight. By adding weight you can throw off the boats stability and and unlike trim tabs it’s harder to adjust for conditions. Also it’s critical it not shift and cause some real issues. But aren’t you are defeating the purpose of the lighter weight aluminum hull provides by adding weight? It must effect speed, fuel economy etc.?
Not an aluminum guy but I would guess trim tabs, suspension seats and adjusting speed for conditions are your best bets. I’m sure the metal boat guys can speak from experience.
 
Trim tabs would help but you have to be careful adding weight. By adding weight you can throw off the boats stability and and unlike trim tabs it’s harder to adjust for conditions. Also it’s critical it not shift and cause some real issues. But aren’t you are defeating the purpose of the lighter weight aluminum hull provides by adding weight? It must effect speed, fuel economy etc.?
Not an aluminum guy but I would guess trim tabs, suspension seats and adjusting speed for conditions are your best bets. I’m sure the metal boat guys can speak from experience.
Thanks, Ziggy. I do have hydraulic seats and that helps for sure. Of course, no issue when it is calm but when it gets choppy is when I need to go slow otherwise the passengers won't be happy. Your point is very valid in regards to adding weight. Perhaps my next investment should be adding trim tabs. I used to have a glass boat and loved it but this aluminum boat was such a fantastic deal that I couldn't pass.
 
I understand due to the weight, aluminum boats are more subject to bouncing. I usually add some weight to the bow of the boat and that helps. I'm also thinking of adding trim tabs to my 22' boat. Is that all I can do to help reduce the bouncing?
Trim tabs make a big difference, with motor trimmed down as well boat presses though with less pounding. But it is still aluminum, they bounce.
I use 10 and 12 year boys to shift the weight around when needed. " go sit in the cuddy "
 
fuel in the belly, tabs down somewhat in an oncoming sea, suspension seats and adjust speed so you dont lift. watch for waves with no back on them, be ready to pull back on the throttle so the boat comes down easier.
 
I understand due to the weight, aluminum boats are more subject to bouncing. I usually add some weight to the bow of the boat and that helps. I'm also thinking of adding trim tabs to my 22' boat. Is that all I can do to help reduce the bouncing?
You might want to consider a prop change to one that offers stern lift (4 blade). I change mine to correct a porpoise issue and found it rode better in light chop after making the change.
 
The fore-to-aft center of gravity (weight distribution) should be about 1/3 the fore-to-aft length (waterline) of the boat from the stern; 1/3 up from the stern.
Otherwise, you are dealing with a downside of AL boats; they cannot mfgr them with curves/bends as complex as can be done in FG.
 
I understand due to the weight, aluminum boats are more subject to bouncing. I usually add some weight to the bow of the boat and that helps. I'm also thinking of adding trim tabs to my 22' boat. Is that all I can do to help reduce the bouncing?

Are you talking about the boat porpoising in flat(ish) water or pounding in the slop and chop?
Porpoising is not limited to aluminum boats, my skiff became very stable with the pre-set trim tabs.
Aluminum boat pounding in the chop is straight physics.
 
Plenty of good info already but just in case you're interested in some theory detail...

From a design perspective, there's a few ways to look at "pounding in a chop".

If you think about what that is, it's "getting airborne and landing hard" right?

So the choices to fix it are either methods of not getting airborne, or methods of softening the landing.

Aluminum boats are prone to pounding because they're light, so they want to get airborne; they transmit shock because they're rigid; and often the bottoms are shaped to get maximum space on minumum power, so the V isn't super deep (among other design choices like wider beam which can be desirable...but which also contributes to a harsher ride, all else being equal).

Post-manufacture, since obviously 99.999% of us would never try to change the depth of the V on a boat, all the solutions are going to revolve around either changing the mass of the boat, so that when it hits the water after getting airborne it doesn't come to an instant stop, or preventing it from getting airborne, which is what the trim tabs would help with. If you can keep it down in the water, which is what those exotic OK hulls from Rafnar are about, you won't feel it slam, because that "slam" effect is the rapid deceleration of a falling boat, being stopped by the water.

Anyway trim tabs will probably be your best solution, because they'll tend to force the nose down in a chop and reduce the distance you fall, and the further the fall, the faster you're going when you hit the water.
 
Some excellent feedbacks. As mentioned, no issue in calm seas but pounding happens even in smaller chops. I mostly fish in calmer water anyways but time to time, we all can find ourselves in some bigger waves and choppy waters. Thank you all!
 
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