bertram31.com

I understand that each boat is unique, but I'm curious about the speed at which your boat typically planes. I'm contemplating making some adjustments to my hull design to achieve the lowest possible planing speed, in addition to installing oversized trim tabs. My goal is to enable my boat to plane at speeds of 15 knots or less.

My boat would plane at 15 knots without tabs. Since I installed I can go a bit less than.

I plane off at around 12 knots. No tabs

I’ve never had a problem at 13.5kts planing off. Sometimes lower depending on the conditions.

My experience agrees with the comments above. My boat easily planes at 15 knots. My trim tabs are stuck at what I assume to be neutral position.

Same. Planes at about 13.5 knots. No tabs.

I'm taking the bait...

Why do you want to achieve the lowest planning speed?
Why was 15knots the semi-target speed?

Now that you pretty much know that is pretty much standard, what is the next move?

I'm guessing trolling or extended range...but could also be why I like that slow cruise area...fast enough to somewhere, comfy cruise for guests, Not burning heavy pushing a ton of water so economy can be good for short rides meant to last a long. Its a nice spot to let motors warm up before going...


My ol 31 had the original 165 fiberglass tank with 440's, no tabs. In that configuration, she ran great at low speeds. Once I had to change tank, going larger to 220 gallons and having more tank further back I found when I was low on fuel the boat was tough to plane at lower speeds. My thought was the larger tanks with nose high had all the weight aft. The smaller tank kept the weight centered more. Pushing up the throttles the boat was fine, leveling off and having fuel run forward more. But still slowing down in seas coming off the throttles some the ass would squat n fall off plane easy. It was at that point the tabs went on, pretty much took care of that problem...that and keeping tank either @ 1/4 or over 1/2 full....or running a faster cruise.

I'm mostly just thinking out loud as I wonder.

Big tabs are one thing, but modifying the hull I'd be a little leary about. The reason is when running mid to higher cruise, the boat does not need to have that bow pushed down. I can see it as being detrimental dong that. But hey, you know what you want and why...just tossing info out there.

Carl

Interesting you said boat does not plane off as fast when low on fuel. I never paid attention to that, now I have too. I can say that once I hit a half tank the cruise speed starts increasing, so I would think getting on a plane should be quicker.

Now this will drive me crazy until I run the tank down.

Tony Meola wrote: ↑Sep 25th, '23, 20:33 Interesting you said boat does not plane off as fast when low on fuel.

Tony, that is kind of what I said, but not what I meant. Now try to figure that one out...lol


Yes, when light on fuel the boat can pop on plane quicker and cruise faster.

My point is when at 1/3 or 1/4 tank the boat will squat more. More squat makes it tougher to get on plane and stay on plane "at low speeds". Yes, light on fuel I could push throttles forward quicker and that squat means little...but IF I wanted to cruise at those lower speeds it wasn't great. When did I want to cruise slow...running in low light, poor visibility, in seas, or a howdy ride to no place in particular?

Maybe a better way to say it, I find an empty-ish tank like a badly trimmed boat with Bubba Joe n his beer buddies sitting on the transom. Yes, tabs or accelerate away from that spot n all is good. And in truth, it is not bad, it is just that I found my boat performed better at all speeds, at all tank levels with the smaller original tank sitting further forward. Also with the extra weight n torque of the diesels, this has become less of an issue. That said at low tank levels I still use a bit more tab at low speeds. And that is what this topic is about, low-speed planing.

I sure hope it stops raining n the fish start biting soon. I'm tired of thinking about this stuff...

Carl

Believe it or not, I got it. I am in the I don't need tabs camp. But I have looked at some of the newer blades type tabs. They seem to be real interesting since you do not have anything extending out from the stern.

Rain Rain and more rain. My summer was screwed up anyway so why not let the weather wipe me out completely.

Whenever I look for a "new" boat, I check at what speed I can get it to plane off. I've been out too many times when 13-15 knots was as fast as was comfortable, and I don't want a boat that's wallowing around trying to get over its bow wave at those speeds. Same with my B20--it'll plane at about 13 knots. I've been on small centers that won't plane until 18 knots or so, and if its rough out, the wallowing around where you can't go fast enough to plane off without getting knocked around just doesn't work for me.

The Blade-style tab is not so new anymore Tony. I wanted the blade tabs when I started looking for tabs; that was right after I had to change out the original glass tank that was being eaten by the ethanol. So when was that when the mandate for year-round ethanol became a thing around here, maybe 15 years ago?

Anyway back then the price difference between the new blades n the tried n true Bennett tabs was huge. Aside from performance, I wanted to save coin at the pump. It just didn't make sense back then.

Anyway, if you don't need them, you don't need them. I ran my boat for 10- 15 years before I felt they would be beneficial. That is only because I changed the boat configuration by installing that bigger tank moving more weight aft.


I agree with you 100% John. Yes, going faster riding over the waves is an option at times, but it can come at a price. I personally like to have the option of doing either when possible.