Planing

rickalan35 · Post by **rickalan35** » Thu Jul 17, 2008 10:51 pm

Last week-end I took two of my marina neighbors (both commercial pilots) down the lake a couple of miles and on the way back they coaxed me into opening up the throttles a bit (I am not noted for horsing my boat like I sometimes do my motorcycles)............ bottom line is that they got me to back off the trim tabs a bit at 3000 rpms and as the nose came up the boat ran better and the rpms dropped to 2700.

I have obviously been running the boat with the nose pinned down too much when up at speed. But I must say that it's not "natural" for me to be able to actually feel when the boat is running "free" of too much nose down trim tab.

One of the pilots had a hand held GPS that indicated 24 mph (not knots) at that rpm.

Comments??

Rick

Stripermann2 · Post by **Stripermann2** » Fri Jul 18, 2008 7:37 am

Depending on seas, wind etc. You will always need to adjust attitude of boat. Trimming bow-down too much will surely slow a boat down as well as too much bow-up will surely slow a boat down.

Watch your gps speed and try to dial in a comfortable trim at a desired rpm. Also, instead of using throttles to slow a boat down a bit when planing/cruising, try bowing up with the tabs. This will slow the boat. Once you need to pick the speed up a bit, simply bow down again to aquire the resumed speed. Don't use the throttles if you don't need them, it's easier to adjust the tabs, more fuel efficient then trying to sync the throttles back again.

Too much bow down will dig-in and you will lose immediate steering control if quick turning is needed. As well as turning your boat from an efficient planing hull to a displacement hull.

ScurvyDog · Post by **ScurvyDog** » Fri Jul 18, 2008 8:24 am

Just after I got my F32, I played with this exact topic. I to am a commercial pilot, what difference does that make you ask? We are trained to notice and think about very small adjustments that create large reactions. On my F32, when I initally go on plain, I need full nose down trim tabs to push the bow down. This is at about 15 kts. Once my speed is above about 18 kts I start taking away trim tabs to run more effeciently. By the time I am nearing the full throttle mark (which I have only done twice) I have next to no trim tab out. The top speed I noted with 305 engines was 27 kts or 28 mph. I was very lighly loaded with fuel and water. Trim tabs create drag and push the bow in creating more drag, thus slowing us down. We do need them initally to get our big beasts to come up on plain but as speed increases so does the reaction of our big tabs.

TADTOOMUCH · Post by **TADTOOMUCH** » Fri Jul 18, 2008 8:55 am

Wow,

I wonder what percentage of F-32 or any boat owner are pilots? I am one as well and have also played around with the trim and speed quite a bit trying to find the best cruise set-up for the least amount of fuel burn. I have twin Chrysler M360's at 250 hp each. I can get up on plane without the tabs and my fast cruise rpm is about 2700 rpm with no tabs I get about 24 kts and with minor nose down trim I get 26 kts. WOT doesn't give me much more other than fuel burn and engine stress so I have only done that a couple times just to see where it was 3200 rpm and 28 kts.
Slow cruise is about 2200 rpm with medium trim down to give me 20 kts
I can stay on plane til about 17 kts and then it requires too much tab and loss of steering to go much slower.

This is all on calm seas. Rough or moderate seas really change the way you want to trim the boat. I prefer to have no trim in a moderate to rough following sea as most of you have found out the boat can get a little squirrely in following seas.

Stripermann2 · Post by **Stripermann2** » Fri Jul 18, 2008 9:09 am

I've logged about 15 hours in a Cessna 172 RG!!!

(Many years ago...) does that count???

captainmaniac · Post by **captainmaniac** » Fri Jul 18, 2008 9:55 am

TADTOOMUCH : 24 knots at 2700 RPM and 20 knots at 2200 rpm ? I have the same 360s, and get nowhere near that. Mind you I have almost 1600 hours on them, but didn't think they were that tired! What props are you running, and have you renovated the interior or stripped out any weight ?

prowlersfish · Post by **prowlersfish** » Fri Jul 18, 2008 7:09 pm

TADTOOMUCH you are way over proped or your tachs are way off

jordan · Post by **jordan** » Sat Jul 19, 2008 12:38 pm

With my 76 F-32 and 318s, I'm running about 14 knots on the GPS at 2700 rpm. I use the trim tabs to help plan off but then bring them back up. I burn about 1 gal per mile at 2400 rpm (11-12 knots) at a slow plan or the same gals burnt at 1800 rpm (7-8 knots) not planning. I prefer to run the slower speed for the peace and quiet and hoping it will save the engines. I ran it at 3000 rpm (16 knots) last weekend only trying to out run a storm on Lake Superior and only once to see top rpm. (3900 rpm starboard, 4050 port)

Jim

obeejr · Post by **obeejr** » Sun Jul 20, 2008 8:25 pm

With my Crusader 350's and 16X16 props on my F32 I get 16+ knots at about 3100 rpms with no tabs. Speed goes to 18+ knots with the tabs down, which means my fuel economy is up also. Unfortunately, with a lot of tab the bow digs in, and since the stern is almost flat handling gets squirrelly.

captainmaniac · Post by **captainmaniac** » Sun Jul 20, 2008 8:44 pm

I may be taking this thread in the wrong direction, but here is Water Music's 'speed curve'... is this in line with what you other F32 owners with 360s are seeing? I have over 1570 hrs on the engines, they are almost 30 years old, and I don't know for sure how the previous two owners treated her the first 21 years of her life...

1500 RPM 8 Knots
2200 RPM 10 Knots
2600 RPM 15 Knots
3000 RPM 19-20 Knots
3500 RPM 25 Knots
4000RPM 27 knots (only done twice in the past 8 years, once to see what it would do, the other to get under a bridge and escape a storm on Lake Ontario (else ride it out for another half hour)).

ScurvyDog · Post by **ScurvyDog** » Mon Jul 21, 2008 5:59 am

Wow, It is really interesting the speed difference in the F32's with different props, engines and higher time blocks. I didn't mention, the speeds I reported above were on 305's 50 hours after a total rebuild.

jddens · Post by **jddens** » Mon Jul 21, 2008 9:39 am

I have an F30 flybridge crusier and my speeds/RPM pretty much match Captainmaniac.....power is FI 350's, 330hp ea.......200hrs .we seem to be all over the board here......is it props and transmissions making this huge difference????

TADTOOMUCH · Post by **TADTOOMUCH** » Mon Jul 21, 2008 4:32 pm

Yea my tachs are probably way off. They don't agree with each other and not the same on lower helm and flybridge so my tach numbers are probably way off. My engines only have 410 hrs on them and I am not sure what props I have by they are OEM.

wowzer52 · Post by **wowzer52** » Mon Jul 21, 2008 6:24 pm

My F-32 has 15x15 props with 351 windsor Mercs and planes at 14 to 16 knots 2800 to 3000 rpm depending on the water and tops out at 28 knots gps @ 4100 rpm. Before the new bottom paint I had to do 3000 rpm just to get up.

Stripermann2 · Post by **Stripermann2** » Tue Jul 22, 2008 7:14 am

My F32 has Crusader 270's, 16X16 original sized props. I will cruise at between 18-19 knots @ 3100 rpm, flat seas, calm winds.

I generally don't start working the tabs until I'm between 2500-2800 rpms, then she lays right down. Boat is usually loaded and with the half tower, she's a bit heavier.

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