Author Topic: What am I doing wrong  (Read 3637 times)

Offline dbohara

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What am I doing wrong
« on: May 27, 2024, 02:05:32 PM »
20' Tolman Standard with 90 hp 2 cycle Yamaha.  Weather forecast was 5-10 kts wind from SW, 1 foot seas and bay and inland waters a light chop.
We left Carrabelle, FL going to Dog Island harbor, a distance of only 5 miles.  Wind was a definite 10 kts with 1' chop from SW.  we went due south to get in lee of island than due east to the harbor, no problem.  We were at the island for 3 hours and right before we got back aboard, I noted the wind had picked up to at least 15 kts with gusts to 20 from SW.  The seas were immediately 2' chop but by the time we got to the midddle (going NW) the seas were 2-3' chop making us slow down.  Soon the chop increased to 3' with some 4 and 5 footers.  It was slow wet going with lots of slamming and rolling.  BTW, motor was trimmed all the way down to keep the bow down.    Chop increased as we approached our goal to some 5 footers and at least one 6 footer that had us all say "OH Shit"  We got back ok.  However, I am really disapointed with the Tolman as it was really uncomfortable and did not feel good at all.  One boat passed us about our size going about 1.5X our speed and I noticed his bow was down.  I estimate our speed at the end was only 10 Kts and may not have even been planing,
What am I doing wrong?

Offline Kobuk

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Re: What am I doing wrong
« Reply #1 on: May 27, 2024, 09:46:04 PM »
I don't know of anyone who runs a 20' class skiff, of any manufacture, on plane in 3'-5' chop...!  :o

My last trip was six weeks ago.  It was FAC for most of the week, but our last few days saw wind N at 15-20 kts, which generated relentless 4' chaotic seas straight down Valdez Arm (NOAA chart 16708). We were light on fuel, but had 2 chests full of P-cod and spot shrimp on glacier ice, and an 80# pound halibut packed in about 150# of snow in the bottom of the skiff...so it was a pretty good slog from central PWS back to Port of Valdez.  Back in the harbor next day the conversation in the parking lot went like this: "Hey, nice boat! We saw you in Sawmill last night! We were the 26' North River (an ~8000# aluminum boat with big twins) that followed you in. Man, it was gnarly out there! We were wondering what you thought of it...?"   

Nobody runs on plane in those conditions.
« Last Edit: May 28, 2024, 12:19:24 AM by Kobuk »
https://www.fishyfish.com/boards/index.php?topic=5536.0
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Offline jim shula

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Re: What am I doing wrong
« Reply #2 on: May 28, 2024, 06:27:56 PM »
Did you build the boat with the specified 12 degree transom angle?  There was an addendum in later years for a 15 degree transom angle to increase the ability to drive the bow down by tucking the motor in further.  At this point you could add transom wedges or a doe-fin/whale tail type stabilizer to the lower unit of the motor.

Offline dbohara

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Re: What am I doing wrong
« Reply #3 on: May 28, 2024, 07:16:56 PM »
Yes, I did build her with the 12 degree transom angle.  The 15 degree discussion came well after my build.

So, would this "Doe-fin" thing really work to push the bow down?  Seems like an easy thing to try.

For that matter, does motor trim really work at low speeds to push the bow down effectively?  I can actually see it work when I'm on a plane but its less obvious at low speed in chop

Offline luk diver

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Re: What am I doing wrong
« Reply #4 on: May 28, 2024, 09:06:04 PM »
 Been running a Dolphin plate for 22 yrs. First on 100hp 4s yamaha and now 140hp suzuki. Played a lot over the years and due to cavitation issues (our o/b is offset 12" from centerline) we went the plate. Tried hard to avoid it as Oldtimers feel (Sal DeMurcio, that should ring bells with Steve Dampier) as it's extra drag? Hard to fathom considering it's not really even in the water, except underside. Gives us a lot of ability to use trim for various conditions. I know it's different with smaller Tolmans but works on ours. Then again we're also running a elect. offset so can trim the o/b for height. B & B

Offline GlacierBoats

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Re: What am I doing wrong
« Reply #5 on: May 29, 2024, 06:05:00 AM »
Been running a Dolphin plate for 22 yrs. First on 100hp 4s yamaha and now 140hp suzuki. Played a lot over the years and due to cavitation issues (our o/b is offset 12" from centerline) we went the plate. Tried hard to avoid it as Oldtimers feel (Sal DeMurcio, that should ring bells with Steve Dampier) as it's extra drag? Hard to fathom considering it's not really even in the water, except underside. Gives us a lot of ability to use trim for various conditions. I know it's different with smaller Tolmans but works on ours. Then again we're also running a elect. offset so can trim the o/b for height. B & B

Whether anyone agrees with me or not, I would say that both the Widebody and the Standard run a bit high in bow-up trim when on plane or approaching being on plane.  The Doel-Fin is just one planing fin that exists, and the first one I believe.  Other planing fins exist.  Without redesigning these boats, they are what they are and are close enough - with a long history of success and happy customers.  Renn stated that the Standard is a wet boat (which means it splash-splash-splashes along more than slicing through waves) and is why he strongly suggested using the auxiliary spray rails along the f'w'd chines.  The non-standard transom angle also makes it harder to trim the boat using the outboard.  A transom angle of 14 plus/minus 2 degrees is the ABYC standard that boat motor manufacturers design around - don't fight it.  You can use transom wedges to correct your motor mount to a 14 or 15 degree transom angle (both are fine for a Standard).  As for the Doel-Fin, note that there are several 'planing fins' (aka 'planing stabilizers') on the market and they tend to be designed for optimal performance at different speeds.  Some are for high speed planing while others, such as the Doel-Fin, are designed to take effect at slower speeds.  For the Standard, I do recommend the Doel-Fin if you're not happy with the trim (when approaching planing and when on plane).  If I had a Standard, I'd correct the motor mount with wedges first, try it out, then consider the Doel-Fin.  And like I said ... both the Standard and the Widebody could use a bit of refinement to help with pounding, 'splashing', and trim ... trim when approaching planing and when planing.  I offered, to Colin, to do some of these (relatively minor) tune-ups to the designs, and he was all for it.  Someday, when time permits, I'd like to do this ... just for the good of the community, no payback to me.  I think it'll have to wait for me to retire, however, and I think I'm going to be working a day job for about another year or so.

PS: Doel-Fin efficiency ... ANYTHING that changes trim away from the boat's no-fins/no-trim tab planing angle is going to reduce the efficiency of the boat.  And for each degree of change, all the various 'solutions' will reduce the efficiency by about the same amount.  I suggest doing what you have to do and not worry about it.  Pick the trim tab or planing stabilizer fins that appear to address the issue that you wish to address, e.g. slow speed trim adjustment or high?, and go with it.  Be happy.  You have a great boat!

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Offline dbohara

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Re: What am I doing wrong
« Reply #6 on: May 29, 2024, 12:57:29 PM »
I'll try the DoelFin plate and let y'all know

Offline GlacierBoats

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Re: What am I doing wrong
« Reply #7 on: May 29, 2024, 02:35:08 PM »

Yeah ... for the speed range that you're talking about, the Doel-Fin is where I'd start too.

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Offline Kobuk

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Re: What am I doing wrong
« Reply #8 on: May 30, 2024, 09:05:27 AM »
Take a look at Permtrim.  They make one that pairs very nicely with the Yamaha.  I have one on my F70 and like it a lot.  That said, by my experience seemingly subtle nuances between different props can make a huge performance difference...and the symptoms of a poorly performing prop won't necessarily be solved by a fin.  Personally, I'd endeavor to be 110% confident I had optimal prop performance dialed in before resorting to installing a fin plate.

Here's the link: https://permatrimmarine.co.nz/  I got mine straight from the manufacturer in NZ...it was cleaner, easier, and less expensive than dealing with the US distributor/retailer.
« Last Edit: May 30, 2024, 09:12:53 AM by Kobuk »
https://www.fishyfish.com/boards/index.php?topic=5536.0
Started: 3/2019
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Offline Lyle

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Re: What am I doing wrong
« Reply #9 on: May 31, 2024, 11:23:55 AM »
I don't think you are doing anything wrong.

 Conditions are what they are. Hulls are what they are. I don't compare one boat to another unless I'm buying one.  All you can do is keep an eye out for the wx and anticipate, than adapt to conditions or wait it out. I keep the radio on and listen to the chatter-usually gives you a heads up. Your in a seaworthy enough boat ,but it is light. Might feel a bit different in a production boat that weighs a half ton more- but will still be sloppy in the conditions you faced. If we start pounding badly in chop, I try various speeds/course changes/ human ballast changes to fine tune. 10 mph in that kind of chop seems like pushing it. With the numbers you gave it's a .5 hour run at 10, .666 hour at 7.5, etc.
 I like to make those kind of days a "learning exp"  ;)
 Best part of your post was "we got back ok", glad it worked out.

 BTW, we ran from Dog Is/ Alligator to Steinhatchee one day last year. Lots of fog all the way, than crab pots as we got east!  Stein- Cedar Key, than Clearwater. Beautiful area all. Skipped Carabelle as there were large flotillas of Great Loopers heading in there!
Remain in neutral and move on to the next target
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Offline fishooker

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Re: What am I doing wrong
« Reply #10 on: June 14, 2024, 05:53:48 PM »
20' Tolman Standard with 90 hp 2 cycle Yamaha.  Weather forecast was 5-10 kts wind from SW, 1 foot seas and bay and inland waters a light chop.
We left Carrabelle, FL going to Dog Island harbor, a distance of only 5 miles.  Wind was a definite 10 kts with 1' chop from SW.  we went due south to get in lee of island than due east to the harbor, no problem.  We were at the island for 3 hours and right before we got back aboard, I noted the wind had picked up to at least 15 kts with gusts to 20 from SW.  The seas were immediately 2' chop but by the time we got to the midddle (going NW) the seas were 2-3' chop making us slow down.  Soon the chop increased to 3' with some 4 and 5 footers.  It was slow wet going with lots of slamming and rolling.  BTW, motor was trimmed all the way down to keep the bow down.    Chop increased as we approached our goal to some 5 footers and at least one 6 footer that had us all say "OH Shit"  We got back ok.  However, I am really disapointed with the Tolman as it was really uncomfortable and did not feel good at all.  One boat passed us about our size going about 1.5X our speed and I noticed his bow was down.  I estimate our speed at the end was only 10 Kts and may not have even been planing,
What am I doing wrong?
I am not sure if what I did is right or wrong. I felt somewhat similar suspicion as you do so I bought 5  appr.50LB bags of stone sold at Home Depot - total about 250lb - And placed  on the bottom of the bow instead of anchor line. It balances whole look of the boat more leveled. I tried while I was with a marine surveyor.

Offline TFreeburg

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Re: What am I doing wrong
« Reply #11 on: June 14, 2024, 10:01:50 PM »
I’m not sure about understanding the fuss here.
When you tie down your bow you will have to work hard to defy the forces - but the outcome will be a great displayed bow, with a moderate displacement. And the outcome will be a modest semi-vi, and it’s going to fly through the water, and when it becomes a fully loaded boat, you will have no regrets.
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Online KenB

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Re: What am I doing wrong
« Reply #12 on: June 23, 2024, 10:07:54 AM »
I'll try the DoelFin plate and let y'all know

Hey Guy! Congrats on getting the boat done, anyway! Im sorry she's not come out exactly as planned, but I think you got a few positives going for you:
- if anything breaks, you know how to fix it.
- everything is where you want it, because you put it there.
- I don't think there's another 20ft powerboat that should be out in 5-6' waves. period.

It's been my experience, especially in wind-blown chop, to remember that your tolman is less dense than water. In other words, it's a called a "skiff" for a reason. It's not a displacement hull and it certainly isn't a deep vee. So don't run it like one or expect the same performance. Its not a bertram 27 or formula 233... Skiffs go "up and over" the slop, not through it.

PHOTOS PLEASE! And be safe!
best,
KenB

"HOW CHEAPLY CAN A TOLMAN SKIFF BE BUILT AND JUST HOW  MUCH IS SACRIFICED IF COST IS THE PRIME MOVER?"
- Bruce Armstrong   

"I can tell you that either a nice BFT or a big YFT is an absolute riot on a Tolman. The boat is so light it's like the old man and the sea..."
- Dave Nolan (RIP)