flapbreaker
New member
I have a Honda 90 main. It came with a hydrofoil on it and the boat also has trim tabs. Just wondering if I really needs the hydrofoil on there? Any input?
Hydrofoil really necessary?
- Thread starter flapbreaker
- Start date
flapbreaker-
The trim tabs and the hydrofoil do different things, although they have some overlap.
The trim tabs are for lateral trimming as loading changes, and for holding the bow down in chop to smooth the entry.
The hydrofoil adds planning area at the rear for a faster hole shot, promotes planning at a lower speed, and can add stability in chop and waves (lengthens the hull's pitch axis).
The hydrofoil also increases the bow up/bow down (pitch axis again) trim function of the motor as the plate becomes effective in this manner when the water rushing past flows at more oblique angles. As the angle is increased, it gradually induces more drag and lowers efficiency and gas mileage.
Both trim tabs and the hydrofoil add to the difficulty in controlling the boat in a following sea as they present extra area for the surging energy of a following, lifting wave to swing the stern to one side and potentially broach the boat.
It's probably even more complicated than this, but what I'd suggest you do is get throughly familiar with how your particular boat handles with the tabs and hydrofoil, then remove the hydrofoil and see if you can "feel" the difference in handling characteristics, and go from there.
Whether or not the hydrofoil is of advantage may partially, at least, depend on the conditions in which you boat.
Good Luck, and let us know what you find out! Joe.
The trim tabs and the hydrofoil do different things, although they have some overlap.
The trim tabs are for lateral trimming as loading changes, and for holding the bow down in chop to smooth the entry.
The hydrofoil adds planning area at the rear for a faster hole shot, promotes planning at a lower speed, and can add stability in chop and waves (lengthens the hull's pitch axis).
The hydrofoil also increases the bow up/bow down (pitch axis again) trim function of the motor as the plate becomes effective in this manner when the water rushing past flows at more oblique angles. As the angle is increased, it gradually induces more drag and lowers efficiency and gas mileage.
Both trim tabs and the hydrofoil add to the difficulty in controlling the boat in a following sea as they present extra area for the surging energy of a following, lifting wave to swing the stern to one side and potentially broach the boat.
It's probably even more complicated than this, but what I'd suggest you do is get throughly familiar with how your particular boat handles with the tabs and hydrofoil, then remove the hydrofoil and see if you can "feel" the difference in handling characteristics, and go from there.
Whether or not the hydrofoil is of advantage may partially, at least, depend on the conditions in which you boat.
Good Luck, and let us know what you find out! Joe.
A
Anonymous
Guest
Joe, great explanation, like always :thup
...daoh, back on track: I have tried 2 different types of hydrofoil; both ones cause too much stern-lift, because it is from the center, (the lower-unit) causing the boat to feel --- tippy :!: while underway. I wonder if there is on that does not cause so much lift :?:
The StingRay hydro' was fierce for it, cuz its wing-shaped, the other brand (i forget) was cooler looking, and on-sale... so I tried it (after giving my other one to my sister for her little deep-vee boat) seemed to be less of an issue on a deep-vee-hull :|
Never-the-less, all I had for years was the "poor-mans-trim-tabs" hydrofoil. Try it
... BTW... who put this cute lil "poobutt" (
) in here. I likem 
...daoh, back on track: I have tried 2 different types of hydrofoil; both ones cause too much stern-lift, because it is from the center, (the lower-unit) causing the boat to feel --- tippy :!: while underway. I wonder if there is on that does not cause so much lift :?:
The StingRay hydro' was fierce for it, cuz its wing-shaped, the other brand (i forget) was cooler looking, and on-sale... so I tried it (after giving my other one to my sister for her little deep-vee boat) seemed to be less of an issue on a deep-vee-hull :|
Never-the-less, all I had for years was the "poor-mans-trim-tabs" hydrofoil. Try it
... BTW... who put this cute lil "poobutt" (
) in here. I likem josepepper
New member
Just replaced a honda 50 with a Yamaha 90hp. I have trim tabs that auto adjust and have tried every manual adjustment to no avail. The problem is with the flat bottom on this boat no matter how I trim the motor or redistribute weight the stern sways and becomes uncontrollable over 15knots if there is a lot of chop or side wakes from passing boats. It's extremely dissapointing as I spent 10k on a fine engine and thought the extra power would solve these problems. I know part of this is due to the basic design of the light hull with the flat bottom but there must be something I can do to modify the hull, engine etc... to allow this boat to track properly at speed under other than completely calm conditions. Any suggestions would be greatly appreciated.
Danny
Danny
Trading a 50 for a 90, hmmm, almost double the power :roll: Might be that there is more involved here than just a need for speed. Might be helpful to know what boat, and what kind of load on board. Some folks have had very good luck with the "Permatrim". Can't say I would want "auto" trim tabs, I guess I would rather push my own switches. :wink Do a search on the site for "permatrim" and you will find a ton of entries, with probably, some very helpful info.
Good Luck,
Harvey
SleepyC
Good Luck,
Harvey
SleepyC
Not sure how much this applies to the larger boats but, on my 16 they work well together. Here's a quote I made from a different thread.
"I just got back from a full week of cruising it the Traverse Bay area and was shocked as to how well the trim tabs worked. We rode in a variety of conditions and with the exception of one day with a 4 foot chop, they worked great. I found that by working the trim tabs in conjunction with the Permatrim on the motor, I was able to regain high speed cruising into the wind and light chop. I was able to regain the top speed that I had lost from all of my weight add-ons. Only one bad thing. I have to be careful slowing down or running at a slow speed with the tabs down. One tab can catch more water than the other and turn the boat violently. They are best suited for high speed cruising and side-to-side leveling. No more moving the cooler or twisting in my seat. Definately worth every penny."
"I just got back from a full week of cruising it the Traverse Bay area and was shocked as to how well the trim tabs worked. We rode in a variety of conditions and with the exception of one day with a 4 foot chop, they worked great. I found that by working the trim tabs in conjunction with the Permatrim on the motor, I was able to regain high speed cruising into the wind and light chop. I was able to regain the top speed that I had lost from all of my weight add-ons. Only one bad thing. I have to be careful slowing down or running at a slow speed with the tabs down. One tab can catch more water than the other and turn the boat violently. They are best suited for high speed cruising and side-to-side leveling. No more moving the cooler or twisting in my seat. Definately worth every penny."
Danny, you have to be kidding. There are hundreds of these boats with 90's and they run very well up to about 30 or maybe 32 knots--above that they get a little squirlley--but nothing like what you describe. You need to have a member who knows the boats take alook at your boat, and ride with you. Something is way amiss.
First I would look at how the boat weight is distributed. Second get rid of the manual, "adjustable" trim tabs--they may be the problem. I would personally put on both hyraulic or hyraulic electric trim tabs, and the Permatrim on any 22 or 25-but that is my preference after having owned both a 22, with no tabs at all, and a 25, with only trim tabs and then adding the Permatrim. The permatrim allows the bow down in heavy chop--and it allows planing at lower speeds.
Good luck
First I would look at how the boat weight is distributed. Second get rid of the manual, "adjustable" trim tabs--they may be the problem. I would personally put on both hyraulic or hyraulic electric trim tabs, and the Permatrim on any 22 or 25-but that is my preference after having owned both a 22, with no tabs at all, and a 25, with only trim tabs and then adding the Permatrim. The permatrim allows the bow down in heavy chop--and it allows planing at lower speeds.
Good luck
Wandering Sagebrush
Free Range Human
Wow, what you're describing is something I have not heard of, nor have I experienced it on my CD 22 with Honda 90. Is there any chance that you have a stuck trim tab? I can't think of anything else that would create a situation like you're describing.
I did add a Permatrim plate to my boat to help with chop (and it really helps), but other than that it's a stock boat without trim tabs. One thing that I did notice is that if I try and get high speed with the engine/Permatrim trimmed all the way down, the boat gets a severe lean to the right (as I recall) and wants to turn. So, as I get up to higher speeds I trim the engine and it's just fine.
Good luck finding this one. I am pretty certain that it is not the engine.
Steve
I did add a Permatrim plate to my boat to help with chop (and it really helps), but other than that it's a stock boat without trim tabs. One thing that I did notice is that if I try and get high speed with the engine/Permatrim trimmed all the way down, the boat gets a severe lean to the right (as I recall) and wants to turn. So, as I get up to higher speeds I trim the engine and it's just fine.
Good luck finding this one. I am pretty certain that it is not the engine.
Steve
I'm getting one for Christmas (already told the wife what I want :wink: ). As I've posted before, I'm not happy with the stern heavy attitude of our 25. Even at maxed out trim, it still runs too bow high, IMO. It will only get worse when I add the weight of a kicker out back.
Same on our 25. I have to counter steer to overcome the torque forcing the boat over/into a turn. The first time it did this it took me by surprise. I've thought of adjusting the small skeg on the cavitation plate, but I've just never gotten around to it.
I have Bennet hydraulic tabs on my 22. After reading all posts about Permatrims, and almost everyones positive responces I added one as well. I did notice a slight difference in the boats handling, but not enough to warrent the cost of the Permatrim IMHO. But that is just my 2cents
Chuck
Bootleg Hooch
Chuck
Bootleg Hooch
In any boat if you get the bow down too much, it will cause "bow steering"--which basically lets the sharp part of the bow act like a rudder, adn will throw the boat off to one side or the other.
If the "Auto Trim Tabs"--horrible things--were all of the way down--it could cause this type of action--loose those tabs. It is rare that you trim boats all of the way down.
When working into any heavy weather--into or with the seas (and even cross seas) it is a combination of steering, throttle and trim. In offshore racing boats, there is one man who does the throttles and trim--and in some boats one separate man for both throttles and trim, as well as another who does just the steering. Sure it is a bit more work, but that is what makes the boats ride well in heavy weather. You do have to work at it.
If the "Auto Trim Tabs"--horrible things--were all of the way down--it could cause this type of action--loose those tabs. It is rare that you trim boats all of the way down.
When working into any heavy weather--into or with the seas (and even cross seas) it is a combination of steering, throttle and trim. In offshore racing boats, there is one man who does the throttles and trim--and in some boats one separate man for both throttles and trim, as well as another who does just the steering. Sure it is a bit more work, but that is what makes the boats ride well in heavy weather. You do have to work at it.
Hi All,
The last post said it all you need to work the tabs and trim angle to set up for the conditions now. Change course and you will need to trim again. I came from slow trawlers and learning to use trim tabs and motor trim was a new thing for me. Keep on playing with them and you will learn to get it right.
I boated a lot with an oversized friend and when ever he moved I had a finger in the tabs.
Fred M.
The last post said it all you need to work the tabs and trim angle to set up for the conditions now. Change course and you will need to trim again. I came from slow trawlers and learning to use trim tabs and motor trim was a new thing for me. Keep on playing with them and you will learn to get it right.
I boated a lot with an oversized friend and when ever he moved I had a finger in the tabs.
Fred M.
I have run a Permatrim for the last year and recently took it off to do some more experimenting. The only thing I can definitely say it did was allow me to plane at 10 mph and get impressive fuel economy. However running any faster than 12-13 mph and fuel economy went way down. The new Honda is really sensitive on fuel consumption versus engine loading. You have to watch your rpm versus boat loading to be sure you don't drop from 3.5 mpg to 2.5 mpg. Without the Permatrim, I can cruise economically up to 17 mph and still get good economy going slower but not quite as good as with the Permatrim. In my situation, I feel the Permatrim was adding a lot of drag to lower unit. I couldn't raise the motor any higher without a jack plate. Right now I am running without the Permatrim. I don't think I will be putting back on.
20dauntless
New member
Anyone have any idea of whether the SST or Permatrim creates more drag at high speeds? I agree with Tom that the new Honda 90 (the fuel injected one) is sensitive to loading and engine speed. It seems that it is very fuel efficient until around 4400rpm but after that it burns a lot more fuel. I've done trips with 2 people and fairly lightly loaded and cruising at 4400 rpm and gotten 4.4 nmpg, but that can drop to 2.5 nmpg with 6 people and a lot of gear cruising at similar rpms. Just out of curiosity Tom what hole is your engine mounted on? I'm thinking mine is mounted a little low and bringing it up one hole might help with economy...
Back on topic, I do like my SST. The ability to plane very slowly is great when you are heading into a steep chop, and I don't care about a little loss of top end speed. I have the factory installed Bennett tabs. If I had to do it again I'd probably get bigger tabs. They are fine with light and balanced loads, but that's not always possible for me so it would be nice to have more flexibility and not have them deployed so much.
Back on topic, I do like my SST. The ability to plane very slowly is great when you are heading into a steep chop, and I don't care about a little loss of top end speed. I have the factory installed Bennett tabs. If I had to do it again I'd probably get bigger tabs. They are fine with light and balanced loads, but that's not always possible for me so it would be nice to have more flexibility and not have them deployed so much.
My engine is as high as it can go without redrilling the top bolt. I can't do that since it is about an 1.5 inches from the top of the transom. With the Permatrim installed any rpm above about 4200 and fuel consumption jumps quickly. Without the Permatrim, I hit steep portion of the fuel consumption curve at 4500 rpm.
At least in the Tom Cat, it makes little difference in top speed or fuel economy. In this boat it runs on the surface. In the C Dory, it was under water, so i suspect a little drag, BUT, it got the boat on plane faster and my feeling was the fuel economy was better--speed about the same.
Wandering Sagebrush
Free Range Human
Tom,
I don't believe that I am seeing any great jump in fuel consumption with my boat. We have a Honda 90 with carburetors. I typically run (light load, full of fuel) at around 4200-4400 rpm and 20-22 mph when water conditions permit. WOT is around 5400+ for me, and I was surprised to see it hit 31mph when I cleared the bar into Tillamook Bay a couple of weeks back. On that trip, we were offshore for about 6 hours, probably ran 8-9 miles each way in moderate chop, and trolled all day on the 90. My guess is that I burned between 6 and 7 gallons of fuel.
I'll let you know about loaded cruise (and altitude effect) after the Lake Powell trip.
Steve
I don't believe that I am seeing any great jump in fuel consumption with my boat. We have a Honda 90 with carburetors. I typically run (light load, full of fuel) at around 4200-4400 rpm and 20-22 mph when water conditions permit. WOT is around 5400+ for me, and I was surprised to see it hit 31mph when I cleared the bar into Tillamook Bay a couple of weeks back. On that trip, we were offshore for about 6 hours, probably ran 8-9 miles each way in moderate chop, and trolled all day on the 90. My guess is that I burned between 6 and 7 gallons of fuel.
I'll let you know about loaded cruise (and altitude effect) after the Lake Powell trip.
Steve
20dauntless
New member
Steve, Tom and I (and others I'm sure) have the EFI Honda 90, also known as the BF90D. This engine has all sorts of Honda technology like VTEC, BLAST, and Lean Burn Control. My belief is that at some point (based on load and RPM) the computer changes the timing fuel map and requires more fuel.
That being said, this is an excellent engine. It's smooth, quiet, starts instantly, and has no problem pushing the C-Dory even when loaded very heavily.
That being said, this is an excellent engine. It's smooth, quiet, starts instantly, and has no problem pushing the C-Dory even when loaded very heavily.
BaseCampAnne
New member
Back to the original question...I got one of these on the advice of Don Anderson of the Jenny B. Thanks, Don!
I have learned that it is very strong and have heard in a Coast Guard Auxiliary class that it can be used in an emergency (when the engine is OFF) to help with getting someone out of the water, or at least somewhat higher when trying to recover someone from the back of the boat. I don't think Gus, my lab, will find it useful, but someone with very little upper body strength can stand on it and find it useful to be lifted up out of the water a bit....
Anne Cox (in the process of joining the retired and wondering how to pay for everything) :?: :!:
I have learned that it is very strong and have heard in a Coast Guard Auxiliary class that it can be used in an emergency (when the engine is OFF) to help with getting someone out of the water, or at least somewhat higher when trying to recover someone from the back of the boat. I don't think Gus, my lab, will find it useful, but someone with very little upper body strength can stand on it and find it useful to be lifted up out of the water a bit....
Anne Cox (in the process of joining the retired and wondering how to pay for everything) :?: :!: