Ok, Crucify Me

[Yachter Yat]

Meister:  Just looked at stickball's Hunter pics and noticed he's running a 3 blade prop.  Curios as to whether or not you've tried a 3 blader??  I've never had occasion to run a 4 blade on any of my boats as I was always under the impression the benefit provided by that extra blade was somewhat offset by the inherent 'drag' due to the added blade area .  
   Notwithstanding props, I still say that bottom paint.....along with the kicker, two batteries and any other weight you carry, is bound to levy a fairly substantial tax on your performance; especially with respect to time-to-plane. Needless to say, it would certainly be interesting to see the difference with that bottom polished, one battery and the kicker left in the garage. I love that Hunter, but (like my 16 SC) I came to learn, even a seemingly minor amount of additional weight on the backside of these small hulls can make a huge difference.
   In any event, have fun and please keep us posted.

Yat

[fishmeister]

When I bought the boat, I got a box of "stuff" with it (most of it turned out to be useless).  There was on old, beat-up three-blade prop in there.  I never ran it.  As noted, the boat had a new 4-blade on it (albeit over-propped).  So, to answer the question, I've never tried a three-blade prop.  I'll admit that I don't have anything to truly compare against.  But, some of my travels include my local river and Diablo Lake.  The river has channels that are constantly changing.  Diablo Lake (man-made, for those unfamiliar) has a long and relatively narrow canyon at the head of it.  This is where I fish that lake.  In both cases, good "bite" and turning response are important.  I've read that a four-blade is better for this so I chose to stick with that.

The boat already had the dual batteries when I bought it.  I like the added "comfort" of having a second battery available, if needed.  I'm not willing to ditch a battery.  I also use my cuddy space (what there is) for gear storage. and don't have room to move a battery there.  So, I'm afraid that the batteries (both of them) are staying put.

I prefer to troll when fishing.  Most of the time, I'll run the kicker for this.  It's much cheaper on gas and saves hours on my main.  Also a factor is that some of my fishing (trout and sockeye salmon) is best at a really slow speed.  I'll admit that my 9.9hp kicker is probably a bit more than I need with a SH.  I'd probably do just fine with an 8hp.  But, money is an object for me.  When I bought the kicker, I also wanted a motor that I could remove and drop onto my 12' Lund, if needed.  I also like knowing that my kicker has enough oomph to push my Arima home, even against the river current, if needed (has happened with my old main motor).  So, the kicker also stays put.

You are correct that this does add a substantial weight to the butt-end of the boat.  Getting up on plane with that weight is the problem that I'm trying to solve here.

I wholeheartedly, 100%, agree that the boat would look much better without the bottom paint.  I also imagine that it might help a little on the performance to have it waxed/polished.  I certainly would not have put it on as it's totally unnecessary for what I do with the boat and how I store it.  But, I just don't have the ambition, or money, to have it removed right now.  Maybe later.

[Yachter Yat]

   Well.....I don't know. I hear you, but judging by what you posted, I can think of only two helpful alternatives that might help:  As painful as it might be, the first is (obviously) to get that bottom clean. The second, (which might be considered 'minimal') would be to swap the two group 24 batteries in favor of a single group 27 deep cycle. Following that, I suppose carrying as much weight forward as possible would be the only other option.

Yat

[fishmeister]

Had the boat out yesterday for crab (MA8-1).  Actually had some really nice water and was able to open up to WOT for enough time to get some decent info.

I was able to to get 28.5mph/5750rpm @ WOT.  That's only a loss of .2mph from prior to foil installation.  One clarification is that, although not really strong at the time (right near slack tide), I might have had a little "help" from the tide.

For a true test, I'll have to get onto a lake (no current).  But, the top speed loss that I thought I had may not be nearly as bad as I originally thought.  If I've lost 1mph or less, I'll consider that a success as I rarely have the need/desire to run that fast anyway (I prefer to cruise a little slower to save gas).

As already noted, the foil definitely helps with planing and trim control.

I'll update this as I get more info. 

[Baba]

Just for reference... yesterday I got out on the river for exercise, not glassy, but wasnt ocean either... 31.6 mph at 5800 max rpm; fuel flow was sucky: 9.2 gal/hr; but I never travel usually WOT... 15-20mph is rippen' in the ocean (I need to to clock my actuals in the ocean someday). Main motor mounted with a permatrim (which does help, and takes a little extra fuel, but not bad if looking at my spreadsheet), and trim tabs set at 2, main motor trimmed up just a little, with a slight tail wind (2 mph). My boat I know is heavy, 3350 lbs with the trailer. Fuel tank (23 gal) was 3/4 full, just 1 person solo, but lots of stuff in cuddy, big seats/suspension, auto pilot, alum wheelhouse, 2 batteries, kicker, etc... not to mention, I usually carry about 400+ lbs more in crab pots/puller or salmon gear, ice, tackle, snacks, wife, etc.

1985 17' SC with a 90 Yamaha 4 stroke. 4 blade alum prop (see chart for size)


(ps. pic of stern is old, since then, swapped out/upgraded ez-steer mount on main, and turned the kicker attachment upside down)

[La-Z-Buoy]

Baba, I would say that your top speed is pretty good considering your pushing A LOT of air with your pilot house. I've noticed on my previous soft top boats that if the soft top is up my MPH takes a hit compared to having it down.

[christianbrat]

15'11" with a 90 and PH.. can squeeze another 1 or 2 out of it.

[Baba]

Wow, didn't know  a 90 could do 40 @ 8.3 ; that is really good; with a hard top to boot; is your 16'r got less weight? shows what my boat is capable ?

I'm still not convinced I could maybe dial my prop just a bit betters, but i don't don't know how? or not ? My 5800 max @ 9.2 gpm just shows generally how heavy I am; I don't necessarily think it's too ass heavy, but I don't know.

[christianbrat]

8.3 remaining, not my fuel flow. Not sure what my flow is at that speed but probably not that economical haha

[Yachter Yat]

  Funny, but while you guys are talking about performance, I'm still trying to decide what species of wood Meister would most favor for his "Crucifixion".    Since he's from the NW, do you suppose it should be something like quarter sawn Red Cedar?  Hey......just asking.

Yat

[christianbrat]

that would smell pretty pleasant

[fishmeister]

that would smell pretty pleasant

Yeah, right up until you hung me on it!!   

[Baba]

Christian,

Red Ceder sounds good.

btw,

What size and brand, model prop do you have ? 4 blade? I didnt know that 16 has a 90.

baba.

[christianbrat]

Christian,

Red Ceder sounds good.

btw,

What size and brand, model prop do you have ? 4 blade? I didnt know that 16 has a 90.

baba.

I have a stainless Honda 3 blade 13.25×17. Totally awesome setup

[Baba]

Hmmm., maybe try a 17?  Im gonna call Phil at Turning Point next week and ask what he thinks if I went from my Alum 4 blade 13.5x15 to Alum 4 blade 13.25x17 ?

Im stuck on the idea that the 4 blade is more stable in ocean, with my weight.

\ I like the idea of Aluminum gives me maybe a chance of not breaking my lower if I ever hit something... but wonder if its worth $125. to find out what my results are ? ... In fact, he may even let me test it and return it if no bueno.

It would be nice if my mid range gph goes up, ie run mid range at lower rpm...  and I can still attain 5700-6000 WOT, Im still trying to wrap my head around what optimum WOT has real effect on mid range...I think that WOT is an important parameter to be at near max designed rpm, Ive heard that's key for good engine longevity to not lug the motor, even if running at WOT is very seldom.

Any thoughts?

[fishmeister]

Well, I think I'm going to put one more "update" to this thread as a "wrap-up" just in case anyone wants the info in the future....

I don't have any detailed spreadsheets to offer.  I've been running the boat in a variety of water and load conditions.   

I can say, definitively, that the hydrofoil has helped my trim control.  I have a lot better control of the boats trim with the motor trim control than I had before installing the foil.  Could I have gotten this with tabs?  I'm sure I could.

When I was able to get onto open/smooth water, I only lost about .3mph off of my top-end.  Since I rarely try to run that fast anyway, I'm fine with that.

Can I get the boat onto plane easier?  Absolutely a "yes".  In fact, last weekend, I was at Baker Lake for the Sockeye opener.  I had the boat quite heavily loaded with camp gear and coolers of ice for two nights (and my wife is still struggling with the "pack light" concept).  It took quite a bit of time to get the bow to come down.  But, once I reached speed and the bow started to drop back down, I was able to pull back the throttle, trim up a bit, and cruise at 25mph without even needing to be at WOT.  I didn't even have to shift every possible item to the front of the boat.  I had a very nearly identical load for a trip on the same lake for Memorial Day prior to getting the foil.  I wasn't even able to plane the boat at all.  So, I'll call this a definite improvement.

Does the foil cut into my fuel economy?  I'm still not certain as to what, if any, impact the hydrofoil has had on overall fuel usage.  I do think my overall MPG might have dropped a little (.5mpg or less).  But, when I'm unable to plane (or struggle to get there), my MPG is definitely much worse.  So, while I may have taken a slight "hit" on economy while on plane, I'm hoping that being able to plane quicker/easier may offset that enough to be close to a "wash".

Overall, I'm satisfied with my SESport 400.  It has done what I wanted it for, and at a more economical price than trim tabs.  Installation was quite easy.  I used the "no-drill" mount option so I still have a cavitation plate that hasn't been "violated".  Two things that I'll note for anyone else who opts for this....(1) The mfgr advises not to over-tighten the bolts when installing or they can snap.  Please trust me that this is correct info  .  If you snap the bolt, you may have to go searching for a replacement.  A SS 1/4-20 x 1.25" carriage bolt was harder to find than I expected.  Ended up at Tacoma Screw for one (really nice guy actually gave me the bolt).  (2) There are some online reviews that mention them just "falling off".  One thing the mfgr recommends is that you should re-tighten the nuts after a use or two.  This is also good advice.  I was able to tighten the nuts about a quarter turn after the first use.  Mine seems to be rock-solid now.  I expect that some of these reviews are from folks who didn't follow this recommendation.

I know that trim tabs are revered/sacred here.  In fact, I initially hesitated in starting this thread (hence the title).  I'm sure that tabs have their place and probably do have some advantages over a hydrofoil.  For those who have them and like them, that's great.  But, after starting this thread, I found myself a little surprised when some others chimed in and said that they were also running "whale tails".

Summary....If I had the budget and was willing to move my transducer, I probably would have gone with tabs.  But, since that was not reality, I went with the foil.  I don't regret my choice.  While not necessarily the "perfect solution", it's good enough for me.

[fishmiester]

I have smart tabs on my 17 s.c. and I love them. Power is a 2010 Tohatsu 90 TLDI. And I usually run pretty heavily loaded., But, on my previous boat, a sea hunter I was running an older 50 Johnson, twin cylinder, with a whale tail. Worked fine, but had to learn to control my motor trim.

[First Light]

Twenty years ago I repowered with a Yamaha 50 HP and the first thing I did was put a Foil on the motor to help get up on plane. By myself the boat literally jumps up on plane. Yes, I too have learned to use the trim control to even out the boat, 25mph @ 4500 rpm. Zero regrets on economy...... its a Sea Hunter!

[Yachter Yat]

  I've never had a hydrofoil on any of my boats so can't really speak with any authority on the subject. The only education I ever get on these is from guys (such as yourselves) who've actually used them, or from articles I've read. In consideration of that, I seem to recall comments to the effect that if the motor was mounted too low, then the foil (being too submerged) could create an excessive amount of 'drag' that could serve to offset some of the potential benefit. Leads me to wonder if raising the motor under this condition might be of some benefit.   
   Course, I suppose cavitation would be no fun either. Hey....with that in mind, does anybody know if there is any evidence that these foils (in some way) help prevent cavitation?    Curios.

Yat

[JDB]

Cavitation... I don't think a fin would have anything to do with the pressure or lack of pressure on a propellers blade.  Now ventilation it does influence (a physical barrier in the water), but only at up to displacement hull speed (anything faster and the turbulence generated is well behind the prop, not sucking air down a whirlpool). 
Maybe?

[Yachter Yat]

    JDB: Yeah, you're right! Thanks for the correction. I should have said 'ventilation'. I actually know the difference between the two, but sometimes use one to mistakenly describe the other.
   So, that aside, why might we suppose these foils could help eliminate, or at least minimize, ventilation? Seems it might be something to research; especially for those considering this as an option.
  BTW, here's a quick esplanation:  https://www.youtube.com/watch?v=5bj5kjh3l9o&t=7s

Yat

[JDB]

Hmm maybe the fin is creating a pseudo tunnel that the water being flung off he edge of the prop has to go through, instead of just creating spray?

Such as the portion of the thrust cone close to the surface is forced rearward, instead of being able to create spray at the surface?

Or, just the physical barrier from the surface at speed, reducing the amount of air taken in by the descending blade? But that kind of doesn't make sense because there are propellers designed to be partially out of the water...

I didn't mean to correct anyone.  The fin might change the hydrodynamic forces on a blade that actually reduce cavitation (but fluid dynamics are not really covered all that well in basic physics, and not at all in toxicology or criminology).

[Yachter Yat]

  Notwithstanding humor, I simply have to say:  If I had a foil on my outboard, I don't think I'd be all that excited about looking down at it (especially during my "normal" cruise speeds), only to discover it running completely submerged.  

Yat

[Yachter Yat]

   Hey......wouldn't it be something if somebody made a hydrofoil that attached to an outboard that would operate like the tail ailerons on an F22? Take a look:
https://www.youtube.com/watch?v=SrxzFUcBPuw
   Would be especially nice if it was controlled by a small "joystick". (Nevermind, I know just what you perverts are thinking)
   Okay,, I'm gonna  brush my teeth now. 

 Yat

[Yachter Yat]

   If I had trim tabs, this is the control I'd insist on. No "thinking" required. 
 https://bennetttrimtabs.com/product/joystick-helm-control-electric-only/

Yat