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PostPosted: Mon May 30, 2016 7:56 am 
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Has anybody tried moving their weight a foot or two aft in an effort to get the main hull up on a plane?

That would involve replacing the seat with a flat platform that one could scoonch their butt backwards on....

Seems like high tens/low elevens (MPH-wise) is the limit of hull speed.

From windsurfing I know that, beyond a certain amount of rocker, getting up on a plane is pretty much hopeless - but I have no idea how much rocker there is relative to planing ability in the AI-2's hull.

I'm thinking it's mostly hopeless.... but if somebody else has put the time/effort in and found some success, I might have to try it.

If it were to work, it would also seem like an invitation to ama shear pin breakage.... but that's another issue....

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PostPosted: Mon May 30, 2016 10:04 am 
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Moving as much weight as aft as possible seems to help a little IMO ( at least on TI's, don't know about the AI), but fact of the matter is the boat has a pointed back end that just sinks into the water (can't plane), on mine when I'm moving along pretty good, the entire stern can go underwater as you approach hull speed.
When you modify the hull to a planing type hull, what you are doing is forcing that big wave behind the boat a few feet.
Hope this helps
FE


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PostPosted: Mon May 30, 2016 11:33 am 
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I have a quarterdeck (platform) that moves you back about 6 inche's on my AI. I find that the 6 in difference will lift the bow slightly and if anything, this slows the boat down a bit. I definitely do not plane although sometimes, on rare moments with the spinnaker, it can feel like it.

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Last edited by vetgam on Mon May 30, 2016 2:17 pm, edited 1 time in total.

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PostPosted: Mon May 30, 2016 12:23 pm 
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Yea the TI is a different animal alltogether from the AI I think, especially when adding big sailsets. The mainsail is mounted so far forward on the hull when on a downwind with both main and spinnaker out, the bow tends to dive underwater and just stays down until you let up on the sails (I'm never willing to letup (lol)) so my boat goes into what I call nautilus mode, talkin about a wet ride (lol), funny it doesn't seem to slow the boat down much at all though.
I suspect this doesn't happen on the AI.
FE


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PostPosted: Mon May 30, 2016 1:45 pm 
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fusioneng wrote:
Yea the TI is a different animal .... so my boat goes into what I call nautilus mode, talkin about a wet ride (lol)...
I suspect this doesn't happen on the AI.
I do not how the Bow-Down-ness of my AI-2 compares, but on Saturday I was out in high-teens/low-twenties and the wetness of the ride was on a par with body surfing.

Sooner-or-later I'm going to borrow somebody's Hero cam and post the results as "One Reason To Get a Spray Skirt".

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PostPosted: Mon May 30, 2016 4:11 pm 
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I doubt you'll get the AI or TI to plane. The hulls aren't shaped to do that easily. Much too narrow for the sailplan to generate enough speed to get it done.


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PostPosted: Mon May 30, 2016 4:54 pm 
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fusioneng wrote:
Yea the TI is a different animal alltogether from the AI I think, especially when adding big sailsets. The mainsail is mounted so far forward on the hull when on a downwind with both main and spinnaker out, the bow tends to dive underwater and just stays down until you let up on the sails (I'm never willing to letup (lol)) so my boat goes into what I call nautilus mode, talkin about a wet ride (lol), funny it doesn't seem to slow the boat down much at all though.
I suspect this doesn't happen on the AI.
FE

Not wrong! So far (still not encountered the right conditions with the new spinnaker) when my TI hits maximum speed, the whole bow back to the mast is covered by an inch or so of water (and I can no longer see my feet or the cockpit floor!), and that is WITH spray skirts!

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PostPosted: Tue May 31, 2016 1:57 pm 
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You have a pretty good model for this with the TI as some of us sail it solo from the rear seat and some sail solo from the front seat. I think this is a reasonably close approximation to moving your weight forward or back on the AI. I dont think much conclusion can be made to which is faster over wide range of conditions. We can make conclusion about which has better control in high winds or a wetter ride but we would "safer" discussing Clinton vs Trump than that topic.

Regarding the TI, if you use the conventional displacement theoretical hull speed equation https://en.wikipedia.org/wiki/Hull_speed , the TI should hit around 5.68 knots. However, I think people under certain conditions see speeds in the 10 knot range. I dont know if you want to call that planing or not but its around 75% higher than theoretical hull speed so its not exactly displacement speed either.

My 0.2 on this (and could be wrong) is that when the hull is moving across the water, some water is accelerated normal to the hull - and if the hull is flat on the water, this is downwards acceleration. Downward acceleration creates a force that tends to lift the hull. If you can create this downwards acceleration (ie, "lift") without dragging water along with it (ie "drag"), that upwards force negates some of the hull drag associated with wave making. To some extent, the down force is similar to making the hull lighter which also reduces wave making drag.

I have a little 15 foot sailing dingy which is sometimes referred to as a planning dingy and it only goes about 40% over theoretical hull speed (TI is higher than this at 75% over - but we would argue if this is really planning or not). I know on my dingy, my weight position does affect how fast it goes and I believe this is related to how efficiently it creates that downward lift vs dragging along water creating this lift. If you can get the highest L/D, you go the fastest and on my dingy, this is with my weight near the center of the boat.

In the case of the AI/TI, you also have wetted surface drag and that is just related to how much of hull area is in the water. I dont think you have any control over that with weight placement.


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PostPosted: Tue May 31, 2016 5:39 pm 
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My take on it is probably just a different way of skinning the same cat....

At hull speed, the wave generated by the hull's motion is the same length of the hull. ie. the hull lies level between the peaks.

As the speed increases, the bow wave gets longer, and the second peak moves back, no longer supporting the hull. ie the hull is now travelling uphill and therefore needs more power.

As speed increases, the wake grows bigger, deeper and longer, making the "hill" steeper (and drag is increasing). The power needed also increases. exponentially

If there is enough power available, and the bottom shape allows the wake to cleanly break away from the hull, the vessel will climb over the bow wave, and sit on top, building up speed.

All this is easily seen with a speedboat, which begins wallowing in the bow wave, stern visibly lower in the water, until it literally climbs up onto the plane.

The foam bustle that fusioneng added to his TI should enable his TI to get up on the plane if he chose to fit more powerful outboard(s).

But for all that, I LOVE seeing my TI sitting on a steady 7-8 knots, bow half-buried, foam up to my knees, and a massive sh*t-eating grin on my face!!!

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PostPosted: Tue May 31, 2016 6:07 pm 
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Yea tony I never back off either
FE


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PostPosted: Thu Jun 02, 2016 4:00 am 
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Yea when it comes to hull planing on a TI, I'm not certain what it all means.
Here is a video of my TI at my regular cruising speed (typically 8-10 mph), I'm guessing the winds were around 5 mph that day. Whether the boat is actually planing or not I have no idea.
https://www.youtube.com/watch?v=tR9oJL6psds

All I know for sure is after I modified the back of the hull so it is rounded similar to the back end of a WETA) there is now a wave that forms a foot or two behind the boat (as seen in the video). The wave forms and stays back there at around 8 mph. The bow raises out of the water around 3-4 inches during normal cruise.
I honestly don't know if it's real or imagined, but the boat seems to ride much higher in the water at higher speeds with the hull mod installed, ( the hull mod is a strap on, that I can put on or remove as needed (takes about 5 minutes to install). I mostly only use it offshore, it stays at home the rest of the time. The problem we have around here is when the wind picks up so does the washing machine chop, in 10-12mph winds we typically have 2 ft washing machine chop around here which becomes very uncomfortable for me in such a small and low to the water boat (a very wet ride even with tramps and spray skirts).

When you speed up to 15 mph the wave is around 3 ft behind the boat, with the bow around 4-5 inches out of the water. The wave keeps moving further away from from the boat the faster you go. At 20 mph the wave is around 6 ft behind the boat, and the bow raises out of the water around 6-8 inches. My max speed with the motors in the water is around 15 mph, if I want to go faster, I must raise the motors, and can only go fast downwind with the spinnaker deployed in winds equal or greater than the boatspeed. However the strain on me, (and the boat) is excessive so I very seldom exceed 12-14 mph anymore.

Truth be known, my boat is pretty much designed specifically for almost directly upwind sailing in low winds, and 90% of the time, that's how I use the boat, I don't worry much about the rest of the stuff anymore, and typically stay home if the winds are over 7 mph. I mostly use the boat for destination sailing, some days I'll do 50-60 milers (yea I tend to use my engines most of the time anymore, I can afford a buck or two in gas). Basically I just don't do well at 3mph in the hot Florida heat (great risk of heat exposure down here in the summer).
FE


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PostPosted: Thu Jun 02, 2016 7:17 am 
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fusioneng wrote:
... my TI at my regular cruising speed (typically 8-10 mph), I'm guessing the winds were around 5 mph that day. Whether the boat is actually planing or not I have no idea.
On my AI-2 8-10 mph does not happen until winds are in the mid-to-upper teens.

Somewhere in the low-to-mid twenties wind-wise, I see brief spurts of low-11's speedwise - but that's about it....and I have been out when it's gusting into the high thirties. Your having 2.something more meters of sail might have something to do with it - as would the preseumably higher k-factor..... but that would not explain low teens and higher speeds to me.

18-20 mph? I would think that your TI is almost certainly planing.

Maybe my next little obsession will be shaping a rocker-free stern add-on like you have.

How do you attach it?

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PostPosted: Thu Jun 02, 2016 2:17 pm 
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The way I made mine was to spray urethane release agent on the hull bottom, then cover the bottom with 4 lb urethane foam. I then used a sureform file to sculpt the foam to the desired shape. I just used taped up cardboard for my forms.
I embedded about 6 pieces of paracord tied to washers inside the foam for attachment to the hull (so everything is easily removed). After sculpting the desired shape I coated with one coat of glass, then several coats of clear polyester resin (because it's cheaper). Sure I could have used gel coat, but that stuff id like $40 bucks a quart (rediculus).
I only did the rear third of the hull (big mistake) because the joint at the front (where the mod meets the hull) became very difficult (hard to seal).
Actually there was a guy in the everglades challenge this year with a similr hull mod, only he did his right (awesome design). He started with cloth taped over the entire hull bottom, with tape holding the entire perimeter down (really clever), he then foamed over the cloth and sculped the desired shape over the entire hull, he even glassed in his bow sprit (brilliant). He then glassed over the whole works and finished out with I think real gelcoat (expensive stuff but way more durable).
Absolutely the smartest and coolest design work and craftmanship I've seen.
My hull mod was around 6-7 lbs, I'm just guessing his was around 11 lbs, but way better than mine.
The urethane and resin is pretty expensive, I think mine was around $250 bucks, I just guessing here, but I would guess his materials were around $700-$800 bucks (but well worth it).
If I ever do another one, I'll be sure to do the whole hull bottom, starting with a cloth layer (his is a really clever design, and well done).
Mine adds about 100 lbs of additional floation to the hull, I'm sure his adds even more.
A good weekend project.
FE


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PostPosted: Fri Jun 03, 2016 1:17 pm 
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Pete:
I think you mis-understand how my boat operates. In this area the typical winds are 3-7 mph 90% of the time. I made a promise to my wife when I bought the TI in 2010 that I would faithfully peddle the boat 15 miles a week (basically as my exercise program) in order to justify the purchase. At the time I thought I was pulling the wool over her eyes with a sneaky move buying a pedal boat with a sail, that could easily go 15 miles every week with only partial peddling effort. Basically the plan was to go out and peddle my 15 miles, but with the sails out, making short order of the task, and have some adventures to boot.
Then summer came and the typical winds when I went out every saturday morning were only 3-5 mph. With no wind the boat only goes 2-3 mph by pure peddling effort, and worse yet we have a lot of current around here, which is often 5-6 mph. So to get my 15 miles in required 10-12 hrs of really intense effort in the 90 deg plus hot Florida sun (ie... sunshine state lol), ten months out of the year. Worse yet I got blown out to sea several times and couldn't get back in no matter how fast I peddled and sailed to the best of my abilities (usually to the point of complete exhaustion and heat exposure).
On our first outing with the boat both my wife and I got blown out to sea and couldn't get back to shore, so she gave me permission to add an emergency gas motor to get us back to safety if the need ever arised, since then I have never taken the boat out in the ocean without a gas emergency motor on the boat (a major safety issue with us, mostly because of the strong currents in our area (SW Florida and the Keys).

Of course right away I started adding more sails to the boat to try and get more performance, I added a 30 sq ft jib and a 130 sq ft spinnaker to the boat back in 2010 so my total sail area was around 260 sq ft of sail.
Unfortunately in no wind all that extra sail area does little or nothing. Here is a video of what it was like for me on a typical saturday.
https://www.youtube.com/watch?v=zW62S1_RfYQ


Here is a video with the spinnaker and main (jib was furled), I was flying 220 sq ft of sail, and was able to get up to 4 mph that day. I remember that day because in order to get my 15 miles in I was out there over 8 hours that day, and got burn't to a crisp in the sun.
https://www.youtube.com/watch?v=gbDjR3YJI08



I have posted about 40 videos of me sailing my TI, and have determined that my videos win the award as the most boring videos ever created, they are all pretty much the same ( all identical to the wake video above), if you look at the water around my boat you can determine the wind speed that day. If it's flat then the winds are around 5 mph or under, if there is 2-3 ft chop all around the boat then the wind is 10-12 mph, I don't do out in anything over 12 mph wind anymore (actually 10 mph). I have a really bad back and can't stand the rocking physically.

Here is a video showing just how powerful generated apparent wind can be. I had my motors cranked up just a little so with no sails and not peddling my speed would have been around 7mph (on flat water). Now you combine my forward motion speed, around 10 mph and add it to the 6-7 mph wind coming at me (I was sailing about 20-25 degrees off the wind (upwind)). That makes the real wind affecting the boat around 16-17 mph, I had great difficulty controlling the boat, and had to stop filming a few time to regain control of the boat, and re-trim the sails. Actually that video was taken at around the same spot as the spinnaker video above, but the winds were 3-4 mph higher (around 6-7mph).
https://www.youtube.com/watch?v=-npwA3izDiw

EDIT: In the above video with my extra sail area, there is tremendous risk of capsizing the boat in those exact conditions seen in this video because of the extra sail area (with 17-20 mph apparent winds on the sails), basically the standard AMA's can no longer prevent the boat from flipping. I have nearly capsized many times, and have pitch poled the boat many times as a result. Not shown in any of the videos here, I recently widened the AMA's on my TI so now the boats is now 12 ft wide vs the previous 10 ft wide. This makes the boat pretty much un-capsizable with the additional sail area and the much higher 17-20 mph apparent winds I typically operate in via apparent wind. Pretty much a necessary upgrade (widen the AMA's) that you have to do for safety reasons. Also at higher speeds the nylon sheer bolts on the AMA's just sheer off whenever you hit a wave, or the AMA goes under, so they need to be re-enforced as well (safety ropes), (just FYI).

Here is a video taken a few minutes later in the same area with the motors off.
https://www.youtube.com/watch?v=HGL9eLWS0iQ


Here is a video taken 5 minutes later in the same area only with the motors running just above idle (which gives me 2-3 hrs of run time per tank)
https://www.youtube.com/watch?v=EGVV6yUBNl4


All the last three videos were taken while I was trying to get to my friends house about 8 miles away up by Anna Maria Island. I was just trying to get there (why I call my boat is a destination boat, I use it to get me where I want to go). Once there, this is the video I shot going thru the canals to get to their house, (this is pretty much what I usually do with my boat). The purpose of my trip that day....
https://www.youtube.com/watch?v=9jFCfBMZKKU

Yea I could have got there with just the sails (the old fashion way) but it would have taken me 6 hrs just to get there, then an hr or two peddling thru the canals, then another 6-7 hrs back (downwind), and that's with my massive 260 sq ft sail set. That would have been around 12 hrs on the water in 90 deg plus intense sun, I would have been burn't to a crisp. Instead I was there and back in under 3 hrs (around 18 miles for the day), I think my average cruise speed was between 8 and 9 mph. I prefer my way much more.... it cost me about a dollar in gas that day, I can afford that. Of course if I had better wind, I could have got there and back much faster, but typically around here that's not in the cards.
All in a typical weekend for me.
FE

https://www.youtube.com/watch?v=9jFCfBMZKKU


I have no idea what it all means, I just go out and have fun every weekend. I haven't made any major changes to my boat in over three yrs now, I just use it as it is. Everyone else can do as they please, that's the beauty of these boats you can adapt them to anything you like.

EDIT: Obligatory safety lecture.... When adding powerful gas engines and massive sail sets to a TI the boat can become quite dangerous, well beyond the design envelope of the craft. I typically only go out only in very light winds and calm seas, and limit the throttles on my engines to around 1/4 throttle. I also have the boat itself considerably hardened and modified to withstand the additional forces experienced in offshore sailing. In higher winds 15-20mph plus, and out in open seas with 3-4 ft chop with both motors operating at max throttle the boat can easily operate 15-20 mph, however the risk of failure of some key components is pretty much a sure thing. In other words because of the apparent winds generated your forward speed (15 mph in this example) added to the natural wind (15 mph, in this example) makes the forces on the masts, sails, AMA's, etc equal to operating an Island with full sail out in 30 mph plus winds, and we all know the results of that. That's why I don't do that (hot dogging offshore) anymore..... If you want to go fast, you have the wrong boat, get an F18 class Hobiecat.


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