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  #16  
Old 09-04-2007, 08:02 PM
Guest625101138 Guest625101138 is offline
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The power output chart attached is for cyclists. Rowing is about the same - maybe a little better for the high power end. Paddling is about the same in long duration and drops off as you get to the high power end. The full-time figure is more like one hour. This is a good place to start if you are considering a 10 minute event.

Most people overrate their fitness. I would expect your intermediate 77kg male paddlers to fit into the fair category so say 2.7W per kg or 208W. Paddling efficiency with good technique is around 65%. So two paddlers can deliver about 270W to the hull.

Power is simply drag times velocity. So if you have the drag curve you can derive power required versus speed very easily.

If you post your final hull design and verify intended weight I can rerun Michlet. It is likely to be more accurate than Freeship.

Rick W.
Attached Thumbnails
Racing Canoe-picture-2.png  
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  #17  
Old 09-04-2007, 08:29 PM
coreym coreym is offline
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Actually, I am a cyclist! When I was more into racing a few years ago I had the opportunity to do a VO2 max test where my power was determined to be 5.1 W/kg. Does that really mean anything for paddling power though? Anyway, I'll post both the V Hull 1 design and the modified Flat Bottom.

Intended Weight1 = 520 lbs = .26 tons 2 people
Intended Weight2 = 850 lbs = .425 tons 4 people

I downloaded Michlet but I have no clue how to run it yet. Also, concerning KAPER and Spilman. Are those just two different formulas for calculating total resistance? Is one generally more accurate than the other?
Attached Files
File Type: fbm V Hull.fbm (17.1 KB, 263 views)
File Type: fbm Flat Hull.fbm (15.4 KB, 219 views)
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  #18  
Old 09-04-2007, 08:59 PM
Guest625101138 Guest625101138 is offline
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Quote:
Originally Posted by coreym View Post
Actually, I am a cyclist! When I was more into racing a few years ago I had the opportunity to do a VO2 max test where my power was determined to be 5.1 W/kg. Does that really mean anything for paddling power though?
That puts you in the excellent category. You must have been young and fit. A regular cyclist. So you have a good understanding of fitness level.

For long duration events, arms/torso are almost as good as legs from an efficiency perspective. They may even be better because there is less circulation involved. I have not found conclusive data on this.

However there is a huge difference possible for any individual with training. You really need to develop technique. The best two-up canoeists I have seen were in an OC2. These enable good upright posture with legs firmly locked for leverage. The backman calls at about every 10 strokes to change sides and they can do this without a break for hours just using a camel back for water supply. Boat self drains for liquid discharge.

The attached OC2 photo gives you an idea of the optimum canoe hull for continuous power output of two adult male canoeists. Turning ability is fair and they have a rudder.

I will do the numbers on your hull later today.

Rick W.
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Racing Canoe-oc2.jpg  
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  #19  
Old 09-05-2007, 05:15 AM
Guest625101138 Guest625101138 is offline
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Corey
I updated the comparison using your hull options. See the attached chart. The power requirement INCLUDES an efficiency of 65%.

The Flat_Hull has a distinct advantage in both load cases. You could expect about 0.5kt faster with it over the V_hull.

You do not get much more speed with 4-up compared with two. This is because you are getting into serious wave making.

I consider both hulls marginal from a stability perspective. The KMt is less than 1ft in both cases. Very twitchy craft and bound to give paddlers an unwanted swim.

The freeboard on the V_Hull is down to 3" when you load it up. It runs a serious risk of swamping as well as tipping. The Flat_Hull has more freeboard and will be acceptable if the water is calm. Obviously you can do something with the gunwhale to improve the situation. I would be considering higher bow and stern unless you intend to enlcose it in some way.

Rick W.
Attached Files
File Type: pdf Concrete_Canoe.pdf (33.5 KB, 295 views)
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  #20  
Old 09-05-2007, 10:06 AM
coreym coreym is offline
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I'm a little confused now. Freeship calculates that there will be less resistance on the v hull than the flat hull at any given velocity. So it seems it should require less power to propel the v hull than the flat hull also at any given speed. I'm trying to improve my KM value. However, rules require the boat to be between 28 and 32 inches wide and less than 20 ft long. I didn't want to make the boat anywhere near 32 inches wide because then the bw value jumps to 2.5 ft or more resulting in a l/b value of 7.5. When swimming, I remember the importance of swimming long in the water. Doesn't a l/b ratio of 7.5 speak death upon the boat?
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  #21  
Old 09-05-2007, 10:27 AM
Chris Ostlind Chris Ostlind is offline
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Whew! That's gonna be a very skinny canoe, Corey. Yes, it will have the potential to be faster if skinnier, but it also marginalizes the stability. If you can sit or kneel directly on the floor of the boat and not in trad canoe style seats, you can restore the stability with some loss of leverage as applied to the stroke power.

Most of the big expedition sea kayaks are in the 28-30" beam category at just about 20-21' LOA, so there are many examples of efficient hulls in this realm. The really fast examples of that genre have been built in the 25-26" BOA region, but they do not carry weight very well. Big kayaks like this come in at about 90-100 pounds depending on how they are fitted out and they have full decks, cockpit rims and bulkheads. With your boat in the 170 lb. category, there isn't much you can do.

A slightly veed hull can be a tiny bit faster and aid in tracking, but it will take away from the primary stability of the design. Since I have no idea as to how experienced you and your paddle partner might be in a boat designed to fly, it will be hard to adjust the design to suit your optimal potential.

If you are up against pairs of other paddlers who have a good body of experience in a tippy boat, then you have to make the decision as to how far you can push the stability component in order to keep pace. Push it too far with limited time to adjust to the boat and you will spend a huge amount of energy simply maintaining your balance while stealing from the thrust potential which drives the boat.

Are you able to get time in the boat prior to the event? Is it possible for you and your partner to get your hands on a big double sea kayak for some training before you shove off with the example craft? Run a sample course if you can get access and get a feeling for the teamwork involved in balance, stroke efficiencies and turning issues.

Keep us posted, will ya?
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  #22  
Old 09-05-2007, 11:10 AM
coreym coreym is offline
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I was hoping to make the mold out of fiberglass in late October or November and use it also as a training canoe by adding some weights. This would give us about 3 or 4 months time to play with it. I should also mention that the concrete will be lighter than water and so even if a little water gets in the boat, it will not sink. In fact, part of the competition is a swamp test in which teams are required to completely submerge the canoe. If it doesn't come back to the surface, you don't even get to race.
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  #23  
Old 09-05-2007, 05:48 PM
Guest625101138 Guest625101138 is offline
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Corey
I have made lots of small human powered boats. I became very frustrated using empirical methods for estimating wave making drag like those offered in Freeship. They are next to useless as far as I can guage for assessing efficient hulls.

I started to make real progress in estimating performance with some precision once I found Michlet. The great thing about Michlet is the optimising element Godzilla. It is my starting point for any design these days.

The hull that Chris initially supplied you is more stable. It has an acceptable KMt at 1.5ft. The small alteration you made to the beam reduces the stability significantly. Interestingly Chris's hull has identical performance, according to Michlet, as your Flat_Hull, which is better than the V_Hull.

You are building a heavy boat for a length of 20ft. Godzilla optimises to 29" with the stability constraint of 18". I did not constrain the rocker so it is straight. I would need to add this if you want better steering. Length is the important factor for wave making and that is limited to 20ft - end of story. Beam gives you load bearing capacity. So the L/B ratio has to take this into account. Heavier boat needs more beam if it is length constrained.

Interestingly Godzilla arrives at a beam of 32" for the optimum 4-up boat. So a wider boat would probably give the best overall performance.

The hull that Godzilla produces for both cases has more rounded chine and it is quite full in the bow and stern. There is no concavity in the plan view.

Also the Units you have set in Freeship are imperial. It uses imperial tons not short tonnes. There are 2240lb/t. This makes a bit of difference to your results.

Rick W.
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  #24  
Old 09-06-2007, 01:04 AM
coreym coreym is offline
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Well, it sounds like I need to learn how to use Michlett then. Are there any PDF manuals or anything for it? Is it very difficult? Constraints, 1000 iterations per second, optimization... it all sounds good to me. I can't thank you guys enough for all your help, this has been amazing!
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  #25  
Old 09-06-2007, 01:55 AM
Guest625101138 Guest625101138 is offline
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Corey
You might find the following useful if you want to use Michlet.

I assume you got the file from this site:
http://www.cyberiad.net/michlet.htm

As Leo prompts " ..... please read the manual...." It is contained in the download as html files.

Some useful hints.
1. Create a new folder called Michlet.
2. Create a new folder called Godzilla.
3. Place a copy of mlt807w.exe in both folders.
4. Place a copy of alleg40.dll in both folders.
5. Place a copy of godzilla.bat in the Godzilla folder.
6. Copy the Flat_Hull_850.mlt file I have attached into the Michlet folder and rename in.mlt. Likewise for the God_850_in.mlt to the Godzilla folder.
7. Double click on mlt807w.exe in the Michlet folder - it should
bring up a new window.
8. Now press <shift> <R> - it will change the window, Now Press < t >
- it will produce resistance curves. Press <Esc> twice then < y >
and it will close the window. You will note there are a whole lot
more files in the Michlet folder.
9. To use Godzilla open the Godzilla folder and double click on
gozilla.bat. This will open two windows - the small one is the .bat
file.
10. Now press <shift> <G> and godzilla will go to work optimising the
hull that I have as the start for your 850lb canoe. You will see all this is in metric so you have to get used to that.
11. Press any key after a few minutes and this will stop godzilla.
12. Press <shift> <R> and < t > to see the resistance curves. Press
<Esc> twice then < y > and it will close the window. You will note
there are a whole lot more files in the Godzilla folder.
13. You can compare the performance of the optimised hull and the
your Flat_Hull comparing ship-output-by-speed.mlt in both folders.
You can just open them with Notebook. Notebook will then recognise .mlt
files as text. I load the data in these text files into Excel for analysing.

If you have any problems getting going then just post.

I see that you need to think about the best compromise for 2-up and 4-up depending on the events involved. A 4-up canoe with WL of 20ft is going to be beamy. A coxless 4 is about twice that length and you can bet it would be close to optimum for the power level of 4 fit men. With that length it will be thin but 20ft will be fat.

Rick W.
Attached Files
File Type: mlt God_850_in.mlt (5.8 KB, 207 views)
File Type: mlt Flat Hull_850.mlt (7.1 KB, 179 views)
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  #26  
Old 09-06-2007, 02:00 AM
coreym coreym is offline
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found the help file in the michlet folder. looks like I'm going to be reading for a while.
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  #27  
Old 09-06-2007, 04:23 AM
Guest625101138 Guest625101138 is offline
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Corey
There is one little inconsistency between Freeship and Michlet when considering stability. Freeship gives the height of the roll axis above the keel (KMt) while Michlet gives it above the centre of gravity (GMT) (assumed to be at the waterline). So the difference will be the draft of the hull.

Once you allow for this they give very similar results. My experence with one critical application verified that they are accurate.

Like I have stated a number of times I think you need KMt around 450mm (1.5ft) to have a usable craft.

Rick
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  #28  
Old 09-06-2007, 06:32 AM
Guest625101138 Guest625101138 is offline
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Corey
I constrianed Godzilla to produce some rocker and it came up with the attached shape for the 4-up boat.

The boat is approximately 0.6kts faster than your Flat_Hull with 4-up and is effectively identical 2-up. So it may not be the best that Godzilla can produce for 2-up but it should give the best overall result.

It is very stable 2-up (KMt = 20") and should be OK 4-up (KMt = 18").

If you work through Godzilla you should arrive at something similar. You can also export the Freeship file to a Michlet input file so you can do your own performance analysis. Freeship will not give drag data as it says it is outside the acceptable range. This is often the case in my experience.

Rick W.
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Racing Canoe-opt_850_linesplan.jpg  
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File Type: fbm Opt_850.fbm (20.7 KB, 211 views)
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  #29  
Old 09-07-2007, 05:42 PM
coreym coreym is offline
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how come the resistance curves in michlet are so wavy? I'm assuming that has something to do with wave cancellation or some other similar effect.
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  #30  
Old 09-07-2007, 06:12 PM
Guest625101138 Guest625101138 is offline
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Quote:
Originally Posted by coreym View Post
how come the resistance curves in michlet are so wavy? I'm assuming that has something to do with wave cancellation or some other similar effect.
Corey
It is the type of boat you are trying to build. If you did not constrain length then the viscous resistance would dominate and the curve would not have the bumps.

Understanding the physics/maths of waves is beyond me. What I do know is that Michlet gives good results for the type of displacement boat you are building. Wave cancellation is certainly a possibility.

Rick W.
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