Tuned Hulls

[Lin Olen]

In my youth I made many models of boats and aircraft, always trying to get better performance. This let to me applying the effects of resonance to the design of a hard chine displacement.

What I wanted was considered impossible but I designed and built a 12 footer that I rowed at 7 miles per hour and get 12 mph with a 2 blade prop on an old 3 hp Seagull outboard that I fitted with an anti-cavitation plate.

My boat did not create any bow wave and gradually accellerated from displacement to planing with a gradual throttle increase. My tuned hull re-absorbed its initial shock wave, a bit like squeezing an apple seed. and left the water flat. I have a photo of the disturbance as I raced past a 14 foot clinker with a 3 HP Simplex inboard.

With a 5 hp Johnson my boat was comparable to a 10 hp Mercury on a 12 foot tinny. I am a novice at posting and need some good advice... Lin Olen

[tom28571]

Lin, I can't be of much help on the computer but I'm sure we all will be interested in following up on your work with the boats you discussed.

[SeaSpark]

Could you explain a little more about the resonating hull, i am not sure i understand from your brief description.

Once i build a paper/glue glider airplane about a foot wide modeled like a box kite:



While airborne the wings started resonating and the contraption glided much further than you would expect. About as far as the most "advanced" paper airplane i was able to make at the time. After some flights/crashes it lost shape and rigidity. I tried to rebuild it but the replicas never flew as good as the first model.

[rwatson]

I wouldnt thank that rowing at 7 mph was all that amazing, its only just above walking speed - and sticking an outboard on to get less than double the performance doesnt sound all that amazing either.

A Bolger step sharpie (Bee Model), 8 ft long running a 5hp outbard gets 20+ mph, so I dont know why anyone said the performance figures you quoted were anything like 'impossible'

[Lin Olen]

I built my tuned hull when I was a 20 yo aircraft engineer, I am now 74. There have been many advances over the years, but I have not seen any that perform as well as my prototype. It was faster than the 14 footer with the long shaft 3 HP Seagull dragging its length through the water while carrying myself and three passengers. Try that with a Bee step sharpie!

[Lin Olen]

A radio apprentice must come to grips with resonance. Radio circuits are tuned to specific frequency that resonates, that is when a tiny input signal triggers a powerful ringing effect in the circuit to which it is tuned, each 'kick' of signal creates an ever higher 'swing' so that the weak signal is greatly aplified. This is only a crude analogy, but the same effect occurs with musical instruments and boats. Unfortunately few people have investigated the resonance effect for boats. If applie successfully it will halve the power requirements of displacement craft and completely eliminate the 'hump' which bedevilles most water craft. My prototype was an open hard chine dinghy made with 1/4 inch coachwood Seaply. At the time it was built the requirements of rowing, sailing, and planing were considered incompatible. I hope this elucidates. Lin.

[Guest625101138]

Lin
I am interested to see a picture and learn more of the concept.

You can attach a picture in the form of a jpg file using the paper clip icon shown above the message window. The window will open when you reply to this post.

If you do not have a jpg image it can be scanned at a photo agency. If you get the photo in digital form then it will be preserved and easily distributed.

I am interested in any ideas that reduce hull drag. I use an engine that is continuously rated at 120W and can peak at 0.5kW for racing. I have been able to get up to 18.2kph with this engine on one of my boats but always looking for new ideas.
http://www.youtube.com/watch?v=hXrQkqy6f-E

Rick W.

[Lin Olen]

A tuned hull causes a renonance in the water that shows up as a surface bow wave and an undulating wake. My tuned hull prevent the sudden rise of water at the bow by spreading its pressure wave over a wide area, then re-absorbing it as the hull passed, leaving the water flat. There is no bow wave as such, or undulating waves in the wake. I do not know how to add photos or drawings to my post. The pictures explain. Cheers

[Guest625101138]

Have you got photos in electronic format. They need to be a jpg or other image file format. Not bmp type.

If they are not in electronic format then you have to scan them or get someone with a scanner to scan them for you.

Once you have the electronic file you can attach it to your next post. I have taken a creen shot of the message command bar and attached it. You will see the same thing when you open your meassage window.

You place the mouse curser over the paperclip icon and click. It will bring up an attachement window. See my second screen dump image. You choose the photo file from your computer and upload it.

Rick W.

[Lin Olen]

Thanks Rick. I have scanned photos as jpeg 300 dpi in greyscale. How to get from photo file to post? Trouble is I have Vista OS on a Toshiba Satellite. Lin.

[Guest625101138]

follow the instructions in my previous post.

Save the photo into your documents on the computer,

Reply to this post.

Attach the photo using the paperclip icon above the reply window. You will get an new attachment window like the one in my previous post. Choose the photo file from your documents folder on the computer. Then upload the file.

After the attach window indicates the upload is complete, submit your reply.

The new post should have the photo included.

Rick W.

[Lin Olen]

Photo tuned hull herewith?

[SeaSpark]

No picture yet, thanks for trying (and Rick for his explanation) i am very curious about your craft.

[SeaSpark]

The maximum file size for images is 2Mb when you scan an image at 300 dpi it is easy to go over this limit. A greyscale image in jpg format should not have to be bigger than 200Kb.

An easy way to make an image smaller is to press the "Print Screen" or "Prnt Scrn" button somewhere at the upper right of your keyboard while the image is in full screen view of your computer.

Next you start the paint (under start- accessories) program that comes with windows and press "edit" and "paste" from the pull down menu.

When you save the image as a .jpg in paint it should be small enough.

[yipster]

i'm impatiently wondering too, has it to do with area rule?