Pics (CAD) of Raingutter Design

Anything related to Raingutter Regatta racing and event coordination.
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Teeeman
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Pics (CAD) of Raingutter Design

Post by Teeeman » Fri Sep 15, 2006 10:28 pm

Here it is, our first RR... trying for a fast boat.

The pontoons are about .5" thick, they'll sink in (at level plane) about .18" (balsa wood).

The rudder is huge to help keep her straight... but it is the actual size of a supplied rudder trimmed some...

the sail is low and enclosed, circular.

We will be using straws.

Weight is about .0433lbs (.7 ounces).

We focused on getting the CG behind the Fb (buoyancy force center)... as a slight rear-heavy design to counteract planing torques from blowing (and the sail is fairly low).

Also focused on getting the sail on top of the CG to minimize steering torques from non-direct blowing.

Construction starting tomorrow.

We have 1-1/2 weeks to practice and troubleshoot.

-Terry

http://i5.photobucket.com/albums/y159/T ... Slide6.jpg

http://i5.photobucket.com/albums/y159/T ... Slide5.jpg

http://i5.photobucket.com/albums/y159/T ... Slide4.jpg

http://i5.photobucket.com/albums/y159/T ... Slide3.jpg

http://i5.photobucket.com/albums/y159/T ... Slide2.jpg

http://i5.photobucket.com/albums/y159/T ... Slide1.jpg


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Teeeman
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Re: Pics (CAD) of Raingutter Design

Post by Teeeman » Fri Sep 15, 2006 10:41 pm

Already changing stuff... I forgot the pontoons were wider to get the .18" depth...


here is what they are supposed to look like.

http://i5.photobucket.com/albums/y159/T ... -15-06.jpg


I figured if a flat bottom is the ultimate, why mess it up with a big gap... oh, BTW, did I mention the Balsa grab-bag we had already had this width of rectangular pieces in it? (laughing!)

I am curious how it will peform... I think a total flat bottom would work fine so long as the rudder sticks down into the water good.

We'll find out I guess.

I want the submersion depth of the pontoons low as well, but the honest truth is I just don't want to have to make any cuts that require my neighbor's band saw to do correctly (I don't have a good table or band saw).

-Terry


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Re: Pics (CAD) of Raingutter Design

Post by BigSilver » Mon Sep 18, 2006 12:58 pm

Looks good although I am playing with the wide open center section aft of the sail and covered deck forward of the sail in order to create a "surface effect" boat. The air pressure from blowing on the sail helps lift the front of the boat. The pressure is trapped under the forward deck and between the hulls aft of the sail. I built a quick project cat and placed it on the table and blew into the sail and the thing jumped off the table and scooted away. I need to get it painted so I can try it in the water. I was really surprised as how quickly the boat was air born off the surface of the table..... Good luck with your Black Pearl.


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Re: Pics (CAD) of Raingutter Design

Post by Teeeman » Mon Sep 18, 2006 3:06 pm

... very neat idea!

Hmmm... not too late to try it for us either... :)


-Terry


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Re: Pics (CAD) of Raingutter Design

Post by Teeeman » Mon Sep 18, 2006 9:36 pm

Check this lesson in life out...

our CAD designed boat was not as fast as one of our throw-together test articles tonight...

no surprise...

1. the design was changed to have a taller sail, the "production guy" (ME!) missed the change in flat-patterning the sail and we had a stumpy sail (per original pics)

2. the little styro boats are LIGHT!


We did 5 new boats tonight, including a Schooner (sp?)... the goal being to take them all to Den tomorrow for "do and don't" lessons.

Here is the kicker: The boat with the grooved flat bottom hull and tall flat sail HAULED DONKEY!

We have since the testing tonight modified our Black Pearl (and it was turning out pretty, now it is kinda fuggered up)...

The other boat (stumpy sail design) was intended to divert some highPress air to the bottom of the boat and ride her on bubbles...
the "high pressure" idea...

ours didn't work.

Our flat bottom designs really pitch up when they achieve good hydroplaning (and haul donkey!)... the air passage we added simply diverted our sail air... and defeated the momentum... it was a DOG.

A truly engineered vessel would have the bubbles diverting much farther aft than ours... something to think about...

something for another day.

In the meantime, big sails are the schniz in our world for the moment and that is what we went with.

I still think the bubbling divertion has promised... combined with a big sail...

BTW... I do NOT credit the v-groove hull with stability.

All our boats had a nice rudder... and went straight.

A flat bottom with a rudder seemed to be the way to go with hull design.

Hmmm, big sail, half-circle shape and bubbles at the 3/4 L mark... that might be a consumate donkey hauler...

Maybe a quick redesign is in order on the bubble boat to test the idea...


-Terry

http://i5.photobucket.com/albums/y159/T ... Boats4.jpg

http://i5.photobucket.com/albums/y159/T ... Boats3.jpg

http://i5.photobucket.com/albums/y159/T ... Boats2.jpg

http://i5.photobucket.com/albums/y159/T ... Boats1.jpg


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Re: Pics (CAD) of Raingutter Design

Post by BigSilver » Tue Sep 19, 2006 8:50 am

Teeman,
Sorry to hear the bubbles did not work out. I think the first and most important step is to have as light a boat as possible. Foam is the way to go for light.... The blow hole in the boat concept I have been playing with consists of a balsa boat using the Scout Kit for materials. Our Webelo 1 den will be building and racing next month so I am doing my research now. I do not know what our rules will consist of so I am taking a stab in the dark for now.... The hulls I am playing with are as follows, standard kit design, split kit cat with hollowed out hulls covered forward deck plaining step, 45 degree inboard sides of hull, surface effect hull with very narrow pontoons 45 degree inboard 80 degree outboard slope covered deck sail mid ship with "blow hole" in deck aft of sail. I need to play with various blow hole configurations so as not to sacrifice sail pressure..... thanks for sharing your work and I'll see what I can post after a few more tests..... Good luck with you flying equine......


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Re: Pics (CAD) of Raingutter Design

Post by Teeeman » Tue Sep 19, 2006 2:44 pm

note the problem with bubbles for us was we didn't make any :)


Moving the hole aft in another prototype tonight (or tomorrow) should let us see if it works.


"flying equine" ?

-Terry


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Re: Pics (CAD) of Raingutter Design

Post by Teeeman » Thu Sep 21, 2006 10:44 pm

FYI, we constructed a Black Pearl not of Balsa, but of styrofoam tonight and it was very fast...

My son made repeated 2.8s passes with a straw... 5' gutter...
without, slightly faster...

just for fun I did a "blowhard" approach sans rudder and the craziest thing happend about 1/5 times... I'd "hit it" just right with my lung blast and the thing would 'flip' to the other end in under .5s!!!

It was crazy!

(we got so pumped about the styro boat we didn't even think to try out the blowhole concept)


If we could master doing that repeatedly, it would be the darndest thing ever to show up to Pack race, build on-site in 10 minutes... and post a .5s run with a flimsy little boat (almost no weight)...


arrrrrghghghghggh!


-T


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