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Hydro Junkie

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Oct 2, 2006
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The one difference I know of is, unless the front of the ram wing is dropped down, the bottom angle is greater, creating more lift in the front. Since your boat has a longer forward bottom, the center of lift is further aft so it may need to be set up a bit differently. This is a case where personal preference comes into play as both ways are known to work. The scale boats I'm building are like yours, as are most built from Newton plans.
 

ChrisHerzog

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Jan 20, 2019
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227
I agree with what HJ in the post above this one stated. The bottom of your sponsons are also different but I do like yours.
 

James Schmidt

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Jun 18, 2013
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316
The terminology aft; It’s used in airplanes too. I’m not sure which side of CG it referrers to. I know it means after, but is that Behind or in front of?

If I understand you correctly, on my longer ramp the lift would occur farther back.

Thanks HJ👍

Chris, I saw your other thread (kits) I agree building is as much fun as racing.
Good looking frame work here. Show us more pics as you progress.

I haven’t had any new progress on my hull lately but will post more on my thread when I do. 82U55 is a cool design.

Thanks for Sharing guys
 

Hydro Junkie

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Oct 2, 2006
Messages
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James, when talking fore and aft, it's always referring to moving forward of your current location or after your current location, meaning moving toward the rear of the boat. That said, when I built my sport 20 Pak, several years ago, I reworked the bottom so that the front's AOA(angle of attack which is an aircraft term, though it does apply in this case) was reduced from roughly 10 degrees down to 5 degrees by moving the break from the sponson transom back 8.5". At the same time, I also lengthened the air traps from 1" long to the same 8.5", though I did make them more scale in shape at the same time.Dumas Pak with left deck installed.jpg
Dumas Pak completed left sponson with deck.jpg
The pictures show how far back I moved the bottom break, that being two frames aft, which should be comparable to the bottom of your boat. According to Grimracer, this is a change that has been done to many of the Dumas Pak builds in his area, allowing the boats to use the more powerful modern engines with less chance of them blowing over. One other change I made was I widened the engine bay to allow for the 180 degree header the Nova Rossi engine uses
 
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James Schmidt

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Jun 18, 2013
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316
Very good HJ thank you! This is my 2nd hydro build so it’s new to me. I’m still learning about hydro dynamics theory.

I always ran monos and cats. I wonder if anyone will come up with an 82U55 Sport 40 kit someday.

Thanks for your help.
 

Hydro Junkie

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Oct 2, 2006
Messages
4,933
Can't say on sport 40 8255 kits since I'm not really a fan of that boat. Granted, it's easier to build since it didn't have tails or a wing in its more popular liveries, just a hull and cowl. That's probably the biggest reason many build it as the Executone, Speedy Printing and Oberto.
As for what you call "hydro dynamics theory", it's not really that difficult. What it amounts to is the center of the boat is a wing. Just like any other wing, it's supported by air pressure under the wing and a low pressure area above it. The prop acts like an elevator, lifting the rear of the wing by it's rotation, thrust angle and depth. The sponsons are kind of like training wheels, keeping the boat balanced, the difference being the inside vertical surface of the sponsons and air traps keeps the air under the boat rather than letting it "spill" along the sides. This is the major difference between yours and Chris' boats. His can spill most the air our at the rear of the sponson where yours traps some all the way to the bottom break. If you look at the last three full sized Miss Madison/Oberto and Homestreet Bank boats, they have an airtrap that runs all the way to the back of the nontrips that is 3 to 4 inches below the rear bottom just to keep air under the boat. I haven't really looked but I'd bet all the rest of the present unlimiteds are similar
 

dave weagel

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Apr 8, 2006
Messages
661
ML 1/10 (sp 40 ) 138-8255 kit available
Or use Dave Frank plans see thread this website
Hydro Scale Creations has the 1/10 8255 cowl



 
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James Schmidt

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Jun 18, 2013
Messages
316
Hey Dave, that’s my thread, The picture of my boat is from the Dave Frank 28” plans. I enlarged plans 30 percent.

When I get more done I will post my progress on that thread. Thanks for all your help and showing us you Dave Frank Gasser.

If any one has not seen Dave’s gas version, you can see it on the thread link he posted. The thing cool too.

Chris your thread is interesting because we can see the different versions of this boat and learn from them.

HJ thanks for explaining how the different designs work.
 

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