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View Full Version : What are the "ridges" shown on this flying boat hull?


phupper
10-26-2008, 10:10 PM
I'm doing a scratch build of the Dornier D0-J. There are long strips that run the length of the hull top and bottom. On the top they could be stiffeners. On the bottom I think they help keep the hull tracking straight on the water.

Are these really necessary on a v-bottom hull like the Dornier?

Thanks!

Phil

**EDIT**
Disregard. Necessary or not, I've already started installing them. Better safe...

1320fastback
10-27-2008, 01:43 AM
Maybe they perform the same task for air on top as they do with water underneath.

Gnascher
10-27-2008, 01:56 AM
Perhaps they are simply to stiffen that big flat expanse of skin on the top of the hull.

stevecooper
10-27-2008, 02:06 AM
Ridges are for stiffening, bub, steve

phupper
10-27-2008, 03:55 AM
"Perhaps they are simply to stiffen that big flat expanse of skin"

"Ridges are for stiffening, bub, steve"

Thanks guys, I've seen those on some older planes, but assumed they had something to do with aerodynamics. On the hull bottom I thought maybe they helped keep the pointy end forward when on water. I'm only putting them on the bottom. It couldn't hurt, and they look kinda cool anyway.:cool:

Thanks!

Phil

Jim Casey
10-27-2008, 11:53 AM
On top, they probably act as anti-slip devices so the crewmembers don't "faw down go boom". Teak is pretty good for being non-slippery and little strips are lighter than an entire teak deck.

On the bottom, the flow tends to squirt out the side of a v-hull. They help keep the flow straight and add a lot of lift at pre-planing speeds. Modern floats have spray deflectors on the edge to do this. Also referred to as chines or strakes.
It's amazing how much the hull, back to the step, looks like my old ski-boat.

pd1
10-27-2008, 06:30 PM
The ridges on the top and bottom of that plane are Hat section stringers.
http://www.aircraftspruce.com/catalog/mepages/hatstringer.php

They are added for strength. That plane was designed in a transition period between wood and fabric and the new all aluminum planes.
Other planes of that period tried corrugated skins, Junkers and Ford for examples.

The design could have originally called for all the structure to be inside the airframe and further analysis called for additional strength.
hence outside stiffeners.
The Piper Cherokee uses them on the bottom of the plane for strength.

Jim Casey is correct in that stringers, chines, booster plates all help a seaplane get up on the step sooner.
I think this design was before that was discovered. I think this might have led to the discovery of that trait though.
There are a few different shapes of "hat sections" some are flattened on the top and look more like a top hat in profile.

Paul
PS, you model looks great.

phupper
10-27-2008, 06:52 PM
"It's amazing how much the hull, back to the step, looks like my old ski-boat"

Actually, I couldn't find any clear photo showing the bottom of the hull. I read somewhere that this hull has a shallow "V" shape, so I made it from my memory of a ski boat hull.:D

I have so much work in this model now, and it's turning out so well, that I'm going to put the stiffeners on the top too. It just won't look like a D0-J without them.

Phil

Bill G
10-27-2008, 06:52 PM
Ridges are there to make more work for modellers.:D
I've always wanted to build a JU52 Mausi, but haven't figured out how to do a good job of modelling ribbed duralumin.