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Topic: Propeller Clearances for the 80' Eldo |
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Greg Viggiano
New Member
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Posted on: Oct 13, 2019 - 1:18am
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Last week, the polished bronze 3D printed propellers from Shapeways arrived and they look perfect (Dick, I'll send you the image to post here).
The question I have pertains to the correct clearance between the prop and the hull. If the prop is 30" in diameter, and the main wing strut drops down 16 5/8 inches, is 1 5/8 inches the correct prop/hull clearance?
It seems like the clearance should be more like 5 inches
Comments welcome
Best regards,
Greg Viggiano
GV |
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Jeff D
Moderator
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Posted on: Oct 14, 2019 - 3:28am
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The Elco prop shaft location drawings weren't much help, they don't directly give a clearance. I've scaled this Elco outboard profile to 10 pixels per inch so I could measure directly from it in my image program. Here's what I came up with:
Prop tip: 2.25 - 2.5 below keel
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Jeff D
Moderator
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Posted on: Oct 14, 2019 - 3:35am
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Here are details from the Elco center prop shaft location drawing, courtesy of our fearless leader Dick Washichek:
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Greg Viggiano
New Member
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Posted on: Oct 16, 2019 - 5:53am
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Thanks for the clarification Jeff -
That clearance seems to be what I have with the 28-inch center prop / strut combination, which is about .156" at 1:16 scale
The part that is confusing me is - with a scale 30-inch propeller (1.875) on the wing struts, and using the struts from Holden8702 scaled to about 16 inches, his struts are measuring about 1.0 inches, and I can't understand why am not getting sufficient clearance. It seems that the struts should be a little longer - around 1.100 inches
GV |
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Jeff D
Moderator
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Posted on: Oct 17, 2019 - 6:59am
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The Elco wing strut drawing shows the wing struts to be 16" from mounting flange to center of where the shaft would exit the strut so Holdens seems to be spot on. The mounting flange mahogany shim between the hull and strut would add about 5/8" more. The wing struts are mounted at right angles to the bottom, not plumb.
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TED WALTHER |
TOP BOSS
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Posted on: Oct 17, 2019 - 9:07am
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Jeff;
Good point, Greg probably didn’t include the shim, an easy oversight for any modeler.
Take care
TED
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Greg Viggiano
New Member
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Posted on: Oct 18, 2019 - 7:26am
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Thanks Jeff and Ted - I'll add the shim, but the clearance still seems too tight for a 30-inch scale prop with a 1.875 diameter. My math shows that there would only be a 1-inch prop-to-hull clearance (.0625 at 1:16).
GV |
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Jeff D
Moderator
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Posted on: Oct 19, 2019 - 6:47am
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Just the 16" strut and 5/8" shim minus the 15" blade give 1 5/8" clearance, plus a little more for the strut angle effectively lowering the tips. Dunno what to tell ya... you should be seeing a 1/10" clearance at least in 1/16" scale.
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Andy Small
MASTER
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Posted on: Oct 19, 2019 - 10:41am
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I don't have any info that the Elco ever used a 30in propeller. only much later did they increase from 28" to 29" (PT-613 series), according to my NARA documentation. |
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Jeff D
Moderator
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Posted on: Oct 19, 2019 - 1:25pm
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I see I have on my website that props were 28" center and 30" wing based on info from a now defunct website. I also see that Dick's Elco Parts Catalog lists 2 different props for each boat, center and wing... with no mention of the pitch or diameters. Andy, do you have any documentation mentioning that all 3 props were the same diameter? Also, the Elco drawings show a prop shaft for PT 545 that was 2.25" diameter as opposed to the standard 2". Do you know of any experiments with the 545 that might explain why the beefier shafts?
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