PT Boat Forum


Moderated by: Dick, Jeff D

The PT Boat Forum ª PT Boats of WWII ª  PT Boats - General

Next Page | Page: 1 of 3

Back to Topic Index Page 5 | Replies: 26 | Pages: [1] 2 3

 Author  Topic: Propeller Clearances for the 80' Eldo
Greg Viggiano

New Member
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Greg Viggiano  Posted on: Oct 13, 2019 - 1:18am
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

jf9UZ.jpg

Comments welcome

Best regards,

Greg Viggiano

GV

Total Posts: 14 | Joined: Oct 1, 2012 - 6:36am | IP Logged

Jeff D

Moderator
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Oct 14, 2019 - 3:28am
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

jfdgS.jpg



Total Posts: 1857 | Joined: Dec 21, 2006 - 1:30am | IP Logged

Jeff D

Moderator
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Oct 14, 2019 - 3:35am
Here are details from the Elco center prop shaft location drawing, courtesy of our fearless leader Dick Washichek:

jfgPY.jpg



Total Posts: 1857 | Joined: Dec 21, 2006 - 1:30am | IP Logged

Greg Viggiano

New Member
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Greg Viggiano  Posted on: Oct 16, 2019 - 5:53am
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

Total Posts: 14 | Joined: Oct 1, 2012 - 6:36am | IP Logged

Jeff D

Moderator
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Oct 17, 2019 - 6:59am
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.



Total Posts: 1857 | Joined: Dec 21, 2006 - 1:30am | IP Logged

  TED WALTHER

TOP BOSS
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of TED WALTHER   Send Email To TED WALTHER Posted on: Oct 17, 2019 - 9:07am
Jeff;
Good point, Greg probably didnt include the shim, an easy oversight for any modeler.
Take care
TED


Total Posts: 2887 | Joined: Oct 16, 2006 - 7:42am | IP Logged

Greg Viggiano

New Member
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Greg Viggiano  Posted on: Oct 18, 2019 - 7:26am
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

Total Posts: 14 | Joined: Oct 1, 2012 - 6:36am | IP Logged

Jeff D

Moderator
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Oct 19, 2019 - 6:47am
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.



Total Posts: 1857 | Joined: Dec 21, 2006 - 1:30am | IP Logged

Andy Small

MASTER
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Oct 19, 2019 - 10:41am

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.

Total Posts: 223 | Joined: Nov 20, 2013 - 9:04pm | IP Logged

Jeff D

Moderator
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Oct 19, 2019 - 1:25pm
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?



Total Posts: 1857 | Joined: Dec 21, 2006 - 1:30am | IP Logged

Next Page

Pages: [1] 2 3


Lock Topic

 

Forum Legend

New Member

Reply to topic

More than 25 posts | Full Member

Reply to topic with quoted message

More than 50 posts | Advanced Member

Edit Message

More than 150 posts | MASTER

View profile

More than 300 posts | TOP BOSS

Email member