PT Boat Forum


Moderated by: Dick, Jeff D

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

Page: 1 of 1

Back to Topic Index Page 172 | Replies: 6

 Author  Topic: PT 103-class "A"-frame mast base(s)
Drew Cook

TOP BOSS
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Drew Cook  Posted on: Feb 5, 2010 - 5:32am
While watching "Devil Boats" recently, I finally got a fairly (though fuzzy) good look at the dayroom canopy base(s) of the two "legs" of the early, 103-class 80' Elco "A"-frame mast and its "V"-shaped rear brace. I've never really seen, in detail, a good closeup of how the mast and brace attached to the canopy before.

The bases appeared to be pieces of wood, about 6" x 12" (can't estimate how thick).

Were these dayroom canopy bases standard for the "A"-frame mast, and does anyone -- Dick, Al -- have closeup blueprints, drawings or pictures of them and the way the legs and brace of the mast were attached to them?




Total Posts: 1284 | Joined: Oct 19, 2006 - 10:44am | IP Logged

Gary Paulsen

MASTER
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Gary Paulsen   Send Email To Gary Paulsen Posted on: Feb 5, 2010 - 6:09am
Found this photo in Navsource of PT 131.
http://www.navsource.org/archives/12/120513102.jpg

Also this Elco Drawing of various PT Masts used.
http://www.navsource.org/archives/12/120510302.jpg

Hope this helps.
Gary


Total Posts: 246 | Joined: Feb 14, 2009 - 6:31am | IP Logged

Drew Cook

TOP BOSS
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Drew Cook  Posted on: Feb 5, 2010 - 7:36am
Thanks, Gary.

You can see those rectangular (wooden? approx. 6" x 12"?) bases I'm referring to in that first photo of the 131 you sent, which looks like it was carrying the domed-series SO radar mast at the time.

Still trying to find closeups/blueprints of the bases and the "A"-frame mast attachment/attachment points to the bases.

-- Drew






Total Posts: 1284 | Joined: Oct 19, 2006 - 10:44am | 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: Feb 5, 2010 - 9:29pm
Do you have Dick's drawings Drew? The mast drawing is ELCO_Roll_5535-2_72SCAN_00321.pdf & 322 and details everything except the parts holding the mast when layed down. It shows that the leg pads are 3" x 5" x 3/16" castings with 2 lugs coming up at the rear for the swivel. They are shimmed against the crown of the day room to level. The leg bottoms fit into castings and have a lug coming out the bottom aft end for the pivot. The front of the pads line up with the front end of the leg castings and front face of the day room framing. The legs are 28" apart at the base. The brace is attached to the mast 48" above the leg bottoms and the 36" wide yard arm is at 96". The top of the mast legs is at 120". The mast legs taper as they go up.

There's also a drawing for the anchor light at the top of the mast, ELCO_Roll_5535-2_72SCAN_00328.pdf.

I saw an interesting note on a drawing about a radar mast. While the old style mast is 90 degrees to the day room top, the drawing stated that the radar mast is to be adjusted so that it is vertical when the boat was at a certain speed. I don't know if this is true for all radar masts.



Total Posts: 2034 | 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: Feb 5, 2010 - 10:36pm
To get the shape right:

Distance from centerline of mast to centerline of legs (legs are airfoil shaped and each leg is laminated from 2 pieces of sitka spruce):
base: 14"
12": 13.75"
24": 13.5"
36": 12.875"
48": 12" (brace)
60": 10.75"
72": 9.125"
84": 7.25"
96": 5" (yard arm)
108": 2.5"
120": legs are trimmed half their width on the inside to form a single airfoil shape

Leg taper (legs are airfoil shaped and each leg is laminated from 2 pieces of sitka spruce)
base: 3.5" x 1.562"
48": 3.75" x 1.687" (brace)
96": 3.375" x 1.5" (yard arm)
top: 3.25" x 1.25"



Total Posts: 2034 | Joined: Dec 21, 2006 - 1:30am | IP Logged

Drew Cook

TOP BOSS
  

    
Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Drew Cook  Posted on: Feb 6, 2010 - 8:23am
Thanks, Jeff -- no, I don't have Dick's drawings. Maybe sometime in the future, but...the wife's been off work at half pay for a couple of months with a snapped lower leg tendon, and the kid's about to return to college, with all the "nickel and dime" (as in $50 and $100) expenses that entails...

I've tried to visualize all the dimensions you listed... 3" x 5" for the width/length of the base pads seems to be about half the size they look, to my eye, from the footage in "Devil Boats" and the pads on the 131 in the photo Gary posted, but, I'm no carpenter.

The reason I'm asking is to see what the bare bases/pads/fittings on the early, pre-radar "A"-frame masts would look like in detail...as when they were removed (sorry, Garth!). I would imagine that these would have been left alone when the masts were removed -- no real reason to rip them off(?).

Generally speaking, I've thought the attachment points would be a pair of solid, half-moon brackets for each leg of the mast (the "lugs" you mentioned?), with pins or bolts through them to allow the mast to swivel for lowering to the rear, with perhaps a similar atttachment for the point of the rear "V"-brace.


Total Posts: 1284 | Joined: Oct 19, 2006 - 10:44am | 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: Feb 6, 2010 - 9:47am
The larger pads seem to have come with the radar installation according to the drawings. The mast and early deck arrangement drawings show small pads, later deck arrangement ones show the larger with no mast at all. But the drawings are just drawings, pads could have been made larger to spread the load out on the day room roof better.

I have a shot from a History channel show (unknown boat) that shows larger pads with an early mast... other than that, the mast base seems to be pretty elusive in images.



Total Posts: 2034 | Joined: Dec 21, 2006 - 1:30am | IP Logged


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