HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jul 18, 2013, 04:41 AM
Registered User
United States, TX, Grand Prairie
Joined Nov 2005
5,869 Posts
Discussion
Cutting a near perfect fit parting board

This guys parting board seems like a perfect fit first time out, no wax or bondo filling in the gaps etc.

Is there are technique to get a parting board like this? thx in advance for any input

erh7771 is online now Find More Posts by erh7771
RCG Plus Member
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 18, 2013, 01:30 PM
Registered DLG addict
NighthawkF-117's Avatar
Minnesota
Joined Jan 2009
1,080 Posts
I think most people will start with a profile of the shape they need on paper. Then cut it slightly smaller than actual profile of the part. Then you would sand and file away until you get a perfect fit.
NighthawkF-117 is offline Find More Posts by NighthawkF-117
Reply With Quote
Old Jul 18, 2013, 02:49 PM
Entropy is happening!
Jim.Thompson's Avatar
Australia, NSW, Bellingen
Joined Aug 2008
7,311 Posts
Quote:
Originally Posted by NighthawkF-117 View Post
I think most people will start with a profile of the shape they need on paper. Then cut it slightly smaller than actual profile of the part. Then you would sand and file away until you get a perfect fit.
This reads good in theory; it's considerably more difficult in practice!
Especially with such a complex shape.
This is just a pure guess, but I wonder if there is a CNC used in this case?
Jim.Thompson is offline Find More Posts by Jim.Thompson
RCG Plus Member
Latest blog entry: Gravity hot wire foam cutter.
Reply With Quote
Old Jul 18, 2013, 03:12 PM
Registered User
United States, TX, Grand Prairie
Joined Nov 2005
5,869 Posts
From talking to the guy it looks like he just cut it as close as possible, clay sealed the back end of the parting board and then cabosil the gaps in the face part to close in the gaps after waxing up the plug really really good.

So my question no is how to get the parting board as close as possible...I mean it looks likes just as long as it's close them I'm cool...I can fill the gaps with filler.

Thx in advance for any input
erh7771 is online now Find More Posts by erh7771
RCG Plus Member
Reply With Quote
Old Jul 18, 2013, 04:04 PM
Duane
Wazmo's Avatar
No. VA
Joined Nov 2004
1,473 Posts
Use a perimeter scribing gauge

Cut a piece of wood with a right-angle corner, tall enough to reach the widest perimeter of the plug when it's sitting on top of the parting board. Cut a groove at a 45 angle from the right-angle corner to hold a pencil. Insert a pencil into the groove and secure it in place. Support the plug sitting on the parting board such that the outermost perimeter of the plug (where you want the parting line) is parallel to the board. Press the bottom edge of the gauge on the parting board, and the vertical edge against the plug. Trace around the plug, making sure the pencil is leaving a mark, but not pushed out far enough to lift the gauge off the board. You may need to resharpen the pencil periodically. Remove the plug, and cut the board just inside the traced line. Sand to fit.
Wazmo is online now Find More Posts by Wazmo
Reply With Quote
Old Jul 18, 2013, 09:08 PM
Registered User
United States, TX, Grand Prairie
Joined Nov 2005
5,869 Posts
Quote:
Originally Posted by Wazmo View Post
Cut a piece of wood with a right-angle corner, tall enough to reach the widest perimeter of the plug when it's sitting on top of the parting board. Cut a groove at a 45 angle from the right-angle corner to hold a pencil. Insert a pencil into the groove and secure it in place. Support the plug sitting on the parting board such that the outermost perimeter of the plug (where you want the parting line) is parallel to the board. Press the bottom edge of the gauge on the parting board, and the vertical edge against the plug. Trace around the plug, making sure the pencil is leaving a mark, but not pushed out far enough to lift the gauge off the board. You may need to resharpen the pencil periodically. Remove the plug, and cut the board just inside the traced line. Sand to fit.
NICE!!!!

Thank you, the simplest is sometimes the easiest and best

looks like I'll have to play with the angle of the pencil but thats about it
erh7771 is online now Find More Posts by erh7771
RCG Plus Member
Reply With Quote
Old Jul 18, 2013, 11:31 PM
Bill from Coffs Harbour
Coffs Harbour
Joined Oct 2010
48 Posts
HI There 7771,, I have previously used the plaster-cine/clay method and trying to cut incredibly close method... they worked but not as effectively as a method a friend showed me...

Cut the parting board slightly oversize... wax and PVA your plug.... and then simply "prop" your plug on the appropriate centre line inside the parting board.. and fill the gap between the parting board and the plug with "splooge" (leaving it a tiny bit high).... let it set.... pop out your plug.... remove the PVA... and sand the top of your parting board flat... and there you have it.. a perfect fit!

Cheers Bill
A parting board for a tailplane... foolishly i did not leave a trailing edge "trough".. a mistake i will only make once.
islandc is offline Find More Posts by islandc
Reply With Quote
Old Jul 19, 2013, 03:43 PM
Registered User
Joined Oct 2006
85 Posts
The one-and-only time I've tried this, I did the following:

1. Lightly dust surface.
2. Place item to be "traced" on surface.
3. Use a drafting triangle to trace the outside of the item, as you would the perimeter scribing guage described above.
4. The drafting triangle will sweep the dust in the shape of the item.
5. Draw a smooth curve around the dust shadow (I marked points about 1" apart, then used french curves to draw the curve thru the points).

This got me within a pencil tip's width of the true shape, which was approximately the accurately of my followup bandsaw cut anyway. The process took ~5 minutes start-to-finish, so it didn't even register a place on the top 100 most time-consuming parts of overall project time.

Cheers,
-Mark
MarkRebuck is offline Find More Posts by MarkRebuck
Reply With Quote
Old Jul 19, 2013, 03:47 PM
Registered User
United States, TX, Grand Prairie
Joined Nov 2005
5,869 Posts
Quote:
Originally Posted by MarkRebuck View Post
The one-and-only time I've tried this, I did the following:

1. Lightly dust surface.
2. Place item to be "traced" on surface.
3. Use a drafting triangle to trace the outside of the item, as you would the perimeter scribing guage described above.
4. The drafting triangle will sweep the dust in the shape of the item.
5. Draw a smooth curve around the dust shadow (I marked points about 1" apart, then used french curves to draw the curve thru the points).

This got me within a pencil tip's width of the true shape, which was approximately the accurately of my followup bandsaw cut anyway. The process took ~5 minutes start-to-finish, so it didn't even register a place on the top 100 most time-consuming parts of overall project time.

Cheers,
-Mark
NICE!

Really good tips here for a first timer, well worth the time to type...

Yeah, looks like if you get the parting board right you can reuse it for more molds...

Keep em coming

regards
erh7771 is online now Find More Posts by erh7771
RCG Plus Member
Reply With Quote
Old Jul 19, 2013, 08:17 PM
Just fly it!
wyowindworks's Avatar
Cody, WY
Joined Nov 2007
6,915 Posts
This is my fancy gizmo:

Mechanical pencil, plywood, CA, and a little fiberglass.
wyowindworks is offline Find More Posts by wyowindworks
Reply With Quote
Old Jul 27, 2013, 05:28 PM
yyz
Registered User
yyz's Avatar
USA, CA, Paso Robles
Joined Dec 2004
2,410 Posts
While not a professional, I've done half-a-dozen, large fuselages and use a slightly different technique.

Rather than try and get a perfect fit between the plug and the parting board, I attempt to get it within a 1/4 inch and then use a 45 degree chamfer bit in a router to cut an angled trough (shaped like a tilted "V") between the plug and parting board.

After accurately aligning and supporting the plug, I then fill the trough with heavily thickened epoxy. Once dry, remove the plug and sand the filler flush with the parting board as islandc does.

Another way to skin the cat without futzing with the parting board,

Mike
yyz is offline Find More Posts by yyz
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Sold E Flite UMX Mig 15 One Day Old and nearly PERFECT Loganradd Aircraft - Electric - Micro & Indoor Airplanes (FS/W) 2 Mar 12, 2013 09:30 PM
For Sale Hoverfly Pro Black board, newest firmware - Perfect condition unfaix Aircraft - Electric - Multirotor (FS/W) 0 Feb 19, 2013 05:35 PM
Discussion What (warbird) kits are a perfect fit for UMX Beast eletronics? XeCutor Scratchbuilt Indoor and Micro Models 10 Jan 15, 2013 12:00 PM
Sold Pike Perfect SL ( near perfect condition) Rich Burnoski Aircraft - Sailplanes (FS/W) 0 Jun 01, 2009 10:29 AM