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Author Topic: D-Box male mould - carving  (Read 2348 times)
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mick66
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« on: July 08, 2012, 01:11:32 PM »

Hi

Starting on a project to build a carbon SLOP power model.  Trying to make a D-Box male mould ... using the "D-Box in a foam clamp" method as described in the past by Joe Maxwell and Phil Ball etc ... as opposed to vacuum bagging.

Any ideas what the best kind of hardwood to use wood be.  I bought a lump of Ash on spec for a couple of quid but it is way too hard to carve easily.
Right now its on the workbench looking at me with 'No way mate' look about it.

Any ideas?

Cheers

Mike
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D-Box male mould - carving
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newg4ff
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« Reply #1 on: July 08, 2012, 03:09:32 PM »

Does anyone know why hard balsa or bass would not work?
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mick66
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« Reply #2 on: July 08, 2012, 04:01:15 PM »

I guess it needs to be resistant to bending or twisting when its wedged into the female part of the mould.  Joe Maxwell used to be able to supply male plugs in the UK but I believe hes passed away now.  Everything I've read always says to use hardwood.  But then theres hardwood and this lump of wood I have.

Obviously some woods carve better than others so I wonder which iss the most suitable for this purpose.

Cheers

Mike
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danberry
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« Reply #3 on: July 08, 2012, 11:04:50 PM »

Basswood wil do what you want.
Easy enough to carve. Tight grain.
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mick66
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« Reply #4 on: July 09, 2012, 03:51:09 AM »

I'll give it a try ... cheers

Mike
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PeeTee
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« Reply #5 on: July 09, 2012, 05:53:55 AM »

Mick

From what I recall from previous FF Forum reports, some people use ready shaped pine skirting board which they then plane and sand to the final shape. Provided the foam rubber is evenly spread in the female part of the mould, there shouldn't be much if any twisting. I'll have a rummage in my Forum reports a little late to see if there is anything I can add.

Happy moulding Cheesy

Peter
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mick66
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« Reply #6 on: July 09, 2012, 09:12:39 AM »

Hi

Thanks for the offer ... I've read that somewhere in the FFForuims too.

Just out of interest seeing as I have it up on my PC anyway ... heres some references I've got already ... but theres nothing better than talking to people 'live' so to speak.

Date   Source   Author      Category      SubCategory   Description
Oct-98   AMI   ---      Construction   Carbon   Carbon construction
Jul-99   AMI   ---      Construction   Carbon   D Boxes
Feb-00   AMI   Stafford Screen   Construction   Carbon   Carbon fibre wings
Mar-02   RCMF   Mark Croome   Construction   Carbon   Kitchen Composites - Part I
Apr-02   RCMF   Mark Croome   Construction   Carbon   Kitchen Composites - Part II
Jul-03   RCMF   Phil Ball      Construction   Carbon   Carbon construction - Part II
Mar-05   RCMF   Trevor Grey   Construction   Carbon   Drax E30
May-93   AM   Dave Hipperson   Construction   Carbon   Carbon construction - Part II
Feb-93   AM   Dave Hipperson   Construction   Carbon   Modern materials
Mar-93   AM   Dave Hipperson   Construction   Carbon   Modern materials
2005   FFForum   Chris Edge   Construction   Carbon   Shell Mouldings
2007   FFForum   Martin Dilly   Construction   Carbon   D Boxes - Herring Bone Press
2009   FFForum   Phill Ball      Construction   Carbon   Sliced Ribs
2009   FFForum   Ray Monks   Construction   Carbon   F1J Booms
2009   FFForum   Mark Croome   Construction   Carbon   Roahcell D Boxes
2010   FFForum   Peter Watson   Construction   Carbon   F1C Model of year
2010   FFForum   Trevor Grey   Construction   Carbon   D Box construction
2011   FFForum   Neil Cliff      Construction   Carbon   D Box construction
2011   FFForum   Ian Kaynes   Construction   Carbon   Teckoa Feather Cut
2011   FFForum   Chris Edge   Construction   Carbon   Carbon Wing Construction
2011   FFForum   Mick Lester   Construction   Carbon   Carbon Tubular Spars
2001   FFForum   Chris Edge   Construction   Carbon   D Box oven
2000   FFForum   John Cuthbert   Construction   Carbon   Wing Incidence Adjuster
2007   FFForum   Chris Edge   Construction   Carbon   Jigs
2003   FFForum   Martin Dilly   Construction   Carbon   Laminated Sliced Ribs
2004   FFForum   Russel Peers   Construction   Carbon   Carbin Spar Jig
2000   FFForum   Stafford Screen   Construction   Carbon   Wing Root & Joiners
2006   FFForum   Ken Oliver                  Construction   Carbon   F1J Tail Booms
2006   FFForum   Mike Francies   Construction   Carbon   Composites
1999   FFForum   Mike Evatt                  Construction   Carbon   Composites
1999   FFForum   John Cuthbert   Construction   Carbon   General thoughts F1C
1996   FFForum   Bob Cheesley   Construction   Carbon   F1B Development - D Boxes
1996   FFForum   Phil Ball      Construction   Carbon   Flapped F1Cs
1995   FFForum   Chris Edge   Construction   Carbon   Quicker composite jigs
1995   FFForum   Stafford Screen   Construction   Carbon   F1C and F1J Booms
1991   FFForum   Mike Woodhouse   Construction   Carbon   Hi Tech Composites
1986   FFForum   Chris Edge   Construction   Carbon   Hi Tech Composites
2003   FFForum   Mike Fantham   Construction   Carbon   Dihedral Joints
1993   FFForum   Phil Ball      Construction   Carbon   Composites for Open Rubber
Jun-03   RCMF   Phil Ball      Construction   Carbon   Carbon construction - Part I
Mar-03   AM   Dave Hipperson   Construction   Carbon   Carbon construction - Part I
Feb-99   AMI   Trevor Grey   Construction   Carbon   Baseboard building jigs
Oct-97   AMI   Andy Crisp   Construction   Carbom   Blue Note F1A
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PeeTee
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« Reply #7 on: July 09, 2012, 09:25:27 AM »

Mike

It was the Trevor Grey article in the 2010 FF Forum report. He makes the male part (the 'plug') from  planed skirting board material. On the female bit the sides are made from MDF trimmed to match the angles of the plug. I was at the forum, and the resulting D boxes looked pretty good to me. If you don't have the forum report, PM me your e-mail addy, and I'll scan the page for you.

Peter
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mick66
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« Reply #8 on: July 09, 2012, 10:44:13 AM »

Hi Peter

thanks for the offer ... looking at it now though.

Had kind of dismissed it a bit as it didn't fit my pre-concieved notions.

Looking again though.

Cheers

Mike
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NormF
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« Reply #9 on: July 09, 2012, 11:17:09 AM »

Have you checked out the D tube method on the CST site? Go to http://www.cstsales.com/d-box.html

- Norm Furutani
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mick66
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« Reply #10 on: July 10, 2012, 11:54:57 AM »

Hi Norm ... thanks for the link ... looks a bit more complicated than what i had in mind.  Think I'll try the foam press method first.

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luthierdan
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« Reply #11 on: July 12, 2012, 12:09:34 PM »

Hello,

I would suggest that you use genuine Honduran Mahogany wood for the mold. It is stable, it also carves and machines well, is relatively light weight and can be finished to provide a very smooth surface.

In times past, Honduran Mahogany was used by mold makers in prototyping parts.

I'm not able to provide any firsthand experience with making carbon wing molds, but as a Luthier (guitar builder) and woodworker I can testify to Honduran Mahogany's good characteristics and workability.

Regards,
Dan McLeod (The Balsa Stripper Guy)
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Tmat
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« Reply #12 on: July 12, 2012, 01:04:40 PM »

I've used hard balsa, basswood and pine to make D-box molds. Twisting is a non issue imo. The d-boxes, after they come off the form, are totally flexible in torsion and can be positioned any which way you want. Only after they are bonded to the ribs and spar do they obtain their prodigious torional rigidity. The airfoil is the only thing that's important imo. So I prefer a wood that I can carve and sand with the tools that I have on hand, such as a razor plane and a sanding block.

Tmat
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« Reply #13 on: July 12, 2012, 01:46:14 PM »

In the past I've used basswood for D-box forms.  But after reading Dieter Siebenmann's paper in the 2010 NFFS Symposium, I tried his method with a few variations, since I was not making a full-chord wing skin:

Medium 1/4" x 1" balsa is used for the shaped part, backed up with a piece of 1/4" x 1" aluminum, attached with epoxy. This helps keep the balsa straight over time. Templates are attached to the ends of the balsa and a long sanding blocked used to sand the balsa to shape. Leading edge radius is the most important thing. Be sure to allow for thickness of cf skin and any sort of release film used between cf and form. (I use plastic wrap; no need to wax or otherwise treat mold.) The other important point in making D-box form is that the leading edge must be straight in plan view. As Tony pointed out, the skins are very flexible so twists or bows don't seem to matter.

The templates that Seibenmann used are not the usual airfoil shape. Instead they are bigger all around by about 1/8"+. This allows the sanding bar to ride on the templates without the sandpaper touching the templates, only the balsa form.  For mine, I epoxied a piece of 1/8" sheet basswood to my aluminum sanding block, then attached adhesive-backed sandpaper to that.  To generate the airfoil shape for the templates I placed tracing paper over the desired airfoil print-out, the carefully drew a series of lines tangent to the airfoil surface and set out exactly the thickness of the 1/8 basswood + sandpaper. (I'm sure there is some easier way to do that on the computer, but it only took about five minutes my way.) The tracings  were attached to plywood and this was cut to shape. Rather then drill and tap the aluminum to screw the templates in place, I simple glued them to the ends of the basswood. The only problem was that I needed to trim back the extreme ends of the basswood a bit to allow clearance for sanding. Note that the sanding block is used in a chord wise direction, which does take a bit of getting used to.

Louis

PS I save my mahogany for prop forms; it is nice stuff to carve.




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Tmat
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« Reply #14 on: July 12, 2012, 02:11:28 PM »

Louis,
I've used a very similar method myself in the past. I used a long sanding bar (steel in my case) with metal templates on each end of the balsa/basswood sanded chordwise. Worked very well. As mentioned, if you shim the sanding bar so that only the shims touch the templates, the templates can be made from plywood as they won't wear.

Tmat
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