Sopwith Baby Project - Page 11

Joe Perkel · 3 February 2008, 12:59 PM

Quote:

Originally Posted by j ferguson

Joe,

......I think I would assume that the sides ARE vertical and include the edges in your point geometry for curve-fitting to arrive at the rib geometry.

Do this with both spars if the front spar top or bottom is sloped.

good luck with this, John

John,

Looking forward to trying this ASAP!

From my location here, I cannot see my own photobucket link (filtered) but, I recall last night thinking that I did not like how the bottom edge was lining up toward the trailing edge. That favored the rotation as noted by Pete.

Still, first off I will reconfirm the Spar section (both) and include those edges in the curve geometry as you suggest.

I agree fully with Sid,...it has to fit and fit correctly! I took a quick peek at the Strutter in France and although a bad camera angle, this photo confirms several points.

1) Both cut-outs clear the cap strips

2) The "reversing" curve along the bottom near the aft spar was bothering me. I see it here in their Strutter,...whew!

3) Both the Pup and the Baby share a similar aft spar geometry which differs from the Strutter.

Thanks again!

Joe Perkel · 4 February 2008, 10:37 AM

Things are becoming a bit more clear regarding this issue in no small part due to the input I received from you folks.

Able to confirm now the following.

1) Aft spar is in fact rotated 4 deg forward

2) Forward spar 1 degree aft

3) Sopwith Pup spars also rotated

4) I made a slight error in the rear spar profile in section.

Thanks again!

Joe Perkel · 6 February 2008, 08:44 PM

Have completed inputing the airfoil section into the software. Satisfied enough for manufacture of these late this year based on this "improved" profile.

As suggested,... I incorporated the spar edge geometry into the curve for a now "perfect" fit.

You can see the detail of the curve analysis tools here.....

Wing Structures

As a result of that, I am not quite yet decided, (open to suggestion), on how to go about cutting these. Very...very....very tempted to "cheat" and hand over CAD generated cutting files to a laser cutter for several reasons.....

1) Precision

2) Minimal waste of material due to accurate computerized "nesting" of the stock.

3) In one fell swoop, a pretty good jump start on the project.

Thanks to all again!

Nick · 6 February 2008, 10:59 PM

Quote:

As a result of that, I am not quite yet decided, (open to suggestion), on how to go about cutting these. Very...very....very tempted to "cheat" and hand over CAD generated cutting files to a laser cutter for several reasons.....

Hi Joe,
Nice drawing.
Just thinking out loud but wouldn't laser cutting ply damage the edges
and weaken it for gluing. Have never laser cut wood so don't know. Maybe it's a matter of sanding it back a bit.
Also don't forget to make the webs 1/8" wider to allow for the 1/16" slots in the capstrip (assuming it's done that way like most Sopwiths)
I think making the ribs first is a great idea. They're relatively inexpensive to make and will give you a good idea whether you really like building. There are hundred of bits to make in a project like this and most of them take lots of time.
If you make templates you can use a whole sheet of ply very efficiently much the same way as setting it up with CAD for the laser cutter.
I found the whole process very enjoyable, although the family wouldn't agree as they found their cars under a sea of sawdust every morning!
You soon get a production line going, then you can glue up another rib each day.
Good to hear that start date is approaching

Cheers, Nick

Machinbird · 6 February 2008, 11:03 PM

Joe, you may not want to cut things out with a laser, The laser burnt edge is not suitable for gluing according to a discussion we had with Spadmaker before he was exiled. I need to hit the sack PDQ so would someone else mind looking up the proper thread.

Nick · 7 February 2008, 12:24 AM

Quote:

Joe, you may not want to cut things out with a laser, The laser burnt edge is not suitable for gluing according to a discussion we had with Spadmaker before he was exiled. I need to hit the sack PDQ so would someone else mind looking up the proper thread.

Sounds like good advice to me Joe. Back to the old fashioned way.
1. Make templates and trace out on your ply sheet
2. Cut out with a jigsaw
3. sand down to the line
4. cut out with hole saws & jigsaw
5. Make Tons of sawdust!

Joe Perkel · 7 February 2008, 03:10 AM

Quote:

Originally Posted by Nick

Hi Joe,
Nice drawing.
Just thinking out loud but wouldn't laser cutting ply damage the edges
and weaken it for gluing. Have never laser cut wood so don't know. Maybe it's a matter of sanding it back a bit.

Also don't forget to make the webs 1/8" wider to allow for the 1/16" slots in the capstrip (assuming it's done that way like most Sopwiths)

Cheers, Nick

Hi Nick, & Sid .....(Spadmaker in absentia)

I may have an A&P license, but I've never actually ever "built" a plane before. So this kind of feedback is very valuable!

I've received "conflicting" opinions regarding laser cutting. A former Pitts builder I know swears by it. Still, I have also heard of the edge issue and obviously,..no lasers in 1915.

So, I was curious to see what you all may have to say about it,...putting out a "feeler" when I am not quite sure about something is a great way to tip myself in one direction or the other.

This is enough to sway me towards hand cutting.

Will be giving the wood cutting tool section in my local Sears some business in a few months! Thanks for the photos of your production line and yes, the Baby has the same slots in the capstrips.

Thanks again!

ulpilot · 7 February 2008, 04:16 AM

Joe,

Two suggestions on your ribs.

Suggest you add vertical strips on the front and rear of the spar openings that are the same width as the cap strips. This will give much more gluing area and strength when assembled on to the spars. Also add one at the front where the leading edge attaches. These will not add much weight, but greatly improves the strength of your glue joints.

Second suggestion, is check around for a company with a CNC Router. High end wood working shops and cabinet builders may have one. You'll get perfect cut ribs with out the possible problems that a laser cut may have.

j ferguson · 7 February 2008, 04:58 AM

Joe,
Buck woodcraft here in Marathon, where we are now, has a cnc router and I understand has cut .plane parts for other builders. see Buck Woodcraft. He's an intelligent guy.

good luck with this.

john

Fee2b · 7 February 2008, 05:50 AM

Template or pattern routing would be a low cost and personally feasable method that lies between Nick's and John's suggestions.

Nick's suggestion on one hand:

Quote:

Back to the old fashioned way.
1. Make templates and trace out on your ply sheet
2. Cut out with a jigsaw
3. sand down to the line
4. cut out with hole saws & jigsaw
5. Make Tons of sawdust!

and John suggested contracting out a cnc router.

Your tool requirement would be a router table with router and a pattern bit, drill to start a hole in the lightening holes, and a jig saw to cut out your rough blanks.

Make the pattern out of thicker and durable material (hardwood, plastic,MDF, Masonite, etc.) using the old fashioned way, sand the edges smooth to the line and that is the only one that needs strict attention.

You could gang several layers under the pattern and mass produce in your own workshop. With a shop vac or dust-collector attached to the router table you can cut down on sawdust. A couble of vertical handles on the pattern and you have easy work. When you are done you will still have the pattern to hang on the wall and use again when needed.

observing,

Fee2b

Michael Scheetz