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Need Advice on Cutting Consistent Wing Ribs - 4/24/2012 5:09 PM   
SrTelemaster150



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From: Brasher Falls, NY, USA
Status: offline 		I'm attempting my 1st build from plans. Not really "scratch built", but some of the cutting skill sets are the same. It's a simple 2 X 4 glider so the 21 wing ribs & 2 fuselage sides are the only compound curves I will have to duplicate.

I have a crude scroll saw & a good disc/drum/belt sander so I have the necessary tools. I have some ideas of how to duplicte multiple ribs of the same size/shape. I'll put those out here W/the object of receiving some experienced input/guidence. I worked in a stamping plant for GM some years ago & spent some time in the "pattern shop" where a good freind spent his work days. When they had to duplicate multiple examples they used double sided tape to hold the parts temporarily together. I plan to do likewise. Here is my plan.

1. Cut oversized blanks & tape them together W/double sided tape
2. Apply a traced pattern on the stack W/the same DS tape & cut close to, but not on the pattern line W/the scroll saw
3 Sand "to the line" on the disc sander
4 Apply another traced pattern (cut to the line) on the back of the stack to keep the cutting of the spar notches in line
5 Rough cut the notches on the scroll saw
6 Fine tune the spar notches W/"safe files" checking for a snug fit W/spar scraps
7 Seperate the finished ribs

When I was a youngster many, many years ago, I built countless cheap "Comet" balsa stick models that were not die cut. They only had the ribs/formers printed on the balsa sheets. I used to build some pretty passable WW I biplane & general aviation scale models W/nothing more than my Dad's straight edge safety razor blades & the old Testor's fast drying wood model glue.

I'm planning on covering this plane W/transparent orange Ultracote so the build quality has to be 1st rate.

I'm building it to entertain my 3-year old granddaughter W/short, exciting flights hoping to plant the seeds of R/C flight in her fertile, sharp little mind.





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RE: Need Advice on Cutting Consistent Wing Ribs - 4/24/2012 6:14 PM   
FlyerInOKC



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Status: offline 		If you want to glue them a light coat of rubber cement might work or two small holes using 2X56 screws and washers would work also. I have been using rubber cement on my paper templates for years. I personally don't like to use anything that isn't easy to remove or might leave a residue that could affect gluing. I hope your granddaughter gets the bug! You might also get her a park flyer membership with the AMA. She'll receive a quarterly magazine and be able to view back issues online. In the Park Flier magazine there is a young lady who is currently doing her first build article. The airplane is an electric version of an old timer design and she isn't the only youngster who is a regular contributor. It's a great way of showing her girls do fly and do build airplanes just like the boys of all ages. Show her a few back issues she'll see the ladies of the AMA competing alongside the men and winning. I'm not ashamed to admit in some ways I think the ladies learn at a quick rate then us guys. Model airplane flying is an equal opportunity addiction. Good luck!

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RE: Need Advice on Cutting Consistent Wing Ribs - 4/24/2012 7:04 PM   
kdc



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From: Shenfield, UNITED KINGDOM
Status: offline 		In my opinion there is only 1 way to make ribs, and that is to cut them out roughly oversized ( with a scalpel ) and bolt them together between ply templates.
The centre picture shows the roughly shaped blanks ( they could be rectangles ) bolted together. Also shows the brass tube hole punch for balsa which makes holes exactly to fit the bolts with no slop.
Other pics show the Permagrit sander which is all you need not a disc sander. Also cutting the rib slots with razor saw.

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RE: Need Advice on Cutting Consistent Wing Ribs - 4/24/2012 8:33 PM   
tschuy


 

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Status: offline 		I've done the same thing as kdc and have great success.  Trick is to have a template made of harder material then the balsa wood ribs.

To cut the notches for the spars I do the same thing but will use one of the wifes finger nail files to sand the the notch line. I found them to work perfectly and they come in numerous grit values to meet the hobbiest needs.


Cheers,



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RE: Need Advice on Cutting Consistent Wing Ribs - 4/24/2012 8:57 PM   
carlgrover


 

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Status: offline 		Get "Master Modeling" by Harry Higley. It is an excellent reference for building techniques and includes several methods for cutting out ribs. I would also try and pick up a used bandsaw. Never liked a scroll saw for anything other than inside cuts.

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RE: Need Advice on Cutting Consistent Wing Ribs - 4/25/2012 12:41 PM   
kdc



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From: Shenfield, UNITED KINGDOM
Status: offline 		Clearly the tools you like most and use most are the tools you become most skilled with. So use whatever tool you prefer. However I can see no real need for a bandsaw and the real risk of serious injury to fingers whilst cutting delicate parts. A scroll saw is much safer but even that is not needed for balsa ribs. If you start with a rectangular set of blanks a razor plane quickly reduces them to shape and then a sanding block is used. And when sanding or planing the blanks are held in the vice as shown in my photo and the bolts and nuts projecting are not a problem as they would be trying to put the pack flat on saw table.

Tim's emery board tip is a good one although an engineers file with a 'safe edge' is useful instead.

The rib templates can easily be made with 1/32 ply which can be cut with a Stanley knife for most parts and a fretsaw used for the really tricky shapes. Spar slots are not needed until ribs have been shaped. Make the template a little over length at the TE as it's easy to make the ribs too short otherwise. Beware of making sloppy holes in the balsa as this can lead to variations in shape.

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RE: Need Advice on Cutting Consistent Wing Ribs - 4/26/2012 8:47 PM   
CanDo


 

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Status: offline 		All these techniques work very well. Another method is to simply put a sheet of balsa on a cutting mat, lay your plywood template over the balsa sheet and use your hobby knife (with a new blade) to cut out ribs. When I have several ribs, I stack them, pin them together, cut the notches and lightly sand the ribs to a uniform shape. I have cut out many ribs this way.

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RE: Need Advice on Cutting Consistent Wing Ribs - 4/26/2012 9:52 PM   
BMatthews



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Status: offline 		I do the same as KDC but cut the notches for spars only once in a stack like CanDo describes. And then even though it's a constant chord wing I still number the ribs from one end to the other. That way any minor runouts of the slots are graduated over the entire span so I don't have one rib pulling one way and those next to it another.

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RE: Need Advice on Cutting Consistent Wing Ribs - 5/22/2012 8:56 AM   
Iron Dog



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Status: offline 		I do the same as CanDo, but use formica to make the original template and use a razor saw to cut the crossgrain leading edge.  Works great, as long as you hold the knife at a right angle when cutting. 

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RE: Need Advice on Cutting Consistent Wing Ribs - 5/22/2012 9:56 AM   
highfly3D


 

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Status: offline 		I have also heard routers help to cut precision parts & i am sure you can cut ribs from a template using a router. I am planning to mass produce a kit using this technique.

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RE: Need Advice on Cutting Consistent Wing Ribs - 5/23/2012 10:42 PM   
sidgates



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Status: offline 		I have used the KDC method for years except I usually make my templates out of aluminum. When I do my next scratch build I will try to get the ribs and as many parts as possible laser cut.

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RE: Need Advice on Cutting Consistent Wing Ribs - 5/26/2012 10:09 PM   
BMatthews



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quote:

ORIGINAL: highfly3D

I have also heard routers help to cut precision parts & i am sure you can cut ribs from a template using a router. I am planning to mass produce a kit using this technique.


Using a router to cut out stacks of ribs will result in a huge amount of lost wood and severe dust control problem. I'm pretty sure most kit cutters that did it in the days before CNC and lasers used a bandsaw to slice out stacks of ribs.

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RE: Need Advice on Cutting Consistent Wing Ribs - 5/27/2012 8:06 AM   
highfly3D


 

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quote:

ORIGINAL: BMatthews


quote:

ORIGINAL: highfly3D

I have also heard routers help to cut precision parts & i am sure you can cut ribs from a template using a router. I am planning to mass produce a kit using this technique.


Using a router to cut out stacks of ribs will result in a huge amount of lost wood and severe dust control problem. I'm pretty sure most kit cutters that did it in the days before CNC and lasers used a bandsaw to slice out stacks of ribs.



Yes i agree, but we can cut fuselage sides using a template with the help of a router.

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