Slingsby T12 Gull Build - Page 2

SteveR · Sep 04, 2009, 10:22 PM

Fred, very helpful notes. Following your thread will give me the insights (and courage) to tackle a model with similar framing/covering requirements.

Thanks,

Steve

Fred China · Sep 06, 2009, 10:56 PM

During the building of many scale gliders I have learned a number of things through trial and error re. covering with plywood and they might help others attempting the same thing.
Tools-- a small block plane(mandatory)...for sizing, chamfering, trimming panels.
Box knives. I have a number, small and large. Best for cutting out panels and trimming. Far better than Exacto overall.
Steel straight edge ruler. For cutting straight edges on ply panels.
Scissors for cutting curves in plywood. Not for straight line cuts.
Heat gun for bending ply and a good pair of thick leather gloves.
Contact cement-- any good commercial product but not water base
Lacquer thinner (solvent for contact cement)
I have a number of small glue brushes I bought at the lumber yard ten years ago for .35 cents. Probably $5.00 each now.

I started with covering the fin with 1/64" ply. At the bottom of the fin where it transitions to 1/32" ply I used a strip of 1/64 ply about 1/2" wide and sanded the top edge of the strip to make a wedge shape to bring the covering layer of 1/64" ply up to 1/32" to match the mating 1/32" ply.

From there it is just a matter of making the card template off the framework and tracing to the plywood. The block plane is used to trim the ply panel to the correct size and chamfering the edges for a tight fit.
If you get a little contact cement on the face of the panel it is easily removed with the lacquer thinner after the panel has been attached.
Do not use CA on any end grain of the ply. It will bleed into the grain and look like the devil and you will never remove it.I use CA sometimes on an overlap or on the edge of the ply when I want to be sure that edge is permanently fastened, but never on an end grain unless by accident.
Try and get the panel edges to match at the same level. Sometimes you have to sand under to edge of an adjoining panel to make them match.

Fred China · Sep 06, 2009, 11:44 PM

During the building of many scale gliders I have learned a number of things through trial and error re. covering with plywood and they might help others attempting the same thing.
Tools-- a small block plane(mandatory)...for sizing, chamfering, trimming panels.
Box knives. I have a number, small and large. Best for cutting out panels and trimming. Far better than Exacto overall.
Steel straight edge ruler. For cutting straight edges on ply panels.
Scissors for cutting curves in plywood. Not for straight line cuts.
Heat gun for bending ply and a good pair of thick leather gloves.
Contact cement-- any good commercial product but not water base
Lacquer thinner (solvent for contact cement)
I have a number of small glue brushes I bought at the lumber yard ten years ago for .35 cents. Probably $5.00 each now.

I started with covering the fin with 1/64" ply. At the bottom of the fin where it transitions to 1/32" ply I used a strip of 1/64 ply about 1/2" wide and sanded the top edge of the strip to make a wedge shape to bring the covering layer of 1/64" ply up to 1/32" to match the mating 1/32" ply.

From there it is just a matter of making the card template off the framework and tracing to the plywood. The block plane is used to trim the ply panel to the correct size and chamfering the edges for a tight fit.
If you get a little contact cement on the face of the panel it is easily removed with the lacquer thinner after the panel has been attached.
Do not use CA on any end grain of the ply. It will bleed into the grain and look like the devil and you will never remove it.I use CA sometimes on an overlap or on the edge of the ply when I want to be sure that edge is permanently fastened, but never on an end grain unless by accident.
Try and get the panel edges to match at the same level. Sometimes you have to sand under an edge of an adjoining panel to make them match.
Sanding the face of the panel to make them match also looks like the devil if you go through a ply.

Fred China · Sep 06, 2009, 11:48 PM

Sorry folks. I'll get it right eventually.

Fred

SteveR · Sep 07, 2009, 07:19 AM

Great note, Fred. Fascinating...I would have thought you'd try for a scarf joint with two butting edges of ply vs. the undercut approach you show in your drawing. I guess the ply is too thin for this approach. Any reccos on a good block plane?

TIA,

Steve

Fred China · Sep 07, 2009, 12:24 PM

Steve

Actually I have scarfed 1/64" ply to make a cover for a wing joint but I think it would be harder for a fuselage panel joint where you are trying to get a precise fit. I also make a couple of new sanding blocks for each glider I build using a piece of 1 by 2 about a foot long. One with course sandpaper and one with fine. They are great for leveling or truing the former doublers and also undercutting a panel edge.
The plane I have is an inexpensive Stanley which is alright but I wish I had invested in a better one. The secret is keeping it sharp. I have a very good 2 sided wet stone.
Another thing I forgot to mention. Don't fight a battle with a compound curve with plywood. You will lose. Use separate panels.

Fred

Fred China · Sep 07, 2009, 12:41 PM

Also I forgot to mention.
When bending larger panels I clamp the heat gun in the vise and use two hands for bending. You can get the bend really quite accurate and the panel will practically fall on the framework.

Fred

SteveR · Sep 07, 2009, 05:24 PM

Fred, for some compound curves, have you ever created what is in effect a series of darts in a piece of plywood e.g. cutting slits partway through the length. Then when applied to the framework, the adjacent sides of the slits come together over the compound curve?

Steve

suirendoujin · Sep 07, 2009, 07:30 PM

Fred,
Thank you so much for sharing with us your valuable experrtise with us. I have a couple of question.
When you heat the ply to bend it, do you wet the ply wood beforehand? Or do you just heat it and bend it?
What is a box knife?

Fred China · Sep 07, 2009, 10:17 PM

Steve

No I havn't, sounds like too much work for me. Why not just make another panel. I would think that you would have to have something to back the slit up as you can't glue a butt edge with any success. If the slit were over a brace or some kind of backing I suppose you could but again I think it would give problems. On the Slingsby Falcon 1 I forced a compound curve with 1/64" ply on the top surface of the wing at the very slight bend of the Gull with limited success. It would have been simpler to make two panels. When you force plywood it tends to bite back by glue separation or buckling. I'm a firm believer in KISS.

Suirendoujin

No! I don't wet the ply. I apply the heat gun to the top or outside of the bend only.
A box knife is a cheap plastic retractable knife that has blades that break off in sections. It's called a box knife because it is frequently used for opening cardboard boxes.

Fred

Fred China · Sep 10, 2009, 02:33 AM

Some thoughts while covering
Contact spray cement is no good for this application.

Most Vintage gliders had a pear shape cross section with a pronounced V at the bottom. Start applying panels from the top down. It is easier to finish with an overlap than trying to fit a panel between two others.
Alternate from side to side as the card template can be used for the alternate panel with usually very little modification.

I know the picture of the elevator push rod is silly but these little things save time and a few swear words.

Fred

I still can't get words under the Photos

Capture the ball in the housing and press whole stab and housing against angle bar to engage ball link.

The wing root area covered over pretty well

I changed my mind and am now having spoilers. Servo is under hatch.

Fred

ultralajt · Sep 10, 2009, 02:58 AM

Subscribed!

Thanks for sharing your build here!
I se I can learn much from your building report!

Mitja

Istvan Noszvai · Sep 10, 2009, 05:10 AM

A superb job with that planking!

Istvan

Fred Sanford · Sep 10, 2009, 01:59 PM

Subscribed.
Thanks for sharing your techniques!

philkiteflyer · Sep 10, 2009, 08:51 PM

Quote:

Originally Posted by Fred China

Some thoughts while covering
Contact spray cement is no good for this application.

Most Vintage gliders had a pear shape cross section with a pronounced V at the bottom. Start applying panels from the top down. It is easier to finish with an overlap than trying to fit a panel between two others.
Alternate from side to side as the card template can be used for the alternate panel with usually very little modification.

I know the picture of the elevator push rod is silly but these little things save time and a few swear words.

Fred

I still can't get words under the Photos

Capture the ball in the housing and press whole stab and housing against angle bar to engage ball link.

The wing root area covered over pretty well

I changed my mind and am now having spoilers. Servo is under hatch.

Fred

I have a question Fred, the photo showing sheeting at the root TE shows there is a butt join around the fuse. My Question:- are you relying on the sheeting as part of your 'Structure' or is it just a skin.

The reason I ask is, if you are using the skin as a 'structural' element to hold everthing together, wouldn't a nice straight butt join around the fuse just act like a 'Dotted line' in the event of (bitting my tongue

) heavyish landing? Having just witnessed this exact senerio yesterday. The join just parted leaving two nice pieces of fuselage.

BUT, if your internal framework is your structural element then it wouldn't matter how the skin is placed because it's just to stop the wind blowing through

.

BTW, I am having big problems sourcing 1.5mm & 0.8mm ply so I am very jealous of yours. I have a plan of this glider and my 15yr old son is keen to build it so I am watching with interest to see if there are any tricky bits.

Cheers
Phillip C

Sep 06, 2009, 11:44 PM	#18
Fred China Registered User Join Date: Jul 2006 Posts: 70	During the building of many scale gliders I have learned a number of things through trial and error re. covering with plywood and they might help others attempting the same thing. Tools-- a small block plane(mandatory)...for sizing, chamfering, trimming panels. Box knives. I have a number, small and large. Best for cutting out panels and trimming. Far better than Exacto overall. Steel straight edge ruler. For cutting straight edges on ply panels. Scissors for cutting curves in plywood. Not for straight line cuts. Heat gun for bending ply and a good pair of thick leather gloves. Contact cement-- any good commercial product but not water base Lacquer thinner (solvent for contact cement) I have a number of small glue brushes I bought at the lumber yard ten years ago for .35 cents. Probably $5.00 each now. I started with covering the fin with 1/64" ply. At the bottom of the fin where it transitions to 1/32" ply I used a strip of 1/64 ply about 1/2" wide and sanded the top edge of the strip to make a wedge shape to bring the covering layer of 1/64" ply up to 1/32" to match the mating 1/32" ply. From there it is just a matter of making the card template off the framework and tracing to the plywood. The block plane is used to trim the ply panel to the correct size and chamfering the edges for a tight fit. If you get a little contact cement on the face of the panel it is easily removed with the lacquer thinner after the panel has been attached. Do not use CA on any end grain of the ply. It will bleed into the grain and look like the devil and you will never remove it.I use CA sometimes on an overlap or on the edge of the ply when I want to be sure that edge is permanently fastened, but never on an end grain unless by accident. Try and get the panel edges to match at the same level. Sometimes you have to sand under an edge of an adjoining panel to make them match. Sanding the face of the panel to make them match also looks like the devil if you go through a ply. Attached Thumbnails 13.7 KB · Views: 148 Old carpenters clamp for small pieces 34.3 KB · Views: 120 One panel covers tail skid 23.8 KB · Views: 139 dark and light transition from 1/64" ply to 1/32" 28.0 KB · Views: 149 3 panels top and bottom of side longeron covering 2 former bays each from rear of fuselage. 21.5 KB · Views: 187

Sep 10, 2009, 02:33 AM	#26
Fred China Registered User Join Date: Jul 2006 Posts: 70	Some thoughts while covering Contact spray cement is no good for this application. Most Vintage gliders had a pear shape cross section with a pronounced V at the bottom. Start applying panels from the top down. It is easier to finish with an overlap than trying to fit a panel between two others. Alternate from side to side as the card template can be used for the alternate panel with usually very little modification. I know the picture of the elevator push rod is silly but these little things save time and a few swear words. Fred I still can't get words under the Photos Capture the ball in the housing and press whole stab and housing against angle bar to engage ball link. The wing root area covered over pretty well I changed my mind and am now having spoilers. Servo is under hatch. Fred Attached Thumbnails 23.4 KB · Views: 118 23.2 KB · Views: 121 22.7 KB · Views: 141 18.2 KB · Views: 130 17.0 KB · Views: 121 Last edited by Fred China; Sep 10, 2009 at 02:40 AM.

Sep 04, 2009, 10:22 PM	#16
SteveR Registered User Join Date: Feb 2002 Location: New York Posts: 1,872	Fred, very helpful notes. Following your thread will give me the insights (and courage) to tackle a model with similar framing/covering requirements. Thanks, Steve

Sep 06, 2009, 10:56 PM	#17
Fred China Registered User Join Date: Jul 2006 Posts: 70	During the building of many scale gliders I have learned a number of things through trial and error re. covering with plywood and they might help others attempting the same thing. Tools-- a small block plane(mandatory)...for sizing, chamfering, trimming panels. Box knives. I have a number, small and large. Best for cutting out panels and trimming. Far better than Exacto overall. Steel straight edge ruler. For cutting straight edges on ply panels. Scissors for cutting curves in plywood. Not for straight line cuts. Heat gun for bending ply and a good pair of thick leather gloves. Contact cement-- any good commercial product but not water base Lacquer thinner (solvent for contact cement) I have a number of small glue brushes I bought at the lumber yard ten years ago for .35 cents. Probably $5.00 each now. I started with covering the fin with 1/64" ply. At the bottom of the fin where it transitions to 1/32" ply I used a strip of 1/64 ply about 1/2" wide and sanded the top edge of the strip to make a wedge shape to bring the covering layer of 1/64" ply up to 1/32" to match the mating 1/32" ply. From there it is just a matter of making the card template off the framework and tracing to the plywood. The block plane is used to trim the ply panel to the correct size and chamfering the edges for a tight fit. If you get a little contact cement on the face of the panel it is easily removed with the lacquer thinner after the panel has been attached. Do not use CA on any end grain of the ply. It will bleed into the grain and look like the devil and you will never remove it.I use CA sometimes on an overlap or on the edge of the ply when I want to be sure that edge is permanently fastened, but never on an end grain unless by accident. Try and get the panel edges to match at the same level. Sometimes you have to sand under to edge of an adjoining panel to make them match.

Sep 06, 2009, 11:48 PM	#19
Fred China Registered User Join Date: Jul 2006 Posts: 70	Sorry folks. I'll get it right eventually. Fred

Sep 07, 2009, 07:19 AM	#20
SteveR Registered User Join Date: Feb 2002 Location: New York Posts: 1,872	Great note, Fred. Fascinating...I would have thought you'd try for a scarf joint with two butting edges of ply vs. the undercut approach you show in your drawing. I guess the ply is too thin for this approach. Any reccos on a good block plane? TIA, Steve

Sep 07, 2009, 12:24 PM	#21
Fred China Registered User Join Date: Jul 2006 Posts: 70	Steve Actually I have scarfed 1/64" ply to make a cover for a wing joint but I think it would be harder for a fuselage panel joint where you are trying to get a precise fit. I also make a couple of new sanding blocks for each glider I build using a piece of 1 by 2 about a foot long. One with course sandpaper and one with fine. They are great for leveling or truing the former doublers and also undercutting a panel edge. The plane I have is an inexpensive Stanley which is alright but I wish I had invested in a better one. The secret is keeping it sharp. I have a very good 2 sided wet stone. Another thing I forgot to mention. Don't fight a battle with a compound curve with plywood. You will lose. Use separate panels. Fred

Sep 07, 2009, 12:41 PM	#22
Fred China Registered User Join Date: Jul 2006 Posts: 70	Also I forgot to mention. When bending larger panels I clamp the heat gun in the vise and use two hands for bending. You can get the bend really quite accurate and the panel will practically fall on the framework. Fred

Sep 07, 2009, 05:24 PM	#23
SteveR Registered User Join Date: Feb 2002 Location: New York Posts: 1,872	Fred, for some compound curves, have you ever created what is in effect a series of darts in a piece of plywood e.g. cutting slits partway through the length. Then when applied to the framework, the adjacent sides of the slits come together over the compound curve? Steve

Sep 07, 2009, 07:30 PM	#24
suirendoujin Registered User Join Date: Jan 2006 Location: The Far East Posts: 596	Fred, Thank you so much for sharing with us your valuable experrtise with us. I have a couple of question. When you heat the ply to bend it, do you wet the ply wood beforehand? Or do you just heat it and bend it? What is a box knife?

Sep 07, 2009, 10:17 PM	#25
Fred China Registered User Join Date: Jul 2006 Posts: 70	Steve No I havn't, sounds like too much work for me. Why not just make another panel. I would think that you would have to have something to back the slit up as you can't glue a butt edge with any success. If the slit were over a brace or some kind of backing I suppose you could but again I think it would give problems. On the Slingsby Falcon 1 I forced a compound curve with 1/64" ply on the top surface of the wing at the very slight bend of the Gull with limited success. It would have been simpler to make two panels. When you force plywood it tends to bite back by glue separation or buckling. I'm a firm believer in KISS. Suirendoujin No! I don't wet the ply. I apply the heat gun to the top or outside of the bend only. A box knife is a cheap plastic retractable knife that has blades that break off in sections. It's called a box knife because it is frequently used for opening cardboard boxes. Fred

Sep 10, 2009, 02:58 AM	#27
ultralajt Registered User Join Date: Sep 2004 Location: Ljubljana Brnik, Slovenia Posts: 714	Subscribed! Thanks for sharing your build here! I se I can learn much from your building report! Mitja

Sep 10, 2009, 05:10 AM	#28
Istvan Noszvai Registered User Join Date: Jan 2005 Posts: 99	A superb job with that planking! Istvan

Sep 10, 2009, 01:59 PM	#29
Fred Sanford Registered User Join Date: May 2003 Location: NorMN Posts: 298	Subscribed. Thanks for sharing your techniques!