HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 27, 2010, 03:14 PM
Registered User
Cornwall, UK
Joined Jan 2010
21 Posts
Discussion
Scratch Build 1:5 Standard Cirrus

Hello to everyone here.

Just to let you know I have just started to build a 3 meter Standard Cirrus. I recieved the plans today.

The plans are for a balsa construction but I wish to make the glider from epoxy fibreglass. I have just started on the fuse tonight.

Over the coming weeks I will post up pictures for you to have a look at. I am new to gliders so have many questions, which im sure you guys wont mind helping with.

I plan to build the fuse molds first, then the molds for the wings.

Tony
airbo is offline Find More Posts by airbo
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 28, 2010, 10:24 AM
Registered User
The SKY MAN's Avatar
uk/england
Joined Jun 2008
341 Posts
Go for it Tony
Iain
The SKY MAN is offline Find More Posts by The SKY MAN
Reply With Quote
Old Jan 28, 2010, 02:55 PM
yyz
Registered User
yyz's Avatar
USA, CA, Paso Robles
Joined Dec 2004
2,378 Posts
Fantastic

Excellent project. Get a copy of George Moffat's "Winning on the Wind". He gives quite a bit of attention to the Std Cirrus.

Have you thought about finding an old Graupner Cirrus 75 fuselage to get you a leg up on the project? I believe it was 1:5 scale.

Look forward to following this,

Mike
yyz is offline Find More Posts by yyz
Reply With Quote
Old Jan 28, 2010, 03:23 PM
Registered User
Cornwall, UK
Joined Jan 2010
21 Posts
I have done a few hours tonight, have shaped the bulkheads for the fuse and have started to cut them on the backbone.

I have been looking on the internet for suitable servos for the sailplane. The wing span is 118 inches and should be around 1.5 Kg . What servos do you guys recomend. I think I will need a thin one for the wings.

I would like to have retractable landing wheel and air brakes for the wings, what makes do you guys recommend and what size servos do you think I will need ?

Also I will need a battery, again what is the norm for this kind of sailplane.

One last question for tonight ! I am going to make the sailplane from Epoxy fibreglass, I have used this loads for building full size yachts but what thickness do you think I should use. I have 200 gram per square meter in the shed. I was thinking maybe 3 layers ? will do a test panel soon to see what this is like.

Tony
airbo is offline Find More Posts by airbo
Reply With Quote
Old Jan 28, 2010, 03:26 PM
Registered User
Cornwall, UK
Joined Jan 2010
21 Posts
Thanks Iain and Mike for the encouragement. Even at this stage I cant wait to fly it.
airbo is offline Find More Posts by airbo
Reply With Quote
Old Jan 29, 2010, 04:20 AM
Registered User
The SKY MAN's Avatar
uk/england
Joined Jun 2008
341 Posts
Tony check your pm
Iain
The SKY MAN is offline Find More Posts by The SKY MAN
Reply With Quote
Old Jan 30, 2010, 01:17 AM
yyz
Registered User
yyz's Avatar
USA, CA, Paso Robles
Joined Dec 2004
2,378 Posts
Tony,

It looks great! Nice work. I love the spoke shave in the background.

The Graupner Teck airbrakes are really nice and worth the money. There were a couple of pair for sale in the Wanted/For Sale thread. You can buy them new for around $50 US.

I have a pair I'll sell you but I think the shipping might not make it worth it. The smaller ones would be fine for your ship,

Mike

ps: regarding servos, the new JR DS378s would be great for your ailerons and you could get a way with something less expensive for the spoilers. Futaba also makes a nice slim wing servo that are a little less expensive than the JRs.
yyz is offline Find More Posts by yyz
Reply With Quote
Old Jan 30, 2010, 02:54 PM
Registered User
Cornwall, UK
Joined Jan 2010
21 Posts
Today I have finished cutting out of the fuse parts and have assembled them on a jig. I had some cedar left over from a canoe I made so ripped it down to make the covering planks.

Thanks Mike I will have a look at those servos and air brakes, looking for the book also but no longer in print I will have to search for it.
airbo is offline Find More Posts by airbo
Reply With Quote
Old Jan 30, 2010, 03:59 PM
Registered User
The SKY MAN's Avatar
uk/england
Joined Jun 2008
341 Posts
Looking good
although a lot of work has yet to be done,that hardwood skin should help with the plug shaping and finnishing!
BTW i intend using savox servos in the c30 small light and powerfull also cheap ish 4.0kg pull
The SKY MAN is offline Find More Posts by The SKY MAN
Reply With Quote
Old Jan 31, 2010, 11:12 AM
yyz
Registered User
yyz's Avatar
USA, CA, Paso Robles
Joined Dec 2004
2,378 Posts
Very cool the way you're building the plug. Bondo body shaping filler is great once you get down to the finishing stages. They also make a feathering compound that is good. I used a bunch of it in the EB 29 build.

I'll trade you the Moffat book for that woodworking vice.... Better yet, IM me. I know a guy that knows a guy that can get you that info on the Std Cirrus.

Mike


Quote:
Originally Posted by airbo View Post
Today I have finished cutting out of the fuse parts and have assembled them on a jig. I had some cedar left over from a canoe I made so ripped it down to make the covering planks.

Thanks Mike I will have a look at those servos and air brakes, looking for the book also but no longer in print I will have to search for it.
yyz is offline Find More Posts by yyz
Reply With Quote
Old Jan 31, 2010, 01:39 PM
Registered User
Cornwall, UK
Joined Jan 2010
21 Posts
Thanks Mike, I just did it the same way you would make a cedarstrip kayak, I was going to glass it but seens strong enough, so prepping to paint.

Here are some photos from todays effort.

All going well, I finished off the planking, cut in the cockpit area, and made a massive mess with the filler. Most of that filler will end up on the floor and me !. I used some course epoxy filler made by international, only reason it was left over from a boat build. So far I have used just materials found in my workshop, I think I will need to order some glass and resign for the moulds.

What weights do you think i should aim for the fuse and wings. Here in cornwall UK I think perfect thermal days with light winds will be rare, much more frequent would be windy days. Would this mean I should not fuss about making the sailplane light as possible ? as I probably need to add weight for the wind ?

Any advice for making the wing plug? the plans just have a template for the root and tip of the wing also the outline of the wing.

As you can see on one of the photos, the root template has a undercut on the underside trailing edge but the tip template doesnt. Is there a good way to blend these two shapes togerther ?
airbo is offline Find More Posts by airbo
Reply With Quote
Old Jan 31, 2010, 02:38 PM
Registered User
The SKY MAN's Avatar
uk/england
Joined Jun 2008
341 Posts
Just bought some west system epoxy
6kg for 78 spondulies from east coast fiberglass supplies but as you live near the coast you prob have your own supplier?
iain
The SKY MAN is offline Find More Posts by The SKY MAN
Reply With Quote
Old Feb 02, 2010, 03:09 PM
Registered User
Cornwall, UK
Joined Jan 2010
21 Posts
While the filler is going off nice on the fuse, I have been playing with a idea, its a slighty different way to build the wings.

I plan to make a plug for each wing then make a top and bottom mold. Then use some 2 pack PU liquid foam and fill the inside of the complete mold with the foam, once hardened and if it doesnt stick to the mold I will have a shaped foam core. I will then add the normal stiffining and cover wth epoxy cloth.

Here are some photos of the wing plug.

I need some advice on washout?
I understand this is the down turn of the trailing edge at the wing tip ?
How much do you need ?
How far back does this go ?

What is the key things I need to watch out for for building wings ?

Tony
airbo is offline Find More Posts by airbo
Reply With Quote
Old Feb 03, 2010, 09:00 AM
Registered User
Singapore
Joined Nov 2001
802 Posts
Washout will induce twisting forces on the wing structure due to uneven pitching moment along the span. Thinning the airfoil should be better than using washout. Transit the airfoil to thinner sections towards the wing tip will help to reduce critical Reynold's number.

With relatively higher aspect ratio of scale gliders, it is more important to choose airfoils that works throughout the span. Even some reputable manufacturers chosen to use an airfoil too thick that causes laminar seperations, which makes the model stall-prone, or draggy. I personally own 2 such models, which happened to be fully moulded. I also ever designed and built one such model. Even my 4 metre Pilatus B-4 uses 12% airfoil at root and 9% at tips without washout. The model is a joy to fly.

I'll say, for a 3metre span, scale 15m class gliders, the airfoils at the tips should not be more than 9% thickness. If you prefer using washout, 1 or 2 degrees downward twist at the tips should be enough.
Joe Yap is offline Find More Posts by Joe Yap
Last edited by Joe Yap; Feb 03, 2010 at 09:02 AM. Reason: Additional text.
Reply With Quote
Old Feb 03, 2010, 10:23 AM
Registered User
North Yorkshire UK, on a big hill facing the prevailing wind. Coincidence?
Joined Oct 2007
906 Posts
Quote:
Originally Posted by airbo View Post
I need some advice on washout?
I understand this is the down turn of the trailing edge at the wing tip ?
How much do you need ?
How far back does this go ?

What is the key things I need to watch out for for building wings ?

Tony
Tony,

Washout is the reduction of airfoil incidence towards the wing, so the trailing edge will actually rise towards the tip, relative to the LE, often just for the last 1/3 of wing. It reduces the efficiency of the wing, but aims to improve handling by reducing the stall speed of the narrower tips.

There's been some good threads on this over the years, but the view seems to be that a carefully selected combination of modern root and tip foils can remove the need for any washout at all, but you either need to know what you're doing aerodynamically, or you could just do what I normally do and copy a successful commercial design! Either way, you'll need to build it accurately, especially with those narrow chords. Are you planning on flying a prototype wood-winged version before you make the moulds, just to check all is OK?

I'll wait for the real experts to join in.

Btw quick work with the fuselage!

Rog
Sutton Bank is offline Find More Posts by Sutton Bank
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion 1968 Miss Bardahl (1:10 scratch build) Capt.Crash Racing Boats - Electric 157 Jul 08, 2011 11:47 AM
Discussion AK8 1/3.5 scalish 5 meter scratch build Bernd Brunner Scale Sailplanes 19 Jul 24, 2010 03:35 PM
For Sale 5 - nib Cirrus cs 201 servos , 5 grams each , coreless motor Dennis Everett Aircraft - General - Radio Equipment (FS/W) 0 Jan 05, 2010 08:57 PM
Sold 3 Art Tech AS100 9g nano servos,1 Cirrus 4.4g,1 Cirrus 5.4g tdab Aircraft - General - Radio Equipment (FS/W) 2 Oct 07, 2006 05:37 PM
1:27.5 Akula: Scratch Build himszy Submarines 47 Nov 10, 2005 06:06 PM