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Schempp-Hirth Standard Cirrus - 3 Metre span**

Posted: 31 Mar 2020, 19:20
by GaryBridge1
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My first glider build. Purchased the laser cut short kit from Sarik hobbies. The quality of the laser cutting is superb, leaving minimum sanding. Started on the fuselage, which is in two halves and am now planking with 1/4" wide strips of 1/8" balsa. Time consuming, but worth it

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 31 Mar 2020, 19:57
by Martin Gough
Nice work.

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 01 Apr 2020, 15:23
by GaryBridge1
Thanks Martin; just had a look at your build thread on the Reiher II. Have you got any further on it? Looking good too; where did you get the kit from? Regards Gary

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 01 Apr 2020, 16:46
by Martin Gough
HI Gary
I haven't touched it for about a year but should be able to do some soon
if the lockdown gets extended. Got the kit from Lasercut Sailplanes from
memory its a Cliff Charlesworth one. Should be nice when done.

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 01 Apr 2020, 22:09
by B Sharp
Hi Gary. If it is from Sarik and it is a 1/5 scale Std Cirrus I suspect that it is from the Mike Trew plan. I have a copy of this plan tucked away in a drawer someplace and it is a little further down my build list. Good luck with the build, I will watch it with interest.
Brian. :)

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 02 Apr 2020, 08:27
by Cliff Evans
It is the Mike Trew plan.

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 04 Apr 2020, 20:21
by GaryBridge1
Martin Gough wrote: 01 Apr 2020, 16:46 HI Gary
I haven't touched it for about a year but should be able to do some soon
if the lockdown gets extended. Got the kit from Lasercut Sailplanes from
memory its a Cliff Charlesworth one. Should be nice when done.
That's good, when I built my Mossie, initially I was on it 24/7; but as time went by work and house moves got in the way and the build got shelved a few times. Eventually finished & flew it successfully after seven drawn out years. Lets hope your build is quicker than that? Thanks for the info.

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 05 Apr 2020, 19:16
by SedB
That indeed looks like it's a lot of work!
Once the fuselage is sanded to shape, will you cover it with glasfiber?

Daniel

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 10 Apr 2020, 20:08
by GaryBridge1
Hi Daniel, Yes planking is quite tedious, but with a model of this size, it's the only way to get the balsa to go around quite tight curves. After sanding I am planning to cover with light glassfibre. I will use peel ply which reduces the amount of resin and also enables an easier final sanding to finish, prior to painting.

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 10 Apr 2020, 20:51
by GaryBridge1
Repeated build and planking on starboard side. With most of the planking complete, the fuselage is stable enough to remove from the building board and test fit together with a couple of elastic bands.
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Quite pleased with how they match together.
Prior to gluing the sides, I need to place the Elevator and Rudder servos in position forward of CofG and route/secure the snakes. Also, I will need to build the wings so that I can get the alignment of dihedral correct.

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 15 Apr 2020, 17:52
by GaryBridge1
In preparation to build the wings, I cut out all the ribs (28) in all for each wing. Ribs 1 to 3 have a 1/8" ply doubler. I noticed that none of these ribs had the cutout for the brass wing joiner, however the Root facing rib (top of photo) does have the cutout. So using the plan, I've been able to cut these out on ribs 1 to 3, taking into account the 2 degree dihedral and then glued the balsa ribs to the 3 ply ones.
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Then, I cut the Wedges from 1/8" Spruce for supports of the brass wing joining strip. My trusty Japanese saw is excellent for the fine cut required.
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Also cut the brass wing joining strip and dry fit over plan.
That should sort the dihedral out. :D

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 18 Apr 2020, 10:53
by GaryBridge1
Starboard wing built, with spruce spars. Next stage is to sheet the under side with 1/16" balsa, from the main spar to the rear, requires removal from the board and turning over.
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Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 18 Apr 2020, 11:37
by Peter Balcombe
Just a thought Gary, but why not sheet the upper surface first whilst the bottom is still in position?
If you do the bottom first then you will need to ensure that the sheeting attaches to all the undercambered areas.
Peter

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 19 Apr 2020, 15:05
by GaryBridge1
Hi Peter, On the plan, notes are quite sparse, but it does list an order of tasks to complete the wings. So I've just followed that and gone ahead with sheeting the underside first, to the rear of the main spar. It went well with no unforeseen problems. What I found a bit unusual with this plan for the wings, is that there aren't any jig tags on any of the ribs. So the only way to ensure the ribs are in the correct position, was to make sure the upper and lower spruce spar, were at 90 degrees to the building board all along the wing span. I managed that by cutting a few pieces of wood with a 1/4" slot and placing them at intervals along the plan. Here's a photo of the sheeting done so far and one of the simple jigs I made to keep the spars perpendicular whilst gluing the ribs in place. Once the glue had dried, it was then a simple matter of adding the 3rd spruce spar at the front, which slotted into every rib easily without any fettling, giving me confidence that the ribs are correct. Would sooner have jig tabs though?
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Next on the list was the vertical grain webbing, which all went in place nicely forward of the main spars.
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Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 19 Apr 2020, 18:30
by Peter Balcombe
Gary,
It doesn’t really matter how you do it as long as the skins are attached to the ribs etc., but most importantly, the wing has the correct incidence all the way along.
You need to make sure that you have the correct amount of washout built in (if any- as identified on the drawing, usually at the tip end trailing edge area somewhere). The top & bottom spar edges will not necessarily be perpendicular to the bench.
Make sure that this is correct/wing TE jigged, before you attach the top skin which will then ‘lock-in’ any wing twist - intended or otherwise.

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 19 Apr 2020, 22:03
by GaryBridge1
Appreciate the advice Peter. There is wash out toward the end of the wings, which looks right.There is no mention on the plan of putting an intentional twist. It did mention; however that prior to gluing the vertical webbing, it was a definite requirement to have the lower and upper main spars at 90 degrees to the board. So I've been quite conscious of not getting any twist at all. I'LL try my upmost to jig the wing prior to putting any top sheeting on.

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 20 Apr 2020, 08:17
by Peter Balcombe
Hi Gary,
The intentional twist is the washout often applied at the tip end which twists the TE up a bit to reduce incidence & avoid the tip stalling before the rest of the wing (tip stall). :)

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 20 Apr 2020, 16:36
by GaryBridge1
Okay, understand. The washout is achieved on this model by the shape of the outer ribs, which effectively gives a slight twist, although the spars remain at 90 degrees.

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 26 Apr 2020, 20:41
by GaryBridge1
Having built both wings and sheeted the bottom of each to the rear of the main spar, my attention turned to installing the brass wing joiners in each wing and through the fuselage. I realised quite quickly that the spruce wedges I'd cut from 1/8" Spruce for supports of the brass wing joining strip weren't quite right, even though I'd used the plan drawing. So I re-cut some more, making sure that the 2 degree dihedral was maintained on each wing.
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Having repeated the same on the port wing, time for a test fit on the fuselage, before I commit to gluing the wedges in.
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Starting to take shape, so it's on to sorting the ailerons/fitting of aileron servos and air brakes next. :)

Re: Schempp-Hirth Standard Cirrus - 3 Metre span

Posted: 04 May 2020, 18:07
by GaryBridge1
Managed to fit the Air Brakes and Aileron Servos into each wing.
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Also glued in balsa hinge blocks and balsa support strips along the ailerons. When the top sheeting is complete, I'LL be able to cut the ailerons away from the wing prior to shaping and hinging.

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Next steps are to position the brass tube in each wing for the incidence pins. Then I'LL be able to sheet the top of the wings and forward of the main spars with 1/16" balsa. Just waiting on a delivery of brass tubes and steel piano wire. Whilst waiting I'LL finish off planking the fuselage and position the snakes for Rudder and Elevator. :)

Re: Schempp-Hirth Standard Cirrus - 3 Metre span**

Posted: 21 Nov 2020, 21:37
by Andrew Ray
Hi Gary, lovely build. This was my second scale glider but the first successful one (the first was Mike Trew's Swallow which spun in on it's maiden), I built this back in the late '70s or early '80s when you could get a glass fuselage and foam wings for it. Needless to say I have a soft spot for this model and looking forward to seeing your progress.