Grob 104 Speed Astir

I recently purchased a Speed Astir IIB and I'm in the process of getting it sorted for the next flying season. I'm interested in getting information from current and previous 104 owners regarding their tips, hints, and suggestions on flying the 104 as well as maintaining it and possible upgrades.

I'm currently replacing the pitot static lines and the wiring. I hate mice! The ship is equipped with an Edo Aire 551A which seems to be quite power hungry. There appears to be a voltage drop when transmitting as the Cambridge MKIV vario is affected every time the PTT is pressed. I'm reworking the wiring to get rid of any voltage drops including larger gauge wire and fuses versus the currently installed breakers. I will also reroute the wiring to try and limit any interference issues. I'm also considering making up a 14V battery as well if the problem persists after redoing the wiring.

Once these issues and the interior are replaced I will start to refinish the gel coat. When I bought the glider the control seals (other than the elasti-flap)were in really bad shape. The rudder seal was missing although I could see adhesive residue on the right side and there was a deteriorated fabric seal on the top of the stab and elevator gap. There were no turbulator strips either on top or bottom of the wing. In doing research I've seen the Eppler 662 will see some improvements with turbulators and have the info on placement from one of Udo's threads. Does anyone know what type and size of strips are best for this application? Also are other 104 owners using mylar seals on the rudder and elevator and if so what size seems to work best? Any internal seals?


I'd like to thank Guy "DDS" and "Skimmer" for there insights and help along the way so far.

On Thursday, January 24, 2013 9:20:09 AM UTC-5, Greg Delp wrote:
There appears to be a voltage drop when transmitting as the
Cambridge MKIV vario is affected every time the PTT is pressed.

Depending on serial number, some of those were EXTREMELY sensitive
to RF, so you may not have a voltage drop.

I'm reworking the wiring to get rid of any voltage drops including
larger gauge wire and fuses versus the currently installed breakers.

Use modern automotive-style fuses and not crappy old
cylindrical style (the latter very prone to corrosion
and of fuse and holder end caps, with consequent voltage drop).

Have fun !
Best Regards, Dave

On Thursday, January 24, 2013 6:20:09 AM UTC-8, Greg Delp wrote:
I recently purchased a Speed Astir IIB and I'm in the process of getting it sorted for the next flying season. I'm interested in getting information from current and previous 104 owners regarding their tips, hints, and suggestions on flying the 104 as well as maintaining it and possible upgrades. I'm currently replacing the pitot static lines and the wiring. I hate mice! The ship is equipped with an Edo Aire 551A which seems to be quite power hungry. There appears to be a voltage drop when transmitting as the Cambridge MKIV vario is affected every time the PTT is pressed. I'm reworking the wiring to get rid of any voltage drops including larger gauge wire and fuses versus the currently installed breakers. I will also reroute the wiring to try and limit any interference issues. I'm also considering making up a 14V battery as well if the problem persists after redoing the wiring. Once these issues and the interior are replaced I will start to refinish the gel coat. When I bought the glider the control seals (other than the elasti-flap)were in really bad shape. The rudder seal was missing although I could see adhesive residue on the right side and there was a deteriorated fabric seal on the top of the stab and elevator gap. There were no turbulator strips either on top or bottom of the wing. In doing research I've seen the Eppler 662 will see some improvements with turbulators and have the info on placement from one of Udo's threads. Does anyone know what type and size of strips are best for this application? Also are other 104 owners using mylar seals on the rudder and elevator and if so what size seems to work best? Any internal seals? I'd like to thank Guy "DDS" and "Skimmer" for there insights and help along the way so far.

Hi Greg. I've had a Speed Astir II since 2004. I think Udo was talking about using the zig-zag turbulator tape that Tim sells on Wings and Wheels. Hope you enjoy your Speed Astir!

Uncle Fuzzy

Any idea which size zig zag or does it not make much difference?

Well I'm finishing up the interior restorations for now and moving onto the exterior. I'm thinking I will try and refinish the glider in Gel Coat as it will be a little more forgiving for my first refinish and I can do it at home without the worries and hazards of Poly. I've begun the hours of sanding with many many many more to go. I'd like to find a supplier for a Gel System. What are everyone's thoughts on which one to use based on pricing, ease of use, and long lasting? I don't want to do this again in the near future.

I'd also like to get some pointers from someone who has refinished a glider and preferably more than one in the North East/New England area. I live in CT and would travel to any of the nearby states to have someone look over my prep work and possibly help me spray the horizontal and elevator as a practice piece. I know there are lots of experienced folks nearby and I'd love to use their wisdom.

I have been flying with a Cambridge C-Nav for 14 years now. I believe this is very similar to the Mark IV Vario. Try connecting to the Mark IV to it's own power source even if just temporarily to see if is a power issue or an interference issue. I had intermittent interference issues when I had the Terra 720 radio installed. I don't recall having any issues since installing the Becker Radio. I installed two batteries and ran the radio and vario off seperate batteries, so I know it was an interference issue.

Brian
HP16T

I got the wiring all replaced and there is very little to no change in the vario indication now when transmitting over the com. On to the sanding.

On Friday, March 1, 2013 8:55:45 PM UTC-8, Greg Delp wrote:
I got the wiring all replaced and there is very little to no change in the vario indication now when transmitting over the com. On to the sanding.

Excellent! It will be nice to have another Speed Astir back in the air.

Just noticed this thread, but you've apparently fixed the vario or have it pretty much under control. In case the problem reappears or others reading this have the same crazy vario readings, here's my experience with what could be the same thing.
Do you have a CAI audio module? I had a similar problem in an LS4 with an old CAI vario and the AU-10 audio unit connected to it. Dave Ellis told me how to fix the problem... While many people insisted the radio needed a separate power supply from the vario!
There was an electrical ground loop built into the Cambridge AU-10. Cut the trace which connects the negative power bus to chassis inside the audio unit. If it's almost gone now, this may be due to new paint on the panel, new mounting screws or something like that.
The ground loop will only be a problem with a conductive instrument panel, which I think the G104 has.
Jim

I finally got the chance to fly the 104. I have a few issues to try and sort out.

First the airspeed indicator seems to read lower than the actual speed. I will test the pitot static system for leaks as well as against a known good ASI.

Second, while checking out the Cambridge MKIV vario and the MKIV Director it was obvious that the Vario was not behaving correctly. I think it may be over compensated and hope the video below may help someone more experienced could determine if this is in fact the case. The Winter mechanical seems to indicate fairly accurately. It is connected to the TE probe and a flask. The MKIV is connected to the aft fuselage static ports(4) and pitot tube. The director is connected to the pitot tube and the forward fuselage static ports with the other pitot static instruments.

The mechanical vario seems to display correctly while cross checking the altimeter. The MKIV seems to indicate opposite especially while changing speeds, which can be seen in the video while changing flap settings. Then it sometimes stabilizes and almost matches the mechanical.

Any suggestions? I haven't had the chance to fly on a smooth day yet.

http://www.youtube.com/watch?v=d6yhK... p9RTsTlUdCZJw