Redshift Mk I (New Purchase)

[Konrad]

Well here are the results of last nights work.
I added some Kevlar reinforcements to try to keep the flaps on the wing before I add a full surface span repair with Kevlar.

The result was less than satisfactory. While I got a good lay up, the bandage is distorting the hinge line when flaps are dropped past 60°. These patches were allowed to fully cure while the flap was in profile. This results in there being a lot of pull when the flaps are lowered.

Next time I'm going to try to do the same layup, but will drop the flaps down to 70° while the epoxy is still green. Then allow the epoxy to fully cure while the flaps are down. This should allow the Kevlar to lay down tight against the inner skin and unload the kevlar threads (the green epoxy should slide a bit). I just hope the flaps stay in alignment with the wing.

 

[Konrad]

I looked at some of my other wings from way back when. I see that with the wings from FVK the flaps drop to 70° by their own weight. These are Kevlar hinges. I see the models built by Sanda have a polypropylene hinge. These are stiffer but it appears that the polypropylene stretches rather than pop.

I need to get this hinge problem under control.

 

[Hank GB Z]

Don't be come Un Hinged Konrad....

 

[Konrad]

LOL

Bad pun!

 

[Doc James Hammond]

Just another quickie: Modifying the hinge gap and depth is best done with a steel file as it won't readily cut into the kevlar. A lot of people use diamond files which will easily compromise the hinge itself. Steel files are slower its true, but a lot safer.

Just to cancel out that whole statement, the new machine in progress to do this job uses a diamond wheel! But hopefully its under very good depth control.

Cheers,

Doc

 

[Konrad]

Tool life is critical. Carbon weave is surprisingly abrasive!

Already done. I can now get the flap to travel to 90° with the new Kevlar hinge. I used an old steel triangle jewelers file to gain skin clearance. Tool steel will still fuzz the Kevlar.

What I don't like about my process is that I have to time the epoxy cure. It's not critical but it means I can't do the hinge lay up in the evening and go to bed. So I'll have to wait until the morning to do the other half.

 

[Konrad]

Well, that worked out great! The flap hinge is now a lot stronger and allows a lot more range of motion than the OEM hinge!

Please note; that the hinge distortion at 90° is gone. Also that the skin under the flap now has twice as large a skin relief as the ailerons. And that the flap servo needs to be placed to the outboard extreme of the servo bay window to clear the ballast tubes.

Well this cost me about 4 days of time. But, I'm very happy with the results.

 

[Doc James Hammond]

This is the latest Engineering Change - thicker Kevlar and anti tear strip at the cuts.

Waiting for news on the 45 degree orientation, as right now we use 90/90 tape but might have to cut strips.

Spada mould production begins next month.

Doc.

 

[Konrad]

With 45° bias there are twice as many fibers going across the hinge line. Also there is some flex (side to side to allow fibers to "share" the loads.

I'd like to see a hinge doubler under the control horn. Watch out for the thicker doubler area distorting as the surface is moved down to extreme ranges. (I think I'm using 3.7oz 45° bias kevlar).

And if it isn't too late the flap servo window and surface horn need to be moved outboard 15mm to allow for 30mm x35mm servos (based on the Redshift Mk1). Or at least 10mm for 30mm x 30mm servos. You might recall the serpentine pushrod issue with my first Redshift.

 

[Konrad]

I'm now thinking. Can Aeroic supply a peel ply finish to allow proper bonding of the under control horn double should the builder want to add this? I don't think adding extra height to the lay up will result in a good hinge. But if this doubler is added after the surface is cut, one can lay up this material with the surface at 60° deflection. This will unload much of the tension on the fibers. But a peel ply finish would help considerably with post production bonding issue

 

[Doc James Hammond]

I'm now thinking. Can Aeroic supply a peel ply finish to allow proper bonding of the under control horn double should the builder want to add this? I don't think adding extra hight to the lay up will result in a good hinge. But if this doubler is added after the surface is cut, one can lay up this material with the surface at 60° deflection. This will unload much of the tension on the fibers. But a peel ply finish would help considerably with post production bonding issue

Konrad...I love your thinking, but unfortunately you are the ONLY ONE on this planet, no, in this galaxy that would come up with something like that.

Sorry my friend, but that is one detail that won't make it.

Cheers,

Doc

 

[Konrad]

LOL.
Well, it did hurt (much) to ask.

That is the bane of my existence. My ideas have to pass the financial realities of the bean counters. Now if somebody can come up with an easy process to add the bonding texture then we could see progress.

By the way if anybody is wondering a peel ply finish is a finish much like shark skin. For bonding it is far superior to any surface prep derived by sanding.

 

[Doc James Hammond]

Konrad - on bikes we use fine sharp sand in the epoxy.

Doc.

 

[Konrad]

As I know little of composite construction. We should discuss this over a cognac next time you are out this way.

 

[Doc James Hammond]

Sounds like a plan.

I'll bring a bottle of duty free - what kind do you like? I'm not much of an expert on Brandy.

Whiskey? Oh yes, I know those.

Cheers,

Doc.

 

[Konrad]

Actually, if I'm to have a cohesive discussion an Arnold Palmer is probably best.

 

[Konrad]

The epoxy has fully cured and the hinges still move. So back to installing the wing servos.

I decided that I want 110° of total flap motion (20° up to 90° down. That means that I will want the servo neutral to correspond with the flap down 35° (20+35=55 which is half of 110°). It is at this 35° neutral point that I glue in the servo tray. What is nice about this neutral setting being defined by surface movement, rather than surface alignment. Is that if I need to change the servo arm I can without bind issues. That is if I need a larger servo arm I can cut down the extra motion on each side of the servo neutral.

I find that with the Redshift that the best IDS push rod length for the flaps is 54mm using the KST X-10 mini. There is no room for error, with the flap window and the ballast tubes in the wing. In fact I'm concerned that I won't have enough span wise motion to disengage the servo splines to service the servo. This is why I'm do one flap at a time (should I need to re-engineer the drive).

 

[Konrad]

Sorry this is going to be a bit of a bitch session.

CAD, or more to the point poor CAD work drives me nuts! Far too often folks confuse CAM with CAD. CAD is Computer Aided Design. The key concept here is Aided Design!
Design is Form Fit and Function! Now I admit it has been 20 plus years since I actually drew out anything in CAD. Back then I was using Catia v5. Key to this work was to check Form and Fit. This included clearances need to actually build assemble the system. I'm sorry to say that with this Redshift Mk1 this was not done. We had the leverage issue with the V-tail and then this horrible issue with fitting the flap servo.

I'm not going to guess where the fault lies, be it with the contract, or data supplied to the CAD driver. But as delivered one can't install the flap servo in adherence to standard accepted practices. THERE IS JUST TOO MANY INTERFERENCE ISSUES WITH THE STANDARD 10mm x 30mm x 30mm SERVO!

I'm sorry Doc, but since your name is on the design credits I have to ask what was the intended shape (Part Number) of the flap servo. I know we covered this a bit here. But this just drives me nuts. I hope that the Spada wing has addresses these fit issues.

Now I do have to say that the CAM work looks nice. Assuming there wasn't a lot of hand fitting of the molds.

OK, I'll step off my soap box, rant off.
Sorry about that.

It was good to wake up this morning to find that the epoxy had cured. I hooked up my servo tester and found that the second to last of the smaller IDS servo arms actually gave me close to the amount of surface movement I wanted. With the way I had placed the surface spoon (control horn) I was actually a bit short on throw. With OpenTX and Mike Shellim's templets I can expand the servo motion to get the desired throws.

I know that the Redshift supplied by Aeroic came with Doc's servo trays. With my Redshifts I'm using the the Servorahmen IDS system. What follows is my attempt to install the flap servo with the Servorahmen system. This is a personal preference issue and nothing against the actuation method used by most manufactures.

The first thing after re-hinging the flaps was to remove the factory installed control horns. Now based on what I learned with my first Redshift I knew that the placement of the control horn was way too close to the ballast tubes and wing box (you can see this with the need to use a serpentine push rod). So I had to move the control horn (spoon)outboard. What limited this was the placement of the flap cover recess. If I was going to cut into the recess flange and not into the bottom skin I could only move the spoon 4mm to 5mm. This makes the installation of a 10mm thick by 30mm x 30mm servo very tight!

The Key concerns were avoiding the ballast tube end, placing the servo fore and aft inside the window provided, push rod alignment, and clearance to remove and install the servo after the IDS was installed.

I found that the best IDS components were the second from the smallest servo arm and a 54mm push rod. This allowed the placement of the servo close to being centered in the window (the servo is forward 1.5mm). With me squinting my eyes it looked like I could get the flap servo installed and still not violate the servo window.

Well. the problem was that one needs to be able to replace the servo. One can't bolt together the assembly and glue it in place. One needs to get at the screws and have clearance to slide the servo out of the control arm splines. To gain the needed clearance I had the thin the ballast end cap by cutting a trough to allow the servo tab to nest into. I also needed to remove all but about 1mm of the inboard window flange. And because of some lead angle issues I had the thin the back side of the rear mounting brace.

All is not perfect. Even with the 10mm servo biased 1.5mm towards the LE the rear of the servo violated the window flange height. It is still below the wing skin, but just barely by 0.15mm. This is why I didn't add any carbon doubles to the servo pocket. I hope I can make a servo cover that is still flat.

So with sacrificing some servo cover flange I think I was able to actually fit a flap servo into the Redshift wing! Now for the hard part doing it again on the other side.

All the best,
Konrad

P.S.
I wonder if this was the intended servo? But overal length is close to the same as the X10 mini but at half the torque and twice the price. Actually the only thing this servo solved is the cover issue.

 

[Doc James Hammond]

Sorry this is going to be a bit of a bitch session.

CAD, or more to the point poor CAD work drives me nuts! Far too often folks confuse CAM with CAD. CAD is Computer Aided Design. The key concept here is Aided Design!
Design is Form Fit and Function! Now I admit it has been 20 plus years since I actually drew out anything in CAD. Back then I was using Catia v5. Key to this work was to check Form and Fit. This included clearances need to actually build assemble the system. I'm sorry to say that with this Redshift Mk1 this was not done. We had the leverage issue with the V-tail and then this horrible issue with fitting the flap servo
I'm not going to guess where the fault lies, be it with the contract, or data supplied to the CAD driver. But as delivered one can't install the flap servo in adherence to standard accepted practices. THERE IS JUST TOO MANY INTERFERENCE ISSUES WITH THE STANDARD 10mm x 30mm x 30mm SERVO!

Lets just say that there was a lot more wrong than that. Some it was my fault, but some of it was not. Most of the problems were fixed before the models actually went Into production or I would not have let them out.

I'm sorry Doc, but since your name is on the design credits I have to ask what was the intended shape (Part Number) of the flap servo. I know we covered this a bit here. But this just drives me nuts. I hope that the Spada wing has addresses these fit issues.

I hope so too. I have worked pretty hard on the new design, and still am actually. Having said that, your frequent deconstruction posts have been really helpful. This is the kind of thing any designer needs, or he just goes merrily on his way thinking that nothing is wrong.

Now I do have to say that the CAM work looks nice. Assuming there wasn't a lot of had fitting of the molds.

Moulds were fine, but the design and machining work was not done by the original CAD modeller.

OK, I'll step off my soap box, rant off.
Sorry about that.

It was good to wake up this morning to find that the epoxy had cured. I hooked up my servo tester and found that the second to last of the smaller IDS servo arms actually gave me close to the amount of surface movement I wanted. With the way I had placed the surface spoon (control horn) I was actually a bit short on throw. With OpenTX and Mike Shellim's templets I can expand the servo motion to get the desired throws.

Mike is a real guru - and apart from that he's a real Gent.

I know that the Redshift supplied by Aeroic came with Doc's servo trays. With my Redshifts I'm using the the Servorahmen IDS system. What follows is my attempt to install the flap servo with the Servorahmen system. This is a personal preference issue and nothing against the actuation method used by most manufactures.

The first thing after re-hinging the flaps was to remove the factory installed control horns. Now based on what I learned with my first Redshift I knew that the placement of the control horn was way too close to the ballast tubes and wing box (you can see this with the need to use a serpentine push rod). So I had to move the control horn (spoon)outboard. What limited this was the placement of the flap cover recess. If I was going to cut into the recess flange and not into the bottom skin I could only move the spoon 4mm to 5mm. This makes the installation of a 10mm thick by 30mm x 30mm servo very tight!

The Key concerns were avoiding the ballast tube end, placing the servo fore and aft inside the window provided, push rod alignment, and clearance to remove and install the servo after the IDS was installed.

I'm hoping that the internal topography of the new wings will alleviate those problems. The new Ballast tubes are 10mm shorter (But still probably can carry too much ballast for FAI rules)

I found that the best IDS components were the second from the smallest servo arm and a 54mm push rod. This allowed the placement of the servo close to being centered in the window (the servo is forward 1.5mm). With me squinting my eyes it looked like I could get the flap servo installed and still not violate the servo window.

Well. the problem was that one needs to be able to replace the servo. One can't bolt together the assembly and glue it in place. One needs to get at the screws and have clearance to slide the servo out of the control arm splines. To gain the needed clearance I had the thin the ballast end cap by cutting a trough to allow the servo tab to nest into. I also needed to remove all but about 1mm of the inboard window flange. And because of some lead angle issues I had the thin the back side of the rear mounting brace.

All is not perfect. Even with the 10mm servo biased 1.5mm towards the LE the rear of the servo violated the window flange height. It is still below the wing skin, but just barely by 0.15mm. This is why I didn't add any carbon doubles to the servo pocket. I hope I can make a servo cover that is still flat.

So with sacrificing some servo cover flange I think I was able to actually fit a flap servo into the Redshift wing! Now for the hard part doing it again on the other side.

Konrad, I wish I'd had you sitting beside me when I put pen to paper on this one - though it was a LONG time before IDS. To be honest I really just put the servos where I thought they would be most effective while avoiding most of the other wing internals. That was about the extent of it at that time.

One good thing - models can now be ordered "IDS Friendly" (Or in other words with the servo horns supplied - but not fitted)

All the best,
Konrad

P.S.
I wonder if this was the intended servo? But overal length is close to the same as the X10 mini but at half the torque and twice the price. Actually the only thing this servo solved is the cover issue.

MKS or KST as I remember.

View attachment 7991View attachment 7992View attachment 7993View attachment 7994

Hi Konrad - I have inserted some comments here and there.

Doc.

 

[Konrad]

Glad to hear you are aware of these issues.

You have in the past admitted your errors when I complained about them. Like the Non-FAI radiuses nose. I'm not interested in the who, I just would like the errors to not propagate to the next iteration.

I like the IDS friendly option.

As to being there at the design stage. All I can say is that I have the insight of 20/20 hindsight. That is I see the problems after the tooling and models are made. It takes a special eye/ mind to catch these problems during the initial tooling up stages. CAD was to help with this.

All the best,
Konrad