Redshift Mk I (New Purchase)

[Konrad]

This is what greeted me when I looked down the ballast tube with my borescope. You can see that the 32mm spacer blank is all the way out of the ballast tube. Also there is no sign of the rear ballast stop.

Now what puzzled me for a while was that after cutting the access slot I found that the ballast stop had fallen back in place leaving the spacer outside the tube somewhere in the tail boom. I assume that while handling the fuse to cut the slot the stop found its place. This was just one of those odd things!

It pains me to say it but I did not sand the ID of the ballast tube when I installed the rear ballast stop. The epoxy had noting to bite. There was a nice solid epoxy band. But with no teeth in the tube it was very easy for all that mass to break the poor bond.

Luck would have it that the break was clean, making it very easy to reinstall the rear stop. To keep this from happening again I used 3 steel pins to pin the stop to the ballast tube and fuselage.

Now all I have to do is make an epoxy fillet around the rear of the stop and finish with a carbon fiber layup repair across the access slot. This should result in more fibers across the fuselage joint than what was found prior to the crash.

Now to fix the aileron hinging!

 

[Konrad]

I just realized that I might be able to benefit from some forethought on my part. (This is very rare for me). I recall that I set up both sets of my carbon Redshift wings to be interchangeable. So while I don't think I can repair the wings (torn aileron hinges) in time for Sunday's race. I'm now thinking that I can use the wings from my first Redshift on this fuselage that has the 96° V-Tail. I think all I need to do is recalibrate the servos. This is very easy to do with Mike Shellim's F3F templet. I'll make a new model in my radio, copying this model and copying the aileron and flap curves from the first Redshift.

This is one of many benefits to staying with one model type for a long period of time. Not only does it allow one to become very familiar with the idiosyncrasies of the design. But if done correctly allows one to have spare parts to support your racing schedule!

 

[Konrad]

More Zhou magic. I'm trying my damnedest to find something positive to say about this. All I can come up with is that at least Zhou has his processes under control. Both slip on noses showed no fiber in the nose bulb!

 

[jure]

Konrad wrote => "More Zhoe magic, NO FIBER IN THE NOSE BULB"
reminds me of my interaction with the production team : "where in the documentation it says that this feature is optional ? "
my father would say "ad libitum" instead of optional ...

 

[Konrad]

That looks good. I added a lot of "long fiber" chopped carbon to make an epoxy fillet to hold the ballast stop from the outside (inside the tail boom).
I sanded a flat spot across the access slot to allow for a fiber build up repair. I used about 4 or 5 layers of carbon roving and cloth with fibers going in all directions.

I cut the access slot at the point of the weak seam as I knew that after the repair there would be more fiber across the repair than there was in the original seam.
What concerns me a bit is is the bonding area. I'm thinking of adding another layer to the outside, and not sanding it down to the original profile.

Anybody have any input on this repair, particularly the contact area?

 

[Konrad]

Good news PPG just told me that they have received their titanium oxide (white pigment). So I should expect my paint order in a few days.

 

[Konrad]

Well, that worked out easier than I thought it would! Those that know me, know I and software don't play well together. But this time I have to hand it to the developers of OpenTX and Mike Shellim for his F3F templet. Swapping the wings was a plug and play affair. Other than a flight test the old used wings fit and operate on the "New Purchased" 96° V-Tail fuselage just fine. Copied the curves from the old Redshift wings over to the new model and all is fine. I did have to reverse one flap servo. I found this odd as all servos are KST. But after reversing that servo the TE is doing what I want. I did change the FNU (Flap Neutral) point 2 or 3 numbers. But I think I do that every time I fine tune these programs.

Thank you OpenTX and Mike Shellim!

It looks like I will have at least 2 Redshifts and a Schwing Corsa 108 to race in Sundays F3F race at the slot. Yes, I still have 2 Stregas and an Alpha 2.8 if really forced.

 

[Konrad]

Well, that bonding fear was unfounded! I crashed this fuselage straight down from about 40meters. The slot repair held just fine even with the minimal bonding area. You might get an idea of how much force was applied to the fuselage as the wing joiner crushed the fuselage for more than 10mm!

 

[Konrad]

Well the repairs start.

 

[Konrad]

Guys, I'm looking for help.

I need some process improvements with my Kevlar hinge repairs. For partial tears I've had good luck using scrap styrene pusher to keep the Kevlar down.
See this repair.

Now with control surfaces that have been fully torn off I'm seeing a failure rate with this repair of close to 50%. As you can see in the attached photos it looks like the styrene pushers are not keeping the kevlar down on top of the inner wing skin. When I try to bring the control surface and wing together there is a tendancy for the kevlar to bunch up and form a fiber arch. This arch makes it all but impossible to keep the control surface in alignment with the wing.

I fear that I'll need to make styrene pusher that are wide enough to span the hinge line. Yet not be so thick as to need a lot of manipulation to install with the wet kevlar hinge material.

Yes , I know about using 3M 5300 compound to make the improved silicone hinge.

 

[Doc James Hammond]

Mylar tape.

Doc.

 

[Konrad]

On the outside or as the carrier for the Kevlar? Is there a published process?

 

[gp49]

@Konrad, I think I posted some for the links before but just in case here it is: Opus Hinge Repair on your 'fav' site. Not sure if you want to go as far as he did but the repair looks sound, BUT requires removal of skin from the opposite side and then patching it using his technique . . This guy has some really good ideas about composite glider repair. Use 'Show Attachments in this thread' in the "Thread Tools" menu to get all the pictures..

His Opus Hinge Repair: https://www.rcgroups.com/forums/showthread.php?3078637-Composite-repair/page3#post40442495

His composite repairs posts: https://www.rcgroups.com/forums/showthread.php?3078637-Composite-repair

 

[Doc James Hammond]

On the outside or as the carrier for the Kevlar? Is there a published process?

Just on the outside Konrad. Because the kevlar has to be bonded inside the wing structures, we tend to over-think the whole thing.

Tape worked great for decades and the newer 3M mylar tapes are really good.

Doc.

 

[Konrad]

@Konrad, I think I posted some for the links before but just in case here it is: Opus Hinge Repair on your 'fav' site. Not sure if you want to go as far as he did but the repair looks sound, BUT requires removal of skin from the opposite side and then patching it using his technique . . This guy has some really good ideas about composite glider repair. Use 'Show Attachments in this thread' in the "Thread Tools" menu to get all the pictures..

His Opus Hinge Repair: https://www.rcgroups.com/forums/showthread.php?3078637-Composite-repair/page3#post40442495

His composite repairs posts: https://www.rcgroups.com/forums/showthread.php?3078637-Composite-repair

LOL,

Yes I had seen this thread, thank you. I see a lot of potintial issues with it. Not that mine is straight forward. My method often results in not needing to follow up with a paint repair.

 

[Konrad]

Just on the outside Konrad. Because the kevlar has to be bonded inside the wing structures, we tend to over-think the whole thing.

Tape worked great for decades and the newer 3M mylar tapes are really good.

Doc.

Over-thinking and fixing things until they don't work is my thing!

There are 2 levels of repair. One is to regain functionality, taped on surfaces. Another is to maintain original configuration, kevlar fiber as a live hinge.

Do you have a 3M P/N I can look up?

 

[Doc James Hammond]

I used this stuff, its pressure sensitve and works well.

https://www.3m.com/3M/en_US/p/d/b40071908/

Doc.

 

[purview]

as my flap detached I fixed it only with silicon glue inside to get more bonding flesh and tape on the outside to make it stiff (just classic hinge tape).

..as you write above #90 the bunch up tendencies of the control surface — is this a repair process issue or an material issue? maybe try a glue stopper to prevent the hinge fully soaked from resin as one solution too.

 

[Konrad]

It is a process problem.

I want as much weave fill as possible for good bond on the small inside contact area.

Kevlar still keeps some fiber integrity when the matrix is flexed (epoxy is broken).

 

[purview]

race 10th of July Konrad, any results on this ship? f3xvault is a bit lazy with data updates...