Aeroic Alpenbrise 4m (F3F Gag Racer)

[Konrad]

I was pleasantly surprised that the Alpenbrise 4m is a known quantity on this forum.

This thread will be to document my build of the Aeroic Alpenbrise 4m glider.

The impetus for my purchase was that Aeroic was very late on the production of their new F3F racer to replace the ill conceived and poorly received Redshift F3F racer. I didn’t see any F3F racers at my Local Hobby Shop. But saw the Alpenbrise for a lot less money than the current well established F3F racers are selling. Reading the FAI airframe requirement for an F3F ship it looks like there are only 3 specification that need to be met. All up weight 4kg max, max wing loading of 75 grams per square decimeter and a nose radius of 7.5mm. Looking at the specs' for the Aeroic Alpenbrise it looks like I should be able to meet the requirement with a little rework to make a legal (gag) F3F racer at the same time have a large sport slope ship.

My Alpenbrise was from a late 2022 production run early 2023 release and had a lot of quality lapses*.  I will try to point these out and my solutions. It is hoped that this will help folks assess their own model purchases.

Taking a look at the advertised weights it was clear that if I wanted an FAI F3F racer I’d need the “Sport” layup. The Super Sport layup has a lot more carbon and may result in the weight being over the 4kg limit. So I purchase the Alpenbrise in the sport layup to try to keep the weight below 4Kg. Running my numbers it looks like it will be close! It looks like I’m within 3% of the 4kg limit. I hope I don’t end up over the limit.

Looking at the model it is clear that the model lines are based off of the classic Multiplex (Tangent) Alpina 4001. To us old timers this is a nice classic look. The problem with the Alpina and many of the older models is that they can’t be used in FAI competition as the nose doesn’t meet the FAI F3B nose requirements of a 7.5mm radius over a 90° arc in all attitudes. These requirements still results in a rather pointed nose for a 4m glider. I was shocked when I got home and actually measured the nose radius to find that the Aeroic Alpenbrise was sporting a grossly undersized nose radius. I was a bit shocked that the designer would chose such a pointed unsafe arrow like nose in today’s litigious environment. I also can’t see why he would want to exclude sales to those of us that would want to use this airframe in any of the FAI competitions.

To use the Alpenbrise as an F3F ship the first upgrade was to re-profile the nose to meet the FAI F3B nose requirement. Easy enough to do, as there is alot of material in the nose to alow the re-profiling of the nose. Now that I had an airframe that might make a legal FAI F3F racer, it was time to look at the quality of the model to see if it could stand up to the riggers of competition.  More to follow.

* The owner of Aeroic has since visited the factory in China and claims that the quality issues have improved by an order of magnitute since the release of my model. I can say that the replacement wings for my model (mid 2023 production) do show a marked improvement in quality.

[SP250]

I'm surprised you are even considering the Alpenbrise as an F3F race airframe Konrad.  I live close to one of the best west facing slope soaring sites in the UK (Long Mynd) and have seen on many occasions the F3F competitions and not one of the competitors uses any model over 3m span, generally around 2.5m to 2.8m.  I have to assume that it is because of the agility and tight turning radius needed to be competitive.  A 4m Alpenbrise is not going to get anywhere near the regular models currently in use over here.  May be totally different over your side of the pond of course.
John M

[Konrad]

John, the physics are the same on this side of the pound. Did you not see the word "Gag". Here that means bad joke.

The main aim of this ship will be to have a large sport model. Reading the FAI specs and those of the Alpenbrise it looks to me that with a little work I can get the Alpenbrise to meet the FAI F3F regulations. While not shown yet the Alpenbrise comes with a 6 surface wing option. I will be using this in an attempt to get the roll rate needed to run the gates.

But yes you are correct the Alpenbrise as delivered is wholly unsuitable for the FAI competition. That 4 Kg limit will remove any ability for me to custom rig the ship with ballast. This will result in the Albenbrise being only suitable for the low end of the FAI F3F allowable wind speeds.

For the coastal racing venues the Albenbrise doesn't stand a chance even against the dud Aeroic Redshift. But for some of the inland sites it might be fun to see the Alpenbrise mixing it up with the Freestylers and Shinto as these sites are often thermal lotteries.

Again nobody thinks the Alpenbrise is or can be made into a serious F3F racer. Heck, I think my Schwing Corsa 108 (2.7m) would make a better F3F ship. And yes I've re-profiled the nose removing that dangerous nose profile to make that ship F3F legal.

P.S.
The RCRCM Strega is not compliant with the FAI F3F rules as the nose is too narrow in plan view (top/bottom).

[Konrad]

I like seeing that the designer has chosen to place the servos in the tail fin. This addresses the issues often found with long push rods running down narrow tail booms.

Now I’m often puzzled why designers don’t fully commit to ideas or the concepts they are implementing. For example with the Alpenbrise the designer is still trying to actuate the large rudder from the extreme lower end of the rudder. Driving a surface from the extreme end is a bad practice if looking to get the most out of the surface. First holding the surface at one extreme allows the flexibility of the surface to absorb much of the motion, such that little of the command makes it the other extreme end of the control surface.   To counter this the surface has to be built a lot heavier than otherwise would be needed to add the required stiffness in the structure. The second hit against driving the control surface from the extreme end is that it does nothing to control the vibratory response of the surface. This is a major concern when it comes to delaying the point at which the surface will go into flutter. One does not want to attach the control horn at a vibratory node. For the first order response, this means at the ends or the middle of the control surface. It looks to me that the designer is trying to leave the option open, for marketing reason, for the use of push rods going down the tail boom. I don’t understand why, but please don’t fall into that trap .

 I’m showing how I actuate the rudder. While I can’t control the weight of the rudder structure. We can get a lot more rudder power (control response) by moving the actuation point up along the hinge. Here I’m also concerned with the loads placed on the tail boom. For this reason I’ve chosen to switch the servos from what is shown in the Aeroic manual. I wanted to place the larger more powerful and durable elevator servo down low in the fin to align the mass of the servo with the tail boom. As the rudder servo will now be up high on the fin its mass now needs to be dealt with. This is why I’m using a 9 to 11 gram class of servo. Most high voltage, high quality servos in this class are powerful enough electrically for the actuation of the rudder. You might notice that I’ve tried to place the rudder servo as low as practical in the fin in the upper servo window. A concern with lowering the servo was to keep it away from the elevator actuation spherical joint (This elevator rod needs a spherical joint on each end)!  My concern is that the small gear train in these small class of servo can easily be damaged. I’ve found that the use of an external bearing servo tray adds a great deal of durability to the servo gear train. They also add a lot of rigidity to the actuation system, aiding in the postponing of flutter. Since I’m using an external bearing support I’ve chosen to use the Servorahmen IDS. These are a great value and work great with the live hinge we see on most composite models. They also have the added benefit of lowering the control system’s aerodynamic drag.

My particular model has the rudder hinge and upper servo window on opposite sides of the fin. This is the first time I have set up an IDS with the servo tray mounted on the same side as the hinge. I had some concerns with coming up against the 3 point actuation line, but the geometry appears to actually be superior to mounting the tray on the side opposite the hinge.

I had some concerns with my model about cutting the vertical fin’s rear drag spar to allow the IDS push rod to pass. This is because the stiffening carbon patch on my model did NOT span both the forward fin half spar and the rear drag spar. This forced me to add my own carbon patch to tie the two spars together. (Sorry my photos of this did not come out well.) I’d have also liked to have seen the factory carbon stiffeners span past the drag spar and stop near the live rudder hinge. As I was going to cut a hole in the drag spar I added some more carbon aft of the drag spar on the skins as an alternate load path around the pass through hole.

[Ratz (Bruce)]

Following with Interest

Bruce

[dephela]

This sailplane is indeed designed for racing. The Alpenbrise website says it's both an F3F machine but also a GPS "Triangle Racer", this is a new class that seems to be taking off.

https://gps-triangle.net/wp-content/uploads/2020/03/regulations_sport_en_V1.5.pdf

[SP250]

Looking at the stats for both SS & S lay-ups of the model, neither are suitable for the Light class of GPS triangle racing.  The SS version is too heavy at 3.4kg (max allowable is 3.0kg).   And the lighter S lay-up is over the wing loading max of 30g/dm2.  So that leaves the Sport GPS class where max weight is 7.0kg and it would also come inside the wing loading max of 75g/dm2.  However it will be compromised by being a metre short on span (max allowable 5m) and hence more difficult to see at long distance compared to a 5m model.  So when compared against the current Chilli/Thermic and other European made models being used, I suspect it would be at a severe disadvantage unless you have super distance eyesight.  People who were using 4m models have already retired them and gone up in size to 4.7 to 4.9m in the sport class.
John M

[Konrad]

Dennis, This would be great news for the safety reasons alone. Do you have a link to the Aeroic web site? Last time I looked Aeroic only had a Facebook page. I refuse to have anything to do with Facebook!

Hammond was incensed that I would want to change the esthetics of his design for safety reasons and to comply with the F3F specification.  
https://forum.alofthobbies.com/index.php?threads/alpenbrise-design-notes.3594/

If the Alpenbrise is being advertised as an F3F racer, Aeroic would (if being ethical) have to re-work their tooling. There would also need to be a lot of work done in the lay up of the model. My particular Alpenbrise will be very close to the maximum allowable weight of 4kg. Working my numbers for the 8 servo “Sport” Alpenbrise I have less than 40g of head room before I reach the 4kg limit. This is far too close for a manufacture to be advertising the model as being an F3F racer.

As to GPS triangle racing the Alpenbrise is both too heavy and too small to be any kind of contender is that class. Here in Northern California the 4 meter class of model has been shown to be wholly inadequate a model for the GPS racing. Having said that, if I can’t meet the F3F requirements I will reconfigure my Alpenbrise as a GPS racers, knowing full well the Alpinebrise isn’t competitive at all. I have a lot of old Aveox  motors and some deep geared Hackers.

I should reiterate that the Alpenbrise is only a sport model with a nod to the esthetics of the great Alpina of old. It wasn’t designed to compete in any competition class. With some redesign work it might fit some competition classes. But it never was designed to compete.

P.S.
John, Thank you for your analysis of the suitability of the Alpenbrise as a GPS racer.

[Konrad]

Now this goes under the category that you can't make everybody happy.

Aeroic has supplied the Alpenbrise with wiring harnesses. At face value this would look great. But for modelers who would be looking at the level of model we have our own ideas as what would be the best harness configuration. This is a personal preference but I like my 6 pin Multiplex connector to be assembled such that the fuselage side is male (plastic) and that the wing hold the female receptacle.

Also with the long leads there is a real advantage with using a common bus bar electrical architecture. That is all the servo in the wiring loom share a common positive and negative lead. This saves significant weight with the lengths of wire we are dealing with in the Alpenbrise.

So I'd like to see Aeroic not supply us with the wiring harness. Heck, the supplied harness is for a 4 servo wing. I'll be using a 6 servo wing. This could be shown in a price reduction or help with their profit margins. Honestly I'll be replacing the all the wiring harnesses.

[Konrad]

Back to some actual building or issues with the build.

As stated earlier I'm real close to the F3F weight limit of 4kg. This is driving me to reevaluate my choice in servos. Earlier you might have noticed that the rudder servo was a KST HS08. But to save 1.5 grams I'm changing over to the X08+. My understanding is that these have close to the same gearbox. You will also have noticed that I've changed from the MKS 6130 to the KST X10mini again to save 2 grams of weight in the tail.  3.5 grams might not seem worth it (and its not) but multiply this by the moment arm of 3:1  that's 10.5 grams I don't need in the nose, for a total weight savings of 14 grams! With only about 40 grams to play with this extra 14 grams of head room is dearly needed.

Things to note the external bearing tray for the rudder servo is down as low as is practical limited by the need to clear the upper spherical joint of the elevator push rod. Unfortunately this means half the epoxy rake is not under any part of the fin's skin. I've left the rake as supplied by Servorahmen in the hopes that I'll have enough weight head room to be able to tie both sides of the fin together. If I'm at or over my weight limit I still have the option to remove this epoxy rake.

I'm also showing where I placed the elevator servo. Again I've swapped the elevator and rudder servos to lessen the landing loads on the tail boom. I also think that the elevator servo wouldn't properly fit in the upper window. I go into more detail in this thread.
https://www.hippocketaeronautics.com/hpa_forum/index.php?topic=27528.0

But to clear the drive pin I had to lower the servo mounting tray a bit too far down the fin. This is forcing the tray to hit the boom radius. As such I've had to sand a matching radius into the  servo tray.

[SP250]

"P.S.  John, Thank you for your analysis of the suitability of the Alpenbrise as a GPS racer".
You are welcome Konrad.
I always enjoy your detailed analyses and build info, as you go into each and every aspect.  We can all learn from it with our own builds even if we don't have the time to record everything as you do.
John M

[Konrad]

I found these note and thought I should post them. With the undersized and often misplaced servo windows making it all but impossible to reach all the servo mounting lugs. This often drives the external bearing from being a secondary mounting feature to a primary mounting feature. Please be aware of this when setting up your servos.  Note; that I'm still using the full contact area of the servo tray. I think that the bonding area is the Achille's heal of the servo mounting. But I'd have still liked to have used all the servo mounting lugs. I have concerns with the servo mounting as shown in the Aeroic manual where only 2 screw mounts are defining the load path into the frame. (I'm at a loss as to why the bearings were removed) This may be fine for low non-catilivired loads but at the size and weight of the Alpenbrise this is just unacceptable in my opinion.

Here you will see that while I too am forced because of the window placement to only use 2 of the 3 mounting lugs. I'm using the external bearing mount to keep the output shaft stable but to also keep the servo body from flexing (rotating) in the mount. Both the smaller x08 mount and the larger x10 mount are doing this.

As a side note I found that the Servorahmen X08 frame would benefit from the chamfer of the corners adjacent to the servo lug (both with the frame and the hold down bar).

[Konrad]

John, Thank you for noticing that this does take some extra time and added work to properly bring these concepts forward for discussion.

As you know engineering is the science of compromise. If in my builds I'm showing what I'm doing that is clearly opposed to what I see in the manual and what I think is going against what I think the designer intended. I had better trying to document the what's and why's as to my actions.

It is my hope that this will help all that are reading this and finding themselves in a similar situation. While I hope my builds will show details specific to the model being build, such as clearance issues. I hope that I've give a detailed account as to why I've chosen to do what I'm doing so that others might apply this to their own situation.

I've recently learned that some folks have labeled me an internet bully for this. That is I notice an issue. I define the issue. Ether with detailed drawings (cartoons) or references to others more learned than myself. I then go on to demonstrate my solution to the previously defined problem. This often leaves the original designer feeling defensive for making what in my opinion was the inferior compromise. Please note the word compromise.

I also like to engage in discussions with folks like you. That is I will question your statements in hopes to gain a better understanding of your position. In the end I hope to have learned a thing or two.

I will admit that I don't use these forums as mutual admiration societies. I'm looking to discuss ideas that stand on their own, and don't need our reputations and personalities to be seen as legitimate.

All the best,

Konrad

[Konrad]

This sailplane is indeed designed for racing. The Alpenbrise website says it's both an F3F machine but also a GPS "Triangle Racer", this is a new class that seems to be taking off.

https://gps-triangle.net/wp-content/uploads/2020/03/regulations_sport_en_V1.5.pdf

Dennis, I just spent some time looking for that web site. I can't say as I found it. But I did find the new Aeroic web site, so much better than the Facebook page.
https://www.aeroiccomposites.com/alpenbrise-a157-4m

I have to admit that I'm a bit ambivalent about this. On one hand I happy to see that Aeroic isn't falsely advertising the Alpenbrise as an FAI F3F ship. On the other hand I'm saddened to see that in the prevailing years Aeroic hasn't addressed that dangerous pointed arrow like nose.


WOW!!
The manuals are showing practices that are down right dangerous!! Please if any of you have any influence with the importers in your area. Please ask, no demand, that they put pressure on Aeroic to correct these. This is a safety issue that concerns all of us slope glider drivers!

I may have to start a thread detailing these lapses in engineering first principles. I don't want to do this as it just saddens me that a firm would be so blind to safety. I hope that placing financial pressure through the vendors will be enough to get Aeroic to move to change their manuals.

I will be doing exactly this with my Local Hobby Shop and importer of the Aeroic line in the USA, Aloft Hobbies
https://alofthobbies.com/

[Konrad]

I think I’ve adequately covered the actuation of the tail surfaces

Now I’ll move down the fuselage.

Here I’ll be talking a bit about quality.

And here is where I have to step up on my soap box.
I hate it when folks use stereo types (even positive if such a thing exists) to imply something.
The owner/designer of Aeroic time and time again uses the term European Quality or that the picky Europeans find the quality more than adequate.
First the Europeans are no more demanding to exacting standards than anybody else.  What? The peoples from the other continents are happy go lucky slobs that wouldn’t know quality if we held it in our hands? We all want the products and services to perform as described and intended regardless of our continent or origin .

In one of my engineer positions I was tasked with assessing quality escapes in aerospace. I can say that every skilled craftsman I’ve dealt with, regardless of the continent they are on or from,  has tried to produce the best product they can with the tools and materials management supplies.  I can say that ALL quality issue can be traced back to management, or lack there of!

Firms like Apple and Boeing are having many of their components/products manufactured in China and Asia. These are of the highest quality because the management has clearly defined in the contracts what is expected and has placed resources (spent money) to ensure that these requirements are met!

Few firms are producing models of the quality we see in Vladimir’s model. Not because Vladimir's model is based in the Ukraine  but because Vladimir’s model is run by a world class modeler that uses his products. As a result he supplies his team with the best tools (time being one of them) and materials to produce the best models.
http://f3j.in.ua

Stepping off my soap box.

Most fuselages today are made by the wet seam process. That is the fuselage sides are joined together while the lay up is still green (wet).  This often requires that the fibers spanning the part line be manipulated. This can allow the fibers to lift away from the mold resulting in voids in the finish. Most firms will employ a bladder to push back the fibers to keep them against the mold to minimize this fiber pull away. You can see that my fuselage has a lot of voids in the finish. And it looks like there was an issue with the bulk of the fiber seam not laying down properly in the inside of the fuselage. You can see this as it looks like the kevlar had to be post cured ground. I suspect that with my particular fuselage the bladder had failed as this would explain the voids and the seam quality. Unfortunately I examined 4 other Alpenbrise 4m and all had similar issues with the fuselage part line. I know think this is a process issue.

I want to be clear the fibers that did cross the part line were many and well bonded to the other side. I actually think the bonding area was a bit larger than anticipated and as a result the fuselage appears to be a bit heavy. This is unlike the previous OEM where there were little or no fibers carried across the fuselage seam. You can learn of my trials and tribulation with Schwing Corsa 108 here, I think the fuse issues start on page 14.
https://forum.alofthobbies.com/index.php?threads/schwing-corsa-2-75m-secondary-market-purchase.2799/page-14

Also I like to see the use finer weave cloths as it just helps with the finished look. I also like to see molds, process, and lay ups that don’t require so much post cure clean up. Note there is a lot of kevlar fuzz at the cut lines.

Now I see a lot of damage in the Alpenbrise wing boss. This can be traced directly to trying to fit the wings to the fuselage. There was/is a huge issue with tooling as it has allowed the wing pins and the fuselage bores to not line up! I think my pin alignment bores were out of round something like 0.5mm and has cracked the lay up. This is just inexcusable as I think this is directly as a result of poor engineering practices in the drawings/CAD work!

[Konrad]

This probably goes under style as much as the wrong engineering direction.

The Alpenbrise has to my eye a rather poor looking wing to fuse junction, as the lower part of the wing and fuse join at an angle of less than 90°. This is a NO-No if you follow Sighard Hoerner (of the Hoerner tip) writings in Fluid-Dynamic Drag. Also I see the fuselage cross section getting smaller as we go aft along the wing junction. Again this is a NO-NO per Hoerner but is also goes against the ideas of Inverse Pressure Gradient Matching per Arnold (AR-5 Fame). As we would actually want the fuselage cross section to be getting larger as the wing cross section in getting smaller towards the aft end of the airfoil. As this drag goes up by the cube of the CL it can be a significant amount of drag as we pull through a high "G" turn.

I try to go into this in a bit more detail in The Good, The Bad, and The Ugly here.
https://forum.alofthobbies.com/index.php?threads/the-good-the-bad-and-the-ugly.3096/

I also don't understand why the designer if crippling the fuse at the wing junction with a triangle cross section didn't carry this to the tail boom. The triangle tail boon has been shown (by firms like TUDm) to produce a boom that is much more tolerant of landing mishaps than the classic round or oval shape. It looks like the designer chose to use some of the bad features in the fuselage cross section put failed to use the this triangle for its added strength in the tail boom.
(Note; the boom is not a pressure vessel nor is it transmitting much torque. Landing loads should be the main concern in designing the tail boom of today's RC slope ship)

[Konrad]

Yikes!!!  I just found a major failure in Aeroic’s QA program!

Normally I like to do my build threads in the order in which I built/assembled the model. But here I’ll jump ahead.

The first set of wings that I received with my late 2022 build had the Sine Wave Spar’s web misplaced. Such that part of it had totally slid off the spar caps. I saw this as the web had made a slight protrusion into the outer skin. Not only could you see the discontinuity in the skin but in spots you could feel it. As this happened in the outer 1/3 of the wing span I wasn’t too concerned as the wings really are of a stress skin construction and the skins are made up of heavy carbon cloth.  

As I thought this was a problem with the factory/engineering process and I had seen much the same issue with Aeroic's previous OEM. I contacted my dealer and Aeroic to discuss my concern with the build process and suggest that Aeroic examine their molds as I feared that the web might have left an impression in the molds.

I hate to put stuff into the land fill prematurely and as I thought that the wing even with this misplaced shear web would be more than adequate for my intended use (Front side slope and F3F racing all low speed stuff. No, DS loads) I planned to use them.

Much to my surprise Aeroic (Hammond) offered to supply me with a replacement set of wing under warranty.  Please recall that I didn’t ask for a warranty adjustment as I thought the condition of the wings would meet my performance criteria. In another step, ether to support his dealer or his customer, Hammond (Aeroic) allowed me to make a custom request for this replacement wing at no additional charge.

I asked that the replacement wing be supplied as a 6 servo wing. This is becoming so popular that the USA dealer (Aloft Hobbies) now only carries the Alpenbrise as a 6 servo wing.

The problem I just found with the replacement wings (June 2023 DOM) is that the gap seals as delivered are so large as to limit the upward direction of the aileron and flaps. This is easy to do as the addition of the gap seals is done by hand after the wings have been released from the molds. My concern is, that with my set of wings, nobody did the inspection/adjustment to ensure that the control surfaces would move adequately after the gap seals were formed.

We the customer shouldn't have to have a fully set up composite shop to assemble these high dollar molded models. Luck would have it that I have some of the basic skills and tools to accomplish this.

My set of wings only allowed the control surfaces to move upwards 13°. After cutting back the gap wipers with a vibratory saw I now have my ailerons moving in the upward direction 33°. I left the flaps alone as I think 13° is adequate for any of the camber changing I’ll be wanting to accomplish.

To be clear this was a failure in the Aeroic’s QA program. This issue would have been caught had Aeroic actually had a robust QA program to find fit and function issue prior to reaching the customer. There is no excuse for this, heck Covid 19 happened a while back. This is clearly a management problem. If the release form would have given a minimum required range of motion the inspector would have seen this issue and had the wings reworked at the factory. This would have added cost, as the management would have to supply the inspector with an inclinometer. But how much did it cost, with a hit to Aeroic's reputation having the customer make the adjustment?

If you have any model from Aeroic, please check that the control surfaces will move the amount stated in the manual prior to doing any of the build!

[OZPAF]

Interesting coverage Konrad.

While I imagine it is hard to stay small and then control the composite work done by overseas workers - I know it has been done successfully by others. I'm thinking specifically of the DS - dynamic soaring model - the Transonic DP by Spencer Lisenby, who uses Western Europe composite workers.

 http://www.dskinetic.com/transonicdp.aspx

I think JH would have been better taking this approach, as this would have gone a long way to establishing a good reputation.

The model you have appears to fall well short of the finish of the West European models that I have seen, but I'm sure with the care that you are applying will produce a good model.

It's just unfortunate that this degree of rework/finishing was required in the first place.

John

[Konrad]

I've tried to give or show Hammond the tools we use in industry to generate modern drawing, and to control quality. These have fallen on deaf ears. Time and time again we get products like I'm showing.

Now to be fair most folks don't know how to assess properly designed and manufactured composite models. As a result they are often just concerned with the shine and price. That's on us! In my builds I try to show what to look for and the why I think XYZ is important.  Yes, I also try to cut through what I see as sales hype.

Aeroic is in that uncomfortable position of not being anywhere near the quality (engineering and finish) of the top end firms. Nor are they priced with the bottom tier manufactures like RCRCM or RGMCN
https://www.rcrcm.com
https://www.rgmcn.com/h-pd-51.html

Honestly I have no issues with the Asian composite worker. If given the tools and materials by their management they can and do produce exquisite work. The key is management, the contract and the effort put into QC & QA.

I'm again jumping ahead a bit. But since my photo showed is so well I need to level set expectations a bit. Aeroic's products are nowhere near the top end of the quality scale. They are in the USA only about 60% the cost of the high end models. While I really have problems with Aeroic's poor engineering when it come to system integration and mechanics. I can't really fault them for the finish as I'm not paying much for the model. Here we get a 4 meter composite model for under $2K in the USA. But even for $2K if a product doesn't work it is still a waste of one's money. Again that is why I go into such painful detail to help those get the best from their purchase. I'm not trying to help or hurt sales just level set expectation.

The Aeroic line is using a heavy weave in their layups. One can be see this as this bleeds through the finish (the small dots around the light source). This is so pronounced that you can actually feel this and some of the under skin support structure (spar caps). Now any aerodynamicist will tell you this will destroy any hope of maintaining laminar flow over the wings. Unfortunately this nullifies most of the benefits we gain from the molded model. As a result of the surface finish, those wiz bang airfoils aren't performing as the charts would lead you to believe.

Aeroic is using the heavy weave as a cost cutting effort. The higher end OEM are often using "spread tow" cloths to try to eliminate the weave bleed through and the resultant poor performance as a result of the surface finish.

P.S.
Thank you for the kind words.

[Konrad]

Staying with the wings both sets show nice separation lines with the control surfaces and the hinging actually has a bit of relief. This should take off some of the stresses on the kevlar cloth hinges.

The original wings, late 2022 manufacture, had a lot of problems with the installation of the control horns. The installation of these horns result in the binding of the control surfaces at around 22°. This is because the horn laid across the hinge itself.

I attribute this to the fact that the control horn barb (leg) it too thick to fit inside the control surface. These control surfaces are unusually thin as a result of the “high energy” double cusped airfoil Hammond is using. For reasons I don’t understand these control horns are not cut/supplied to fit into the space made by the control skins. It is clear to me that by the slight distortion of the top skin, that the builder tried to seat the control horn aft of the hinge line. But because the horns are too large they sat across the hinge. You can see this in the bulge in the bottom skins when the surfaces is deflected upwards. This is another example of the persistent problem Aeroic has with system integration. I think is comes from the lack of understanding of the fit function in most CAD programs. This kind of interference problem can easily be found by proper modeling of the all the components being used and then checking for tolerance stack up. To me this was another classic engineering failure, not as Hammond so often likes to claim a “Friday Build”.

Another system intigration failure is that the standard 10mm thick servo will not fit the pocket for the outer ailerons. This is forcing the user to use an 8mm thick servo if he wants to stay within the airfoil profile and not use bulged servo covers.

[Konrad]

When I made my requests for the custom wing I asked that the wings not be cut for the classic surface control horn.  I have to admit I was pleasantly surprised when I cut back the oversized wipers and found these wide IDS spoon pockets. I was even more impressed when removing the wipers to make room for the IDS spoons that the inner and outer composite are joined above the spoon pocket.  I say this as the skin above the spoon pocket is less than 0.3mm thick. I go into more detail about this here.
https://forum.alofthobbies.com/index.php?threads/composite-control-drive-installation.1449/

[Konrad]

At the risk of sounding like a fanboy or worse writing ad copy for Aeroic, here goes.  I’m impressed that the Alpenbrise is using an industrial adhesive to bond the wings together.

This is a huge improvement over the traditional method of using an epoxy and Cab-O-Sil slurry to bond the cured epoxy components that make up the wing. Bonding cured epoxy components with epoxy is rather difficult. This is why, like in my fuselage critique, I state that normally this is done with green (partially cured) parts as this promotes a bit of a chemical bond and not just a mechanical bond.

Every model I’ve received  NIB form brands like RCRCM, RGMCN and TJIRC has had issues with the upper and lower skin delaminating (de-bonding) at these glue joints as soon as I’ve removed them from the shipping box. I’m so impressed that Aeroic has heard the dealer and customer feedback on this issue.

These two sets of Aeroic wing for the Alpenbrise have appeared to be well bonded. The later mid 2023 production date has much nicer glue fillet in the area that can be seen through the servo window. This is a bit of showman ship as the areas of the web that can’t be seen without a borescope look much like what I’m showing in the late 2022 production wing.

P.S.
I should have said earlier that the servo pocket doesn't fit the standard 10mm thick servo with the 30mm by 30mm mounting pattern. This is forcing me to use the 8mm thick servo in the outer aileron servo pocket. This has me just shaking my head that I need to fit such small servos in a large 4 meter ship!

[Konrad]

One down five more to go!

It is looking like the use of a 55mm push rod will place the servo tray very close to the middle of the servo window. Unfortunately the 55mm push rod is not found in the normal  Servorahmen X-08 mono IDS package. There is a supplemental set of smaller pushrods. The 55mm one is the second from the largest push rod. I’m also finding that the ailerons need the smallest servo arm to maintain as much of the servo resolution as possible. Please note that it looks like I had to sand the aft part of the epoxy rake about 1.5mm to allow the servo tray to fit between the upper and lower wing skins. Tying the upper and lower skins together through the rake adds a lot of stiffness to the area where the servo tray is ultimately bonded. I go into a bit more detail on the installation of the IDS and servo trays towards the end of this thread.
https://forum.alofthobbies.com/index.php?threads/servorahmen-ids-servo-mounts-etc-step-by-step-install.198/page-3

These are the shorter push rods I needed.
https://alofthobbies.com/collections/servo-frames/products/short-mono-pushrods-for-ids-system-6pc

[Konrad]

Going all the way back to reply #3 I said my fuselage lacked the carbon patch that spanned both the partial front spar and rear drag spar.
I found this market teaser thread and we can see that at least the prototypes had the lower fin carbon patch spanning the full length of the fin base. This looks to span from the rudder hinge line across both spars and well into the leading edge.
https://forum.alofthobbies.com/index.php?threads/alpenbrise-157-4m.974/page-8

I suspect that this carbon was cut back in an effort to save tail weight, generally a good idea. It could also be that my model was an "S" lay up. And that what we see in the photo is an "SS" layup. Whatever the layup schedule this patch should span from the hinge line to the partial front spar (see green lines).

[Konrad]

There is some misleading information on the Aeroic team build thread on the sales forum. First the wing control surfaces length are not generally to be thought of as being adjustable by the end user. If you were to cut in the third surface from a wing that was cut as a dual control surface (blue) it would be rather small. The 3/6 surface wing needs to be ordered at the time of purchase.
https://forum.alofthobbies.com/index.php?threads/aeroic-alpenbrise-4m-build.3968/#post-52049

There is also some conflicting data on the size of the control surfaces with the 3/6 servo wing. The original sales sheets showed the values in red. The wing I received had the surfaces cut as called out in green. This really is a personal preference thing. Since I plan to use my Alpenbrise as a gag F3F racer I want that middle flap to act more as an aileron than as a flap. This is to help get the roll rate I need to turn the bases (pylons).  Now in landing mode this middle surface will be rigged as a flap.
https://alofthobbies.com/collections/slope/products/alpenbrise

And last, Aeroic is using some terms I think inappropriately. An IDS (Internal Drive System) is different from an external bearing support servo output shaft.
The IDS is an actuation system where the linkages are kept inside the wing (structure) lowering the aerodynamic drag. There are generally 2 types of IDG. The now more common Linear Drive System (LDS)  such as I’m using from Servorahmen. And the Rotary Drive System (RDS) sold by MPJet and made popular in Dr. Drela’s designs.

Most IDS use a bearing outside the servo case to support the servo output shaft. This is needed as deflection of the servo output shaft will have an exaggerated effect on the control surface as a result of the small levers (arms) involved.

As designed the elevator drive (pin) system is an IDS as the actuation system is inside the structure. What is shown in the manual lacks an external bearing support for the servo output shaft. This places an inordinately high demand on the internal servo bearings from the cantilevered servo output shaft.

As the space available for most of the servos is lacking in the Alpenbrise I strongly recommend that all the servos use an external bearing supported output shaft. Yes, even if using the traditional surface control horn. I’m appalled that the Aeroic manual actually shows the destruction (elimination) of the external bearing supports. I don’t know what constraints the author of the manual was under, but it is high time that the manual was rewritten!

Folks when dealing with a model of this weight and speed please put a detailed focus on safety and use sound mechanical practices.