Aeroic Alpenbrise 157 (Konrad’s Gag 4 meter F3F Racer)

[Konrad]

When I made my requests for the custom wing I asked that the wings not be cut for the classic surface control horn. (Thank you Hammond) 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]

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, for example 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. The female housing allows a lot of glue area to bond the connector housing in the wing.

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 per built the wiring harness.  Maybe just supply us with the raw materials. Heck, the supplied harness I received was 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. 

 

With the use of 3 servos in the wing there is a problem with the electrical connectors at the wing part line. I'm using the great Multiplex green 6 pin connector. But 3 servo have 9 leads to deal with. The solution without serial data servo (S-Bus) is the use of a common power bus. That is all the positive leads are electrically tied to the same wire (bus). And all the negative leads are tied to the same wire (bus). Often times this is done at the pin. (See the leads to the RX). Here in the wing, I'm tapping into the power leads close to the servo. This saves me a lot on wire weight as there are only 2 power leads going down the wing. This is saving me 15g in wire weight per wing.

I'm also using the common bus bar architecture for the two rear servos. This is also saving me about 15 grams is wire weight. But as there is a moment arm to this mass I suspect that the total weight saving from this fuselage wire loom will be in the order to 30 grams if thinking of the savings in nose weight.
So the use of a common bus bar is saving me about 60 grams of mass (2oz in old money).

 

In this build I used heavy gauge wire for the 2 power leads and light gauge wire for the 3 signal wires. If I was to do this again I'd use S-bus/ F-bus servos to save even more on the wiring weight). 

[Konrad]

Here I'd like to discuss the selection process for the wing servos. The original 4 surface wing was to use the full size 10mm thick KST X-10 servos, for a total actuator (servo) weight of 114g. The problem was that the aileron pocked would not accept the classic 10mm x 30mm x 35mm servo without a bulged servo cover. Nor would the aileron pocket allow for the smaller 10mm x 30mm x 30mm  mini X-10 servo. This to my mind was just ridiculous for a large 4 meter glider! I think there are some specialty 20+ gram servo that will fit. But for a sport glider I didn't want to pay upwards of $90 USD for an odd shaped servo. (Aeroic needs to call out or define what servos the model was designed to use). 

The undersized aileron servo pocket is forcing me to use a 8mm thick aileron servos. At the weight and speed of the Alpenbrise I'm not comfortable with the 8mm thick servo for the 4 surface wing. To cut down on the loads on the aileron servo I had Aeroic supply me with a 6 servo wing. This allows for a much smaller outboard aileron. I'm now comfortable with the use of a KST HS-08a 8mm thick servo as the aileron servo.  

I was contemplating using the KST HS-08a servo for the center control surface to keep some of the mass out of the wings (moment of inertia). But I was not happy about this as the gears are too small and delicate for this application (flaps). Nor was I 100% comfortable with the power, as I was going to need to use a large servo arm to get the required 120° of surface movement. (The center surface acts both as a flap and aileron).

With the 6 surface wing the flap function is now split between 4 servos. As a result I don't need the power from the KST X-10 servo. Dropping down in weight to the KST mini X-10, I'm still able to use the durability of full size gearbox found in the KST X-10 as the mini X-10 uses the same gearbox. So the servo selection for the 6 surface wing is KST HS-08a for the ailerons, KST min X-10 for the center flap and KST mini X-10 for the inboard flaps. This results in exactly the same actuator (servo) mass as if I was using 4 KST X-10 servo (114g) in the 4 surface wing. 

I like that the 6 servo wing is allowing me to move the center of inertia closer to the center line of the aircraft. I also like the added redundancy of the added servos. Other than cost this is a win/win situation. Yes, there may be a bit of weight gain with the 6 servo wing as I need to take into account the weight of the servo trays and push rods.

I have to admit I'm puzzled at how Aeroic is recommending using the center flap on the 6 surface wing. If one is buying this level of performance airframe one should not be using an entry level TX. Again it looks like Aeroic in their manuals/documentation is not offering their customer the best advice (set up values) to get the most from their purchase. 

Edited January 5 by Konrad

[Konrad]

What I hope will help anyone following is the push rod length I ended up using to center the servos in the windows. I'm using the Servorahmen mono IDS and KST servos. A note about the servo arm for the HS-08a servo. These servo output shafts are NOT the same as the KST X-08 splines. Close, but not the same! To use the arms supplied I heat the arm in hot water to make the plastic a bit more pliable. I then push (force) on the arm HS-08a shaft. This will sort of broach the arm. I remove the arm and clean out any shaving if there are any with a bent pin. Subsequent installation of the arm on to the HS-08a servo are solid as the plastic with constrict to a tight fit after it cools down. This work is best done outside the wing. I'm using the KST HS-08a servo for the aileron, center aileron/flap. I'm using the KST mini X-10 for the flaps. The push rod lengths are 55mm for the aileron, 72mm for the center servo, and 76mm for the flaps.

Note I found that the supplied kink in the push rod used for the center servo (aileron/flap) needs to be removed. This is because this surface needs to move 120°. As these parts are made from a thermoplastic they can be adjusted (bent) with the heat from a covering heat gun. I'm also finding that I need to place this control surface horn (spoon) about 1.5mm forward of the hinge. This to allow the push rod to clear the hinge and allow for the needed leverage in the flap position.

I've found that it helps with the installation if one chamfers the push rod rib. This makes it much easier for the push rod to nest within the arm at the extreme ends of the servo's rotation.

Because the aileron spoon is so short, less than 6mm tall,I had to use the smallest forked servo arm. This still allows far too much linear motion of the push rod. To try to minimized the push rod motion I biased the servo arm aft about 40°. This has the added benefit of giving me the much needed mechanical differential. Unfortunately this still results in me only being able to use 60% of the servo's rotation. This is poor when looking at the mechanical leverage and servo resolution. If I was to do this again I would look at raising the aileron control horn height, even if it means violating the airfoil profile.

 

Well, my conscience got the better of me. Solid mechanics trumps aerodynamic concerns every time, or it should! As I've been harping on the poor mechanics shown in the manual I had to try to get some better mechanics for the aileron actuation. 60% servo resolution is just unacceptable!

 

In one of the photos I'm trying to show what the spoon looks like protruding 0.3mm above the wing surface. This is needed to get the +  30° surface motion with 80% or more servo rotation. This 0.3mm is hoped to not result in much of a drag penalty as it is thought that the air is turbulent at this point on the airfoil. I'm more than willing to take any drag hit for the improved mechanics the taller control spoon offers.

I really couldn't leave so much power and resolution on the table. I spent all of my budgeted hobby time today grinding out my newly installed aileron spoon. I'm happy to report that the "added" layer of composite in the spoon pocket protected the control surface, such that there was no heat damage from the removal of the spoon and epoxy.

I was able to raise the spoon (pivot) about another 1mm. This gave me another 20% or more of leverage. Much to my surprise I now get 30° of aileron motion ether side of neutral with a huge speed differential between the upper and lower direction (This is effectively dynamic differential even if the end points are the same 30°).

Depending on how effective the vertical fin is, I suspect that in practice I'll stop to downward motion of the aileron at 20° maybe 25°. This bodes well for getting these 4 meter long wings to roll fast for entering and exiting the pylon turn.

 

 

Edited January 5 by Konrad

[Konrad]

The Servorahmen IDS spoon has an offset to help address the top skin thickness. This hasn't been too much of an issue until now. With thin wings, Ok thin trailing edges like we see with Aeroic double cusp airfoils, this can limit the amount of up (pull) motion as the spoon binds with the inside of the bottom skin. 

I found that flipping the spoon gained the much needed space to allow for the much needed surface motion. This isn't too bad, but I did have to remove the support legs (injection sprue. Later iterations of the Servorahmen systems did away with this sprue ). (See attached drawings)

 

I’m now allowing the spoon to sit proud of the airfoil less than 1mm. I’m allowing this as I think the air is turbulent in this area and will  not add significantly to the drag.

This can also be an issue with the trying to maintain proper geometry to avoid the 3 point line and keep the spoon inside the airfoil profile. Please look at the geometry at both ends of the surface and servo travel. (I’m sorry for using the classic control horn to show the 3 point line issue. But the geometry is the same for the IDS ).

 

If one looks close at the servo tray you can see the Servorahmen has supplied a micro ledge to allow the epoxy fillet to flow over the tray. This makes a mechanical bond that holds the servo tray in place. 

Please make sure that there is some fillet flowing over this micro ledge before the epoxy fully cures.

Edited Monday at 15:38 by Konrad

[Konrad]

One of the features I like about the Servorahmen servo tray is that they often include an epoxy rake. This is a feature that allows one to tie the upper and lower skins together to make a much stiffer (stable) area for the servo mounting. I needed to sand this rake to match the space between the wing skins to allow the tray and rake to fit between the wing skins. Once one can fit the tray between the wing skins I fill the rake with a very dry mixture of epoxy and Cab-O-Sil. I also wet the inside of the bottom wing skin, this results in a good bond tying the upper and lower wing skins together through the servo tray.   With the Aeroic SS lay up this might not be needed or noticed as the SS is a lay up with added carbon making the wings stiffer than the lighter S lay up.

 

With the added control surface motion on the middle surface on the six surface wing I choose to eliminate the small wall that might interfere with the motion of the pushrod at the extreme ends of the servo’s travel.

 

(Note that the photos show the typical features and are not of the my Aeroic Alpenbrise) 

[Merry Mark]

Very high quality and detailed posts as usual, Konrad. Thanks.

 

Some good winter flying here at the moment.  Planning a new 4m glass model for the summer. 
 

 

 

 

[Konrad]

Thank You.

 

I try to post information that one can use in other products. I hope folks can extrapolate what I show into their specific model. So while the title says "Aeroic Alpenbrise" the how-to information should apply to just about any other molded performance glider.

 

So, what am I looking at in your post, (a Multiplex Heron?)?  Maybe not as the wing tips look a bit different than the Heron.

BTW; I think the Heron is close to the epitome for a foam glider. 

 

Scale gliders is another discipline I hope to explore soon.

Do tell, what are you looking at in a new 4 meter glass ship?

Edited Monday at 19:33 by Konrad

[Merry Mark]

That’s the way I read your posts. 👍

 

It’s my boy’s Multiplex Solius .  As with the Heron, a very well developed, tested and excellent block of foam!  Surprising performance and fun. It’s honed his slope skills in short order and made him a much better general model flyer.
 

Thinking of the Alpenbrise but also interested in some of the Robbe offerings.  I am familiar with the efforts of outfitting a raw ship (flew F3F in the past) and some of the Robbe models are tempting in their PNP variants when balancing time and £/$.

 

👍

 

 

[Konrad]

Love it!

 

I too have looked at the Robbe offering and see a lot of value in the product. The Robbe line seems to be better thought out than many of the smaller boutique shops. I think that many of the boutique shops do offer us products that are a bit outside the mainstream (this is a good thing). Robbe is offering these low volume boutique products through a distribution network that historically has been well set up for the retail customer. 

[Konrad]

I'm finding that I'm liking the use of JB-Weld quick set epoxy to bond the spoons and trays into the wings. This results in a good bond that is rather shock tolerant. The original adhesives shown in the Servorahmen video show them using CA to bond the servo tray in the wing. I've found that the CA bond shatters when subjected to shock loads, like when the wings flex as a result of high G's or my landings. I've also found that the use of CA results in some distortion of the wing skin as the CA shrinks as it cures.

With the use of JB-Weld quick set epoxy we never get that hard brittle Epoxy joint. (Like most 5min epoxy JB-Weld quick set epoxy stays somewhat flexible). I also like that with JB-Weld quick set epoxy there is enough time to get the spoon and push rod in place. Yet the JB-Weld quick set epoxy will set rapidly should you need to hold things in place. Like keeping the spoon against the upper control skin prior to the epoxy setting up.  

When installing the servo tray don't forget to allow the epoxy to encapsulate the micro ledge around the Servorahmen servo tray.

 

 

With Aeroic Composites you always get more than you expect!

 

Here I'm showing that Alpenbrise was supplied with Gurney flaps (molding flash)! This is another Aeroic quality escape!

 

One of my mid 2023 production date wings shows this molding flash for most of the span. It is a lip of no more than 1.5mm high that should have been removed (cleaned up) prior to shipping to the customer. 

One of the main if not only advantage of the molded sailplane is fidelity to the airfoil. Here again the factory and the QA process failed to catch this. Again it is easy for us the end user to fix with a hard backed sanding block. I like to use fresh 320 grit sandpaper when sanding these off, make sure not to radius the trailing edge. You want as sharp (square) trailing edge as possible to minimize drag. 

I know the reason for this escaped was because the factory didn't want to risk the chance of scratching the paint while removing the gurney flap. This can easily be avoided with proper masking prior to sanding. 

Yes, the LE also has some small protrusion (approximately 0.1mm or less). I will be removing these, even cutting into the LE paint. I'm a strong proponent that form follows function. I want my wing to perform to the highest standard even if that means I have to cut into the LE paint, making what looks like a wider part line. I think this is the single reason my models often out perform the same example others bring to the slope.

As some of you might have gathered by now I have problems with marketing terms. This is really gnawing at me with the term "European Quality". I really have no idea what that means. But I know that these many simple quality escape issues can't be what we expect of European Quality or heck any continent's quality.

[Merry Mark]

Yes, JB-Weld is good stuff, good too for repairing cracked motor mounts etc in goalies where they are subject to vibration. 👍

[Konrad]

A bit about epoxy. I'm of the opinion that generally epoxy isn't suitable for our application without some additive added into the mixture. For example these model structures are made from a material called Fiber Reinforced  Plastic with the plastic being the epoxy (xFRP, x being the type of fiber). 

 

In most of my mixing of adhesive epoxies I add Cab-O-Sil or milled fibers to change the epoxy's properties to better match my application. J-B Weld has added metal (dust?) to allow the resin to better match the properties of metal (what metal is unknown). I've found that his metal additive helps the resin resist impact fracturing.

 

As a general rule I hate 5/6 minute epoxies, they never give me the performance I'm looking for! For example the set time is so fast that the resin often doesn't saturate the surface teeth. Also most 5 minute epoxy have a low tensile strength of around 3kpsi. And last the cured material is often too flexible for my use. 

 

Prior to this build I used long cure time epoxies with some Cab-O-Sil added as my servo tray adhesive. This was taking me forever to set up a wing, as I would only glue in one tray at a time until its epoxy cured. I did it this way so that I wouldn't disturb the tray while fitting to other trays. With the 3 tray wing it would take 3 days to assemble a wing. 

 

I'm finding that J-B Weld Kwik epoxy I get the propertied I what in a servo tray adhesive. With the large contact area of the Servorahmen tray the 3kpsi tensile strength isn't a problem. I think the added metal filler adds shock resistance and at the same time hardens the resin adding some much needed stability to the 5 minute resin.

 

Now we come to a potential problem with fast cure epoxies. As a result of the exothermal reaction of the curing epoxy the heat can cause issues with expansion and then shrinkage as the epoxy cools. 

 

With the wing servo trays I don't see any distortion in the top skin of the replacement wings from the mid 2023 production run. Now I do have a significant distortion from the rudder servo tray and maybe some optical distortion from the elevator tray on the 2022 production fuselage.

 

I suspect that the layup under the rudder  tray is a rather dry layup as the distortion is so great that it has formed a bubble near the tray. This bubble looks like a result of expansion. Most adhesive distortion looks like it is a result of adhesive shrinkage as the resin cools. 

 

I don't know the mechanism of the surface failure, but I do see some localized weave bleeding through indicating to me that there was some heat involved. It won't be until I try to repair this bubble that I might get a better idea as to the failure mode.

 

 

Edited Wednesday at 16:32 by Konrad

[Konrad]

Historically one of the few things I actually like about the Aeroic manual is that they generally state the aft CG point. This is nice when it comes to setting up the ballast tubes. Knowing this I set my initial CG at the recommended CG of 108mm. I have to admit that at this stage of the build I wasn’t keen on spending any more money than I already had. I was disappoionted that much in the product! So I grabbed a spare 18650 2 cell stick battery and set my CG at 108mm (this was to prove to be a mistake on my part). I had to wait a few weeks for when I and the winds could meet at the slopes.

 

The day finally came and I was able to maiden this Alpenbrise at the SLoT in California, USA. The winds were about 17m/s and coming straight into the face of the hill. The winds were also a bit turbulent, add to the fact that when the winds hit the face head on there is a very strong rear rotor on the back side of the ridge, as a result the landing can be very technical.

Recall that at home I set the CG to 108mm per the Aeroic manual. When I was at the flying hill I noticed the turbulent air so I added 48 grams of nose weight. I walked to the cliff's edge and tossed her out. 

WOW, no surprises she looked to be in level and straight trim. Did the dive test to check the CG. Again just about perfect with no noticeable pull out at the end of the run. The only trim setting I needed to do was add a bit of down trim with the trailing edge down (more camber) in climb mode. I also added a bit of up trim with the trailing edge up (less camber) in reflex mode. 

Now what has me excited is the roll rate. I was a bit concerned that the roll rate of these 4 meter long wings would be inadiquate when looking to use the Alpenbrise as an F3F racer. Well, with the 6 servo wing and the large vertical fin I was pleasantly surprised at how fast the roll rate was and how easy it was to keep the nose on point. The Alpenbrise rolls just as fast as my other large Aeroic bird the 3 meter Redshift. Unlike the Redshift it was easy to keep the nose on point at various entry speeds. I'm still playing around with the differential settings and rudder mix. But I'm surprised at just how much of these setting I'm removing from my initial radio set up. I still have more work in the radio to get this incremental performance out of the Alpenbrise.

On the subject of the radio I really need to thank Mike Shellim of RC_Soaring.com for the F3F-60-8S templet. This radio programing templet is what has allowed me to extract the high level of performance from the Alpenbrise. While Mike claims that the templet is unsupported, he did help me with 2 issues I had. One was as down loaded the snap flaps are not activated in "Pump" mode. This was easy to activate, in the templet one needs to go the CH17, and on  first mixer line, open the mixer editor and enable FM5:Pump in the Flight Modes field.

The second issue is that Mike has no way of knowing what differential your plane or linkages will require. So he has set the differential to default at "0". He does document this in the set up guide with this statement,"Diff for flaps and inner flaps is fixed (default 0%), and not adjustable in the air. (Diff for ailerons is adjustable)". The “and not adjustable in the air" gave me hope that there was an adjustment. The templet does allow for the adjustment but not on the fly. This is still something I have to work on. Like I said I was taking out a lot of the aileron differential I added, when setting up the program, during the maiden. I assume I added too much differential in the aileron to flap mix. This can be adjusted with the channels 3 & 4,  and 7 & 8, you can set the diff value in the first (Ail) mixer line. Note the sign and value should be the same within each pair, this is assuming the linkage is symmetrical between both wings.

I have said this before, it usually takes me about 10 test flight before I think I have a glider in proper trim. With the more advanced gliders such as this one it may take me a bit more effort to reach what I think is the optimum trim. But with Mike Shellim's templets the ability to adjust the variables is there in the templet.

Now a constant theme running through out this thread is my effort to correct the poorly thought out and presented Aeroic manuals. Again Aeroic appears to be crippling their product with how to rig the center flap. I read something about putting the flap on a switch to activate the configuration/action you might want from the inner flap. This looks to me to be very limiting and ups the pilot workload. Again I don't know the limitation Aeroic is working with. I do know that I can't program radios that use master/slave programing architecture. Since the great Multiplex Profi 4000 (circa 1990) I have been using mixer based programing architecture. By the way the Mike Shellim templet is for such programing architecture, OpenTX and EdgeTX. I'm hoping that Mike will release a set of templets for the FrSky Ethos radio system OS.

After this test flight I can now say that this exercise has resulted in a glider that can actually run the F3F bases and to it respectably. No, the Alpenbrise is not competitive with todays real F3F races. But given some good air and a good pilot she won't be on the bottom of the standings. I think I have so much potintial in this model that I changed the battery configuration to get some of the lead out of the nose. (This is to be read; I spent some money to get a better battery configuration, 21700 2 cell side by side 21700)!

https://www.rc-soar.com/edgetx/setups/variants/index.php

 

Edited 7 hours ago by Konrad

[Konrad]

Here are some numbers from my Alpenbrise after the maiden. 
After I got home the CG was found to be at 106mm to 107mm from the leading edge, remember the added 48 grams of mass. All up weight was just shy of 4.6 Kg. Elevator in race trim (wouldn't snap) 9mm, full up 11mm, Down 14mm with an elevator setting of 10mm down for crow landing.

Flaps are rigged to offer 12mm up when mixed with the ailerons. Down is showing 80° flap.

Ailerons are going up 21mm (24°) In crow they go up about 14°) 

Mid span flaps go down the same amount as the inboard flaps. Upward motion is splitting the difference between the upward flap and upward ailerons.

Rudder is all I can get about 24mm, with a aileron to rudder mix using about 7mm

Again I'm impressed at the roll rate. I'm also impressed at just how violent the induced snap can be. It really is impressive to watch such a large model tumbling. She recovers rather fast.