DJ Aerotech Chrysalis F3-RES to F5-RESt

[Konrad]

On the competition circuit the last two years haven't been kind to the DJ Aerotech Chrysalis lite F3-RES. Most of these problems can be traced to a nagging problem with the V tail flutter on the high start.

In the USA it is getting difficult to get enough workers to man the lines for a classic TD comp/ even a low key comp like an F3-RES contest. As a result there is a lot of talk about adding electric motors to launch the models rather than the high start.

So using this thread as inspiration I've decided to convert my DJ Aerotech Chrysalis lite F3-RES ship into an F5-RESt.

Element 2 pure glider

Would 2 deg. up elevator be a good starting place to set the elevator neutral on the Element 2? (Two with respect to the bottom of the wing.) Id rather not have my first launch end up in a bonk.

forum.alofthobbies.com

This gets rid of the nagging problem with the V tail on the high start, get rid of the high start!

Glenn noted that his conversion of a light 2 meter needed a lot more down thrust than anticipated. So I aimed my nose block downward mainly to meet the upward flow of air from a glider falling through the air. This nose droop added to the down thrust. I'm hoping that I don't need a lot of motor to elevator comp.

For more detail you can follow a long with this conversion over at HIP.

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www.hippocketaeronautics.com

I have to admit I've forgotten just how fun (relaxing) it is to shape wooden blocks.

 

[Hank GB Z]

Konrad,


Looking good so far. I’ll be interested to see how this goes. I need to finish a model (or two) then I want to start my Pilot Cilantro which is 2M REFt. Maybe next spring we can have a fly off.

What motor are you using? Also what spinner is that?

Hank

 

[Konrad]

Ok I'll post some engineering data as it currently stands. I have to admit this is not a sport set up, mainly because of the cost. That Hacker set up is a bit out of line cost wise. But as these are kits and not ARFs I can see using what works best after having spent so much time building the basic model.

The motor is a Hacker A10-7L with 4.4:1 gearbox, prop is a 13x10, ESC is a Castle Creation Talon 15, batteries are Thunder Power 450 3 cell. Expected AUW is 435 grams (same as the high start glider).

The spinner (not listed on Aloft's site) is a neat 25mm F5K spinner from the same OEM. A problem is that there are no prop blades that fit this spinner/hub. As such one will need to fit the blades to the Z hub. one needs to be cognizant of the stresses put on a the blade and take responsibility for the modifications to the blades. As the power and RPM are low there shouldn't be too much risk from the modification of the blades.

CN Spinner 30mm

Intended for the electric thermal pilot who is looking to reduce drag to the absolute minimum. The lower drag profile is achieved by utilizing an offset yoke design that allows the propeller blades to fold closer to the fuselage than is possible with a straight yoke.We stock these spinners in 30...

alofthobbies.com

 

[Konrad]

Shoot (that's pronounced !@#$) it looks like I need a new set of glasses! I was doing an initial balance check after shaping the nose block and it looks like I was using a 3 cell 750 mAh battery rather than a 350 mAh pack. I thought something was off when I cut the nose off, as I had first calculated that the motorized glider would need a longer nose not a 17mm shorter nose. Both set ups, glider and motor glider, are balanced at 87mm. Also both are coming in at 435 grams. I fear I lost the opportunity to lower the weight by extending the nose and using 350 to 450 mAh cells.

I have to say I'm a bit annoyed with myself!

 

[Hank GB Z]

Weight issues aside I like the new nose shape better than the old one.

Hank

 

[Konrad]

Yep the old nose looks like a tongue depressor!

 

[Glenn Beer]

FYI... On the element 2. I wound up with 8 deg down thrust measured with respect to the wing’s chord.

 

[Konrad]

Thanks Glenn, I recall you saying as much.

It is my experience that if needing more than 3° down thrust with a conventional layout such as this, there are other trim issues. Usually needing more than 3° of down thrust is a strong indication of being too nose heavy. That is one has to carry too much up elevator trim. This makes the model very sensitive to speed changes. (Zoom into a climb during the dive test.)

Those of you with sharp eyes might have seen that I cut the nose off with a lot of right thrust. While I do have some right thrust built into the nose it really isn't as much as the cut off would indicate. Right thrust is added to control the "P" factor (NOT Torque) as a result of the asymmetrical thrust from the prop. As the model is light and the prop has a high pitch the asymmetrical thrust shouldn't be too great. So I sanded a lot of the right thrust out. Yes I have some right thrust but mainly to make sure I don't have any left thrust. These fast climbing ships often don't need too much right thrust.

 

[Konrad]

A little more work on this. I've glassed the nose, a habit I do with just about all my built up models. The 0.5 oz glass cloth adds stability to the finish and may add some strength. This is staying within the bounds of most F3-RES rules as this isn't thought of as a unique composite molding. This kind of glass work is a typical model finish process used to stabilize the wood, be the finish iron on film or paint.

Now what I've done is add the inlet cooling holes. These are directed to the rotating part of the motor. A nice feature of this model is that I've used the nose block as a tight fitting baffle (1mm gap 2mm diameter) so that most of the air (inlet drag) is used to cool the motor's rotor.

So far so good. Now we hit a snag, what comes in must go out. The outlet is the tail boom. As you can see this is wholly inadequate! Normally you want the outlet area to be much larger than the inlet area. This is because the out going air has expanded as a result of heating up.

Now I hope I'm not just kidding myself, but I'm hoping that over a time weighted average I can get rid of enough heat while gliding as to shed this unwanted heat with that little outlet. That is to say I hope that the motor has enough mass as to allow the motor to run for 5 to 9 seconds without damage. And then what little airflow there is, can carry away the heat from the heat soaked motor and battery.

 

[Konrad]

Started to recover the fuselage. While stripping the covering off I see that I left 8cm of glass off the pod. This was done because some of the regional rules for F3-RES at the time only allowed 1/3 of the fuselage to be finished in glass. This wasn't a well thought out regulatory restriction. So I have the front 1/3 of the fuselage finished in 0.5 oz glass cloth. Then I have a gap between the glass of the pod and the carbon tail boom. This does nothing but make it more difficult to finish and it allows a weak point in the structure. BTW: The rules at the time only allowed the carbon tail boom tube to reach into the pod to the 50% point of the wing cord.

If something seems odd, look to the regulatory requirements before blaming the designers/engineers.

 

[Hank GB Z]

Konrad,

The re build is looking good.

On the glassing only part of the fuse. Does that include the tail surfaces in the over all length?

Hank

 

[Konrad]

Thanks.

As I read the rules it stated glassing 1/3 of the fuselage length, not over all length. Now F3-RES is not governed by any association, definitely not the FAI. These are regional rules. most are based on some german set of rules, with minor word changes like specifically allowing fiberglass as a finishing technique.

The aim of the rules was to bring back simple balsa built models. It was thought that high performance (high cost) models like Vladimir Models Simply the Best and the Pulsar type models with their molded LE and fuselages where too expensive. This is why most F3-RES rules state that unique molded parts are not allowed. The "unique" part does allow for standard molded composite parts. This is why we see carbon tubes in the wings and as tail booms. We also see cured carbon strips in the wings. These are standard supplies and not uniquely molded parts.

The 1/3 fuselage rule was aimed to still keep the molded fuselage out of the class but a nod to the way models are really built. Also the way landing points are awarded was to remove any advantage that the composite fuselage might have with the classic lawn dart landing. Lawn dart landing aren't allowed.

The Chrysalis lite F3-RES was DJ Aerotech's first entry into the class. It wasn't built on a clean sheet of paper. It is an extension of the Chrysalis 1.5 meter glider. While a fantastic model it does have two issues. First the nose it too short. Most models need about 30 grams of lead nose weight if covered in anything other than So-lite (no longer available). Most Chrysalis Lite are coming in over 400 grams (mine in high start trim is 435g). The second is the fuselage tail boom is too small in diameter. This results in the V-tail control arms being too short to control the flutter while on the high start.

As the Chrysalis lite F3-RES is now an obsolete design I was trying to add some life back into mine. I failed, as I cut the nose too short. I fear with my retro fitting a motor, the Chrysalis lite will still come in around 435 grams. (With the upgrade balsa V-tail it is looking like the AUW will be about 422 grams)

The new Monarch Ascension F3-RES is a nice model, with the lessons learned from the Chrysalis lite added. The Ascension is coming in under 400 grams.

2M Monarch Ascension Sailplane (F3-RES)

Shop now for Quality Radio Controlled Balsa Sailplane, Handlaunch Glider and Electric Kits. Buy Small Business and get the personal attention you deserve. In business since 1993 with new products coming soon!

www.djaerotech.com

 

[Konrad]

Other than retrofitting some aircraft from IC power I don't understand why so many electric designers opt to use firewall mounted outrunners. This place the cooling fan to fight the incoming air! To my way of thinking the proper location for the motor mount is in the "spinner ring". This often places the rotor (fan) to allow it to draw air through and across the motor.

While it is true that an electric motor is far more efficient than an IC engine (80% vs 12%) there is still a bit of heat that must be shed. In my planes I want whatever cooling drag I have to suffer to be used to its full potential. This is why I like tightly baffled motors preferably set up as a pressure cowl.

In this retro fitting of a motor to my Chrysalis lite glider I'm using the nose block as both a motor mount (spinner ring) and tightly fitted baffle. Please note that the inlet air is directed on to the rotor and that the rear fan is helping draw air into the motor.

 

[Konrad]

Well well well, I must have found a TARDIS! After cutting the nose too short and adding an electrical assist the weight of my Chrysalis lite has dropped from 435 grams to 405 grams. The key to this is changing from the original bass wood V-tail to the upgraded balsa and diagonal reinforced V-tail. The original V-tail weighed 31 grams with Ultracoat lite covering. The upgraded V-tail comes in at 19 grams covered with So-lite. This is what saved my bacon after cutting the nose too short. (Heck I might still have to take off another 5mm or 10mm of the nose after test flying)! With a 35 gram 350 mAh 3 cell battery the balance point is 85mm. Still a bit nose heavy but in the ball park. I'm so glad I don't need the weight of the 750 mAh battery. Now I'm off to find a TX and RX that actually talk to each other!

 

[Hank GB Z]

Konrad,

That looks great! I like the weight savings too. Can't wait to hear flight reports.

Hank

 

[Konrad]

Thanks, I like that I was able to engineer my way out of the corner I built myself into. OK, I had to just throw money at it to get the upgraded balsa V-tail.

I was hoping to fly her today but I can't get my new X-lite S to talk to my new ACCESS Archer RX. I can get a bind with between the X-lite S and G-RX8 on ACCST. So it looks like I'll need to darken Aloft's doorway, on my way back from flying, asking for customer support. While I'm there I'll need to look into getting a programing card for the Hobbywing 20 amp ESC.

You back home with family and building supplies? The µ-Sinbad I got from you is rapidly coming to the front of my building que!

 

[Hank GB Z]

Yeah, i'm back home. I opened the irons you sharpened and they look great. I'll set up some of the block planes this weekend. I've been working on my Jing Models 13" sopwith triplane. The guy who gave it to me has cancer so i thought i should finish it while he can appreciate it. I hope to have her buttoned up this weekend. I just need to get a little bit of paint for some of the details.

I bought an Archer Rx from aloft. I'll experiment binding it to my X 9 lite. I never bothered to flash the old recievers to ACCESS since the ACCST worked.

Hank

 

[Wayne]

Konrad - the receivers come with a newer firmware than the transmitters! Found this out myself last weekend. So, here are your options:

-Don't use access.

-Upgrade the firmware on your transmitter to use ACCESS and also update all other non-ACCESS receivers, then rebind.

I'll be doing the updating on mine. Need to anyhow. Then I am set for the future. Probably take an evening to do the easy planes in my garage. Pulling receivers is the harder part. (Or maybe I'll replace them all with ACCESS and sell the old units here..? I am kind of lazy and do like the new Archers.

 

[Konrad]

Wayne, Thank you! It is always good to learn that it isn't just me when it comes to software implementation issues. I assume you meant the ACCST v1.x.x and ACCST V2.x.x
So am I to understand that ACCESS is built upon ACCST tech. Not that there is anything wrong with that but it would have been nice if FrSky had documented that! (It is looking like there are 2 major versions of ACCESS).
So pre 2020 ACCESS is built on ACCST v1 tech and post May 2020 ACCESS is built on ACCST v2 tech, This might explain why some of my older X series RX that I've converted to ACCESS actually work. While my new (native)Archer series (2 week old purchases) did not register

This in the form of a flow chart might be a good addendum to the great manuals you and Lothar offer. I doubt it is anything FrSky can conjure up or would even be willing to host on their site.
(GUYS THIS IS WHY IT IS SO IMPORTANT "WHO" YOU BUY YOUR EQUIPMENT FROM. MUCH MORE SO THAN THE LOWEST PRICE)!

While I have a lot of 6 year old FrSky TXs. I bought the X-lite S to move into the modern era . So I'll try to follow the FW propagation to come up with a workable software combination.

All the best,

Konrad

P.S.
Aloft does have the Hobby Wing programing cards for the FlyFun ESC. Don't bother trying to program the ESC without it!

 

[Konrad]

Wayne again thank you! This worked as it should have the first time. I think FrSky missed an opportunity to make it more difficult. I up loaded the file (ISRM S 2.1.0 frsk) per the readme file and with the help of the process in Lothar's manual and it worked the first time. With my new ARCHER R4 the reg and bind process went as I would have expected.

I wish FrSky would document their ACCST/ACCESS interdependence. Without proper documentation the best one can say about FrSky's code is, it is sloppy! With proper documentation I would have had 3 hours more hobby time to set up my ESC and prop on my F5-RESt. FrSky is looking to be a very expensive brand when looking at the hobby hours to get things going that should be compatible right out of the box.