DJ Aerotech Chrysalis F3-RES to F5-RESt

[u2builder]

Konrad, Thanks for the discussion of the 25mm spinner/prop, Chrysalis E-Lite 2 M, Ascension, original 2m Chrysalis and YJ . The boom issue of the Chrysalis Lite is interesting as it relates to the difficulty of getting tapered CF booms sized for 2m gliders.

What I would really like is a kit or even plans for a 1.5 m balsa built up E-DLG type with an elliptical wing at a reasonable cost. It would not have to be competition grade. This is what I'd like to play with at my small tree lined field in front of the house. I tried a Mimi 1 m plans built DLG but I discovered that I am too old to throw it. I put a motor on it, and it is OK, but would like a 1.5m wing. There is just no way I could consider spending hundreds of dollars on a fragile molded glider that could easily wind up stuck in the top of a tall tree. I may try the Chrysalis 1.5 m electric. It is RES but the price is very reasonable. Or a 1.5 m E-YJ, more expensive, smaller wing area, but lighter. Just doing some research now.

 

[Konrad]

@Glenn Beer your decalage is negative (lifting stab)? Does the Element still pull up, out of a dive (dive test for CG).
My Chrysalis Lite F5-RESt is still very nose heavy and has a fixed stab, unlike the full flying stab of the Element. After I find the correct CG (around 90mm) I hope to have a decalage of less than a degree positive (stab pushing down). (This is just a paper exercise as the dive test and feel are are what control this). Moving the CG aft will result in even more down thrust as measured from the stab.

I test for the thrust line after I set the CG. With the plane in full power level flight I kill the power. At that instant if the plane pops up that indicates that there is too much down thrust. If it tucks it indicates there is too much up thrust. I like my planes to jump forward when I apply power. I don't want her to lift her nose and go into a loop, or worse go into a stall!

Normally I only need about 2° of down thrust. I'm wondering if as a result of the polyhedral wing that the alignment with the center of lift (drag) and the thrust line means that we will need more down thrust than most straight winged models. (I think my Chrysalis thrust line is closer to the wing than that of the Element. Meaning I think I'll need less down thrust than the Element).

Redo fatigue-Ah the joys of flight test!

All the best,

Konrad

 

[Hank GB Z]

@u2builder

This might work for you. https://outerzone.co.uk/plan_details.asp?ID=4617

Hank

 

[Konrad]

@u2builder I don't think other designers are having supply issues with their 2 meter ship carbon booms. DJAreotech just wanted to keep the mass out of the tail. Don would have liked a larger diameter thinner walled tube. As he didn't want to push the push rods through the tube side walls, with the structural issues that entails. He was forced by the small ID of the boom to use too small a set of control horns.

Yikes, a small tree lined field sounds like a horrible place to try to fly a small glider. Those trees must cause havoc with turbulence near the ground making thermal detection (and formation) all but impossible. Then there is the steep decent over the trees with the speed build up upon landing.

As counter intuitive as this is, I like larger gliders for small field work. The added mass helps cut through the turbulence, and the added control of proper lift dump devices (crow) allows for a steep short field landing pattern.

There are few 2 meter balsa kits with fully articulated trailing edges. But with the new class of 6 gram servo these should now be practical.

 

[Konrad]

Nice!! The Thornburg Sunbird looks great! With a bit of rework to the tail and rudder she should be fine little HLG (old school).

 

[Konrad]

Just got back from test flying the Chrysalis Lite F5-RESt.

Wow what a nice ship, she is actually lighter than the Chrysalis Lite F3-RES glider from DJ Aerotech. I also love the added flexibility the motor provides. Here is a video of the first powered flight, I hope this posts.

What you are looking at is the climb from a prop with far too steep a pitch. Flying this prop was much like driving a speed boat. Adding full power only makes the prop stall. Later I learned that if I allowed the Chrysalis Lite F5-RESt to accelerate in level flight then pitch up into a climb I had unlimited vertical. Climbing like I did in the video never let the ship go fast enough to allow the prop to hook up. This indicated to me that I need to change the prop from a a 12 x 13 to a 13 x 10. (Stopped by Aloft and picked one up).

You can also see the dive test (left to right) where she pulled up into a stall. It took another 1.5 to 2 grams on the tail to tame this. I had good control as witnessed by the tight circles over the gape vines! I also need more up elevator comp when the spoiler comes out.

Now much to my surprise I need a bit more down thrust, maybe 0.5 a degree as she will rotate up into a climb under full power. With power on she won't stall. But I want to be the one that tell the model to pitch up into a climb not the speed of the ship.

With the 350 mAh 3 cell battery I got 5 good climbs follower by 10 minute thermal flights and still had about 30% left in the cells. I think the batteries are just about perfect.

By the end of the day I think I added about 5 grams of lead to the tail. This indicates that I'll need to cut off the nose and shorten the nose another 8mm.

 

[Konrad]

Well, it is looking like the weather is going to be a bit unstable for the next few day. So I think I'll cut off the nose and shorten it. For a host of reasons I think I'll be limited to only being able to take out 12mm off the nose. This will allow me to remove the 5 grams of lead I added to the tail to get something close to a neutral trim and gives me the opportunity to add a bit more down thrust.

While the shorter nose will allow me to loose most if not all the tail weight the real reason I want to shorten the nose is that the thin carbon tail boom is very susceptible to the added mass whipping the boom snapping the boom! I was thinking of reinstalling the basswood tail, but its added mass still keeps the load on the tail. Also the heavier tail add some of this mass above the boom adding even more stresses.

 

[u2builder]

This is really deep tuning. It is great that it flew so well in the most recent iteration and that it actually lost weight fromthe glder version.

I had four noses on my little Mimi DLG that I eventually motorized, first because of a crash as a DLG, then to balance it better, then to add a motor without a spinner and folder, and finally with a spinner and folder. I am using the same spinner with a much smaller motor and a little 6x3 Ebay prop with correct hub diameter and pin size that I had to modify. I couldn't find the 6x3 Graupner with 5mm hub and 2mm pin hole in stock. I modified the spinner and the hub just enough so that the back of the prop blades was just a little in front of a ruler sighted to align with the back of the pin holes. Is this enough to allow the prop to open fully? Also, how do you balance a folder like this where you can't tighten the pins? I weighed each prop blade and they are the same? Is that good enough? It seems to run smoothly and flew fine on its first couple flights. It is hard to find a day when the temp is above freezing with no wind in NH!

 

[Konrad]

That was a maiden flight I was just doing basic tuning. Finding the center of gravity is fundamental to any further trim/tuning work.

As to balancing of props. I think one needs to understand static balance and dynamic balance. Dynamic balance requires finding the center of mass of each component (blade) and to remove mass to move this point so that both blades have the same mass and and the same Center of Mass. (Most folks don't do this, so don't worry too much about it). Locking down the blades leads me to think you are basically concerned with static balance.

As to the the back of the blade going straight out, this is rarely the case with folding props. With the pivot pin and the CofM being in line, the back of the blade will often look like it is raked aft when looking at the prop disk from the side.

As to spinner clearance you want to allow the true center of mass to be 90° to the axis of rotation with this line drawn through the pivot pins. You will know when the blade can't reach this state by the huge vibration!

The end point is as you say; it seems to run smoothly. So the actual out of balance condition is of no concern to most. Just get it to run smoothly.

Not sure if this makes it any clearer. The blade looks raked aft (red lines) the pivot pins (yellow line) are 90° to the axis of rotation (green line). The center of mass for each blade would be found somewhere along the yellow line should you extend the line. ( Sorry the flash cast a shadow).

 

[u2builder]

Thanks Konrad, Very clear. Great graphic. I guess I removed a bit more than necessary but there is plenty of hub left. And I learned something!

 

[Konrad]

We aim to please.

Now a bit of fine tuning. I noticed that I had spoiler elevator comp of about 25%. What bothered me was that if I moved the spoiler control fast (as I tend to do) the comp curve came fully in while the spoiler was still trying to reach fully open. What I like about the OpenTX is that there is a way to slow down the mix while not slowing down the servo speed. I added a slow value of about 0.3 seconds. This seems to allow the elevator comp to stay indexed to the rate of spoiler opening rather well. Please note that my spoiler to elevator comp curve is NOT linear.

Spoiler Drag link

I hate spoiler! With that out of the way here is how I like to actuate spoilers. This set up is known as a drag link. It maintains a possitive connection with the spoiler and servo. Does not need or use any springs or magnets. Adjustments are easily controled by the radio's end point and /or...

forum.alofthobbies.com

P.S.
I see that by the end of the day I had the elevator comp as high as 35%

 

[Konrad]

It pains me to have to cut into a perfectly good working ship!
Here I've removed 12mm off the nose. This effectively is moving 50 grams of mass aft 12mm. I didn't remove more as this would then mean I would have to rework the whole radio installation.

I have to admit I was shocked to see how much I had tapered the nose in only 12mm.

I hate to say it but I think I'll still need a gram or two of lead in the tail.

 

[Konrad]

Sometimes it's great to have a spare kit around. I used the cut out waste filler for where I cut through the lightening holes.

 

[Konrad]

Sometimes I think the best hobby tool is the sanding block!

The added down thrust was a bit more than I planned at 0.7° to 0.8°. For all I know this might be perfect. I was aiming for 0.5° to 0.6° all based on a SWAG as a result of flight testing.

 

[Hank GB Z]

Konrad,

Looking good. I wouldn’t have thought to cut the fuselage there. I would have cut the nose and reshaped. Your method seems simpler.

Hank

 

[Konrad]

Thank you Hank.

That's one way to do it. But as I already had the motor mount, cooling holes and pressure cowl in the nose block, I wanted to save it. Also I really didn't want to loose that nice shape.

Now I was surprised at how much the fuselage cross section changed in only 12mm! That is why I had to add the plywood filler and add some filler wood to the inside of the fuselage sides. I feared I might sand through the sides trying to blend into the nose block.

 

[Konrad]

Here is a photo of the inside. I didn't show the filler blocks earlier. Also I think one of the keys as to why my Chrysalis Lite hasn't seen flutter is that I support the ends of the push rod with a large blade support.

 

[Konrad]

Well, I still need 2 grams of lead in the tail. Now I'm doing crazy things to cut down on the nose weight. I've Swiss cheesed the nose block. (You might be able to see one of the lightening bore in the lower left part of the nose block in the previous post). Also I recall a great C/L builder who said of lightening balsa blocks, that one should be able to see light pass through the block. This is a great way to find thick (heavy) spots in ones carvings. He also said it you don't break through in a few spots your block work is likely too heavy. Here I'm able to get light to pass through the hatch cover on my Chrysalis Lite.

 

[Hank GB Z]

Konrad,

Can you move the servos back closer to the CG? That seems the fastest way to move the CG back.

Hank

 

[Konrad]

Yes, but I really didn't want to do a whole other radio installation. That to my mind this is a lot more work than just cutting off the nose. Anyway, a gram or two down low on the the tail boom shouldn't be any worse that the original basswood stab with its added 12 grams or so more mass up high.

I have to keep telling myself that this is a conversion from a built Chrysalis Lite F3-RES ship to a modified spec Chrysalis Lite F5-RESt. I did not start from a clean sheet of paper.