LDM

My Feedback: (15)

I guess I read the book "FW for Dummies" lol , I never put that much thought into my Pica Dora or FW, my goal was forward rake for ground clearance, proper angle for scale appearance and I would let throttle and flying skill determine stall speed.

vertical grimmace

My Feedback: (1)

I actually had to add an extension to them from the stock length to get them right. For what it is, the Pica 190 has a reputation for being pretty accurate scale wise. It is just the sheet tail surfaces that kind of blow it.

dgiatr

ZROOSTER thanks for your kind words!
i have a fiala 23x8x3 blade prop in my ESM SPITFIRE 50CC which is 15,5 kgr! (after a repair from a serious crash), plane flies very well for a dle 55 ra engine. i think you can use a dle 55 ra engine with minimal cowl cutting and swing a nice big 3blade prop, of course it wont be a 28 inches prop for that plane but in any case i think its far more better than a 2blade prop. i dont like putting static props in my plane and i thing that plane the most of its time stands still on the ground so a good looking and functional prop is what i ask for. as i have said before fiala props are very effective and light props and you can swing relatively big props with not so many power. Currently after some breaking in my fw 190 d9 i swing a 24x10 3 blade fiala prop and plane flies very scale-like (of course i have a 3w 75 cc on it).

https://www.youtube.com/watch?v=HbKM81LX9tc
https://www.youtube.com/watch?v=fTBo...-nrFLhgNo57dSw

i am currently doing some scale details on an esm p40 50cc using a moki 75 cc and 24x8x3 blade fiala also....

zrooster

Good looking P-40! Thanks for the response. I agree that I should be able to extract "good enough" performance from a smaller diameter 3 blade prop. My intent is to do some testing before I make the final decision on prop... Would like to test actual thrust, not just RPM. Constructing a device in my head that would allow me to do so...something involving a track, a block that slides along it with the firewall attached and a force meter (usually these display force in newtons, but should be easy math to convert). Unless someone is aware of a device like that-that already exists!

vertical grimmace

My Feedback: (1)

That would be an interesting experiment. Especially if you compared it to the known best 2 blade props being used which are Mezslik, Xoar and Vess.

zrooster

Exactly! Intend to test against two blade options. Seeing as how the ARF isn't presently available, I'm tempted to go ahead and order the motor and some props and get to it!

vertical grimmace

My Feedback: (1)

I have seen a sled type device created. I think the guy used high end drawer guides (Hafle?) This was being used to test electric motors. I would think a good digital pull scale (fish) would work fine, as it would just be a comparative measurement that you need. Of course, knowing exactly how many lbs. of thrust you are getting will let you know if it is enough to fly the plane. Comparing the RPMs you get relative to the thrust readings, again compared against the type of prop used, could prove to be valuable info to many. I will be interested to see any results that you come up with.

zrooster

Ah! Digital fish scale might be a nice affordable option. Found this: http://www.testequipmentdepot.com/pr...FeXm7AodlGEAVA Guess it does read in pounds of force, so no need to convert, but just a bit pricy. Think I'll just go with the fish scale. Think I've settled on the XYZ, so I'll order that, then establish a baseline with a known performer (2 blade) and try out a couple of different 2 and 3 blade options. Sled style with "wheels" on a wooden track is what I envisioned. Eyelet on a vertical structure on "the back" and another on the sled...fish scale inbetween. Should be pretty easy. Going to hit Lowes tomorrow to look for materials.

vertical grimmace

My Feedback: (1)

If a fish scale is not something that can be found, as I honestly have never seen a digital one, you may incorporate a regular mail/kitchen scale. These are readily available. The thrust jig that I saw used one of these with an "L" arm, with the proper angle/geometry to push on the scale as the engine pulled away. Think of a bellcrank, pivoting at the point. Either way, It is totally doable. I am going to guess that there will be a prop or 2 that are clearly better than others. I saw data on the difference between the Mezslik carbon, and the Xoar and Vess, and it was pretty profound. These were measured with telemetry while flying. Not sure you are going to wanna drop too much coin on a bunch of props. The Mezslik's are pricey, but the Zoar and Vess are reasonable. I will assert that you will not find a 3 bladed prop that will perform as well a a 22-10 Xoar, so that may end up being your bench mark.

Also, It will be important to note that the performance of the prop is not going to be fully judged by static thrust. There is no true measure until a particular prop is flown. Also, considering you have an electronic ignition, there is a window that you have to remain in, regards to RPM.

Joespeeder

Hey Guys,

When trying to narrow down prop purchases I use this calc to get in the ballpark. http://personal.osi.hu/fuzesisz/strc_eng/

It works very well when comparing props on electric set ups and has also proven useful on gas/glow engines.

I start with a known set up from real world testing(either mine or reported on the forums) and note those results including the Required Engine Power.

Then I start changing the prop info and adjust the rpm to match the known Required Engine Power.

Note the Pitch speed and Thrust.

While the results may be off a bit, it is very useful to compare props and it will tell you if the prop you'd like to use will be better or worse than the known set up.


It will also tell you if that cool prop you want that feels so strong actually has enough pitch speed to fly well. We've all seen guys get a good fish scale reading for a project but the prop doesn't have enough pitch speed to fly well....

It's not perfect, but it will save you some money narrowing down the props to buy and test. It's served me well.

Joe

zrooster

XYZ showed up yesterday and I'm starting to set-up my test stand. Haven't ordered any props yet...was trying to decide what to use for my baseline. Looking back over the thread, I know ticteck has a 53 in his and a bunch of flights on it so I thought I would go with whatever prop he's using. Anyone know which one he's got on his plane? As stated this would be my baseline. I'm also going to try a couple xoar 2 bladers and a fila 3 blade.

thunder21

My Feedback: (2)

zrooster, at one point, ticketc was running a TBM 22x10 prop. I'm not sure if that's what he's still using. I'm using a Vess 22b prop which is approximately 22x10. I have about 50 flights on mine and it's running fine. I used a Xoar 22x10 and it was pretty much the same.

Make sure you check the timing on the motor because a lot of them come with the timing way too far advanced and that leads to poor performance. The proper timing is 28deg BTDC. I'd also suggest getting better spark plugs than the stock ones. I got the Rcexl Iridium CM6 spark plugs and they have performed flawlessly.

zrooster

Thunder, thanks! I'll order a xoar 22x10 for my baseline. I guess the plus side of having to wait for the ARF is I can focus on getting at least one system (one of the more important ones) optimized before I dive into the rest of the plane. I've started assembling materials for the test stand, which brings me to the next question: mounting. Since the XYZ doesn't come with standoffs or anything, what did you use to mount your motor? Might as well mirror the mounting method Im going to use on the plane, on my test stand...

thunder21

My Feedback: (2)

I built up a plywood standoff and glued and screwed it into the firewall like ticketec. If you look through the thread pictures, his picture is much better. I used long enough bolts to go through the firewall and into blind nuts on the backside.

zrooster

Did you have to install the blind nuts into the firewall, or were they already there?

vertical grimmace

My Feedback: (1)

Here is a video of this plane flying with that engine. Maybe you could PM this guy ( i forgot his name in here) to pick his brain with the set up. If I am not mistaken, he is using a 22-10 prop on this engine. Seems to be a good combo.

https://www.youtube.com/watch?v=AJJdNJoGacU

zrooster

Thanks! Have a 22-10 Xoar (use Xoars on all my 3D gassers) on order from Tower and Fila 21-10 and 20-10 3 Blades on order!

vertical grimmace

My Feedback: (1)

Sounds like your off to a great start. I will be interested to see how this progresses, as I do have 2 airframes that are worthy candidates for this engine. A Giant scale Top flite corsair, and a Holman FW 190 D9.

zrooster

How do you like the Top Flite bird? I've shied away from top flight (and many others) because I'm tired of ironing wrinkly skin! In fact, I'm tempted to glass the wings on the ESM bird when I get it!

vertical grimmace

My Feedback: (1)

My Corsair is a kit. Big box of sticks! It is actually a little ways down on my list, before i get around to that one. The way to avoid wrinkly covering, is to fiberglass and paint! I will never use a heat shrink plastic on any aircraft I build again. Not even a small sport model.

zrooster

Makes sense to me! I wish I had the time and skills to kit build. As it is, I barely have time to put together an ARF...part of the attraction of the ESM bird for me is that they already glassed the fuse for me, at least. Too many time consuming hobbies as it is plus I'm still transitioning from active duty to civilian life and the new commerical job.

ticketec

My Feedback: (2)

Hey guys'

i still lurk around here !! Haven't flown my Dora for at least 3-4months now. Sold my car and bought the wifey a new sports car that doesn't fit models in too well, and have been playing with turbines too much ��

i installed new blind nuts for the firewall. Not a big drama to do.

As as for the prop on the XYZ, I started with the TBM 22x10. I tried a 22x8 but is was really not good at all. Not enough airspeed to make the model comfortable at all. I then changed to a cheapie carbon 22x10 and it was great! For the life of me I can't remember what brand it was because I now have a Zoar 22x10 and its ok, but the carbon prop was better. Unfortunately I dsmaged it when I flipped the dora quite a few months go.

thanks

dave

zrooster

Dave, Appreciate the prop info! Sounds like the xoar 22-10 is about right for my baseline. I'm working on setting up my test stand while I wait for props to show. Per VG's recommendation I'm basing my stand on drawer rollers and a fish scale. If you don't mind, let me know if you have anything to add to Thunder's input on mounting. Seems straight forward...built-up ply with blindnuts...

ticketec

My Feedback: (2)

Yep, It's that straight forward. just ply plates and then re-drilled the firewall to suit the new mounting pattern. as already stated I just reused the original ones off the firewall. just insert the bolt a fwe threads and tap the head of the bolt. the nuts will come away pretty easily.

Might have to go through this thread myself to see if I posted where I bought the carbon prop from. I actually think it may have been HK but I'm not 100% sure.

I posted this video here ages ago but in case you missed it, She has the carbon prop on and the XYZ singing along!

https://www.youtube.com/watch?v=dICM...1BJZcl-jAwIEDw

Thanks

dave

zrooster

Dave,

Great vid! That motor sounds amazing. One thought it inspired is, would a carbon fibre 3 blade (lighter than wood) be light enough that it would compensate for the added weight of the additional material (somewhat...enough?)... The xoar arrived today...so progress continues.

One additional question: What is the approximate thickness of the ply you added?

Also, just want to make a point clear here: I may have come off here as being a bit self assured and overbearing and I want to apologize for that. For those of you in Denver, you might be familiar with the school I attended about 60 miles to the south of you up in the hills...you know...the one with the funny chapel. I suppose those qualities are stereotypical of graduates of that institution! In all humility, I want to point out that anyone can learn to fly, but not anyone can learn to be a good scratch builder. I am confident in my area of expertise, but I am a relative novice in the scale world. I appreciate everyone's mentorship on the subject and hope I can get my hands on one of these ARFs in the near future!

Cheers!
G