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General control line discussion => Open Forum => Topic started by: Crist Rigotti on May 07, 2020, 07:04:25 PM
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I built a Walter Umland Sakitumi over the last month. First stunter I've built in 3 years. Looks like the weather will cooperate this Saturday for first flight.
Some stats:
Wing span: 55.5"
Wing area: 621 sq/in
Weight: 45 1/2 ounces with battery ready to fly
Solid and transparent Monokote used
Bad Ass 3515-710 motor
Spin 44 esc
Igor's active timer
Dinogy 6S 1800mah battery which weighs 260 grams.
Some mods I did was to move the canopy forward, lengthen the nose about an inch, and added a little more sweepback to the fin trailing edge. Made the fuselage 3/4 inch wide.
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Looks great! I assume that this the plane that you are talking about on the line length thread.
How about a few more shots of the nose with some detail on battery and electronics installation. How/where is the active timer/sensor?
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How's this:
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Looks great Crist!
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How's this:
Looks great! So, question, have you tried replacing the JJ 12AX7s in the motor controller output amp stage with NOS Telefunken ECC-83s? Howard says it works about the same, but the pre-launch beeps are much more engaging and not nearly as gritty.
Brett
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Hi Crist! Good to see you re-engaged with it. I hope you're all well and safe, love to seeya sometime.
Will H^^
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Very nicely done Crist, hope to see you and it in the circle sometime somewhere.
Blessings
Allen
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Hi Crist! Good to see you re-engaged with it. I hope you're all well and safe, love to seeya sometime.
Will H^^
Thanks Will. I'm planning on making the NATS, and of course FCM along with some other Midwest contests.
We are all well and safe. All the best.
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Very nicely done Crist, hope to see you and it in the circle sometime somewhere.
Blessings
Allen
Thanks Allen. We'll see you at the NATS and FCM for sure.
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Looks great! So, question, have you tried replacing the JJ 12AX7s in the motor controller output amp stage with NOS Telefunken ECC-83s? Howard says it works about the same, but the pre-launch beeps are much more engaging and not nearly as gritty.
Brett
I'll leave that mod up to Howard! Though I do miss the glow from those 12AX7's!
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Crist, very tidy electronics with the shortened leads and the direct plug into the ESC, like your previous. Do you expect any difficult is leveling/keeping level the sensor? It looks secure enough on your super grip.
A reverse pitch prop if I see correctly? What pitch and what rpm range are you aiming for? Yes, that will be line length dependent, so maybe Brett will re-engage and help.
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Looks nice Crist, hope to see it at a contest this year.
James
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Crist, very tidy electronics with the shortened leads and the direct plug into the ESC, like your previous. Do you expect any difficult is leveling/keeping level the sensor? It looks secure enough on your super grip.
A reverse pitch prop if I see correctly? What pitch and what rpm range are you aiming for? Yes, that will be line length dependent, so maybe Brett will re-engage and help.
I don't expect any difficulty at all.
Yes reverse pitch prop...for now. I have a special tractor prop I'm going to try once it gets trimmed out. Right now it has a APC 13x5.5EP cut down to 12 inches.
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Looks nice Crist, hope to see it at a contest this year.
James
Thanks James. Maybe next month in St. Louis!
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Hi Crist,
Long time no see. I love your Sakitumi, it is a surprisingly good flying airplane, I am sure you are going to like it. With all the Igor stuff in there, it should be awesome.
Wayne and I built one about 5 years ago (I've attached a photo below), the only real change we had to make was to the elevator control horn. The one in the kit was average in length and the control response was off the chain. We ended up using a radio control aileron horn that we could screw up and down to find just the right length. I'm not sure why it was like that, it might have been tail heavy, we were running a 5S 3300 MaH battery in the front, but it is a short nose and it was before we knew to move the CG forward for electric, so maybe it was tail heavy. Tail heavy or not, once we got the long horn on there, it was a pretty awesome flyer.
We went to Joe Nall a few years back and we both flew the Sakitumi. We also talked Derek Barry into flying it in profile as well. That dirty dog ended up beating both Wayne and I with our own plane. Hah . . . it was great fun.
We ended up dorking it somewhere - don't even remember why, not too bad, so we gave it to Will Davis who fixed it up and is flying it still to the best of my knowledge.
I hope you have a lot of fun with it and will look forward to hearing how it flies - Jim Smith
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Hi Jim,
Thanks for the kind words. My CG is at 20%. about 1/2 inch aft of the plans CG at 15%. I'm using an aluminum elevator horn with the push rod set at 1". The bell crank end is at 3/4" per plan. It does seem to have a lot of elevator throw. I'll fly it tomorrow for the first time so we'll see.
Yeah, I hate to get beat by my own airplane too! Reminds me of a story. During one of the NATS that Paul Walker was the ED, I had entered my profile electric airplane. After it was over Paul asked if he could fly it. He did a nearly 40 point take off and during the first pullout of the RWO, he said "Oh", and then proceeded to put up the best flight that airplane ever did by a wide margin! At least a 500 pointer! So good my buddies said that that would be the best flight the airplane will ever fly! They were right.
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Love you color scheme on your Sakitumi. I see you followed the unwritten rule that you must use transparent film on a Sakitumi wing to show it great internal rib structure. LL~
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Love you color scheme on your Sakitumi. I see you followed the unwritten rule that you must use transparent film on a Sakitumi wing to show it great internal rib structure. LL~
Yeah, I saved about 3/4 ounce over solid color Monokote!
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Crist,
What are you using to hold your sensor in place under the wing? Nice looking airplane.
Thank you,
John
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Yeah, I saved about 3/4 ounce over solid color Monokote!
It's wild what a weight difference the solid colors vs transparent colors have!
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Crist,
What are you using to hold your sensor in place under the wing? Nice looking airplane.
Thank you,
John
3M Dual Lock
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It's wild what a weight difference the solid colors vs transparent colors have!
y1
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Nice looking ship, Christ!
Best of luck with it.
Tom
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Thanks Tom.
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Crist,
I see the master craftsman has created another beautiful airplane. It looks great! Congratulations.
Looking forward to seeing you this summer and getting in some "friendly" flying competition(and lie swapping) >:D
Best regards,
DennisV
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What battery are you using? Very nice and neat.
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Sanitary is the only word I can think of.
great job.
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Christ,
Very nice looking ship!
Thanks
Joe
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Crist,
I see the master craftsman has created another beautiful airplane. It looks great! Congratulations.
Looking forward to seeing you this summer and getting in some "friendly" flying competition(and lie swapping) >:D
Best regards,
DennisV
Thanks Dennis. Yeah, I'd like to get in some "friendly" competition and lie swapping for sure.
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What battery are you using? Very nice and neat.
Dinogy 6S 1800mah
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Sanitary is the only word I can think of.
great job.
Thanks Warren.
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Thanks Joe. See you at the NATS?
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Crist,
Yes we will be at the NATS!
Joe
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I built a Walter Umland Sakitumi over the last month. First stunter I've built in 3 years. Looks like the weather will cooperate this Saturday for first flight.
Some stats:
Wing span: 55.5"
Wing area: 621 sq/in
Weight: 45 1/2 ounces with battery ready to fly
Solid and transparent Monokote used
Bad Ass 3515-710 motor
Spin 44 esc
Igor's active timer
Dinogy 6S 1800mah battery which weighs 260 grams.
Some mods I did was to move the canopy forward, lengthen the nose about an inch, and added a little more sweepback to the fin trailing edge. Made the fuselage 3/4 inch wide.
Crist,
Really nice job and incredible low weight. Congratulations.
Is the Jeti spin 44 going to get you through the pattern? I know it's half the weight of the 66.
I went on line and eyeballed the Badass offerings. Stuff looks great! So, good choice.
Good luck with your new model.
Charles
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There's just something about trans red monokote ,,,
This is the .25 Saki but the same "trans monokote" rule applies. These are great flyers at any size, you will have a ball with yours. Needs a hollow Igor 3-blade though.
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Looks awesome Crist!
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Crist,
Really nice job and incredible low weight. Congratulations.
Is the Jeti spin 44 going to get you through the pattern? I know it's half the weight of the 66.
I went on line and eyeballed the Badass offerings. Stuff looks great! So, good choice.
Good luck with your new model.
Charles
Thanks Charles. The Spin 44 is plenty of ESC for the weight of the model. My average current is about 16 amps.
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There's just something about trans red monokote ,,,
This is the .25 Saki but the same "trans monokote" rule applies. These are great flyers at any size, you will have a ball with yours. Needs a hollow Igor 3-blade though.
Yeah, transparent Monokote rules the Sakitumi's!
Not so sure I want to spend that kind of money on a prop....yet.
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Looks awesome Crist!
Thanks Steve.
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I flew it this morning. After getting the lap speed to 5.2 on 62 foot line eye to eye and the handle neutral, I started to see what it can do.
The model is tail heavy at 20% CG. I added about 1 1/2 ounces to the nose and it was much better.
The elevator as set up per the plan is way to twitchy for me. 3/4 bellcrank pivot. My handle line spacing is at the minimum and the elevator push rod is at 1 inch from the hinge line. There it was much more comfy. I'll install a longer elevator horn and increase the handle spacing some. If I were to build another one, I would increase the stab area and decrease the elevator area the same amount and use a 1/2 to 5/8 bell crank pivot for the push rod.
The 6S 1800mah batteries might not cut it in the long run. After 2 full pattern flights, I put back in 1550mah average between the 2 flights, which is 86% of the battery capacity. Even with the more efficient BA motor. Not real happy about that. I thought that I would use about 1350mah (75%) for a full pattern. Looking for options right now.
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Hey Crist,
You can easily go to a larger battery since you had to add 1.5 oz to nose anyway, this way that nose weight will at least serve a purpose other than compensating for what could have been designed out. I think someone here asked if you had lengthend the nose, must be someone familiar with the Sakitumi.
Maybe Walter will see this and make a few minor changes. A longer nose would help align the CG in a better place. We used a 5S 3300 MaH battery and physical space was an issue as well. I can’t remember if Walter makes it as an electric model kit or glow.
I like your idea about changing the stab to elevator ratio. I remember as a kid our Dad started Wayne and I off with Ringmasters (Sterling used to put some gosh awful wood in their kits) and then graduated us to Top Flite Flite Streaks (McCoy Red Head .35). Lol . . . we didn’t get to have Fox .35’s until we could complete the AMA pattern and we wore out those McCoys in one summer. It always amazed me as an eight year old how the Streak could do any maneuvers with such a little elevator compared to the gigantic one on a Ringmaster.
Keep the flight reports coming. One day maybe I’ll get to see it fly, that would be awesome. Not sure if Wayne and I will attend the Nats this year with the Covid-19 crap still hanging around. I’m not so worried about the folks in Indiana, but the Nats draws people from all over, many from hot spot areas. I know it is likely a small risk, but that virus is no joke for susceptible people, particularly those not aware they are susceptible. Since mass testing is not quite here yet, it is somewhat problematic.
Just waiting to hear what AMA says on June 10th. Not sure I want to be at appearance judging with 100 of my best friends who may not even know they are asymptomatic. We had a young police officer here die from it because he was unaware of a condition he had. Lol . . . I hate the Chinese communists.
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(McCoy Red Head .35). .....and we wore out those McCoys in one summer.
It took the whole summer? I used to get about 50 good/great runs after break in which took FOREVER! LL~
Ken
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Wow! Beautiful ship Crist! Typical of your outstanding workmanship and attention to detail. It is what a model should look like. Very glad to see you back at it.
Brother Bob
Thanks brother!
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Hey Crist,
You can easily go to a larger battery since you had to add 1.5 oz to nose anyway, this way that nose weight will at least serve a purpose other than compensating for what could have been designed out. I think someone here asked if you had lengthend the nose, must be someone familiar with the Sakitumi.
Maybe Walter will see this and make a few minor changes. A longer nose would help align the CG in a better place. We used a 5S 3300 MaH battery and physical space was an issue as well. I can’t remember if Walter makes it as an electric model kit or glow.
I like your idea about changing the stab to elevator ratio. I remember as a kid our Dad started Wayne and I off with Ringmasters (Sterling used to put some gosh awful wood in their kits) and then graduated us to Top Flite Flite Streaks (McCoy Red Head .35). Lol . . . we didn’t get to have Fox .35’s until we could complete the AMA pattern and we wore out those McCoys in one summer. It always amazed me as an eight year old how the Streak could do any maneuvers with such a little elevator compared to the gigantic one on a Ringmaster.
Keep the flight reports coming. One day maybe I’ll get to see it fly, that would be awesome. Not sure if Wayne and I will attend the Nats this year with the Covid-19 crap still hanging around. I’m not so worried about the folks in Indiana, but the Nats draws people from all over, many from hot spot areas. I know it is likely a small risk, but that virus is no joke for susceptible people, particularly those not aware they are susceptible. Since mass testing is not quite here yet, it is somewhat problematic.
Just waiting to hear what AMA says on June 10th. Not sure I want to be at appearance judging with 100 of my best friends who may not even know they are asymptomatic. We had a young police officer here die from it because he was unaware of a condition he had. Lol . . . I hate the Chinese communists.
Yeah, that's the plan I'm looking at. Going to a 6S 2200mah battery. The added weight will work out just about right. The big problem is finding them at a reasonable price. I like Rhino and Zippy Compact batteries but HK is out of stock right now. Hyperion is having a good sale on their Graphene HV Lipos but the word is that HV lipos in general don't last very long. Of course I'll be using them in the 4.2 volt mode. Anybody have any experience running HV Lipos in the LV mode?
Next good day of flying looks like Monday. I did extend the elevator horn to 1 1/4.
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Yeah, that's the plan I'm looking at. Going to a 6S 2200mah battery. The added weight will work out just about right. The big problem is finding them at a reasonable price. I like Rhino and Zippy Compact batteries but HK is out of stock right now. Hyperion is having a good sale on their Graphene HV Lipos but the word is that HV lipos in general don't last very long. Of course I'll be using them in the 4.2 volt mode. Anybody have any experience running HV Lipos in the LV mode?
Next good day of flying looks like Monday. I did extend the elevator horn to 1 1/4.
LiHV is a different composition. So if you only charge it to 4.2v per cell, you're not going to get the correct run time. It's the same as only charging your regular batts to 4.0v per cell. I run LiHV batteries all the time in my "other" hobby.
Maybe look into, pyrodrone.com
This one is like 45 bucks. The GNB line is exceptional quality also.
https://pyrodrone.com/collections/batteries/products/pyro-drone-graphene-2200mah-6s-22-25v-75c-by-who-cares
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TP has a 6S 2250. But at $73 it ain't cheep. However they do run a sale once in a while. Unfortunately the PROLITEX SERIES 25C does not come in a 6S. The PROLITEX SERIES 25C seem to be the battery of choice in a 4S setup.
https://www.thunderpowerrc.com/collections/2250-mah-1/products/tp2250-6se55
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AliExpress has many 6s2200 batteries for around $35 +/- https://www.aliexpress.com/w/wholesale-lipo%206s%202200mah.html
Banggood has several offerings as well. https://usa.banggood.com/URUAV-22_2V-2200mAh-65C-6S-Lipo-Battery-for-RC-Racing-Drone-Helicopter-p-1570517.html?utm_source=googleshopping&utm_medium=cpc_organic&gpla=1&gmcCountry=US&utm_content=shopping&utm_campaign=usg-pc¤cy=USD&createTmp=1&utm_source=googleshopping&utm_medium=cpc_bgcs&utm_content=frank&utm_campaign=pla-usg-all-pc&cur_warehouse=CN
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Hey Crist: Fantastic looking plane, You and your family Stay safe!!
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n~ n~ n~ Holy cow, put an FP or LA on it and go have a blast. VD~ ;D
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Hey Crist: Fantastic looking plane, You and your family Stay safe!!
Thanks Lee. You keep safe too.
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n~ n~ n~ Holy cow, put an FP or LA on it and go have a blast. VD~ ;D
How long can you hold your breath. Hope you and the gang are doing well.
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I built a Walter Umland Sakitumi over the last month. First stunter I've built in 3 years. Looks like the weather will cooperate this Saturday for first flight.
Some stats:
Wing span: 55.5"
Wing area: 621 sq/in
Weight: 45 1/2 ounces with battery ready to fly
Solid and transparent Monokote used
Bad Ass 3515-710 motor
Spin 44 esc
Igor's active timer
Dinogy 6S 1800mah battery which weighs 260 grams.
Some mods I did was to move the canopy forward, lengthen the nose about an inch, and added a little more sweepback to the fin trailing edge. Made the fuselage 3/4 inch wide.
Crist,
Thank you for igniting my interest in the BadAss motors. I took a look at their offerings. They have plenty of information on their website, text and drawings.
You selected the 3515 and I'm curious as to why? Unless my findings are incorrect, the 2826 would also do the task. You're model is light, really light. Also a 4cell 3300 may be a bit lighter unless you needed the nose weight for balance? Is the 2826 and a 4 cell 3300 a good match?
My Stuka is at 49 oz and I believe the 2826 can do the trick, unless I missed something, which is my question.
Did I miss something?
Charles
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Crist,
Thank you for igniting my interest in the BadAss motors. I took a look at their offerings. They have plenty of information on their website, text and drawings.
You selected the 3515 and I'm curious as to why? Unless my findings are incorrect, the 2826 would also do the task. You're model is light, really light. Also a 4cell 3300 may be a bit lighter unless you needed the nose weight for balance? Is the 2826 and a 4 cell 3300 a good match?
My Stuka is at 49 oz and I believe the 2826 can do the trick, unless I missed something, which is my question.
Did I miss something?
Charles
Charles,
I chose the 3515 because that is what I'm currently running in my other profile and my full fuse stunt ship, both around 580 sq/in. The reason I'm running a 3515 in my full fuselage stunt ship is that I found here in the Dallas heat, the 2826 was running a little too hot. BTW, a characteristic is that they just run hotter than the 35mm motors. So I'm running a 3515 Cobra or BA is that simply they run cooler than a 2826. Yes, a 2826 or even smaller will/might do for the Sakitumi. Since all my models use a 35mm motor, it is easy to use a component from another ship if I have to.
According to my ECL spreadsheet a 46 oz airplane with a motor run for 5.4 minutes:
3S = 3650mah battery
4S = 2700mah battery
5S = 2200mah battery
6S = 1800mah battery
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Charles,
I chose the 3515 because that is what I'm currently running in my other profile and my full fuse stunt ship, both around 580 sq/in. The reason I'm running a 3515 in my full fuselage stunt ship is that I found here in the Dallas heat, the 2826 was running a little too hot. BTW, a characteristic is that they just run hotter than the 35mm motors. So I'm running a 3515 Cobra or BA is that simply they run cooler than a 2826. Yes, a 2826 or even smaller will/might do for the Sakitumi. Since all my models use a 35mm motor, it is easy to use a component from another ship if I have to.
According to my ECL spreadsheet a 46 oz airplane with a motor run for 5.4 minutes:
3S = 3650mah battery
4S = 2700mah battery
5S = 2200mah battery
6S = 1800mah battery
Crist,
What a guy!! Thanks for the information and reply.
Will you be leaning towards the Cobra in the future with other purchases or the BA?
Thanks again.
Charles
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Crist,
What a guy!! Thanks for the information and reply.
Will you be leaning towards the Cobra in the future with other purchases or the BA?
Thanks again.
Charles
Let me run the BA for awhile before I answer that.
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Here's an update after 2 more flying sessions.
I used a heat gun to slightly twist the wing to get the wings level. And I mean slightly.
I had 3/4 oz tip weight to start with and removed 1/4 oz. Much better.
Fabricated a new elevator horn. The old horn had the holes lined up with the hinge line but was not 90 degrees to the push rod. So it gave me more down than up. Made a new horn that is 90 degrees to the push rod and has the holes lined up with the hinge line.
Went with a 11 1/2 inch prop instead of 12 inches. Battery draw after a 5 1/2 minute flight is anywhere from 1400 to 1450mah. Or 78 to 80%.
Still has the 2 ounces of nose weight. New batteries have been ordered.
The airplane is flying decent now with only 1 exception. And the is the 3rd corner of the Hourglass. The outboard wing drops during the corner. It drops enough so I can see the bottom of the outboard wing. Even when I go easy on that corner it still drops, not as much when I hit hard , but still drops. Everywhere else in the pattern the airplane handles well. Any ideas as to the cause and fix would be appreciated.
The overall thoughts are it is a very good flying airplane with a very nice corner. Unfortunately, it suffers the fact that in a nice square corner, it does not want to stop turning. A common problem with flapless stunters. I found myself overturning most square corners because of this.