Author Topic: New Electric Twin project back on track (Read 149790 times)

Mark Scarborough · « **Reply #100 on:** February 16, 2011, 09:21:00 AM »

and with three props,, you could use smaller diameter props and still have MORE prop disk area,,
hmm that means an even lower slung undercarriage,, wo hoo, can you say low rider

Larry Renger · « **Reply #101 on:** February 16, 2011, 10:18:28 AM »

I seem to have unleashed a Frankenfurter!

PerttiMe · « **Reply #102 on:** February 16, 2011, 10:39:52 AM »

Perhaps this is blasphemy but I was reminded of an Electric Twin R/C project I followed on rcgroups:
http://www.rcgroups.com/forums/showthread.php?t=1075719&page=23

PJ Rowland · « **Reply #103 on:** February 16, 2011, 03:05:29 PM »

Second wind is a phenomenon in distance running, such as marathons or road running (as well as other sports), whereby an athlete who is too out of breath and tired to continue suddenly finds the strength to press on at top performance with less exertion. Some scientists believe the second wind to be a result of the body finding the proper balance of oxygen to counteract the buildup of lactic acid in the muscles. Others claim second winds are due to endorphin production, while still others believe it to be purely psychological.

Sounds like a great name to me.

3 x Prop version? I think you do a twin then progess to 4.. No baby steps.

Dean Pappas · « **Reply #104 on:** February 16, 2011, 03:33:06 PM »

Wait a cotton-pickin' minute here!
I thought the whole point of the twin was to eliminate the trim problems caused by spiral airflow and GP with couterrotating props.
A trimotor ... SIGH

later,
Dean P.

PJ Rowland · « **Reply #105 on:** February 20, 2011, 04:44:29 PM »

Like this you mean??

Would have been a very essoteric name - Second wind is cool.

John Miller · « **Reply #106 on:** February 21, 2011, 09:45:51 AM »

Hey Bob, this project just seems to get better and better. I really like what you're doing. I'm soo looking forward to the flight reports on this one. I hope to be able to see it perform. Have you considered a trip to the NW Regionals?

I also plan on gleaning as much info, from you, on electric twins, for my next Twin PF.

John Miller · « **Reply #107 on:** February 21, 2011, 01:16:03 PM »

Sharp Bob, It's looking good.

It's my good fortune that I live just down the road from both Gordan and Norm. What I hope to learn from you are settings, more towards the motors, and batteries, some esoteric things like which is the best way to set up the counter-rotation, lefty-righty, or righty, lefty.

So far, all the twins I've flown have the props both rotating CCW. So my interest is high on the outcome, knowing how those previous twins have performed with them both going the same way. I'm hoping that my long held assumption that at our sizes, counter rotation is of little benifit, is false

.

Dave Adamisin · « **Reply #108 on:** February 21, 2011, 01:43:05 PM »

Quote from: Dean Pappas on February 16, 2011, 03:33:06 PM

Wait a cotton-pickin' minute here!
I thought the whole point of the twin was to eliminate the trim problems caused by spiral airflow and GP with couterrotating props.
A trimotor ... SIGH

later,
Dean P.

The center motor just needs a C-rot prop. Simple?? Yes I am.....

Howard Rush · « **Reply #109 on:** February 21, 2011, 01:45:46 PM »

Quote from: Bob Hunt on February 21, 2011, 11:30:29 AM

I sure loved the way his Profile Pathfinder Twin flew!

Me too!

Tim Stagg · « **Reply #110 on:** February 21, 2011, 03:06:45 PM »

e-flite 10's huh Bob....I thought I was the only e-flite motor user out there, let me know how they work out for ya

Tim

Larry Renger · « **Reply #111 on:** February 22, 2011, 09:23:13 AM »

gorillabobsrc.com has counter-rotating motor systems in a couple of sizes....

Jim Pollock · « **Reply #112 on:** February 24, 2011, 10:40:39 AM »

And,

I'm supposing Bob's motors will be counter-rotating as well - right Bob???

Jim Pollock

Howard Rush · « **Reply #113 on:** February 24, 2011, 12:46:00 PM »

It will be even more fun when you get the props mixed up and take off.

Darkstar1 · « **Reply #114 on:** February 24, 2011, 12:48:48 PM »

Bob
Does E-flite plan to have spinner cutouts for pusher props for sizes up to 2.5 in.

Larry Renger · « **Reply #115 on:** February 25, 2011, 07:55:30 AM »

How about contra-rotating motor systems for both nacelles. No need to experiment then!

Keith Renecle · « **Reply #116 on:** March 04, 2011, 01:12:43 AM »

Hi Bob, I need to come back to my question that I asked earlier about how do you work out how much power to use on twins or multiple engined stunters. I seem to remember that Dean also said he would give it some thought. Your choice of E-Flite Power 10 motors seems like a good idea. When I checked the specs out on their website, they rate them as .10 glow engines. In C/L terms there is no way that these motors could be rated this way. They weigh 120 grams or so, and the size windings etc. indicate that they would at least be equivalent to a .25 to .30 glow engine.

PW's bomber used 4 x FP.15's but there is no way that multiplying this out to be a single .60 would fly a 2.8 kg. bomber. So, once again, it would be nice to know how you work this out. Maybe Howard has this figured??

Just by the way, what size props did you finally decide to use? Thanks.

Keith R

PJ Rowland · « **Reply #117 on:** March 06, 2011, 02:27:25 AM »

I dont know exactly what the formular is either..

Spitfire was : 6417 Lbs

Lancaster : Empty 36,900 lbs, Maximum Takeoff 68,000

Both aircraft used the Merlin engine..

6417 X 5.6 = 36000

I just weighed a little model built for an OS 19 called an Aerobat. Typical 22 " That weighs 20.5 OZ.
Doing the same maths
20.5 x 5.6 = 114 oz

So in theory that is the same power to weigh to lifting ratio.. - I don't have the required aerodynamic knowledge to explain why - once you go to 4 engines you can carry more weight that you think - and Yes your correct ..

4 x 15 = 60 and there is no way a 60 would pull around a 110oz aircraft.

The Lancaster proved the similar concept - running 4 x 19 = 76 and mine was heavier at 118 - 120 oz Interesting enough - Like PW - I found you can still do maneouvers on 3 engines - 8's squares ect..

The model will also fly on 1 engine - well - staying airborne is flying ..

Perhaps some of the more learned folk out there can expain the answer - Both bombers proved what the full sized counterparts found, that you can carry more weight. - I've read reports that the Lancaster was quite nimble in the air - I found the same - quite surprising..

I've never dabbled in twins - so I am also keen to read the expected answer into how do you select the engine size - and is it a similar ratio for twins as it is for 4's??

Does the math's halve when you run a twin..

Instead of 5.6 times - its reduced to 2.8 ?

Loaded weight: 17,700 lb Mosquito
6417 Spitfire

6417 x 2.8 = 17 967

Interesting............

Going on that theory, im sure you can calculate what you would require.

Keith Renecle · « **Reply #118 on:** March 06, 2011, 05:53:24 AM »

Interesting data........thanks PJ.

Mark Scarborough · « **Reply #119 on:** March 07, 2011, 10:00:21 AM »

I am NOT Bob, but I have thought about twins, ( and more) Were I to want to calculate this, My technique would be simply to look at the watts available for power. Pretty easy with electrics

Dean Pappas · « **Reply #120 on:** March 07, 2011, 10:02:15 PM »

Hello Gang,
Hello Keith,
The more things progress, the more the basics don't change!
Stunters require between 0.6 and 0.7 Watt-hours of energy per ounce of weight to fly the entire schedule. An additional 33% of energy capacity is needed so that the battery is only 75% depleted.
Soo, if Bob builds the COIN/Second Wind/Passed Wind at 58 ounces, then it will require 37.7 Watt-hours to fly the schedule. (I used 0.65)
If he runs a 4S pack at 14.4V then this will result in 2.6 Amp-hours of consumption over 6 minutes. The average current will be 26Amps because 6 minutes is 1/10 hour.
The battery should be 3.5 Amp-hour capacity for safe margin, but some of us will be tempted to run the 3.3 Amp-hour battery at 80% capacity for the weight savings.

One prop ... two props ... three props with contra rotation thrown in, it's simply an energetics problem.
The plane and lines offer drag which depends largely on lap time, and the motor has to drag the ship's weight to the top of the circle the customary number of times per schedule.
Okay, contra-rotating prop assemblies would offer an improvement in efficiency!

Sorry if the math is boring,
Dean

john e. holliday · « **Reply #121 on:** March 20, 2011, 09:52:34 AM »

Bobby is so great. I talked to him at VSC a little. Too many people at times to converse. He told me he is completely sold on electric. I guess being able to fly in the neighborhood at 0700 hours is good. Yes he won Classic again and after the banquet he stated he was told to not bring the same plane again. I think he said it was 9 years old. After my experience again with needle settings maybe electric might be the way to go for all out competition. But, I still like the sound of a good engine run in stunt. I was kind of startled when the electric entry in Classic cast a shadow as it flew over head(really I was outside the circle). I didn't even hear the prop noise. But, Bob asked if I had been keeping up on this twin build. That is why I am here reading it again on Sunday morn before Church. Also waiting for the final result of his Oosama plane(chech spelling) could be Usaama. He is a power house and his little talk after receiving the Keeper Of The Flame Award was inspiring.

Ward Van Duzer · « **Reply #122 on:** March 25, 2011, 12:50:30 PM »

yep Doc,

It was "USA" on the inboard wing, and "AMA" on the outboard!

W.

Howard Rush · « **Reply #123 on:** March 27, 2011, 10:38:23 AM »

Quote from: john e. holliday on March 20, 2011, 09:52:34 AM

Bobby is so great. I talked to him at VSC a little. Too many people at times to converse. He told me he is completely sold on electric. I guess being able to fly in the neighborhood at 0700 hours is good. Yes he won Classic again and after the banquet he stated he was told to not bring the same plane again. I think he said it was 9 years old. After my experience again with needle settings maybe electric might be the way to go for all out competition. But, I still like the sound of a good engine run in stunt. I was kind of startled when the electric entry in Classic cast a shadow as it flew over head(really I was outside the circle). I didn't even hear the prop noise. But, Bob asked if I had been keeping up on this twin build. That is why I am here reading it again on Sunday morn before Church. Also waiting for the final result of his Oosama plane(chech spelling) could be Usaama. He is a power house and his little talk after receiving the Keeper Of The Flame Award was inspiring.

It's Bob that doesn't cast a shadow. You didn't see him near any mirrors, did you? Same deal; he doesn't show up in mirrors.

Airacobra · « **Reply #124 on:** April 04, 2011, 12:52:22 PM »

I love to catch up on this thread Bob. I am excited to see each progression you make on this bird and I can't wait to see the final product. It certainly won't be your average stunter that's for sure.

Mark Scarborough · « **Reply #125 on:** April 04, 2011, 03:54:25 PM »

Quote from: Bob Hunt on April 04, 2011, 01:55:35 PM

Thanks, Keith:

Yeah, I'll be very upset if someone asks me if it's a modified Nobler... $:-\$

Bob

anybody in their right mind can see that its a modified fancherized twister,, I mean come on! really,, sheesh,,,,

seriously, it looks really sharp

Matt Colan · « **Reply #126 on:** April 04, 2011, 05:05:11 PM »

Looking absolutely FANTASTIC Bob!!!! Keep the pictures coming!

Dennis Adamisin · « **Reply #127 on:** April 04, 2011, 05:22:09 PM »

Boldly going where no one has gone before...

Tom Niebuhr · « **Reply #128 on:** April 04, 2011, 05:46:00 PM »

It's a twin. So, it is obviously a modified DC-3!

Looking great Bob. Keep the pictures coming.

PJ Rowland · « **Reply #129 on:** April 05, 2011, 03:57:24 AM »

Looking smooth..

Must be easy being bob hunt........ cruise out win the vsc for the hundredth time, float home, keep working on a simple little project, electric twin with full retract system, and be as cool as ice doing it.

Pure class all the way.

When do you hope to :

A: Start the paint prep work
B: Have it buttoned up for Pre-flight ?

PJ Rowland · « **Reply #130 on:** April 05, 2011, 10:38:37 AM »

HAHA

I'm not really that familiar with the retracts thing - interms of how they intergrate with a model - so It will be interesting to see how they work with your twin and to see them 1st hand.

The perception I get (about you ) is from seeing the work - it looks orderly, organized, clean and consise - with a very slow deliberate methodical approach. Like you have all the time in the world to get things done! - I havent even painted my Nats model yet and I feel Im the only one "behind"

Re: the Pitbull - Thanks

- Its what dad is going to fly in advanced - he likes it - As i wrote - its basically a nobler slightly modified with more of today's thinking design wise.

Hey you can credit a new design revolution .... and steal that from me - after all I stole - blatently I might add the caprice colour scheme just in Green /gold

I often check out this thread - Seeing this ship fly at the Nats is certainly in my top 3 things I want to do a the Nats.

Keep it up ,you continue to inspire everyone.

Bill Little · « **Reply #131 on:** April 07, 2011, 05:10:24 PM »

Like I said before, Bob has finally worked out how to implement Einstein's theory of time......... it just slows down for him.

Watching this project (and knowing that it will be successful beforehand!) is a joy. Everyone knows to look out when Bob gets dedicated to something.

Bill

Dean Pappas · « **Reply #132 on:** April 19, 2011, 03:32:24 PM »

Atsa nice!
Glad to see you put Buddy to work!
Dean

Dave Adamisin · « **Reply #133 on:** April 19, 2011, 03:37:29 PM »

Quote from: Bob Hunt on March 29, 2011, 06:45:53 AM

Hi Howard:

That might have something to do with my cousin, Bram Stoker... $:-\$

Bob Hunt

PS: Thanks, Doc, for the kind words. Was great to see you again in Tucson. - Bob

Stoker or Stroker??

wwwarbird · « **Reply #134 on:** April 19, 2011, 06:16:17 PM »

Very cool plane Bob and it's looking great. Looks like most of the "hard" work is done. Glad to see your back on it. What's your timeframe goal to have it done?

I also caught your Mig 3 mention above. I've always thought that plane would make a super cool model but yeah, gotta keep that sleek nose to have it look "right".

PJ Rowland · « **Reply #135 on:** April 19, 2011, 06:23:41 PM »

What's your timeframe goal to have it done?

4th July I would imagine

PJ Rowland · « **Reply #136 on:** April 21, 2011, 06:01:26 AM »

Twins are a great place to cut your teeth for the more serious multiengine stunters your 1/2 way there.

It looks GREAT - really really impressive- as far as design ,style and cues are concerned, its the best looking most stylish twin I've even seen. ( ive seen a few)

Crist Rigotti · « **Reply #137 on:** April 21, 2011, 06:39:50 AM »

Looking very good Bob.

PJ Rowland · « **Reply #138 on:** April 22, 2011, 07:15:28 PM »

It was meant as a compliment....

Most twins I've seen were scale style jobs...... the french twin at the worlds.. windys' twin's - and a few other twins which escape my mind ( Gordon delaney perhaps... I cant QUITE recall.. ) I think it was called Too much - or Too trouble... Soryr for being vague on that.

What i mean was classical AMA Stunt ships have flowing lines and stylish cue's this is the first time I've seen a twin that takes its styling lines from classical ship shapes. - Very impressive.

wwwarbird · « **Reply #139 on:** April 22, 2011, 07:43:18 PM »

Quote from: Bob Hunt on April 21, 2011, 06:30:57 AM

I'm pretty sure that I'll be happy to stay with twins for a while, although I have given some thought to a tri-motor set-up with counter-rotating props on the motors in the nacelles on the wing and contra-rotating props on two motors in the fuselage (four motors and four props...). Of course a dual pusher-puller contra-rotating setup on the wing (front and back...) one contra-rotating setup in the nose of the fuselage (if you are counting, that would be ten separate motors and props...) might be a doable option.

I want to see someone try to launch that one!

John Miller · « **Reply #140 on:** April 25, 2011, 10:56:48 AM »

Great build sequence Bob. I like your solution for aligning the nacells. You are absolutly corect in paying great attention to the alignments with multi engined stunters.

Gordan came up with a method for doing the alignment, that was slightly different, but worked fine. I don't think his twin would have flown as well if the alignments weren't right.

Allan Perret · « **Reply #141 on:** April 26, 2011, 09:01:15 AM »

Looks like some "seckret potion" you got in that there jar.

Seriously now, you use nitrate or buty to attach the carbon fibre ?
Also can cf be worked around compound curve wingtips (and your nacells in this case), or do you have to piece it ?
Would there be any benefit to putting a layer of cf on top of the silkspan, or is that a bad idea ?

Crist Rigotti · « **Reply #142 on:** April 26, 2011, 09:22:02 AM »

Bob,
What's the little note pad for on the bottom of the holding fixture?

Crist Rigotti · « **Reply #143 on:** April 26, 2011, 09:59:18 AM »

Ahh, I see. I usually keep notes on where I am in regards of how many coats of dope have been applied, etc. The older I get the more notes I use.

Allan Perret · « **Reply #144 on:** April 26, 2011, 12:26:54 PM »

Quote from: Bob Hunt on April 26, 2011, 09:23:17 AM

I do not see any need to put CF over the silkspan on the covered wing. I do, however, carbon the entire wing prior to covering with silkspan. I remove the carbon from the open bay areas by sanding against the edges of the cap strips and the wing framing (LE and TE sheeting) to insure that there are no "sharp" edges that might later cut though the silkspan. The carbon adds very little in weight and it adds tremendous strength. I know that others do not believe that the carbon adds much strength. I feel that it adds a lot of torsional rigidity to the airframe. I also feel that all the planes I've covered with the .2 ounce carbon mat fly better in the wind than did models that I've owned that were not carbon covered. The carbon adds much stiffness.
Later - Bob Hunt

I was thinking a layer of cf on top of the silkspan would add a lot of puncture resistance for a small weight gain. I recently got careless while handling one of my models and poked a hole in it, and it is covered with polyspan (regular).. I tried the lite version of polyspan a while back after talking with you, but I didnt like it. Took too many coats to get it filled, seemed like more work for little if any weight saving. Why did you choose silkspan for the twin vs polyspan ?

Matt Colan · « **Reply #145 on:** April 26, 2011, 03:42:24 PM »

Bob this plane is so cool to read about and all the cool things about it!!! I'm really anxious to hear how the gear are going to retract!

John Paris · « **Reply #146 on:** April 26, 2011, 05:02:29 PM »

By the way, my good friend, Rich Giacobone gave me a bunch of Kim Chi jars (Kim Chi is a type of Korean Cole Slaw) that have extremely wide openings. They are just perfect for our use as dope jars. It's very easy to fill the brush and clear the top of the jar.

Later - Bob

[/quote]

Bob,
That particular jar held a medium sized radish "kimchi". A lot chunkier than cole slaw, plenty of spice and pretty delicious.
John

wwwarbird · « **Reply #147 on:** April 26, 2011, 06:12:04 PM »

Looking good Bob! It's always one of the most satisfying parts of a build when you're finally able to permanently attach the major components and it starts to look like an airplane.

Maybe I missed it elsewhere, is that Polyspan on the open bays?

wwwarbird · « **Reply #148 on:** April 26, 2011, 06:29:42 PM »

10-4 Bob, I'll be watching. Even though it's "only" electric, it's still really cool!

I'm just taking a break myself at the moment between the final coats of clear on my Umland "Super Combat Streak", another satisfying step!

Allan Perret · « **Reply #149 on:** April 26, 2011, 06:58:38 PM »

Quote from: Bob Hunt on April 26, 2011, 01:38:47 PM

I'm pretty sure you would be sorry that you covered over silkspan or Polyspan with carbon.

Why is that, because of the extra weight ?

Author Topic: New Electric Twin project back on track (Read 149790 times)

Dave Adamisin

Dave Adamisin