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Author Topic: Conversion of Dumas, Comet, Herr and Guillow rubber band kits to R/C - General  (Read 17966 times)
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mikempp
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« Reply #50 on: May 31, 2013, 08:56:25 PM »

we sure are lucky to have all the small RC stuff/motors and batteries we didn't have not long ago.
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davidchoate
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« Reply #51 on: September 17, 2014, 09:32:41 AM »

I got pretty good at building and linking up Rd control, but need now help on choosing the correct motor/battery/prop recipe. How do you guys with more experience do it?
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Konrad
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« Reply #52 on: September 17, 2014, 10:25:44 AM »

Watts per pound is usually the first criteria I use. In the old days I was often forced to go as low as 35 watts per pound. This gave very scale like performance (read flew like a dog) for general aviation aircraft. I sometimes start with 50 to 75 watts per pound. This gives some leeway for poor piloting (cross controls and uncoordinated turns). I like the 75 to 100 watts of power. This will allow me to perform loops rolls and most aerobatic maneuvers without first diving to gain speed. It also keeps the weight down for nice predictable landings. I have to add that I really like to do touch and goes. A lighter wing loading really helps with the slow flight regime.

I like to select a prop that allows for a pitch speed that is at least 2.5 time the stall speed. I then select a prop diameter that keeps the current under the rating of my equipment all the while keeping an eye on my watts count.

This is an approximation I use to find the stall speed of our models on paper. I got this Keith Shaw one of the pioneers of scale electric flight. Sorry for the english units.

Stall speed = 3.7 * square root of wing loading

speed in mph
wing loading in oz/sqft


Dave,
I don't know for sure what you are building but I think it is a Guillow series 300 model. Today I would look to power mine with 2 cell 250 mAh 25c battery, A 10 to 15 gram outrunner motor with less that 2300Kv, a 5 x4.3 prop for a 2000 Kv motor and a 6 amp speed controller with BEC.

I and many other have also used some of the 2 cell E-Flight UMX model guts with great success in the 18" to 25" wing span models.

Start a thread with your build and we might be able to give you specific recommendation.

All the best,
Konrad
« Last Edit: September 17, 2014, 11:46:29 AM by Konrad » Logged

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FranciscoB
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« Reply #53 on: November 18, 2014, 03:02:52 PM »

As my first attempt at RC, I'll be building this one and convert it to a 3 channel. I will be using the electronics from a WL Toys F939 (not sure about the propeller):

http://www.outerzone.co.uk/plan_details.asp?ID=758

Therefore, this  thread as been a great help and I'd like to thank you all for your input.

I've been building static models for over a decade and am confident enough to tackle a rc conversion of a balsa kit. I have built a couple of rubber-band Veron planes and this doesnt look very different. Not sure what kind of hinges I should use nor about motor positioning angle...
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« Reply #54 on: November 18, 2014, 11:37:22 PM »

While I'm sure you can build one of these models. I have to warn you that they make very bad R/C trainers! Their size and weight make them fast and not very durable.

I use the iron on film as the hinge. Some have had good results using some old floppy diskette for the old hays of computers. Then there is the old way of sewing a figure 8 hinge with a silk (kevlar) thread.

I use 3° to 4° down thrust and 2° to 3° of right thrust as a starting point for motor angles.

All the best,
Konrad
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FranciscoB
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« Reply #55 on: November 19, 2014, 08:19:48 AM »

Thank you for your input. I'm training with a 33" span, blue-foam electric glider similar to:

http://www.onesheetkits.us/index.php/products/osg/

However, I really enjoy working with balsa. The possibility of building "scale looking" planes or other popular designs from plans is exciting in itself.
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Konrad
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« Reply #56 on: November 19, 2014, 10:44:09 AM »

Sorry, I can't see that plan you link to on outerzone.

That glider should make a good slow trainer.

In general  find that these rubber band conversion models make a good 3rd RC model.

I share your passion for balsa.
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« Reply #57 on: November 19, 2014, 12:26:45 PM »

Sorry, it's this one from Veron, the Aeronca Champion:

http://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=799&mode=search

I have built Veron's Comper Swift and found their plans are clear and easy to follow, with all formers ready to transfer to the wood, etc..
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Konrad
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« Reply #58 on: November 19, 2014, 03:27:10 PM »

Looks to be a good project.
Please do post a building thread. I'm sure there will be folks that are interested and willing to help.
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daveh
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« Reply #59 on: December 28, 2014, 04:35:39 PM »

On the subject of control surface hinges, I have found that plastic tracing film bought from local art shops works well. I simply cut slots in the trailing edges of the wings, tail or fin and insert pieces of film about 8mm square then add a few dabs of CA; the slightly rough surface of the tracing film helps the CA fix it firmly in place. After cutting corresponding slots in the control surfaces they are positioned on the hinges, held in their full deflection positions and a few more dabs of CA applied (I use a thin piece of wire dipped into a couple of drops of CA on a piece of polythene to control the amount of CA). The CA both fixes the hinges in place and strengthens the wood around them. I have used this method on models ranging from an electric R/C Frog Tomtit with 1/16 sheet tailfeathers (being very careful cutting the 4mm deep slots) through KK Eaglets, Frog Goblin, West Wings Hawker Hart and some ODs from 18in to 30in spans up to a 36in span motorised glider. Some of these models, including the 36in span one, have been flying for over 5 years and have made at least a couple of hundred flights. One of the main advantages of the method for scale models is the absence of visible hinges and for small models there is very little resistance to control deflection - I generally use 1.7 gram linear servos and they are not strained in any way.

Hope this is of interest.

Dave H   
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« Reply #60 on: December 28, 2014, 07:17:48 PM »

Thanks Dave, and welcome to HIP.
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« Reply #61 on: January 26, 2015, 05:02:42 PM »

Hi all,I'm new to the forum. Although I've been flying R/C since 1969 I've just started with "Indoor R/C" . I'd like to build a high wing scale model with a wingspan of about 17 to 20 inches. I'm planning on using 3 Nano servos,a micro receiver,and an ESC. Any hints on which would be a good model to start with and what motor/esc/prop combo? Great Forum BTW...Phillyskip
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« Reply #62 on: January 27, 2015, 03:47:46 PM »

Phillyskip,

For simplicity I reckon you can't go wrong for a model that size using Parkzone's AR 6400 or 6410 receiver, which has a built-in brushless ESC and two linear servos, with one of their AS2000 servos if you need more than 3 channels, and a PKZ3624 brushed motor/gearbox unit as used in the UM P51 etc. I've had success using this setup in models such as the old Keil Kraft Eaglet and Frog Goblin kits, both 24 inch span, the little 18 inch Frog Tomtit biplane, an 18 inch scale OD of an Eastbourne monoplane and the Golden Age repro 25 inch Curtiss Robin. The equipment I described is easy to obtain, simple to use, and with a 240 mAh LiPo battery I get a good 8 minutes flight if just cruising or 5 minutes if doing aeros outdoors with the Tomtit.

Hope this is of use.

Best wishes

Dave 
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« Reply #63 on: January 27, 2015, 04:13:51 PM »

Thanks Dave I much appreciate your response. I didn't think anyone was listening to me....Smiley I was thinking of using the Park Zone stuff,but I use a HiTec Optic 6 Tx and I don't think they're compatible. Please correct me if I'm wrong. Anyway,  this is the equipment I have on hand and will probably be building a plane larger than I originally planned. I haven't decided on the plane yet. Here's what I have: 1400kv brushless out runner motor to turn a 6 to 7inch prop,a Hitec Minima receiver,a 10 amp ESC,3 HiTec Nano servos and a 2S 250ma Lipo battery. Since you're now my hero what would you build with this equipment in mind? Again thanks for your response.....Phillyskip
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daveh
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« Reply #64 on: January 27, 2015, 05:20:52 PM »

Phillyskip,

Having been strictly a free-flighter until I decided that over the years I'd had enough of climbing trees, fighting my way through hedges and exploring the rougher parts of the countryside in order to recover models (as well as losing models into the blue yonder), I only came to R/C (or radio assist) a few years ago during the 2.4 GHz revolution and adopted Spektrum gear. Hence I'm not sure about the equipment you describe. Regarding the Tx/Rx/servo combo though, the only real effect it is going to have on your choice of model is weight. There are lots of very detailed and complex calculations for the sort of models any particular motor/prop/battery combo will fly but for the sort of sport/scale models I am interested in I think that the simple watts per pound rule of thumb suffices. Basically you need at least 50 watts per pound of model weight with the following rough guide: 50 to 80 w/lb for powered gliders, slow flying sport and scale; 80 to 120 w/lb for faster and more 'sporty' models getting into aeros etc.; and 120 to 180w/lb for advanced aeros or EDF jets. Above that we are getting into electric Saturn V country. The other way of assessing suitable power plants is to make sure that the static thrust your motor/prop/battery produces is at least 33% of the model weight going up to 80% or more for the above categories. Hence, for your motor you will need to find out the power output using a 7.4 volt battery and/or the static thrust with various props (remembering that whatever prop you use must not result in the motor exceeding its rated amperage). Therefore you really need to get the performance characteristics for your motor from the manufacturers or to ask whether anyone on the site has the figures. Quite a few of the manufacturers or retailers have these details on their web sites. Personally, I always start by taking a rough guess at the eventual weight of the model then looking at the different motor/prop combination figures on web sites such as Micron Radio Control (for indoor and small models) or Robot Birds and building up from there. They are UK firms but there are lots of US manufacturers and retailers you can explore. I've also found that the better retailers are generally very helpful and willing to advise on such matters and I guess that a few more queries on different threads of this site would bear fruit from those far more expert than me.

I'm sorry not to have been more specific in answering your query but I hope that the above is of some use.

Dave

PS  Forgot to ask - do you have any more details of your motor type, maker etc?

   
 
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« Reply #65 on: January 28, 2015, 11:02:08 AM »

Thanks Dave I much appreciate your response. I didn't think anyone was listening to me....Smiley I was thinking of using the Park Zone stuff,but I use a HiTec Optic 6 Tx and I don't think they're compatible. Please correct me if I'm wrong. Anyway,  this is the equipment I have on hand and will probably be building a plane larger than I originally planned. I haven't decided on the plane yet. Here's what I have: 1400kv brushless out runner motor to turn a 6 to 7inch prop,a Hitec Minima receiver,a 10 amp ESC,3 HiTec Nano servos and a 2S 250ma Lipo battery. Since you're now my hero what would you build with this equipment in mind? Again thanks for your response.....Phillyskip
On first read your equipment is on the heavy side for modern conversions of the sub 20" ships. What you show would work rather well in the 24" to 30" sized ships but might be a bit fast for indoor work. Can you give us some more details as to exactly what you have brand name and size of the motor and 10 amp ESC? What you post doesn't tell us much. The weight of your components would help us a lot. Have you any specific models in mind?

Unless you are building a gossamer type model I don't like to recommend the smaller Spektrum linear servos. I have used the Spektrum SPMSA2030L 2.3 gram linear servo with some success in the sub 24" models (less than 80 grams). Please be aware that these do not use the standard servo connectors but rather the JST-SHR (1.0mm) connector. You can read about some of trials with the smaller servos here.
http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=11737.0

Hitec Optic 6 on 2.4gHz protocols are NOT compatible with the Spektrum/Parkzone DMS2/DSMX Rx protocols. Now as I think the Hitec Optic 6 is a moduled radio you might be able to buy an after mark Tx module that is compatible with the DMS2/DSMX protocols. http://hobbyking.com/hobbyking/store/__1120__1117__Radios_Receivers-OrangeRx_Transmitter_Modules.html
I don't know if the Optic has channel mapping or not so the output might not match the control input for the rx and servo "brick". I'll leave it up to you to research the details on adding a DSM2/DSMX module.

Since you have been in the hobby for some time, I'd like to recommend that you look at this radio FrSky Taranis.
http://www.alofthobbies.com/radio-gear/frsky-transmitters.html


Most of my gummy band to R/C conversions fly on 7 to 15 watts (Amps x Volts).
As to power density, most models can fly at 35 to 50 watts/pound in a very scale cub like manner. 50 to 75 watts/pound gives more of a sport/Sunday type flying experience.  75 to 100 watts/pound gets you into good aerobatic flight (dives not needed to perform a loop). 100 plus watts/pound is in the insane realm, vertical and post stall maneuvering range known as 3D flight.

All the best,
Konrad



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« Reply #66 on: January 28, 2015, 02:43:47 PM »

Konrad thanks for taking the time to respond. The all up weight of my motor,esc,receiver,battery,and 3 nano servos is 65 grams. The motor according to the seller can turn a 6-7 inch prop, it's rated at 60 [email protected] 1400kv. To be perfectly honest I'm not interested in buying anymore "gear" as I have enough stuff already,but do appreciate your suggestions.

I'm thinking that a plane the size of the Guillows Fairchild 24 or the Dumas Eindecker(30inch) might be worth looking into. Another plane that we use to fly outside on .049s is called the Luton Minor....It flew well and would adapt to indoor flying as it was able to turn very tightly without falling off on a wing on 3 ch.operation.

I was also thinking about the large Guillow Stuka or Hellcat....As I did build both of them for R/C years ago using a GMark .061 engine and 4 Cannon Micro Servos. I do realize that these two would probably not be good for indoor use.

Anyway I'm having fun thinking about all of this and once I decide on a plane I'll get started and do a step by step on the forum Ok? Cheers,Phillyskip
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« Reply #67 on: January 28, 2015, 04:29:30 PM »

Konrad thanks for taking the time to respond. The all up weight of my motor,esc,receiver,battery,and 3 nano servos is 65 grams. The motor according to the seller can turn a 6-7 inch prop, it's rated at 60 [email protected] 1400kv. To be perfectly honest I'm not interested in buying anymore "gear" as I have enough stuff already,but do appreciate your suggestions.

I'm thinking that a plane the size of the Guillows Fairchild 24 or the Dumas Eindecker(30inch) might be worth looking into. Another plane that we use to fly outside on .049s is called the Luton Minor....It flew well and would adapt to indoor flying as it was able to turn very tightly without falling off on a wing on 3 ch.operation.

I was also thinking about the large Guillow Stuka or Hellcat....As I did build both of them for R/C years ago using a GMark .061 engine and 4 Cannon Micro Servos. I do realize that these two would probably not be good for indoor use.

Anyway I'm having fun thinking about all of this and once I decide on a plane I'll get started and do a step by step on the forum Ok? Cheers,Phillyskip
Your power system is far too heavy for the 20" stuff. The Hellcat makes a fantastic conversion. It has one of the better airfoils for R/C of the Guillow stuff The Dauntless also make a great R/c model. I too did the Gmark and Cannon stuff in the late 70's. But with todays radio and power the "big" Guillow should be very doable in a dual court basketball arena. The 30" stuff does not need (or work well) with the ultra micro stuff. For the 30" stuff I think you are set with the possible exception of wanting bigger cells.  Please let us know what you decide and start a thread here on Hip so we can share your experience.
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« Reply #68 on: January 28, 2015, 04:53:10 PM »

I'm going to take your advice and go for a plane with approximately a 30"ws. I'll keep everyone posted....Skip
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« Reply #69 on: February 17, 2015, 06:05:58 PM »

I have decided to convert a Guillows 34" "Giant Scale" STUKA for outdoor flying....Yes I know that we spoke of "being safe"(I'm hardheaded) and going with a 30" high wing or parasol type plane,but the Stuka intrigued me,and will present more of a challenge to build,and to fly. I have a 10ampESC,and a couple of 250 2s Lipo (larger ones as well)batteries.The motors I have on hand are a Hacker Inrunner #20B with prop drive and a 28mm out runner 1400kv. Not sure which motor would be better for the STUKA. I'll buy another motor if I need to. The receiver is a Hitec Minima. I'll need 2 more (have 3 now) Hitec nano servos as I'm going to have flaps and build some sort of micro siren for those  crowd pleasing dive bombing runs! (He,He)

Has anyone here had any success with the Guillow's  34"Stuka? My experience with 60" Sport Scale Stukas was that they flew just fine. I will do a pictorial once the kit is started. Thanks Much,Phillyskip
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« Reply #70 on: February 18, 2015, 11:06:09 AM »

The Stuka is a challenging model but very doable.

The first issue is that the wing incidence is far to high for an R/C aircraft. Change the wing saddle so the incidence is about 0.5° to 1.0° to the stab measured on the bottom of the flat bottom airfoil. On the airfoil, if keeping the one found in the kit, do whatever you can to add some radius to the bottom leading edge (Philips entry).

Also build in a lot of wash out in the wing tips, like 3° maybe as high as 6°.

Flaps on this size and type of model usually result is poorer performance, as the added weight and complexity are not compensated for in changes to the airfoil performance.

The next issue is the landing gear. Do try to use a torsion bar style with the torsion bar part running along the bottom of the inner gull wing panel. then place the torsion bar anchor as high into the wing or fuselage as is practical. If it was my model I'd add a drag link to the lower part of the strut to limit aft motion of the landing gear in the spats.

The Hacker B20-15 is a good motor if used with a gear drive. The 28 mm 14K KV outrunner does not tell me enough to know what motor this is. But what i think you want is a 40 gram to 60 gram motor that will yield enough power to supply you with 50 to 75 watt per pound for the finished weight of the model.

All the best,
Konrad
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« Reply #71 on: February 18, 2015, 12:04:25 PM »

Thanks for all of your suggestions and will follow your advice.They all make sense to me. I'm thinking that with my gear a RTF weight of 10 oz is in the ballpark? What do you think? Can't wait to start on the kit,but I've got a 100" Meister Scale Me109 on there now that is almost done. As you can tell my "likes" are all over the place.....PhillySkip
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« Reply #72 on: September 15, 2015, 09:50:27 PM »

Reading through this thread I see that I've failed to mention thrust lines for these R/C conversions. As a general rule you will find that you wind up with about 2° to 3° of down thrust datum from the stab. This addresses the zoom (climb) tendency from the high chamber airfoils we often find in these rubber band free flight models. Some of the larger models actually have airfoils that are closer to that found on the full size and might not need this much down thrust.

If your power choice is low or your wing loading is high you might be forced to fly with the wing at a high angle of attack. This often results in a large "P" factor as the downward blade of the prop is making more thrust than the upward going prop blade. When viewed from the cockpit a clockwise rotating prop would need some right thrust to help correct this prop induced asymmetrical thrust.

As a general rule I build in some down and right thrust if for no other reason that I don't want up and left thrust. Should I need to make adjustments I often use K&S brass shim stock on radial mounted motors. Using washer often results in too much of a thrust line change.

All the best,
Konrad
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« Reply #73 on: December 02, 2015, 04:18:36 PM »

Konrad:
I saw the bit where you mentioned the use of small diameter CA tube. I assume this is similar to what the DLG guys use ... the "etched teflon" stuff.

Where do you get it?

Do you etch it?

Regards-
Dave


(PS: looks like I asked you about this in 2012 and you posted your pics and info ... )

Smiley

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« Reply #74 on: December 02, 2015, 05:30:17 PM »

So are we good?

Don't know what the DLG use.

I do etch the outside of the CA capillary tube prior to glueing it to the balsa structure. I sand the surface of the tube with 400 grit sand paper. Then I glue down the tube with CA and then I follow up with "canopy glue" to encapsulate the tube. I'm sure how well anything bonds to the teflon so I want to make sure the tube is held in place mechanically.

As I'm lucky to still have a Local Hobby Shop I get it form him. I think he uses Smith Industries adhesives as his supplier for the CA capillary tubes. For these small models the length supplied is adequate.

All the best,
Konrad
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