Freewing SU35 Build Questions
Well I figured it was time to step it up this building season by trying a twin. As I have enjoyed flying the larger foam models this summer, the SU35 from HK looks like it will fit the bill nicely so there should be one arriving at more door soon, hopefully. Before I start picking up the remaining parts, I wanted to get some advice from you experts. I spent much of the weekend reviewing many of the threads on this forum and did not see any specific threads on the this build. I must admit that in my review I did pick up some other good info. This forum provides valuable information to the hobby so keep the comments and advice coming guys. OK back to the questions, if anyone has any experience or advice on this model, please don't hesitate to comment. My intent is to run the model with 6s and will likely not employ the vectoring as I like to fly scale, not 3D.
The model is setup for twin 70mm edfs and comes with two counter rotating fans. I am wondering if the counter rotating fans is a requirement in models. My full size aircraft experience indicates that this is not normally a factor as aircraft with the engines close to the aircraft center line are less susceptible to torque problems. It also reduces the maintenance requirements for setting up two different engine configurations. For this reason I am leaning towards two fans with the same rotation unless convinced otherwise. This way I only need to buy one type of replacement fan. Now on to power plants. One of the options is to use the fan units that come with the kit and mate them with motors. Lots of good info from Erik S and Erik K on 70mm setups so please chime in guys. As it appears right now the only real contender is the Eflite BL32 2200Kv other then the DR Mad B2970 2600Kv. The other choices are to go with a CS fan which many of you have seem to have had good experience with or install a complete fan unit/motor. I have been running many of the Dr Mad units (50mm, 64mm) and have had great results so I am considering either the 70mm 11 blade alloy 1900Kv (1700W/74 amps) or the 70mm 10 blade electroplated 2600Kv (1500W/60 amps). There are other fans but these two seem to be the lighter units. The other question is on batteries and whether to go with two single 6s packs to power each motor or run both off a single battery but this would obviously significantly increase amp draw. My intent is to use two Turnigy AE 100 amp ESCs. If there is any interest me doing a build review on this model let me know. Thanks guys. Cheers Marty |
Re: Freewing SU35 Build Questions
Nice project Marty!
If I hadn't have had the SU34 before I likely would have one too. As for power I think the stock setup is fine if you don't mind the noisy fans. Perhaps some careful dynamic balancing would improve things to an acceptable level. I did see pairs of Freewing 12 blade fans (one counter rotating) for sale on Ebay at a very reasonable price with free shipping. I think they were setup for 6S. Roughly $200 total which isn't bad considering they come with motors. I would personally go this route for the sound and the fact that these motors will take full 6S power. I built a couple set of twin 70mm fans for 6S using very cheap turnigy motors but they wouldn't have has much power as the freewing set. The SU35 begs to have as much power as possible for high alpha flight. I also feel the thrust vectoring would be a great thing to have since it worked really well in my SU34. It made for some really neat aerobatics and flat spins. Since the real plane had vectored thrust, why not? As for battery, I would run just one large 6S to power both fans for less chance of asymmetric thrust. If you wanted to build your own fans the BL32 eflite motor will run the Changesun 12 or 10 blade fans with plenty of thrust on 6S. I'm just not familiar with the motor shroud fit and adapter size needed. This is why I would go with the Freewing set to have all parts needed, then just dynamically balance them if they don't run smoothly. Good luck! PS counter rotating fans may be a benefit for high alpha and 3D flying that the SU35 is capable of. Not so much for typical fast forward flight. I remember my single engine F16 would torque roll if flown straight up till the airspeed dropped to zero, so there is some torque created by an EDF. |
Re: Freewing SU35 Build Questions
Thanks for your comments Eric. I have looked at the Freewing fans on Ebay but they seem to be pretty pricey when you need to buy two of them. At the moment I am leaning towards the eflite BL32 motor as I currently have one of these in my Eflite F4 and it seems to produce good thrust with reasonable current. Not sure about the stock fan yet. I guess I will wait until the model arrives and then make a decision. More to follow.
Marty |
Re: Freewing SU35 Build Questions
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Arrived home after work today to see a big parcel waiting for me. Yup it arrived and I felt I better post a few photos. This is a big model. The kit came well packaged with no damage. The stock fans look like they are of reasonable quality but the dapters are only 4mm so if I go with the Eflite BL32 motors (5mm shaft), I will need to find a suitable adapter. Also I see that HK has CS 70mm fans in stock which is another option but again they come with only 4mm adapters. I will continue to investigate and make a decision soon as I want to order everything before the holiday season. Also planning on using metal gear servos for everything.
Cheers Marty |
Re: Freewing SU35 Build Questions
Nice model, Freewing is very quality foamy.
I will buy two balance 70 CS fan with motor like Eric suggested . You will appreciate more the sound and you will fly way more relax. I have a mig 29 , both fan go to the same direction , no problem. |
Re: Freewing SU35 Build Questions
My setup -Twin BL 32's with changesun 12 blade fans. The stock fans/motors wouldn't even move it on our field (grass) but if you have a paved runway maybe ok. The BL32/12 blade set up was enough to take off from wet grass.
https://www.youtube.com/watch?v=lLDm...hxd9h4W8BHw7Lw |
Re: Freewing SU35 Build Questions
Thanks for the input guys. Eric S how did the CS fans fit into the fuselage and where did you find a 5mm adapter for the BL 32s. I was trying to avoid having to do any carving of the foam to fit another fan unit in as the stock 6 blade fans fit perfectly including the inlet ring. I was thinking that I might try the Dr Mad 2600Kv 6s motors on the stock fans. I have read a few reviews saying they were pretty strong and dependable motors and on the smaller blade count fan they shouldn't pull too much current. Also with the high wattage (1700) capability they should produce descent thrust. Otherwise I will likely go the route you did. Do you have any info on what the stock fan motor setup was that you used with poor results compared to the CS10/BL32 setup.
Thanks Marty |
Re: Freewing SU35 Build Questions
The 12 blade CS units do require some foam removal to fit, but there are other options. The Freewing counter rotating 12 blade units can be bought for $100 without motors and come with a 4mm shaft mount. They are drop in for any Freewing 70mm and are available from Hobby paradise & RC Castle. I ordered them as complete units with the freewing motors but had one Freewing motor crap out right away. I ordered a replacement but it was funky as well, so I gave up on them and have since installed them with the Dr mad thrust (which are rebranded cyclone power) 2200kv motors in my other Su35 (i've turned it into an Su37). They are listed @ Hobbyking as having a 3.17mm shaft but they are actually 4mm. I've not yet tested this set up yet but will be sometime in the next few weeks. The 5mm shaft adapters are from Xflightrc.hk. but the BL32 motors are expensive compared to the cylone power/Dr mad thrust units. On another note, the CS 10 blade & XRP 14 blade impellers do fit in the stock freewing shrouds nicely but you would need 2 shrouds for the standard rotation impellers as the stators are reversed on the rev. rotation units. I found this out the hard way.
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Re: Freewing SU35 Build Questions
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Christmas brought me the remainder of the parts that I needed for this build so it was time to start putting everything together. This is a very nice ARF and requires little time and experience to put together. The majority of the effort required is to install all the servos and power plants. It was a nice surprise to see all the servo extensions already installed and labelled. Each of the servo locations has its own plastic tray with cover so it is only a matter of dropping the servos in, hooking up the provided control rods and installing the covers. After much thought about what servos to use I went with the old faithful HXT 900s for the majority of the control servos with exception of the elevator which I am using the larger digital metal gear Turnigy MX345S. I did have to trim all the trays slightly for the HXT 900s to fit and for a measure of security put a drop of silicone under each servo to keep it snug in their trays.
After all the discussion about EDFs and motors, I decided to go with the stock fan units and mate them up to the DR Mad Thrust 2600KV 6S motors. There has not been very much info on this setup so I thought I would give it a try to see what kind of performance this setup would produce. As the fans are only 6 bladed, I figured the higher KV would provide the additional thrust. The fans fit perfectly so there was no requirement to do any foam shaving. The motors fit nicely into the fans which are the same 70mm fans HK sells as I order a couple additional ones for backup. At $6 each it was cheap insurance. Surprisingly the ones that came with the model balanced up nicely. To power the fans I am using Turnigy AE 100 amp ESCs on each fan. I have these on three other models and have had good results so decided to use them on this setup. Also as I was not sure what current these motors would pull I figured a littler larger was better. It took an evening to get all the connectors soldered up and add the 12 gauge wire extensions to the ESCs. The DR Mad test stand that I just picked up came in handy to test each fan unit. No more mounting fans in wood make shift stands. I do not know if anyone else is using one of these but it is a great piece of kit. The only problem I had with mine is that it only reads thrust in metric. For some reason the mode button does not work so it does not provide thrusts in oz/lbs. I will see if HK can send me a new control panel for it. I was pretty impressed with the performance of this rather inexpensive setup. The following is the result from each EDF: Battery - new fresh charged Turnigy 5000 mah 25-45C. Thrust - Right Fan 1.84kg, Left Fan 1.82kg Max Amps - Both fans put out the same 58 amps each Max watts - Right Fan 1293w, Left 1296w EDF/Motor/heatsink Weight - 260g each Of interest is the fact that when I first ran each fan without the inlet ring I was only getting about 1.4kg from each fan. The ring made a significant difference. The shipping foam container makes an excellent tray to lay the fuselage in to allow working on the underside and the installation of ESCs and EDFs. Once I had the fans setup I installed all the flying services temporarily to make sure everything fit properly. So far so good. The next step is to put everything together and then play with the CG. After that it will be setting up the thrust vectoring. I expect I will have to pickup a new radio for this. Will keep you advised. Hope Santa was good to everyone. Cheers Marty |
Re: Freewing SU35 Build Questions
congratulations on a nice model. Should fly like a dream
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