SCALECRAFT

My Feedback: (13)

Hi All

This is a BVM F-16 that was never finished. It was modified very well by a guy who I purchased this from 1 1/2 years ago. (?) I installed and linked up the hardware along with a few modifications to avoid LE flap failure.

This is going to be an EDF powered BVM with a Dynemax/Scorpion conversion that I will adapt to BVM ducting. I also have a yellow F-16, both from the 1990 production, both with scale gear. I choose the BVM over the Yellow for EDF because the BVM ducting flows cleaner and with out main gear humps in front of the fan.

Air flow in a turbine model for power is not as important to thrust. The turbine is mainly trying to push out of your model.

The idea is to get turbine training so when I put my Wren 54MKII in one of them, I can be familiar with the airframe that gets the turbine.

Steve http://www.youtube.com/watch?v=-mGNjmiBXk4

skyhawknut

My Feedback: (3)

NICE!

However - I wouldn't use the Dynamax in it. The Dynamax is too much fan for the intake - not enough area. It will also be too heavy.

Even the Yellow had problems with the intake area and the Dynamax. Guys have downsized the fans in those to get good preformance. Use a Stufan or the EVF.

SCALECRAFT

My Feedback: (13)

Thanks

I would agree the Yellow"s intake is smaller than the BVM. I figured BVM intake around 13.5 sq in and Yellow around 12 sq.in. Plus the BVM intake lip is designed to avoid a boundary layer separation, which I believe will avoid reducing the area of intake upon separation.

The original Dynamax owners manual states "at leaset 125% of the fan sweep area or between 20 and 30 sq. in". The neither models have that. I could open a cheater flap on the intake ducted. No one would see that either. We'll see how it works first without it.

However, the BVM has the larger of the two intakes, a smoother less angle change, no corner pockets as Yellows intake (Stumax suggests 15 degrees max of change in ducting) which results in less turbulence. The smaller intake in my experience will require a longer take off run which is ok. Once it gets "on step" I don't think I should have problems with performance..

Also the BVM is a lower drag airframe next to the Yellow. BVM has very thin wings, ( hence the flaps on both edges for around 16lbs auw.) H- stabs have razor sharp LE's and V-stab is razor sharp as well. I believe the Yellow to be more forgiving, however, the Yellow will also get LE flaps if its gets the turbine.The only draw back to the Yellow I have is that it is the early poly version.

But the most important reason I am using the power systems I have is because of cost. I purchased the dynemax at a very reasonable price. I've seen it work in the past, EDF will make it work better.

Thanks again.

Steve

gunradd

My Feedback: (9)

Steve the slats look great!
What ever you do keep it light. I saw Dustin flying the BVM F16 at ejets and it was 18 pounds and did not look like fun to land.

RAPPTOR

My Feedback: (41)

Slats are way to big.

SCALECRAFT

My Feedback: (13)

Oh. How big should they be? From root LE to TE and from tip LE to TE of flap please. I can make changes to the Yellow one.

Steve

John Redman

My Feedback: (8)

As stated above, keep it light. They fly nice under 14 pounds.

Also just FYI, the F-16 has LE Flaps, not slats.

They might be a bit large at the tip, root looks close. Hard to tell without doing some measurements. They look good. Main thing is keep them tight!

A little full sacale F-16 info. Not exactly sure of the correct degree deflection of the LE flaps in full deflection but when we would rig them on the full scale, we shot for a dimension of 11.5 - 13.5 inches down meassured from the center of the leading edge at the root to the center of the strake where the leading edge of the flap was at 0 degrees. Most all rigged in around 12.5 inches. I believe it was in the 30 degree area. Easily scaled meassurement using the correct scale of the model.

Also trailing edge flaps maximum deflection was 22 degrees. You have way to much flaperon travel in the full down position and will kill you if you get them down that far on final. Base eyeball setting is the trailing edge of the flaperon should be just about 1/8" below the strake at full flap deflection. Also the flaps on the F-16 are driven through the landing gear handle. Gear down, flaps down; gear up, flaps up. There is a flap switch in the cockpit to lower the flaperons but this is for emergency situations only. Also when the flaperons are fully down for landing, they never go down more, only one will come up. Believe me they are effective!

Leading edge flaps do not deflect until the nose gear is fully off the ground. They stay positioned at a 2 degree up from center position when ever the plane is on the ground.

Just giving the info as the BV F-16 uses scale airfoils and in all the ones I flew back in the day, we never used flaperons if we were under 14 pounds. You can lift the nose and manage power all the way to touch down at very slow speeds.

Good luck.

cmjets

Hi Steve:

Can you put any photo of the servo instalation ? please. Many thanks in advance.

BR fom Spain.

Carlos.
__________________________
http://cmjets.blogspot.com/

SCALECRAFT

My Feedback: (13)

Thanks for the info John. This is an experiment to get values that work. I estimate the flying weight at around 16lbs. This due to 3.5lbs of lipos.

Yes, I will post a pic or vid of the servo linkage.

Steve

SCALECRAFT

My Feedback: (13)

Ok, the first pic is of the LE flap. It is a basic bent wire linkage that extents approximately 3" into the LE flap. It has a brass "flag" soldered to the rod for the ball link to connect to, then a 4-40 all thread rod (or bolt) that connects to a clevis to the servo arm. The flap has a 1mm step that the stops the flap from being pushed up past zero and also acts as a stop for the servo to keep a minor load on the flap. Secure no play is key.

I may also install a locking pin via golden rod wire at the root of the LE flap that slides into the flap and keeps it from movement. It may be on a separate servo or the same flap servo. ??

The other pic is of the aileron/flaperon. Same idea as the LE flap.

The trick to make this group of servos work together is the radio I have. The JR 9303. Basically, the radio has to be in Flaperon mode that control two separate aileron servos,that are on separate channels, not Y-connected, then you mix another channel in as the slave for the LE flaps.

This is what works for me and the radio I have. It took a week of reading the flaperon section, mixing section and mocking up servos and mixes and switches. The mixing is unlimited.

Hope this helps.

Steve

L Turner

My Feedback: (3)

Having fixed 'stops' to limit past zero and past 'full deployment' on your LE or TE flaps can cause over travel / high amp current drains with your servos, particularly with digital servos. You may need some type of overtravel limiter on your servo arms: something like the spring devices that used to be used to prevent overtravel on the throttle servos for gas bangers.

cmjets

Hi:

Thanks for the pics. I have an old Yellow F-16, i hope any day rebuilt and make the LE Flaps.

BR from Spain.

Carlos.
___________________
http://cmjets.blogspot.com/

SCALECRAFT

My Feedback: (13)

cmjets, No prob.

Thanks for the suggestion L Turner, but the spring idea while it works in the car carb linkage as an override for applying brakes and too much travel, would in my opinion on my application allow too much movement when the flaps are under a load. I have servos that have a rating of 88.oz on 6V for each LE flap. Is this enough, maybe. I also have servos that have 208oz on 6v, but have not turned to those yet.

However, I never rule any ideas out, I just see what works with the least amount of trouble to set up.

Thanks again

Steve

SCALECRAFT

My Feedback: (13)

A quick update on the few things I thought were to be problems.

First, my estimated flying weight was around 17-18lbs. Now it looks like no more than 16lbs.

Second, the LE flap "lock" to avoid a load on the servos when not deployed. My solution is to have the servo arm at zero degrees to the control rod. In this configuration the rod pushes on the servo output shaft directly on its center and is not trying to turn it. It works.

Steve

SCALECRAFT

My Feedback: (13)

Now to make the duct adapter for the dymemax to the smaller BVM intake. Also a pic of the cnc cutter I used to make the thrust tube support. I have had it since it was introduced but never use till now. I may have to sit down and learn how to really use that cnc cutter. it can make anything really if you know how.

Note, I am using the one of the nitro version dynamaxs I have to mock up the ducting. 90% Same thing really, with a few minor modifications.

Almost there.

Steve

Shaun Evans

Hi,

I keep hearing about how the F-16 inlet is too small, turbulated, angled, etc., for the Dynamax fan to perform well in it, but it seems to me that someone needs to let the airplane know because in its ignorance of these facts, it seems to haul butt. Of course, a smooth inlet (free of hard transitions and such) is going to be better, but I don't see a performance deficit out n the field...

SCALECRAFT

My Feedback: (13)

I have both (1991 productions) the Yellow and BVM in my shop. The BVM has aprox 1.3 sq. in more of intake opening over the Yellow and no protrusions at the main landing gear area.. Also the radius front of the BVM will minimize or avoid a boundary layer separation. However, the more I work on the BVM, the more I like the Yellow.


I will ultimately make a hybrid of the two models and take the better components from each on my next one.

I would have to agree with you. Dumb airplane just get pushed around the sky at blazing speed.

One issue I have with the Dynamax fan shroud is the way the fan shroud/housing is put inside the intake duct. I am making a ducting to have no angle change at this critical point of where the fan blades tips are nearly out of the air flow at high speeds. The duct will be on the inside of the fan and delivering air closer to 100% of the fan sweep area.

I have yet to see one fail, in any sense of the word. Unless it was before 1988.

Steve

Shaun Evans

Hi,

The BVM kit had a molded resin inlet lip with the kit. I've used that molded piece on several Yellow Falcons. It's not an exact fit since the shape of the two inlets are different but you can heat it up and bend the edges a bit. I don't know how much of a difference it makes, but it sure sounds a bit different. I imagine it helps on the Yellow.

SCALECRAFT

My Feedback: (13)

I had a intake duct liner detach from the fuse intake upon test run. My solution that has worked better than I expected on previous intakes, is to take fiberglass seam tape and put small roles between the intake and fuse. It not only supports the ducting, but also has the ability to avoid breaking away in case of shock. It also adds additional support to the fuse with out distorting it. It is also very light. And a layer of glass on the outside lower lip.

The other thing that the "Yellowaircraft" rcu member pointed out is that the top ducting liner can also detach so, I put a lightweight kevlar seam cap on that one.

I also made a transitional ducting from BVM intake to dynemax. My adapter is made to have a mated connection to stop the duct from getting sucked into the blades and have the duct go inside the dynemax and avoid the step and hard short angle change right before the fan blades as you would have if you put the ducting outside of the dyenemax fan shroud.

Steve

turbofixer

Hi Steve, how is the f16? flown yet?....its scott in china..my email is not always up so I came here

SCALECRAFT

My Feedback: (13)

Hey Scott!!!

Good to hear from you. How's going out there? Since its Tuesday out here right now, around an hour ago I was thinking I should call you to get some lunch, then I remembered your kinda outa town.

F-16 not flying yet. Not in a rush.

I put the power system in it and throttled up to around 40% while holding the model in place. BVM duct caved in. (Like closing off the hose on a vacuum cleaner.) Too old and brittle at around 20 years old. I'm fabricating a new one.

Radio mixes all figured out. Ducting and gear door air cylinders are really the only things left.

A turbine would be way easier to set up generally speaking if your surfaces are secure.

Have fun.

Steve

turbofixer

Sounds cool..yea lunch would be good...they were going to serve frogs for dinner last night ...we went for the schrimp!...Kinda figured the duct would cave...its a big vacume cleaner..be in touch

SCALECRAFT

My Feedback: (13)

My dynemax conversion of the BVM F-16 so far. Coming in at 15.5-15.75lbs.

Lipos are 5300Ma, 6Sx2

Had to beef up the intake duct with kevlar. Kevlar does not block radio frequency and is lighter than carbon anthough not as stiff, but stiff enough.

Also my adapter ducting for the dynemax to BVM intake is made to be inside the dynemax and not on the outside. Better for the Fan area, especially at the blade tips. It is supported by a glass tape as well.

Steve

turbofixer

nice..so is it ready to go?? it looks like you may have room for more batt in the future also for longer flight time

SCALECRAFT

My Feedback: (13)

If it survives the first few seconds, I guess it could have a longer flight time later with the extra batts.

Good to hear from you. Hope all is well

Looking forward to flying this model when you get back.

steve