Brodak P40-B ARF ; Bellcrank Pushrod - Flap Control Horn Misalignment

[Kafin Noe’man]

I've just bought a new Brodak P40-B ARF 
The recommended engine size is .40-.50.

At the moment, I have an ENYA SS40BB, but I can also find a new Brodak 40 and OS LA 46 here in Indonesia.
What would be the best option?

Furthermore, I know that 0.015 Stainless Steel lines are good up to engine size .40, does that mean I have to go with 0.018 lines if I decide to get the OS LA 46?

Looking forward to hearing your advices!


Best,
Kafin

[Dave Hull]

We fly the Brodak P-40 ARFs here with the OS .46LA on .015" stranded steel lines. Works just fine!

I don't have an Enya SS40BB so I don't have a comment there. The Brodak .40 has a very nice run, but I would probably choose the OS .46 for the extra power. They run very nicely, too!

I'm not sure what the rules would be in your location for line sizes and safety. Here in the USA, we are now going by a 10G pull test; ie. if you plane weighs 48 ounces, you pull test the control system to 480 oz. or 30 lb. The lines have to survive that pull. The older table that specified the line diameter based solely on engine size has been deleted.

These are nice flying airplanes, so you should really enjoy yours.

Dave

[gene poremba]

We fly our Brodak P-40 also with a LA46 on .015 X 60' lines. Flies the pattern better than I can....Gene

[Robert Zambelli]

I assembled, evaluated and verified the first prototype ARC version for John Brodak when it was first shipped to me from Sun Models (China).
Although the quality of the plane was excellent, there were a few issues that I had to correct. I sent the corrections back to China and in a short time, they sent us twenty each ARC and ARF, all incorporating my changes.
Both John and I noticed a substantial difference in weight of the unopened boxes, the total weights differing by around 8 ounces.
We attributed that to variations in balsa densities.
Anyhow, I made the changes to the above mentioned prototype, covered and painted it and then started a test regimen.
The goal was to try a number of different engines so that John could make the appropriate recommendations.
Starting with a Brodak 40, I then tried (as I recall) a PAW 29 Diesel, FP 40, LA 40 and 46, Aero Tiger 36, OS non-Surpass 40 4S, SAITO 40 and a few others.
Pat Johnson did one hell of a job designing the P-40. It flew very well with all the engines I tried.
60 foot .015 lines worked perfectly.
Which engine worked best? My personal favorites were the OS 4S and the LA 46. The Brodak 40 was right up there also.
For what it's worth, I built an ARC P-40 for a friend. It weighed 50 ounces with a Super Tiger 46 and flew beautifully.
Kafin - you've got a nice assortment of engines. Since you have one, you might try the ENYA 40. I've been told it's a very user friendly and powerful engine.

Bob Z.

[Colin McRae]

Kafin, I run an Evolution 36 NT on my P40 ARF. For the engines you mention. I would use the OS 46LA. It is a great running engine.

But one critical thing concerning the P40 ARF kit-supplied flap and elevator joiner wires. The ones that came with my ARF are way too flimsy and produce a lot of differential flex in the adjacent control surfaces. This causes the model to roll in certain circumstances.

If I had to do it again, I would have not used the kit supplied thin control surface joiner wires and used heavier music wire. And also not used the flap and elevator mounted nylon control horn design. But use a joiner wire that has the control horn connected directly to the wire. The goal is to have equal control surface deflection on either side of the model.

I would also recommend 0.018 size lines.

(Just wondering if other P40 ARF owners have had the same model roll issue?)

[Dave Harmon]

But one critical thing concerning the P40 ARF kit-supplied flap and elevator joiner wires. The ones that came with my ARF are way too flimsy and produce a lot of differential flex in the adjacent control surfaces. This causes the model to roll in certain circumstances.
If I had to do it again, I would have not used the kit supplied thin control surface joiner wires and used heavier music wire.
The goal is to have equal control surface deflection on either side of the model.
(Just wondering if other P40 ARF owners have had the same model roll issue?)

I have not had any roll problems but....I also saw that too small wire so I used 3/32" wire and lucky boxes on flaps and elevator.
The only thing I didn't like was the small bellcrank and Z bends on the flap pushrod.....but, it flys great....so far!
Generally....not enough glue overall especially on the L/G blocks that fell out after the first landing....which was smooth!

[Colin McRae]

I have not had any roll problems but....I also saw that too small wire so I used 3/32" wire and lucky boxes on flaps and elevator.
The only thing I didn't like was the small bellcrank and Z bends on the flap pushrod.....but, it flys great....so far!
Generally....not enough glue overall especially on the L/G blocks that fell out after the first landing....which was smooth!

Thanks, Dave, for the feedback. Unfortunately, at the time (2 years ago) I was a rookie builder and did not realize the P40 ARF kit joiner wires were undersized and total crap. Live and learn.

Also, our CL flying field is not the greatest (lots of uneven bumps) and a flying buddy of mine recommended against using the ARF wing-mounted landing gear design. So, I made up some aluminum fuselage-mounted landing gear. Less of a 'semi-scale' look, but OK.

[Dave Harmon]

Thanks, Dave, for the feedback.

Also, our CL flying field is not the greatest (lots of uneven bumps) and a flying buddy of mine recommended against using the ARF wing-mounted landing gear design. So, I made up some aluminum fuselage-mounted landing gear. Less of a 'semi-scale' look, but OK.

I saw that and wondered why.....after busting out one block and repairing it.....I opened up the other one and reinforced the structure with plywood and adequate epoxy instead of what looked to be hot glue....and not enough of that! The original L/G blocks are ok in design but don't have plywood doublers on the wing ribs. This is easily fixed if you want to do it. The needed ply doublers are only needed on the inboard and outboard rib of the gear structure. You can likely break the block out cleanly by inserting the original wire and rocking it back and forth until it pops out....that's what I did!
In fact....I am working on another new P-40 right now and I'll bust out those blocks this afternoon...gonna use 1/8" wire instead of that coat hanger wire...and make them about 1 1/2" longer too.

[Air Ministry .]

 " I've just bought a new Brodak P40-B ARF  '

What does it weigh . ?

[Colin McRae]

" I've just bought a new Brodak P40-B ARF  '

What does it weigh . ?

Air, mine weighs 54.6 oz (1.55 kg)

Stock ARF, except that I used aluminum landing gear, not the wing-mounted gear due to our bumpy CL field.

Also, Evolution 36 NT engine w/ EVO tube muffler, 4 oz Brodak oval profile uniflow tank, 11-4 MAS prop, Dubro 2" plastic spinner, 0.8 oz of nose weight (weighted brass spinner nut), and 1 oz of tip weight.

The EVO 36 NT engine/muffler is a bit lighter than an OS 46LA/stock muffler, but as powerful or even a bit more powerful than a 46LA.

[Colin McRae]

I have not had any roll problems but....I also saw that too small wire so I used 3/32" wire and lucky boxes on flaps and elevator.
The only thing I didn't like was the small bellcrank and Z bends on the flap pushrod.....but, it flys great....so far!
Generally....not enough glue overall especially on the L/G blocks that fell out after the first landing....which was smooth!

Dave, please excuse my ignorance being a rookie builder.

I don't understand 'boxes' on your flaps and elevator. Can you provide a better description of your means and methods for your joiner wires, maybe a picture?

Thanks in advance.

[Dan McEntee]

Dave, please excuse my ignorance being a rookie builder.

I don't understand 'boxes' on your flaps and elevator. Can you provide a better description of your means and methods for your joiner wires, maybe a picture?

Thanks in advance.

  Until Dave can get back to you, search out "lucky boxes"  in the main forum and the construction/building sections.
  Type at you later,
   Dan McEntee

[Colin McRae]

  Until Dave can get back to you, search out "lucky boxes"  in the main forum and the construction/building sections.
  Type at you later,
   Dan McEntee

Thx Dan

[Dave Harmon]

Dave, I don't understand 'boxes' on your flaps and elevator.
Thanks in advance.

The pix show a flap from an Oriental.
Nothing really new here but just an example of my take on the 'box' technique to positively secure the flap joiner/coupler wire.
On this flap, I used 3 pieces of ply....the center piece and 1/32" ply caps on each side.
The wire is a snug fit....not loose like in the pix.
I file/sand the slot in the center piece then use 5 min epoxy to attach the caps being sure to keep glue out of the slot.
The wire is not glued in.
On the Oriental flap, I cut a slot and epoxied the box into the flap ensuring the hole is on center with the airfoil.
I used a printer paper 'slip' sheet to sand the box flush with the flap.

On the Brodak P-40 ARF, I measured the box width, then cut off that same amount from the inboard edge of the flap....not using the hole drilled in the flap by the mfgr.....then epoxied the box onto the inboard end of the flap, restoring the original flap length.
When setting up the flaps ....I do this on a surface plate to ensure the coupler wire is in alignment and bend it a little if needed before the wing is mounted on the fuselage.

[Colin McRae]

The pix show a flap from an Oriental.
Nothing really new here but just an example of my take on the 'box' technique to positively secure the flap joiner/coupler wire.
On this flap, I used 3 pieces of ply....the center piece and 1/32" ply caps on each side.
The wire is a snug fit....not loose like in the pix.
I file/sand the slot in the center piece then use 5 min epoxy to attach the caps being sure to keep glue out of the slot.
The wire is not glued in.
On the Oriental flap, I cut a slot and epoxied the box into the flap ensuring the hole is on center with the airfoil.
I used a printer paper 'slip' sheet to sand the box flush with the flap.

On the Brodak P-40 ARF, I measured the box width, then cut off that same amount from the inboard edge of the flap....not using the hole drilled in the flap by the mfgr.....then epoxied the box onto the inboard end of the flap, restoring the original flap length.
When setting up the flaps ....I do this on a surface plate to ensure the coupler wire is in alignment and bend it a little if needed before the wing is mounted on the fuselage.

Thanks, Dave, for the info.

Lots for me to learn here!

[Steve Helmick]

OS .46LA, APC 11.5 x 4 prop, somewhere around 4.5 oz to 5 oz of 10% nitro.

The P-40 appears to be the best of Pat's profile ARF designs. Beware of the covering coming off in flight, though.  Steve

[Colin McRae]

OS .46LA, APC 11.5 x 4 prop, somewhere around 4.5 oz to 5 oz of 10% nitro.

The P-40 appears to be the best of Pat's profile ARF designs. Beware of the covering coming off in flight, though.  Steve

Steve, with all due respect, the P40 ARF model may be a good design, but the Chinese-provided flap/elevator joiner wires are greatly undersized and not of a stiff material. It is recommended to upgrade the wires. I also found that the control pushrod from the bell crank to the flap horn does not align by around 1 inch. I had to dogleg bend the pushrod to align the pushrod with the flap control horn.

[Dave Harmon]

The P-40 appears to be the best of Pat's profile ARF designs. Beware of the covering coming off in flight, though.  Steve

I think there was an earlier Brodak P-40 ARF that was marketed that might not have been as high quality as the later ARF.
It had a clear plastic canopy instead of the black sticker canopy outline.
I have only seen one of the earlier version and while it was a bit different, I don't recall any problems with it.
On my later version airplane I replaced those awful black canopy stickers with Ultracoat that won't come off....I hope.
The covering is well done and has not shown any signs of delaminating or coming unstuck....unlike some of the other ARFs.

BTW....I made a comment the other day about busting out the L/G blocks on the P-40 I am working on.....they seemed to be secure so I left them alone but re-bent real 1/8" wire and lengthened them 1 1/2" to get the nose a bit higher....it just looks a little goofy to me with the short gear legs....even after I bent the tailwheel wire to raise the nose.

The P-40 I am currently flying has a Rojett 51 with the integrated spinner...a really cool item and metal tank made from the Brodak wide wedge tank kit using the plumbing shown on an earlier post.
The tank is plumbed uniflow and I use muffler pressure for a really nice steady engine run.
The airplane weighs 55oz and could be made somewhat lighter without the integrated spinner which required about 1oz under the stab to get it to fly right.
Just going by memory now but at first....I had the c/g at the recommended place but it would not turn very well so I added another 1/2 oz on the tail (for a total now of 1oz) and it improved the performance considerably....it will do continuous overhead eights until it runs outta gas!
Also....the recommended c/g makes the airplane far too nose heavy.

[Dan McEntee]

OS .46LA, APC 11.5 x 4 prop, somewhere around 4.5 oz to 5 oz of 10% nitro.

The P-40 appears to be the best of Pat's profile ARF designs. Beware of the covering coming off in flight, though.  Steve

  This leads to the question, has anyone tried a coat of two part clear airbrushed over all the seams of the covering? I have had this issue with just about every ARF I've ever flown significantly, from the SIG Primary Force to my Top Flite Score, and my Hanger 9 PT-19. The covering either came off or the clear top sheet came off leaving very little behind. . This thought just occurred to me while reading this. You would not need a lot of coverage, just a nice even coat wherever the covering overlaps, That wouldn't add significant weight I wouldn't think. I am pretty sure that Allen Brickhaus would have a local body shop spray a coat of clear on his models, which were usually iron on covering on the wing, painted fuselage and sometimes would paint trim on the iron on covered wings. Just something to think about.
  Type at you later,
   Dan McEntee
   
   Type at you later,
    Dan McEntee

[Steve Helmick]

While I have not flown or owned the P-40 or any other Brodak ARF, I have witnessed the covering come off the outboard wing of one...bottom, I think. It didn't fly well that way, so beware of that. Most ARF/ARC planes have very poor control systems from leadouts to pushrods, horns, and hinges. Some have good covering, and some don't. Often the covering is not really well bonded to the structure, so the buyer needs to go over that and get it really stuck down....or just remove & replace.  Steve

[Colin McRae]

On my Brodak P40 ARF, I did go over the entire model with my iron before it's maiden. So far, the covering has held up OK. But it is a good idea to do it.

[Dave Harmon]

With all the talk about the P-40 recently.....I flew it today....great weather in the Midwest.
Man....that thing really tracks well and is so smooth....Pat did a great job on this one.

[Kafin Noe’man]

Thanks everyone!

I think I’m gonna go with the LA 46. After having some discussion with Martin Quartim from Brazil (he’s ENYA expert btw) he suggests that my ENYA SS40 BB will be too powerful and causing some vibration problems (especially in profile fuselage) in the future.

It is still on the way, the expected delivery date is at December 10, just in time before my birthday on the 15th 🤣🤣🤣

[Dave Harmon]

Thanks everyone!

I think I’m gonna go with the LA 46. After having some discussion with Martin Quartim from Brazil (he’s ENYA expert btw) he suggests that my ENYA SS40 BB will be too powerful and causing some vibration problems (especially in profile fuselage) in the future.

It is still on the way, the expected delivery date is at December 10, just in time before my birthday on the 15th 🤣🤣🤣

I disagree....it will fly great with your ENYA.
This ARF builds up very sturdy and flys great with the ROJETT 51.

[Martin Quartim]

I disagree....it will fly great with your ENYA.
This ARF builds up very sturdy and flys great with the ROJETT 51.

I'm keen to hear about your experience with the Enya SS40BB in a profile model airplane. I've faced my share of challenges while trying to optimize its performance in a profile model. Despite managing to make it work with a 6-pitch prop, the results were less than satisfactory.

The Enya SS40 engine excels at high RPMs, around 10,000 to 11,000 RPMs on the ground, with a low-pitch prop. However, in this RPM range, it became challenging to prevent fuel foaming.

In my view, it's not an ideal choice for a profile model. This engine seems to perform best in built-up midsize models with a wing area of around 600sq.in.

I'm interested in hearing any insights and any successes you've had with this engine.

Martin

[Kafin Noe’man]

Hi, since I pancaked my Vector last weekend, I now have an extra engine to put into consideration.
My engine on my heavy 55oz Vector was ENYA 35XS (the same gen as the ENYA 40XZS). Do you think I can put this engine to my Brodak P40? What is the ideal/target weight for the P40 ARF?

Another question is, why is the recommended engine for P40 is .40 - .50 meanwhile Cardinal that has bigger wing area and longer fuselage length is recommended to use .35 - .46 engine size?

[Colin McRae]

Kafin, my Brodak P40 ARF was built stock, except that I use profile mounted aluminum landing gear. (Our field is somewhat bumpy and not friendly to wing-mounted landing gear.) I also use an Evolution 36 NT with stock tube muffler. The EVO 36 NT is roughly as powerful as an OS 46LA, and a hair lighter. And I am running an 11-4 MAS prop.

The OS 46 LA you have planned will be a great engine choice for the P40. The engine also runs really well with the OS stock tube style muffler it was designed for.

My model with everything mounted (no fuel) weighs 54.6 oz which includes 0.8 oz of nose weight and 1 oz of tip weight.

And I also switched to Dubro pin-style hinges. I personally don't like the CA easy hinges that the kit came with.

I think I have mentioned this before, but it is highly recommended to not use the undersized and weak flap and elevator joiner wires. Way too flimsy causing unacceptable differential control surface flex. It can cause my model to roll with hard control input. If I were to do it again, I would have switched to 3/32" or even 1/8" hard music wire for the joiners.

I also fly my model on 0.018 SS lines.

[Kafin Noe’man]

My P40 ARF is now here, and I've just realized that the position of the pushrod from bellcrank to flap control horn is not in parallel. I'm also planning to use either clevis or ball link instead to z-bend it at the horn.

So is it okay if I make a bend like in the attachment below so the clevis or ball link will be in straight line to the horn?


Best,
Kafin

[Ken Culbertson]

Welcome to ARF land.  It looks like the wing was designed for an offset brazed metal horn and now that they are hard to find, just threw in a nylon one.  If the wing is not in yet I would try and find, or make one.  That is too much offset.  Does Brodak include an assembly manual with pictures?  I would like to see how they hooked that one up!  I found a couple of pix on EBay and they were all like yours with the pushrods severely bent.  A small bend of the bellcrank pushrod at the cutout towards the horn with a ball link on the inside might work.  Don't use a clevis on anything that is not a straight shot.  The link below is the horn I am talking about.  There is a Veco version that sometimes pops up on EBay.  You might want to cut out the exit hole to allow it to not be bent and make some cute covering.  With that angle you need to consider having the bellcrank angled so that the angle of the drive arm is 90 degrees to the pushrod.

https://brodak.com/control-line-parts/control-horns/4-4.html

Ken

[Colin McRae]

Kafin, I did not want to cut into the ARF wing, so I just bent mine to align and used a solder clevis. It will introduce a bit of flex, not optimum, but works OK.

What is more important is to not use the kit provided weak flap/elevator joiner wires. Highly recommended to upgrade to larger diameter music wire.

Also, you will need to notch the flap as the elevator rod will hit the flap and not allow for equal up/down range of movement.

Unfortunately, the horn misalignment issue, and need to notch the flap, are not discussed on the plans nor in the instructions.

[Al Ferraro]

 Add a pushrod guide on the side of the fuselage to prevent pushrod flex when you give it up elevator, it makes a dramatic difference when hitting the inside corners.
Al

[Kafin Noe’man]

Kafin, I did not want to cut into the ARF wing, so I just bent mine to align and used a solder clevis. It will introduce a bit of flex, not optimum, but works OK.

What is more important is to not use the kit provided weak flap/elevator joiner wires. Highly recommended to upgrade to larger diameter music wire.

Also, you will need to notch the flap as the elevator rod will hit the flap and not allow for equal up/down range of movement.

Unfortunately, the horn misalignment issue, and need to notch the flap, are not discussed on the plans nor in the instructions.

Hi Colin, thanks for sharing a picture.
I was actually thinking of doing the same setup as yours. So, how does your P40 fly?

[Kafin Noe’man]

I found a couple of pix on EBay and they were all like yours with the pushrods severely bent.

It also made me curious to see the plan.
Does anyone here have the plan and can share the bellcrank - pushrod - flap control horn setup?


Best,
Kafin

[gene poremba]

 Kafin, on mine i used carbon fiber push rods and anaftermarket control horn that gave me a straight line shot with no offset....Gene

[Dave Rigotti]

How did you accomplish this with the ARF?

Kafin, on mine i used carbon fiber push rods and anaftermarket control horn that gave me a straight line shot with no offset....Gene

[gene poremba]

 Ahhh, good point Dave! Mine was the ARC. ....Gene

[Colin McRae]

Hi Colin, thanks for sharing a picture.
I was actually thinking of doing the same setup as yours. So, how does your P40 fly?

Kafin, my P40 ARF flies reasonably well as is, but there are some issues. The biggest issue is a roll problem if I hit the controls hard as when trying to do a square for instance. But if the maneuvers are not severe it flies well. The roll is primarily caused by the weak flap/elevator joiner wires as well as the flap control horn mounted on the flap which considered together result in a ridiculous amount of control surface differential flex. I also have a fixed offset on the rudder which also does not help. 

I am still learning the various pattern maneuvers and have only been CL flying for about 2 years. I built my P40 about a years ago and am a rookie builder. I got the profile ARF wanting to just get a larger size model in the air fast. I had no idea (or related build experience) at the time on some of the kit design issues, and being an ARF did not want to cut into the model to upgrade things. I know better now. If I had it to do all over again, I would have:

1. Cut into the wing and upgrade the bell crank and control horns and use ball links w/ CF pushrods.
2. Upgrade the flap/elevator joiner wires to heavier music wire (probably 1/8" diameter)
3. Not put in any rudder offset or made it adjustable.

What you may want to change/upgrade on the P40 ARF really depends on your particular goals and on how you want the model to perform. If just for sport flying and basic maneuvers, then I would just bend the stock pushrod to align, use stronger joiner wires, and use no rudder offset which are all easy to do. But if you want to eventually attempt any type of competition flying with your model, then I suggest changing everything I mentioned above.

And I did purchase the Brodak plan drawing (in case I ever had to do a repair). Here is a pic of the bell crank area you requested.

[Dave Harmon]

I finally found the picture I wanted of how I fixed the crummy flap horn arrangement on the P-40 ARF.
I cut 1/4" off the inboard edge of the flap then put on a 1/4" lucky box.
Then I epoxied on a piece of 1/16" plywood on the top and bottom of the flap for support.
Next cut a slot for the horn and epoxied it all together.

I messed up the picture trying to reduce the size....uggghh

[Brett Buck]

And I did purchase the Brodak plan drawing (in case I ever had to do a repair). Here is a pic of the bell crank area you requested.

    Wow, that is one scary drawing!  The backwards bellcrank is one thing, probably not a good idea but not fatal. But it has a secondary effect that causes the pushrods to pull against the keepers due to centrifugal force. They need to go into the horns from the inboard side, not the outboard. However, if you do that, then, the elevator pushrod interferes with the flap.

   For an ARF, you can probably use the keepers, put in a washer on the inboard side of the upright as a bearing AND, cut a groove in  the free end of the pushrod and copper wire to force the keeper wire to stay in the groove, and then a dab of JB weld to hold it together.  This seems like a prime candidate for ball links or some other modification. If building from scratch, I would suggest putting the bellcrank around the normal way and then use ball links at least for the bellcrank-flap connection.

     Brett

[Martin Quartim]

It's intriguing that there haven't been any comments on the Vertical CG. The wing is positioned quite low, and I am concerned that the Vertical Center of Gravity (CG) might end signficantly higher than L.O. point of exit.

If that is the case, I would consider assembling the wing with some dihedral or modifying the fuselage to allow for a higher wing placement.

Martin

[baum58]

Hello to all.
I was able to pick up a Brodak P40 ARF at the Toledo swap meet. I blew my budget last year and the same guy showed up with it this year. 
I read this post and was worried my engine choice  would be producing a nose heavy plane….Not so. Also a weight of 50+ oz was also not appealing..Not so again.

I was shocked to finish the plane coming in at just 44oz. Did I miss something?
Did not modify anything wondering if some internal parts are missing!!!!
Any way, I used:
OS 40FP modified by Tom Dixon
Sullivan 4 oz plastic tank
2 ¼ metal spinner
 
To drop in the OS I needed to dig into the fuze. The OS is a bit longer and  to mount the engine it needed a 4 mm lift to get to the center of the front bulkhead. I copied the tank install from my SIG Primary Force. The overflow and bottom vent are on the inside of the fuze, pointing forward.

At this point I will fly the P40 as is. I have the option to go electric, I have all the parts, we will see!
 Peter

[Dan McEntee]

It's intriguing that there haven't been any comments on the Vertical CG. The wing is positioned quite low, and I am concerned that the Vertical Center of Gravity (CG) might end signficantly higher than L.O. point of exit.

If that is the case, I would consider assembling the wing with some dihedral or modifying the fuselage to allow for a higher wing placement.

Martin

    There is a thread on the forum about adding dihedral to the first generation P-40 ARFs. Another option , espeically if kit built, is to just raise the wing location, I think an inch was recommended. The only one I have seen like that was Dennis Vandekur's models several years ago. He raised the wing and might have moved it forward a bit, I can't remember for sure, but it did fly well!
  Type at you later,
   Dan McEntee