Author Topic: brodaks p-40 arf (Read 5447 times)

roger · « **on:** December 06, 2006, 08:57:08 AM »

any body ever build this arf id like some feed back and some dos and donts
thanks
roger

peabody · « **Reply #1 on:** December 06, 2006, 10:19:17 AM »

It's a good flyer as is and an ever better flyer if the wing is moved UP 1/2 to 3/4"

roger · « **Reply #2 on:** December 06, 2006, 10:50:46 AM »

one would think that an arf plane would be tested and built to what what you explain as flying better because now the the wing slot has to be cut moved forward and the trailing edge hole filled in and modified. also wouldent that make the plane nose heavy?

roger

Bob Zambelli · « **Reply #3 on:** December 06, 2006, 11:09:30 AM »

NONSENSE. I have the original (ARF) plane and the wing DOES NOT HAVE TO BE MOVED. I don't know where these fairy tales get started but, believe me, the plane flies fine as is.

I had the opprotunity to not only develop the first ARF but I witnessed many of them fly and judged many in profile stunt.

The only modifications I made to the prototype were the landing gear angle and some weight reduction aft of the trail edge. These mods were incorporated in the production versions.

It's a great plane - build it as is and forget about moving anything.

I have tested the prototype with the Brodak .40, LA .46, SAITO .40, OS Surpass .40 and PAW .35 diesel. All worked perfectly except the PAW - that was terrible.

Bob Z.

Tom Perry · « **Reply #4 on:** December 06, 2006, 01:21:49 PM »

Quote from: roger on December 06, 2006, 10:49:44 AM

one would think that an arf plane would be tested and built to what what you explain as flying better because now the the wing slot has to be cut moved forward and the trailing edge hole filled in and modified. also wouldent that make the plane nose heavy?

roger

When Rich said up he meant up not forward. Several people who have the ARF/ARC modified it to move the wing higher and claim it flys better. Some say it makes no difference.

I have never seen anything but great reviews on this model. My grandson has the ARF and I have an unbuilt kit. He likes his, I will probably like mine.

Alan Hahn · « **Reply #5 on:** December 06, 2006, 03:01:31 PM »

Mine flies great as is. I can't say whether raising the wing to vertically balance the plane makes that big of a difference. To see if there is any real difference, put heavier wheels (read duBro low bounce wheels) on the mains to add weight to the bottom or use a heavier muffler which hangs low on the plane.

Mark Scarborough · « **Reply #6 on:** December 06, 2006, 10:13:13 PM »

i am now currently building an ARC P-40. I elected to add dihedral to the wing as opposed to moving it vertically in the fuse. This was on the reccomendation of Pat Johnston. I have also converted mine to resemble a P-40-Q model of which one prototype was built. It was lost while being used in an air race capacity. This opens up the paint schemes for me, I can now get a touch more creative as opposed to the camo schemes which were more prototypical. The purpose for moving the wing, or in my case adding dihedral, is to allow the plane to balance on the vertical cg. without this balance the plane will want to flie, in this case, with the outboard wing down, or inverted , wing up. This has also been trimmed out by tweaking a flap, but as noted by others, tweaking a flap is only good for one airspeed and while manuevering it can vary the trim. (these comments based upon more learned opinions than mine)

peabody · « **Reply #7 on:** December 07, 2006, 05:54:01 AM »

Mark:
Yup...that's what I was referring.
We have a bunch flying here and there is a Power Point show of some of the changes that we recommend on the GSCB web site:
www.gscb.us
Thanks

Bob Zambelli · « **Reply #8 on:** December 08, 2006, 05:21:25 AM »

Last night, I decided to see just how much the low wing would affect the (static) C/G.

Hanging the prototype vertically from the leadouts and using a plumb line, I measured the difference in horizontal distance over a given segment of the span.

The difference was 1.35 inches over 48.5 inches.

Arcsin (1.35/48.5) = 1.6 degrees.

So, that's what one has to deal with in the as designed configuration.

Personally, I like Mark's idea. A warbird looks so much better with a bit of cathedral in the wing.

Bob Z.

wwwarbird · « **Reply #9 on:** December 08, 2006, 02:01:50 PM »

Mark S.,

Neat idea going with the Q model for something out of the ordinary, I've considered the same.
I've been thinking really hard about getting an ARC P-40 myself, could you please post some photos of the rest of the kit, particularly the wing?

Thanks!

Mark Scarborough · « **Reply #10 on:** December 08, 2006, 06:34:29 PM »

Noproblem, I will fire up the digital tonight, I am about ready to start covering the wing post haste, but will get some shots of it. Overall I am fairly impressed with the construction. After talking to Pat J, the designer, I weighed my parts. the Horo stab was on target at a touch over one ounce. the fuse was about an ounce heavier than he would like, it is right at 8 oz. The wing is the worst part, it was 11.5 ozout of the box. I ahve added about a 1/4 oz with the doubler of epoxy and glass to reinforce the section where I added dihedral. More details later. If you have any specific questions feel free and I will answer best as I can. My intent for this is to have a good solid practice plane, and backup. I am building a bf 109 next that is based on this same wing and the same basic moments so this is a decent starting point for prepping for contest season.

Tom Perry · « **Reply #11 on:** December 08, 2006, 08:01:37 PM »

Mark,

Since I havent started my kit yet I will be waiting for your results and pictures.

Mark Scarborough · « **Reply #12 on:** December 08, 2006, 11:15:46 PM »

Just for the record this plane was initially designed WITH dihedral, it was elected at some point in production to go against that design and make the wing flat, or so the designer tells me

Alan Hahn · « **Reply #13 on:** December 09, 2006, 03:06:14 PM »

I decided to use Bob Z's technique (hanging plane vertically and using a plumb bob) and my advice to vertically balance my P40 via hanging weight off the landing gear axles. My P40 with a Brodak 40, APC 10.5x4.5 prop and standard muffler weighs 42.5 oz. It took 8.7oz of weight to get the wing vertical.

Even to me this seems too much to add (would bring the total dry weight to >50oz), so I will just continue as is with a little bit of flap offset. My ARF P40 is a real sweet flier. If I was buying another ARF or ARC, I would leave well enough alone. Afterall, why buy an ARF if you spend more time to tweak it up than building your own? If I were building the kit, then I think I would definitely consider the dihedral.

But to each his own!

peabody · « **Reply #14 on:** December 09, 2006, 06:09:11 PM »

As I mentioned earlier...they fly well stock.....but some simple modifications make them really neat....

Dennis Moritz · « **Reply #15 on:** December 09, 2006, 08:09:51 PM »

In our club the P40 is regarded as among the best flying ARFs, if not the best. All of ours so far are set up stock, wing in the standard slot and no dihedral. Some P40s fly better when the fixed outboard flap is warped or re-glued on a down angle increasing the lift of the outboard wing panel. Probably compensensating for the high (in relationship to the leadouts) vertical cg. Trimming the plane in the usual way by seeing differences in upright and inverted level flight, appears to compensate for any difficulties with vertical cg. I believe one of our members finished first in Expert P40 at Brodaks, using a stock ARF P40 setup and trimmed as described above.

Greg L Bahrman · « **Reply #16 on:** December 09, 2006, 10:37:54 PM »

Fun Plane....... Please note that I used the stock aluminum engine plates but I put them under the mounting lugs and used countersunk screws to mount the motor.

steve dinerman · « **Reply #17 on:** December 10, 2006, 06:56:46 AM »

i have bean flying a p40 all summer long.the only modifications i made to it was to add a trim tab in front of the outboard aileron to make the wing level,the airplane turned out tail heavey i used a RC muffler on my la 46 instead of the tung muffler that i would usually use.the airplain flew great until the covering on the bottom of the wing started to come the leading edge.if i was going to build another one it would be a arc.i talked to john brodak about the peeling.he said he knew about the problem and was trying to come up with a fix for it.

stephen dinerman

Mark Scarborough · « **Reply #18 on:** December 10, 2006, 11:34:57 AM »

Those of you whom have built/flown these, can you tell me what your all up weight was balanced and ready to fly please. Trying to get a feel for what mine should target at. thanks

Willis Swindell · « **Reply #19 on:** December 10, 2006, 04:41:32 PM »

I moved my wing up 1/2 inch and made an adjustable outboard flap, filled in the cockpit. I used stock landing gear but would recommend to make them 1/2 inch longer I can only use 11 1/2 inch prop.
Willis

roger · « **Reply #20 on:** December 11, 2006, 10:35:35 AM »

willis saw your plane in pampa looks g-r-e-a-t i loved it. was it an arf stripped down? to what real benifit was moving the wing?

roger

Willis Swindell · « **Reply #21 on:** December 11, 2006, 04:05:29 PM »

It was a ARC. This wasn’t my Idea to start with, but with the first three P40’s we saw or were involved with trimming the out board wing flew low on the first flights. which is no big deal to fix on this plane twist the wing and re tighten the covering or twist the out board flap or twist the would be outboard aileron. doesn’t take much. I moved my wing up a half inch. any way you do it the plane will fly the same. I guess depending what muffle and engine you use you wouldn’t need to do anything. But I have a heavy OS SF 46 and muffler.
I am planning to bash a P40 kit into a aerocobra and leave the wing where it is because of the trike gear.

Mark Scarborough · « **Reply #22 on:** December 11, 2006, 07:26:19 PM »

With regards to flying with flaps tweaked or intentionaly warping the wing. This fix only works when flying at the same speed. If your intent is sport flying more power to you, do whatever you like. However If you plan on flying competitions I would reccomend either moving the wing or adding dihedral to balance the vertical CG. It will greatly reduce the number of odd trim things you will have to deal with. there is another post that goes into this more in depth if you are interested.
respectfully

wwwarbird · « **Reply #23 on:** December 16, 2006, 05:16:41 PM »

Mark S., any chance we can get a few detail looks at that wing before it's covered?

Thanks!

Mark Scarborough · « **Reply #24 on:** December 16, 2006, 11:12:54 PM »

Well Gents I did take a couple snap0s before the wing was covered, not much for detail however unfortunatly. I will attach what I have. I just covered the wing today and it is installed in the fuse. Have the fillets done on one side at this point, tomorrow the other side and details before priming.
As it stands now, assembled minus flaps and elevators she weighs 23.25 oz. the flaps and elevators are 2.25 oz combined so at this stage allup with no landing gear or drivetrain we are talking 25.5 oz. The wing was just a hair over 12 oz bare and after covering it added almost exactly one ouz. the fuse and stab have a coat of finishing epoxy brushed on and all that could be scraped off and then wiped. that added 6 grams.

The wing is covered with fabric type balsarite and Micafilm. I have conducted some tests and think this will be a light surface to paint over. Time will tell.
with regards to the airframe, the elevators needed some attention as the corners where the trailing edge and the inner framing met were not glued that well. I did some triangulation with scrap balsa to reinforce this. The wing is fairly well constructed the only minor gripe was that one of the outermost riblets on teh wingtip did not actually glue to the doubler shaping the tip and I had to do some creative surgery to enable a strong structure there. In order to add the dihedral I did surgery, I made two cuts outboard of the first ribs, I cut just over halfway through the leading edge and trailing edge. Also Note this wing has shear webs about 2/3 of the way out towards the tips so you need to cut those too. Yes I know sounds drastic, well I dont mind sayin I was aprehensive however Pat Johnston talked me through it and assured me it would be fine. I propped the wing upside down on a block that was 5/8 inch in the center and stacked magazines on the tips to gently persuade the wing to take dihedral. I then shaped filler blocks (actually only about 3/32 at the widest point) to make up the gap where the cuts opened. I started with the spar to insure I had good fill there. then gradually without forcing just filled in the gap and used thin ca to stick in the shims. After that was accomplished, I neatly made up some 2 oz cloth strips to reinforce the seam. (hey its on the bottom but still shouldnt look to bad. ) I put one strip over each joint that was about an inch wide then another strip that went from a quarter inch farther out to a point just past the center of the wing. the other side overlaped this peice. hard to describe, if you need more contact me I will try better. I then sanded it genltly after curing to fair it in. This thing is no lightweight out of the box but hopefully if my finishing method works out it will be ligtht enough.
just in the way of a teaser, I will be using NO airdry products in the finishing. the Micafilm will get a thin coat of sandable two part sealer and a dusting of catayzed primer over the seams. the Fuse will get a coat of two part primer and then it will be painted with base clear auto colors. And now for the pictures

wwwarbird · « **Reply #25 on:** December 18, 2006, 03:30:24 PM »

Thanks Mark!

Bill Little · « **Reply #26 on:** December 22, 2006, 02:10:33 AM »

Hi Mark,

I always liked the P-40Q! That will look sharp.

Bill <><

Mark Scarborough · « **Reply #27 on:** December 22, 2006, 08:38:07 AM »

Thanks for the comments, hopefully this weekend will allow getting some primer on it. Paint soon to follow. I plan on using the fact that it was used as a race plane to give me some "legal" lattitude to be creative with the paint work. At this point I am projecting around 44 oz finished ready to fly. Finish will be automotive base clearcoat Urethane.

Mark Scarborough · « **Reply #28 on:** March 05, 2007, 12:22:07 AM »

Finally got the chance to get the primer sanded and start painting. As I mentioned earlier I plan on using the fact that the Q was used in air racing to liberate myself from the camo paint. well I kind of went off the deep end but hey, my next one, the bf 109 will be all camo so what the heck, its still the airracer theme just some bright colors!
first pict is in wetsanding stages, you can see the guidcoat still on part of the wing.
second is with the green applied and the striations.
third pict is with the green masked off and the Purple Pearl applied. If you look at the pict you can see the masking is a slightly different sheen than the surrounding areas.
Next the purple gets masked, and the next magic color goes on.
I experimented on this plane by using Micafilm on the open surfaces. In my initial tests,(I built a couple ten inch long wing secitions to practice on) the results were very promising, excellant adhesion, very nice surface to paint on. The one thing I didnt test, is of course the one thing that is biting me on the behind. It seems that the tape, even when slicked off, is stickier than the balsarite holding the mica film down, so everywhere I have lifted the tape of mask off the surface, it has created some tiny zits! Ah well, it was an experiment, and truth to be told, this was fully intended to be a practice, backup airplane so no concours finish was intended, but I sure didnt plan on it having a skin condition. There is no way to fix it other than a complete reskin of the wing and I am just not going to do it. its not that bad, but It bothers me

Randy Powell · « **Reply #29 on:** March 07, 2007, 02:04:27 PM »

Looks good, Mark,

As Mark notes,the plane was designed to have dihedral so the placement of the wing could be more scale like. I can attest that the plane flies very, very well if built as originally designed. I suspect the the dihedral was removed when it went to production for a number of reasons I can think of. Probably if it is to remain that way, the manufacturer should move the wing up vertically ~1/2" to accomodate the vertical CG.

Author Topic: brodaks p-40 arf (Read 5447 times)

Alan Hahn

Alan Hahn

Willis Swindell

Willis Swindell