RE: Hangar 9 B-25 ARF: Building and Modifications
 

What do you think about the removable horiz. stab? Is everyone gluing theirs on or bolting it on? How about having the servo back there in the stab like the TF one for a shorter pushrod? I realize a servo that far back would need more nose weight. Or is everyone that has one satisfied with the designed servo placement?

Snoop42

RE: Hangar 9 B-25 ARF: Building and Modifications
 

I've studied the manual pretty thoroughly. Right now I'm planning on the elevator servo up front.
And I expect I'll mount the horizontal stab permanently; typically I use both the bolts AND glue. Figure as long as the bolts are there and properly aligned, may as well use the "belt and suspenders" approach! Plus, the bolts make the alignment much easier while the glue's curing.
Just my .02 worth....

RE: Hangar 9 B-25 ARF: Building and Modifications
 

I have already installed a 1 oz, digital servo in the stab for the elevators.
I decided that:
A) I don't like long linkages: too much room for play/ slop and too many trim adjustments needed due to temp/ humidity changes.
B) Since I AM going to make the stab removable, it makes even more sense to mount the servo on it, rather than in the fuselage.

Altho it will add a little weight to the tail, Iam keeping it minimal by using a high torgue, digital yet relatively light servo. Additionally, the long linkage will be eliminated, which may reduce weight.

There is a rib, right in the middle of the stab, so the servo should be offset to one side or the other. I removed a little sheeting for the servo, then installed plywood mounting rails, capped with a 1/4" wide carbon fiber strip. Make sure the rails are nottoo long, or they will interfere with mounting the stab to the fuselage.

I like to build light, and am doing many things to lighten mine up, but sometimes I feel it is better to add a little weight to make it better, and if having the elevator servo in the stab adds weight: so be it.
Speaking of weight: I am wondering why anyone would feel the need for a 5000 mAh receiver/ servo battery pack? How much does THATweigh?

RE: Hangar 9 B-25 ARF: Building and Modifications
 

Just noticed this thread after viewing Electric Conversions on RCGroups. Hope i'm not out of place hear but i just did a run up of my Extreme Flight Torque Revolution motors puchased from Atlanta Hobbies and these motors are the pefrect match for this aircraft for those who are going electric. They are lighter and cheaper than the Axi or E-Flights and are designed for 4-5 cell operation. Using my T/P Extreme 5s 5000 pack i'm getting 1050 watts per motor swinging M/A 14-7 pusher and standard 3 blade props. Using Castle 80 ESC and Spektrum radio. The motors will go to 1400 watts each but i don't see the point of pushing them that far. If i can use these props for flying and i get the speed i want the 3 blade set-up could be a nice scale arrangement. Google Extreme Flight and check out the torque revolutions. Doug

RE: Hangar 9 B-25 ARF: Building and Modifications
 

Hey Doug, I plan on using electric on mine. I was looking at the Skyshark 50 combo with the 60 amp esc and 5 cell 5k battery. Which Torque motor did you test? Skyshark suggested to me that a 13x8 3 blade is where I want to be with their combo. Love to hear how your's performs. Mine is still in the box until the holiday rush is over. Thanks, Jerry.

RE: Hangar 9 B-25 ARF: Building and Modifications
 

I used the bolt and dowel along with gluing the tail on. Used lock tite on bolt. Had to add 1/32 strip balsa on right side to level the tail with wing.
I did replace the tube and wire for the elevator and replaced with Sullivan heavy duty tube. Also used the existing push rod in the inner tube for more strength. Fit nicely.
I used two 2500 5 cell NiMH in the nose for balance and added 2 oz to balance out on CG then added another 1 oz as safety factor after loosing the other plane.
Bill PTC

RE: Hangar 9 B-25 ARF: Building and Modifications
 

I gotta say it: I question the recommended (by Hangar 9) C.G: 3.75" behind the leading edge, where the chord is about 14.375". That's about 26%, which is far less than the other warbirds that I have (usually 30 ~ 33%) . All them have tapered wings, so that is not an issue.
Top Flite recommends 5" for their B-25, and if we assume that because it is 10% larger: the root chord would be about 15.8125", the C.G. would be 31%. That sounds much more 'normal' to me, so I intend to throw caution into the wind and balance mine at least 4 1/4" back (with gear up), or about 29.5%.

Any other thoughts on this? Anyone else question the CG on this plane?

BillPTC: it sounds as tho your's pitched up when you lowered the flaps, and eventually resulted in a stall/ spin. The fact that it pitched up has nothing to do with the CG: MANY aircraft pitch up (and some pitch down) when flaps are lowered. Trim changes are needed, or better yet: program some mixing in which will result in down elevator being added when flaps are lowered. In any event: one needs to be ready to make immediate pitch (elevator) adjustments when an aircraft pitches up. Don't wait to see what happens next: push the nose back down with the elevator control.
And anytime one is flying with flaps and gear down, and at reduced power, one should be thinking of allowing it to descend. Turns need to be descending turns (due to higher stall speeds in turns). Flaps adda LOT of drag, which is why power is needed to maintain altitude.

But then again: maybe I'm all wrong. I'll find out next spring.

I cut my 139 gr. (4.9 oz.) aluminum tube spar down to a 37 gr. (1.3 oz.) / 6" piece for a weight savings of 3.6 oz.
Am I foolish for doing so? I don't think so. Many don't realize how much strength there is in fully sheeted wings, IF they are properly attached to each other. Adding some glass cloth and epoxy to the tops and bottoms at the root seam will bind the wings together in such a way that the strength of the sheeting will be fully utilized. Of course: some weight will be added (glass cloth and epoxy), but I doubt that it will amount to over an ounce.

Keeping warbirds light has always worked very well for me. I especially HATE having to add weight to balance a plane, and I will do whatever I can to prevent having to do so.

RE: Hangar 9 B-25 ARF: Building and Modifications
 

Hi Jim

I am not building one of these, but following your theards vary close, some how it seams I learn a lot from them, but for this old dog please a few more pic's woud help

Bob t

RE: Hangar 9 B-25 ARF: Building and Modifications
 

CorsairJock
Thanks for input. I had not lowered the flap and was at 3/4 throttle making normal left hand turn otherwise I would agree with you. Found this out with my Han9 Supercub but was high enough to recover.
I did try the flapp high and level at reduced throttle to see how much up pitch. 1/2 flap gave none and full gave a little up pitch.
The end resolt of roll over and spin was a stall but could not get out of it.
Finished rebuild(new fus) and added extra 1 oz to nose for next test flight this weekend.

RE: Hangar 9 B-25 ARF: Building and Modifications
 

Hi Jim-
I'm also trying to save wieght. My wing tube is 140 grams and I am considering a carbon fiber wing tube since this would be a substantial wieght savings. My wing tube measures about 8 thousandths less than 25mm. Would you mind measuring yours to see if it is also just shy of 25mm in diameter? These tubes come in a 25mm size.
Thanks,
Tim

RE: Hangar 9 B-25 ARF: Building and Modifications
 

corsair jock, while waiting for mine to come in, i have a set of retracks and stucts needing to be cut to lenght. Would you know the dim. from mounting surface to bottom of wheels. Thanks Bill

RE: Hangar 9 B-25 ARF: Building and Modifications
 

Tim, I thought about a carbon fiber tube also: they weigh roughly 1/2 ~ 1/3 as much, but the best price I could find was about $45 shipped. I measured the outside diameter and found it to be an even 25 mm.

I have 4" wheels (which BTW: are actually LIGHTER than the stock, H9 main wheels) that I will be using on mine, and I came up with a top of strut to axle centerline measurement of 4 1/2" for my RoboStruts. Approx. 9/16" of that length will go into the retract trunion.

RE: Hangar 9 B-25 ARF: Building and Modifications
 

Jim-
Troy Built Models is advertising a 25mm CF tube for $29.95 in December Model Aviation p.44.

RE: Hangar 9 B-25 ARF: Building and Modifications
 

My B-25 is nearly completed. Rather than fly the beast on two unproven new Evolution 36 engines, I mounted them on my trusty ultra stik to log some flying time and test props. I've now logged over one hour of flying time on each engine and tested three different props (APC 10x6, APC 11x4, MA 9x7 three blade). First let me say each engine fired up and flew with very little tweaking. In the over two hours of flying neither engine skipped a beat or showed any sign of dying. I flew the majority of the flights using an APC 10x6. The last flight on engine number one was flown using a MA 9x7 3 blade. The last two flights on engine number two were flown using an APC 11x4. The best prop is the APC 11x4, the APC 10x6 OK with the MA 9x7 only marginal. So what's next? Both engines are now mounted on my Hobbico Twinstar to see how well they work together. If these engines keep performing the way they have so far they'll be flying the B-25 soon.

RE: Hangar 9 B-25 ARF: Building and Modifications
 

Fly my second test flight on HAN9 B-25 yesterday. I hd destroyed destroyed fus on first flight.
Second test flight on replaced fus was OK but overcast day grounded me for another flight. Will proberly put WWII evasion strips on wing.

One-O-Wonder;
What rpm where you getting on the prop test. The stock 10.5x4 3 blade was only turning up 10,000 rpm and was marginial on mine.

Bill PTC

RE: Hangar 9 B-25 ARF: Building and Modifications
 

Just bought one. Have not got it yet. Boy am I excited! Will be watching for tips on modifying it.

Question, other than the retracts, do you need any other special servos for this plane? Will Futaba 3004's work?

The guy I bought this from did not assemble it and said it was a "dealer promo B25J" and that only 20 were built, does anyone know what this means?

RE: Hangar 9 B-25 ARF: Building and Modifications
 

In my opinion: Yes. Well, at least for ailerons, nose streering,and elevator. You WILL need mini servos for the rudders. And I think the flaps could use some servos with a little more torque.

tevans55: If you buy a 25mm carbon tube, AND it is longer than you need: I will buy a 6" section from you. Let me know (e-mail me)

RE: Hangar 9 B-25 ARF: Building and Modifications
 

djsdog --
The "dealer promo" is probably one of those that includes the engines (EVO 35s); they're already mounted. Apparently they did a few of them and sent them to dealers as rewards. No one knew anyhting about them until they got there, and H9 charged the same price for those as the ARF w/o the engines. That's my guess, anyway...

RE: Hangar 9 B-25 ARF: Building and Modifications
 

Anybody venture a guess as to the scale diameter and length of the pitot tube on a B-25B? Actual specs would be even better. Or does anyone have a top or bottom view of this plane that could be used to estimate the dimensions?
Thanks
Tim

Jim- Wing tube is scheduled to be delivered to me on Monday...I'll try to send out to you Tuesday.

I also have been trying to find some documentation on the size of the air intakes in the wing of the "B" model. They clearly are not the size of the "J" model. I have attached the best photo I have found to date...hope this works. I'm going to try to rout out this intake rather than use the supplied intake which is clearly to large. Check out all the tread on that tire...guess they figured there was a good chance they wouldn't be using the tires again.

Just found this second photo of what appears to be a B-25B at Dayton. Great shot of radiator opening! Somethings wrong here...the pitot tube is on the wrong side and so is the nose gear offset. I'll bet someone reversed the negative.

RE: Hangar 9 B-25 ARF: Building and Modifications
 

BillPTC........The target rpm for the Evolution 36s that came in first H9 B-25s is 12,000. Right now I have both of my engines mounted in a Hobbico Twinstar with APC 10x6 props. Each engine tachs right around 12,000 with this prop here at 6,000 ft. The 6 pound airplane takes off easily at half throttle with this combo. I have no doubt the Evolution 36s will fly the B-25 here well. I'm going to use APC 11x4s on the B-25 which also tached aeound 12,000 rpm.

Another thing I'm doing to my B-25 that I haven't heard anyone else talk about is using Hitec digital servos on the flaps. Besides the obvious reason of more torque I'm doing it for two more reasons. First, I used the Hitect digital servo programmer to reverse direction of one of the servos eliminating the use of a reversing 'Y' or two channels of my radio. Second, the programmer allows you to slow down servo speed so that my flaps take about 6 seconds to deploy. A lot more scale and should not have any violent pitch changes either

RE: Hangar 9 B-25 ARF: Building and Modifications
 

MOBYAL

I was told this promo version was built better that the standard ARF's, (better balsa or something) also, I,'ve heard there are two versons or runs of the H-9 B-25 (early and late?) and if so what is the difference?

I don't know if it makes any difference but it just kind of concerned me.

I want to do this plane right and with my limited experiance, I can't even figure out which servos to use. When you build a plane like this, you don't want to get cheap with the equipment but I also do not know if I need to spend $15 bucks for a servo or $50?????

You guys are great at helping me out and I'm great at asking stupid questions!

RE: Hangar 9 B-25 ARF: Building and Modifications
 

djsdog --
I don't know about any differing build quality or different runs. Was just told that some had the engines added.
I'm waiting for my plane now, which is in the batch that's supposed to come in sometime this month.
I have collected everything I need except the airplane, and somewhere on here a few pages back I listed what I've got. So far as the servos are concerned, I just went with what's recommended in the manual, except opted for lower cost JR micro servos for the rudders and the retracts. I bought EVO 46 engines with Slimline Pitts style mufflers and a larger than recommended battery pack, and right now have about $1150 in the thing; it'll be about $1500 total when I get the plane, before I even turn a screw. But you won't have to buy either the engines or the mufflers, so that'll save you considerable $$ right off the bat.
Good luck and let's keep asking questions -- I'll have a bunch when I start, I'm sure -- and comparing nottes.
Al

RE: Hangar 9 B-25 ARF: Building and Modifications
 

Hi folks,

Hope I'm not hijacking Corairs' thread here, couldn't find a more appropriate one.

I finished my H9 B-25 a few days ago and flew it yesterday. It's all box stock, I made no changes to the kit, just installed the stuff and flew it.

Equipment:
Evolution .36's
Servos are all JR DS821's except rudders which are NES341's, retract valve is a DS285.
Hangar 9/Robart retract kit
JR R921 2.4ghz receiver
2x 1500mAh NiMH receiver packs
JR X9303 Tx

It flies extremely well, I'm very happy with the model. First take off was long and straight, with a gentle climbout. Handling is very crisp, responsiveness to aileron and elevator is great. Rudder is not like a aerobatic model but more than adequate, it has a lot of vertical area to overcome. Did some rolls and loops, handled them fine.

I'd have to say the power of the Evo .36's is perfect for the model. They operate easily and economically and have plenty of power. Quite steep climbout's are possible and it will loop from level flight.

I balanced it at the recommended point without fuel and the gear down. Had to add some lead in the cockpit (nose was already glued on), about 10 ounces I think. I didn't check all up weight. At that CG it's perfect, I wouldn't change it a bit. On the second flight I got very slow with full flaps and gear down and was at maybe 1/4 throttle with the nose up, it got mushy and started to drop a wing but a little power and lowering the nose took care of it. It's a pretty forgiving model.

I fly Mode 1 so couldn't really hand the tx around but a M1 friend flew it and was impressed. He did some rolls, loops and cuban 8's with it, looked great.

It lands great. Gear down, half flap, come back on the power and it establishes a moderate descent and is easily flared. Made me look good with some greaser landings. One of the landings I used full flap and it worked well as I was a little hot and high, got it down without building up speed.

I'd been running the motors at home with the EVO three blade props but managed to break one at the field due to my stupidity. A friend of mine on the way to the field stopped by the store and picked up a couple of APC 11-5 two blade props and this is what I flew it with. Worked fine. My field is close to sea level (<100') and unless you're at altitude would recommend sticking the .36's. They fit great in the cowl and are a prefect match for the model. A pair of four strokes might be nice too but it would depend on how easily they could be installed and not have hassles with throttle linkage location and exhaust etc.

It has a great look in the air and was really popular at the field. Not too many twins around and the sound alone is unique.

Craig.

RE: Hangar 9 B-25 ARF: Building and Modifications
 

I dislike having switches and the filler valve mounted externally on the model, but couldn't come up with a location so they're on the outside. The belly pan is easily removed but that space is pretty well filled by the wing. I ended up putting a switch each side of the nosewheel steering hatch, with the air filler next to one of them. They are not directly in the line of fire in the event of a gear up landing, and can't be seen unless you get donw and look for them.

I had some leaks with my retract system initially. There are five tees required, these are supplied in the H9 kit. Most of the leaks are at the plastic tees. I replaced them with Robart metal [link=http://www.horizonhobby.com/Products/Default.aspx?ProdID=ROB225]tees[/link] and the system is now practically leak free. Loses a little after sitting a couple hours but will do several cycles per flight with no problem.

Craig.

RE: Hangar 9 B-25 ARF: Building and Modifications
 

So I may as well order my metal tee fittings now! LOL