fytrjok

My Feedback: (2)

Carlos,
I asked the same question many pages ago and never got a response(understandably). I will tell you that I live at 5280 ft. and the 70's work fine here. The B25 certainly won't win any races but they are at least adequate at this altitude. One thing you need to keep in mind, prop selection is VERY important. My maiden and 1/2 dozen subsequent flights were done on APC 13/8's which peaked at about 9300-9500rpm. I richened both to 9000rpm and they were happy. My last flight was done with MAS 12/7 three blade props flown at around 10300-10500. The plane was sluggish on its takeoff roll and after a roll of about 500ft. into a 15-20mph breeze I was able to horse it off...exciting doesn't exactly fit but suffice it to say that I changed back to the two bladed 13/8's shortly after I landed! You should see that big B25 nearly hovering at full throttle upwind! I will try a set o 3 bladed MAS 12/8's on the next flight (when calmer conditions apply). Then I'll try a pair of APC 13/7's (2 blade) to see if I can get the RPM up a bit. The manual says the 70 FS II"s are most happy at around 11,000rpm where they generate 1.1 horse power. I'll keep you posted on the results next week.

Doug

carlosvaldesb

thank you Doug for your comments ill wait for more comments, thanks

krproton

Doug,

which .70's are you using?

I am using the .70 Surpass II's (no longer available). If you go back and read posts I have written you'll see I preferred the MAS 12 x 8 3-blade props, though the 12 x 7 worked okay and the APC 13 x 6 2-blade performed the best (marginally over the MAS 12 x 8 3-blade).

I use Wildcat 10% nitro 2/4-cycle fuel. We are pretty near sea level, or I think maybe about 700' above, here in Champaign.

What were you asking about the engines? Maybe I missed the post (or just didn't know the answer!).

Tim

sgoen

My Feedback: (5)

Just venting, I have had my brakes on order from robart for about 2 1/2 months now. When I call them to find out how much longer, I get a different story every time. Once it is 3 weeks then a couple of days and then 3-4 weeks. I have also been told that they need to make a part, then they are waiting on another company to make the parts. Sometimes I wonder how they stay in business and if there shop is no in a basement somewhere. I am not sure I will ever see the brakes at this point. I just whis they could get the story straight. Oh well thanks for listening.

norm

Hey Sgoen, Know How you feel, they told me the same but the brakes are now on my B-25!!! patience and persistance!!!

Normand

Greg2102

Normand,

I have enjoyed following your setup for Saito 82s on the B-25 and think I am going to go the same route. Is there room behind the engine and in front of the firewall for a flex pipe exhaust to the other side of the cowling? The VP-30 fuel pump, is that electric or a vacumn system and would the VP-20 do just as good a job since you don't have to drill the engine case with that one?

Thanks

Greg Brown
Greg2102

norm

Greg,

You cannot use a VP20 on a twin set up. You do not have to drill a hole in the crankcase, you only "T" the crankcase vent tube to create the vac / press from the crankcase to activate the pump. You would prefer to use the VP20 I know but it does not work that way. The vp20 oscillate from the engine vibratrion. This oscillation is annuled or counteracted when you have another vibration created by engine #2.

Also the cowl is too small to route a flex pipe to the other side.

Thinking of it, if I would rebuild the plane I would mount the engine with the head @ noon, "right side up", and avoid the extra worries caused by the piston head down....Same result and more reliable.

About the pump vistit the site of the pump and the connection setup for the VP30: this is the link to the connection setup, http://www.perrypumps.com/Pump%20and...s%20System.pdf

Normand

Greg2102

Thanks Normand,

Two VP-30s it will be with a T in the vent line.

If the Saito 82s were sitting on their sides, the left engine with the head facing the fuselage and the right engine head facing outboard would that flex pipe work? Saito also has a part which comes out of the engine and is an immediate 90 degree angle, not the hard pipe but a fitting, I wonder if that would work?

Greg

norm

Hey greg forget about it, not enough room I know the part and it is too big! The exhaust is level with the cowling. Sideways with the exhaust spitting to the floor would also be good but my mind works symetrical.... No matter what it will be noisy and oily...

Really no matter the set up this is the most powerful set up available for this plane @ 1.5HP each side in this size, you cant beat that. You can spin 3 blade MAS 14 x 6 @ 9000RPM and 3 blade MAS 12 x 8 @ 9900RPM. Enough power to spare very surprizingly for the size of this plane. My first feeling was that a pair of 125's would be the least but I flew this plane with the 82's and it is fantastic.

Normand

fytrjok

My Feedback: (2)

Tim,
Us guys up here in the thin air were wondering if the 70's would provide the necessary zip to motivate a 20lb+ Warbird. I think I asked that question about 15 pages ago and never received an answer. I figured it was one post you may have missed...no big deal.Obviously, since I've flown this plane successfully in Denver we all know the 70's work! I'm running a pair of the OS Surpass FSII's (because I had a pair on hand) and they are certainly adequate with the right props. I'd be willing to bet that I will come to the same conclusions as you did re: optimum proppage. However, altitude effects planes and engines significantly as we all know. What you learned by experience, I am reinforcing. Up here (5280ft.) we generally power our models with engines at the upper range of the recommended specs. Since there was no "range" given for the B25 and you convinced me that 70's were sufficient...that's what I went with. After flying the B25 a 1/2 dozen times or so, I'd say 90fs would be the maximum at this altitude. I'm sure some will engineer a way to do that but not me! The 70's work fine and sound great! The plane flys very scale at 1/2 to 2/3 throttle with the 2 bladed prop. At sea level prop choice is not as critical and flaps are a bit more effective. I love taking my heavy metal to Warbird fly-ins at sea level! It's like flying on a big pillow. I've seen guys whose elevator usage would invert their plane in a heartbeat at altitude. I believe flying up here enhances a pilot's skills, not only in flying but in building light as well. Again, you did a great job developing this B25...if it flys great up here on 70 fs's it'll be magnificent at sea level! I will be testing the MAS 12/8's this weekend. I'm hoping they give me the same pull as the APC 13/8's. I'll also be testing the APC 13/7's and I'll bet these will be the best for this plane...but the 13/8's worked very well.

norm

Fytrjok,

Flying at 850mb is thinner air and require longer takeoff and landing run. Definitely you have this against you. It would be hard to answer the question you asked before because you're alone up there! You certainly are able to tell us more about it. My opinion is that since you run the engine leaner than at sea level, you can increase the nitro level and fly your B-25 with 12 x 8 MAS 3 blades. You will increase the torque and run your engines with 20% to 30% nitro will enable you to increase fuel consumption and get that extra power on take off. The speed is not your problem since you fly at theorically the same airspeed, but up there means this bird fly at least 20% - 25% faster than at sea level for the same airspeed.."pressurewize". Take off fly is more or less the same. Landing this plane definitely requires better skills because 25% faster on the landing speed is not to be neglected and mistake are increased by the same. I see your runway is long and brakes would be a good idea on this plane at this height

I have seen your pictures and Kudos to you, you built it nice and certainly enjoyed it.

I just spent the last week-end doing maintenance on my B-25..and after 5 flights, fine tuning it and revising all snags I must have spent at least 60 hours. I'm confident it is ready to fly now.

For the noze strut, iI placed a rubber groomet to avoid a knock on the oleo.
It is also a good idea to verify the wood bblocks holding the servos of the ailerons and flaps to acertain that they are solid as mine were broken loose on 1 aileron and 1 flap, I also placed a 2 sided foam tape between the hatch and the servo , just in case.

I agree with you for the B-25, it is a nice model and requires a TLC and lots of maintenance almost like the real thing, it is a machine!

Cheers,

Normand

camdyson

Hi Normand,

Could you elaborate on the rubber grommet for the nose oleo?

thanks,

Cam

norm

Hello Cam,

Well it is extremely scientific and took me lots of egineering skills to develop this safety system for the front strut, and please do not reveal this to anyone! (what I said)

I remember earlier on this thread you revealed some secrets about magnets and it is good I have all kinds now. Finished are those days screw@%$ with screws, i try to see where I'll install them next, well I'll reveal this secret!

Here is some pictures of my groomet system. Sometimes the simplest is the most effective. I hope it will enable a bounce on the front strut instead of a knock and cause something to break, it has'nt been tested other than on a table but it is promizing for the cost!

Cheers,

Normand

camdyson

Aah, very tricky. Thanks for the tip - might copy before the patent application goes through and I have to pay you.....

RadarController

My Feedback: (2)

Alright guys... I'm kickin around the idea of getting one of these. Couple questions.. What's the deal with the engine selection? I see one guy using a couple 81's. Are a couple 70's not enough juice or is that just bling? As far as the Robarts are concerned. How many gear transitions does one air tank give?

norm

You will get the naswer to your questions in the first 10 pages of this thread. Hope you enjoy this plane.

RadarController

My Feedback: (2)

Anybody a promoter of Saito's? Say the 72 or 82?

sevans16

Radar: the OS FS-70II have been discontinued. Not sure if the FL-70 would be the way to go(enough power). Lots of debate on the OS 70 Ultimate. The 81@ seems to be the new replacement for the 70II. A local flier has one with YS-63 and I hear it does quite well. There are a few on here using Saitos as well. Lots of choices. Just look for an engine you are familiar with or some of your locals can help you with. Since there are two engines I kept mine simple as possible to aid in reliability, ease of tuning and coordination of the two engines.
I forget all the details but: a reg air tank with 100psi?? fill is good for around 6-7 cycles. Most guys are going with the large tank. They added instruction for installing a large tank. Very simple, no worries.

Lots of info here on building if you do get one be sure and read through it all.

RadarController

My Feedback: (2)

Why debate on othe 70 Ultimate? Seems like a light/reliable choice?

camdyson

There's been mixed response to these as some find harder to tune and set up, plus if you apply the KISS principle they have more to go wrong. Plus $$$. No doubt good engines if you're comfortable setting them up reliably. Ditto YS.

Since the 70 Surpass' is gone, the FL 70 ought to do fine - 81's even better but $$$$$.

Norm's Saitos sound a good option too, I just like OS (got a couple of the last 70 Surpasses luckily).

So long as it's oily and noisy (hi TT ), any of these are good once set up I'd expect.

Cam

toreo

Thanks, Heat1960!
anyone know scale pilot for B-25 ?

fytrjok

My Feedback: (2)

Toreo,
Decent 1/9th scale pilots are not easy to find. Most reasonable price is Century Jet (www.centuryjet.com) for a full body pilot...about $25.00us each. They are pretty heavy so I drilled out as much of the insides as possible. Hanger 9 makes a 1/9 pilot bust...probably the way to go unless you're going to build a full cockpit.

Doug

timothy thompson

My Feedback: (1)

test flew e power 6s 2p 10,000 mah 15 min flight omg what a sweet bird at 22 lbs flew great! bomb bay worked flawless. now i can stop freezing and work on my b-17. i still have rivets and screws to add. she flew on 45 10,000mah 75 percent of top power. I ordered the last two batts, so we will have full power

camdyson

xlnt wlle dnoe......

fytrjok

My Feedback: (2)

What, no pics????