RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

...and the last batch.

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Doug,

you and the rest of the guys who are "scaling these out" are killing me! [sm=wink_smile.gif] I mean, I love it! You guys are really getting into these things and making them your own. I'm honored that you are enjoying the B-25 enough to spend all the extra time on it.

Well, with winter setting in I guess we'll have to wait a few months for flying pics.

Keep us all updated on your projects in the mean time.

Looking great!

Tim

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Ken,

I'm really glad to see you made it fine on your surgery! Way to go! :)

Flavio

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Thanks Tim!
Give us a great platform...watch us fly!! Now I'd like to talk to you about ARFing the GS P47.....:D

Doug

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

I don't know why we (Great Planes, Top Flite/Hobbico) haven't followed up the Top Flite giant P-51 ARF with another giant-scale ARF warbird yet--probably too many other things we are working on first. But I do speculate that within time there will be more warbird ARFs and surely some of them giant-scale. Just don't know when. [sm=72_72.gif]

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

fyt nice work there thats the idea. next plane p-38 c-130

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

maybe a b-17???? :D

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

i have to make a area for the lipos . So i use a approach used in full scale i sheeted the section of the top of the fuse where the batts will go. i have 4 big batts to fit in 1 4s 5000mah plaus 1 3s 5000 mah each side. so i wetted the sheeting in ammonia and it went on well. I was gonna quit and my wife comes over and says Tim you are modifying this and doing a great job continue and you will get it done.
FIRST PIC THE FUSE IS UPSIDE DOWN WITH THE CAM POINTED STRAIGHT BACK THROUGH THE COCKPIIT. THE WOOD FLOOR IS A START OF THE LIPO MOUNTING SYSTEM. THE SECOND IS SHOT THROUGH THE HATCH IN THE BOMB BAY. I CAN GET 14S IN THERE! 7S EACH SIDE. i WOULD LOVE TO ONLY FLY 4S EACH SIDE BUT NOT ENOUGH POWER. REALLY NEAT IS ONLY THE STEERING WIRES AND THE POWER WIRES ARE UNDER THE SHEETING AND I AM RIGHT OVER THE CG . SO ACCESS TO ALL IS POSSIBLE. ECALC SAYS I CAN FLY ON 4S FOR 3 MINUTES BUT 9 MINUTES ON 7S EACH SIDE. THERE is plenty of room for the thinner 3s cells. i may have to go a litle up the sides but its all enclosed and wont tangle flight wires. i will tape together the 4s and 3 s cells to make handling easier.

at 12:00 ive got the sheeting glued in and it will work

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

The thing that makes me scratch my head is the fact that the design/kit/plans etc. already exists and has proven to be one of the best large warbirds out here. I know the ARF GS 'Stang differs in some small areas vs. the kit version, but it seems to me that it would be much easier to ARF the P47 than design something totally new. I'm not saying new isn't great, but the GS P47 is just such a good platform. I'd be first in a hugely long line of buyers I'm sure! Just look at how successful the GS 'Stang ARF has been.

Doug

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Finally got my YS 63 mounted today. Spent about six hours getting everything set up. Have to paint the dummy radial now and will then be able to show the completed engine with cowl installed. What a great ARF. As mentioned before, one of the best ARF's I have ever had the chance to put together. Way to go,Top-Flite.

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

You can get a 2 1/2" nose wheel if you request it. 2 3/4" is what our initial information showed it would use. The mains are a scale 16 hole pattern - like the B-25 used. There is also a brake system available.

Dennis

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

A question for Tim (Krproton)..I finally received my plane the other day. I must say you guys put together an exceptional aircraft. I would like to know how you establish the engine size when designing these aircrafts. Is it by size, weight ?? I did have to laugh a little when I saw the wheels that were supplied with the kit. I've seen $100. ARF's with better wheels. All your hard work in designing this beauty and the powers that be choose something that in no way compliments the aircraft. Every kit has it's faults I guess. Better the wheels then say the airframe. I'm just curious about the engine selection since I've had a few planes that when finished with the recommended power plants seemed wofully Under powered. Maybe you can enlighten us in this matter. Thanks Dave...

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Europact,

I have had the same impression when I first saw the size of the plane. I have Saito 82's and I tell you it is well powered and in low level overpower territories. My first impression is that the plane required Saito 125's and still be borderline. The OS 70 Ultimate would probably be the best choice of engine for this plane and in a perfect power range, and trust me all my planes are overpowered because I like Power and speed @ 1/2 throttle.

Your question is good: "how do they come to that conclusion 40- 50 size...?" There must be a simple formula, specially for the Cessna 310 I can hardly imagine 2 x 0S46 in that plane, I'm thinking od 2 x Saito 100 flat twin and still!! Look at the size of it.

For the wheels, do not kid yourself, they knew everyone will go their own way, brakes, scale...too many choice and the plane was priced with fixed gear and those cheap wheels. Fortunately they did not make us pay an extra 20$ for a better quality wheel so they included a 10$ wheel and wire kit to at least get it on wheel meanwhile. Consider those like a temporary solution, some are still waiting for their retracts or scale wheel...Glennis takes 5 week, robart is out of stock for brake or wheels. When your model is put together and you whant to fly you can have a temp solution.

Enjoy your B-25 it is the greatest ARF I've put together.

Normand

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Hi Dave.

Thanks for all of your compliments--except for on the foam wheels--I know, they're not great. :eek:

But hey, even if we included even slightly better wheels, say foamies with a tread or average-looking rubber wheels, people would still probably toss them anyway for Robart's or whatever else is out there. Or, if we included just the right kind of really scale wheels that would please everybody (say like Robart's or something even better), they would be too specialized and may not be able to be used on another model in our lineup. Then, the economies of scale would dictate that the price of the kit be jacked way up to "pay" for the nice wheels. :(

Well, that's all just speculation on my part anyway.[sm=spinnyeyes.gif]

How do we determine the engine size for each kit? First, we start by making an educated guess based upon all the years of experience anybody concerned with the project may have--and in this case it adds up to around 115 years! (I added it up; like around 35 years of modeling experience for my self, over 20 for our primary test pilot (including competition-winning scale experience and twin-engine experience), around 20 years for the Product Manager, around 15 years for the R&D Airplane Team Manager, and at least 25 years of modeling experience for the R&D Department Manager (which also includes several years of award-winning scale experience including wins and appearances at Top Gun, Scale Masters, etc.). I mean, we use all this experience to make an educated guess at what engine size should be used for test flying. Of course the plane's size (what is the B-25, like 88"?), the wing loading (40 oz/sq. ft?), type of model (scale WWII bomber), and the way it is intended to fly (scale-like with reserve power). Then, we go test fly it--and usually each project goes through the evolution of several prototypes--and those get flown too! And every single flight is logged in a book. If necessary (which is usually the case), we fly the model on other engines within the targeted range. Where a precedent has been set, we also consider that. For example, we know that every model in our 1/4-scale "Performance Series" (like the Yak 54 and the Sukhoi) should fly on a 1.60 two-stroke glow and a 50cc gas (don't quote me on those engine sizes--I was just using that as an example). Of course, this all has to be confirmed via extensive test flying.

So, that's pretty much it--we make a very educated guess to start out with, then confirm through lots of test flying.

If you're concerned about how the B-25 will fly with a given power plant, consider everything I have just written. You could also go back to the beginning of this thread and read my comments.

Thanks Dave!

Tim

P.S. Hey, there is something else to this that I forgot to mention. The question of "how do we determine what size engine to recommend for a plane" is premised on the fact that the plane came before the engine. But most of the time we design a plane around a particular engine or design the plane and engine combination simultaneously.

I guess the final answer is that there are many ways the engine requirement and plane size can come about and they are all based on experience and confirmed with test flying. [sm=49_49.gif]

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Thanks for the input. I had one bad experience with a twin that would'nt make it with the recommended engines. I have a pair of OS 70's that will be used in the plane and read here that they should be more than adequate. Better more than not enough. (Try a Lanier Shrike 10 with an OS 32SX and Mac Pipe if your into speed.) I am still waiting for the Air system as they are on Backorder from Robart. No matter. This will give me plenty of time to go through the instruction book and review all the numerous suggestions listed here. Thanks again...

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

I think we should organize a mass formation fly of the B25's this summer...say early June, somewhere at a good central location...hmmmm...like at Warbirds Over Denver. I can see it now...three squadrons passing in review...all with 4 strokes(or e-power with sound:D)...it gives me goose bumps!

Doug

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

What has been the most widely used engine on this plane?? I'm in the process of purchasing one of these and need some advice....I heard the OS .70 was discontinued...Thanks for the input on this ....Rick

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Europact,

For the engines you intend to use are they the surpass series or the ultimate The ultimate 70 w/pump is the better choice.. and replaces the 70 surpass....and you can go straight pipe! www.osengines.com/engines/osmg0875.html . for the subject of speed not for the B-25; For speed, I have a variety of engines...most impressive I own are the Jett engines for speed. Check them out, www.jettengineering.com , ask Dub about an engine that will fit the model you whant to see or at least hear fly by!

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

You may go to posting #11 on page 1...the most popular engine is the OS70 or the Saito 82, my choice is the Saito 82 and this is before I found the OS70 Ultimate which just appeared recently. I had bought the Saito 82's before the OS70 ultimate appeared. I still prefer the HP out of the Saito 82's.

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

question all my superdetailing has left me with a problem no room for a large air tank. i can fit the small 1 3/4 dia robart tanks thru the bomb bay hatch , I will connect two tanks thru a t to double my volume. Ive seen this done to increase the capacity. If i would have thought when i cut the fuse i could have a large tank.

idea 2 take off the tail and slide one in there. i forget how much room there is if anyone hasnt built theres yet could you post a pic of that last former so i can see the size of the hole.

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

What about the new OS81? I have two in the shop and looks like it would be great for the B25. As for me I have couple OS 91FSII and you bet I will fit them in the nacelles, 6' clock, I plan to use MA 3 blades 13X8 props. Like Doug mentionned I start most my planes from sticks but on occasions I still take on an ARF and work-it up! This B25 is great but I have to do it Bruno's way so, the covering had to go (sorry Monokote), the canopy and nose are also going to a new ones, the nose is gone ( got the plug almost ready fo the straffer version), of course I called Dennis at Glennis for the wheels with breaks. The stab and deck section are glued to the fuselage. some micro-balloon here and there, sand,prime,sand,prime..... et voila! Yep I love it, Oh! Forgot, the wood nacelles are going too can't fit the engines propelly on them so I opted for something else, be assured that I have some in mind already!
Keep the pictures coming!
Bruno

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Hi

Have noticed a few posts which mention the OS 70 Ultimate, has anybody used a pair of these and if so did what engine mount did you use. I have found the standard ones do not provide the 5" required distance from the firewall; the beams being too short. Of course this could just be me missing something. (Which is more than likely :eek: )

By the way great thread.

Pad

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Does anyone have any pics of how you ran the throtle are with the new OS .70 II engine. I was getting ready to run the throtle arm and noticed the throtle linkage is on the bottom of the engine mount. You can not turn the engine or the muffler would be on top and on the wrong side. I have not really started to see what I will have to do, but any ideas?

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

there is another mount for the servo. its inside towards the top. look in the manual. it shows it.

dan

RE: Top Flite B-25 ARF (Tecnical, tips, suggestions)
 

Sgoen,

Page 15, 351 to 356 is another way to pass the throttle linkage. You picked the probably best engine... By all means go straight pipe you have a pump. You will not have to butcher up your cowl. Too bad snow invaded us, and your B-25 is not finished I'll be in Elkhart next week I would have packed my B-25 for a flight!

Numerous ways to mount those engine, and the ultimate is smaller, should fit perfectly in that cowl.

Normand