rodney-00

Hello Everyone,
New to the forums and new to rc planes. Started fooling with them last year. This winter I put 2 Great Planes extra 300 kits together one 40 kit and one a 60 kit. On the 60 kit I installed a OS BX-1 108 engine. I was wonder if someone could tell me what size prop would be good for this engine (which is oversized) and plane. Thanks in advance

jester_s1

The owners manual will have the right props listed. You'll probably do best going on the larger diameter with less pitch side of things. That will help it pull verticals better and not get going so fast.

I hope you're going to get some help with the maiden and first flights on those Extras. They are not beginner birds by any stretch of the imagination.

speedracerntrixie

My Feedback: (29)

I'm not sure what effect that Webra carb is going to have on your engine but I found an APC 15X8 to be a real good prop for that engine in an aerobatic model. If you can find an old Bolly CF 15X8 even better. I have run the 108 in a Lanier 1/4 scale Laser, an Aeroworks .90 Edge and a Dave Partick Ultimate bipe. Great engine for this type of airplane.

jetmech05

Get help with your extra's they are not a good second airplane
good luck

kiwibob72

Aerobats like this have a low wing loading, and huge tail fins that keep them tracking like an arrow in the air, and traditionally are a breeze to land as they just float in for landings. The issue with them as a second plane is the size and throw of their control surfaces and the general power to weight of the things.
IF - and i do mean 'IF' they are set up correctly with the right amount of limited throw and expo settings set up within the transmitters settings, and your not an utter idiot on the throttle, they are actually a very good second plane in my opinion, they come out very smooth on the control input's, they track fantastically well and float in for landings at stupid slow speeds (all the traits of a good 2nd plane right?).
I had a Yak54 that was de-tuned in this manner as a second plane, and it flew fantastically. BUT, and again it's a big BUT, you HAVE to get the control settings right. This is the point at which you need to go find assistance if your not already, as there is no simple % to reduce everything by as you don't always get the same thrown from model to model as each has different mechanical setups and needs to be adjusted separately as a result!
Case in point, we have a guy at our club with a 60" MXSR, initially at full throws it was an utter monster for him to fly, it pitched, bucked and over corrected all over the place. 5 minutes spent getting the throws and expo right, and she flew fantastically and it's now his weekend hack that he flies day in day out (in amongst his new 50cc aeroworks bipe that's setup with the same mindset!)

speedracerntrixie

My Feedback: (29)

I would have to agree with that Kiwibob. I had my daughter flying my 33% Laser around before she could land her trainer. The only thing I would add here is that this particular Extra will have the additional weight of that large engine and that weight is all in the nose. Rodney, make sure you get the airplane balanced correctly by shifting batteries to the rear. If you need to move the rudder servo to the tail to get the correct CG then do that too. The worst thing that can happen here is have the CG too far forward and then set too much elevator throw to compensate. Keeping the throws in check, using expo and having the CG in the middle of the recommended range and this airplane will fly like a Sportster.

JohnBuckner

My Feedback: (1)

OK I am really confused I have never heard of a BGX-1 108 or a displacement of 1.08 cubic inch. Although their once was an OS 1.08 but that great engine (got some of them too) is definitely not a BGX-1.

I also have a BGX-1 but its displacement is in fact 2.13 cubic inchs (35cc) and have never heard of a BGX-1 of any other displacement. So that leaves a bit of mystery as to what you actually have? By the way the BGX-1 came with a conventional OS Carb and not a Walbro.

If what you actually have is the OS 1.08 Then great that will be a nice powerful combo with that sixty sized ARF. But if what you have truly is the hugh BGX-1 then that is a grossly oversized engine for that airframe and what usually happens when you do this, there is most of the time big negatives to the conversion and airplane while they can be fun but overall actually do not fly as well as if you had used a reasonable engine combination.

Also one of the negatives is it is going to take a talented pilot to survive with it. So if you are a beginner this airplane(s) are not likely to survive.

Get help and find a mentor.

So what actually is that engine? Its impossible to make a propeller recommendation without knowing the size of the engine.

John

speedracerntrixie

My Feedback: (29)

John, the OS 108 was in fact a BGX-1 not to be confused with the OS BGX 35cc glow engine. I have no idea what BGX stands for but apparently OS feels both engines are in that category. The Carb in the picture is a Webra TN carb off of a Speed 120.

BelAirBob

Looks like a really nice covering job. Post a photo with the wing on when completed. I have been flying the GP .60 for ten or twelve years with an OS .90. I would probably not recommend as a second plane either, but it is definitely not that hard to fly. The wood is very thin to keep light so the plane is very fragile in places. The ABS parts were pretty junky so I would get fiberglass cowl and wheel pants. I have ripped the landing gear off several times so I use nylon bolts to hold in place. The bolts break off rather than tearing the wood. I think I am using a wood 14X6 prop

good luck

belairbob

JohnBuckner

My Feedback: (1)

I think the 1.08 may have been called the BX-1 at one time but not BGX-1 I have two 1.08's in airplanes and after a little digging with a mirror and torch they are cast with the FSR model marking Those two date back a long time I have long since lost the original manuals but a search of the web reveled manuals listed as OS 1.08;FSR and in parenthesis BX-1.

I am holding my BGX-1 in hand and the differences between the 1.08 and the BGX-1 1 are clear. The smaller engines most obvious ID point is the fact it has a round cylinder and the BGX-1 one is square. I also believe SRT that you are right about the carburetor as that is not the 1.08's stock carb in the picture.

So I believe the engine in the picture is definitely not a BGX-1 but a 1.08 FSR (BX-1) and it probably safe to say that most of the prop recommendations in this thread are pretty good but not with the BGX-1.

I too would love to know what all the B's, G's and X's stood for

John

speedracerntrixie

My Feedback: (29)

Ok Now you have jogged my memory and are correct about the 1.08 being BX. Good running engine none the less.

rodney-00

Thanks Guys for all the input. John is correct the engine is a OS Max BX-1 1.08 and the carb is a webra. I also started out flying a Parkzone VisionAire I have about ten flights under my belt with no gorilla glue as of yet (knock on wood). Done the maiden flight on the 300 40 kit it has an OS .46 engine and it flew great. What is the rule of thumb on the expo how is it suppose to be set?Here is a pic of my 300 40, my VisionAire and a small piper cub I built from a kit

OliverJacob

My Feedback: (12)

I fly my Extras with around 35 - 40 % expo. It depends on your max throws.

Just a few months after I started flying rc planes, I got a used Kangke Extra with an OS 46 FX and a tuned pipe. And I found this easy to fly, you just need to make sure not to stall it. It will drop quite a bit before you can recover.
I did spend some time on the simulator, that helped a lot.

rodney-00

I to did some time on simulator

JohnBuckner

My Feedback: (1)

When using Expotential for the first time,
to acheve the desired effect which is less response close to stick neutral positions but still the same throw when full stick is applied, it will be necessary to dial in either positive or negative expotential depending upon the brand radio system you are using.

Hitec or Futaba you must use a Negative or (-) for the soft center and with JR, or Spectrum you will need to dial in Positive (+) expo to acheve the same effect. Be very careful when dialing this in also as with any of the systems its very easy to scroll so fast that you can actually scroll into the wrong polarity so fast that you don,t even realize it. Doing this or just using the wrong expo polarity from another brands system can turn your airplane into an uncontrollable nightmare.

John