Grodus

I was hoping to get some input on engine choice for the balsa bobcat ( not the XL) , I figure there many here that experience with this model.
Except for paint, which is a major hangup for me, I am close to starting the install on my balsa Bobcat. I purchased a Wren Supersport at the same time and that’s what I had planned to put on it but Im reconsidering. I have a Falcon 120 with a Superbee on it that is soon due its second 25hr service. I figure this airframe has 250 or so flights on it and there is not a thing wrong with it besides being “old hat”, so im not sure I want to put the Superbee back on it.
The Bobcat manual states not to exceed 175mph. My F-120 does 155 in level flight and the Bobcat looks to be a little cleaner so it might be very close to the recommended limit. How fast would I expect it to be with a Supersport? I am looking for it to have a bit more zip than the F-120 but I don’t want it to come from together either. I know it’s a proven design but the 3D ailerons on the Bobcat concern me a bit.
I’m thinking I might be happy with a Superbee powered Bobcat and saving the SS for something larger like a Turbinator, putting the F-120 on the shelf for a while. Also, Im not able the 3rd tank in the Bobcat but the 72 or so ounces in the wings is more than adequate for the Bee and Im not sure I could get a 7 min flight with the SS on there without coming up with another tank.
What do you think? The install weight will be about the same, maybe slighly lighter with the SS. Im not looking to make a missle, I fly a Rabbit 90 powered Flash right now and am very happy with it. Will the Bobcat/Bee be boring and not much different than the F-120? Problems off grass? Will the Bobcat reliably handle the SS full throttle level flight?

I appreciate any input you may have.
Cody

AndyAndrews

Kingtech K100...

bevar

My Feedback: (27)

I have a friend who was flying a Bobcat Composite with a Super Bee and it flew great...if that is what you want to use...go for it.

My Bobcat Composite with a P-70 would hit 180 on radar so I think you are fine with the Bee in the WoodCat.

Beave

LGM Graphix

My Feedback: (22)

I have a bobcat xl with a p70, not a lot different than your bobcat. I would use the super sport, you can always throttle back but you can't add thrust that doesn't exist

Grodus

Thats a big block isnt it? I dont know that a K 100 would fit. We could try your K-80 in it and i could loan you my superbee.

Grodus

Jeremy remember your're a longwinger and Im a dirthawker, speed is not everything!.

Cody

Grodus

Thanks Beave, thats helps. I would be suprised if my plane weighed over 16lbs finished and I think thats quite a bit lighter than a composite version. There is the option of having the bee upgraded to a Superbee II that would bump it up to 15-15.5 lbs too.

Cody

roger.alli

I am finishing a Balsa Bobcat std right now as well. Up to priming stage..

I am going to fit a VT 80 which I think is a similar spec to the Super sport, 18 lbs. Having said this I have 2 friends with P 60 powered Bobcats, one std and one XL, these go great as well. I think that either of your engines will work. I guess it is up to you to decide if you want the extra power or lighter weight and longer fuel endurance..

I would however not put a K 100 size engine in one though. You can make it fit, but the model was really designed for the smaller cans.

Great models, and a lot of fun to build.

Hats off to you for building a real project..

Grodus

Thanks Roger, sounds like it will do well whichever way I go. I love the VT80, I think that is a great choice. Here is mine, almost 2 yrs ago. This was just before I learned what pin holes were. It was fun up till that point. I have tried to paint it a couple time since then and it hasnt worked out but I sure know how the sand now. I have since ultracoted the wings and stab, made wing bags, doing evetything I can besides painting. lol

Cody

gooseF22

Ss on a bobcat will be a great combo. Can't go wrong there

A very mild gyro setting on the rudder stops the waggle too. Amazingly so

smitty1001

My Feedback: (29)

Cody,

RAM 500 used to be the go-to on these, so anything you got will be more

sideshow

My Feedback: (11)

A friend of mine has 500+ flights on his original with everything from the RAM 500 to BMT 120 to Jetcat 120. Its a great airframe and you'll be happy with whatever you put in her. I had a Jetcat 120 in my XL and still regret selling her...

roger.alli

Ha-ha. Pinholes!!! I learned all about that when I painted my Super Bandit. So frustrating!!!! The grey top coat that BVM finish their mould with is very thin and if you sand through it, exposing the weave, dreaded pin holes will arrive.. Similar with a glassed balsa wing..

I am now very careful to only sand the minimum of the BVM surface, and when I do go through to the weave, I use this product http://www.amazon.com/3M-05095-Acryl.../dp/B003P6I5KS to fill the pin holes. It is a one part filler which I apply mostly using my finger (gloved of course) and simply wipe the excess off. It is quite thin and not structural at all so is only good for the smallest fill jobs. After priming, if there is any remaining pinholes, I simply apply this filler over the primed surface, sand the area, and reprime that spot. I’ve used the BVM pin hole filler, but find this product to be superior.

You know a lot of modellers simply ignore pinholes and paint over them!!!

It seems that painting is a skill that you can really only learn from practice. Keep at it and try not to be too critical of your own work. Very satisfying though. Hardly anyone bothers any more, in this day of plug and play..

Roger

David Gladwin

I can help you here as I built two of the original Bobcats, one standard with a PST 600 replacing the RAM 500 its 11 years old and still perfect. My other is an XL with. a JC P 70 which is 9 years old and still perfect. Between them they have 600 flights and have been flown in many parts of the world and were regularly flown off a short grass strip in the heat of an Australian summer, no problems !
Probably the most fun and best value model I have ever built/flown, fast, manoeuvrable with no handling vices, it even develops a wing rock to warn of stall approach. The accuracy and quality of the components made them a pleasure to build, too.

There is a caveat however:

When I built the first model for RCJI review I was critical of the servo spec. (I think JR 3421s were spec'd for the elevators and rudders)
JR subsequently issued an advisory that these servos are not suitable for gyro use and several Bobcats were lost following poor elevator response. I recommended and fitted JR 9411 servos to all tail surfaces and have proven perfect, and increase flutter resistance. Several guys contacted me to agree that replacing their original servos with9411s removed the soft elevator problem, so if you have an original kit with the original servo spec. do upgrade them!

A gyro on the rudders improves directional stability, particularly with the gear down and a gyro on the ailerons really smooths things out particularly in rough air.

A Wren Supersport would be perfect for your Bobcat, I am just about to install my SS in my std BobCat for a bit more vertical performance and speed.

Enjoy it!

Regards,

David Gladwin

PS Enjoy yours too, Roger you know how well l they fly!

Grodus

GReat info guys i appreciate it. David i did upgrade the elevator servos and am using a single HS 7985. As far as my install, does the airfame tend to build nose heavy or tail heavy? Not a lot of room to move things around but if they typically require a lot of nose weight it would be nice to know.
Also, I always read about 'flex plates on the BVM airplanes. I didnt see anything in the build manual refering to that but the nose gear unit has them and they are installed. I do not have them on the mains. Are they compatable with the orig Bobcat and are they necessary? Thanks

Cody

David Gladwin

So far as C of G is concerned it required only a tad of noseweight (about one small fishing ball) in the nose of both of my Bobcats. yes it is tight but it all goes in. That said, my two gyros are Weatronic integrated gyros so no space required there.

The main gear is bolted to ply plates on the balsa Bobcat but I believe the composite version uses flexplates. Not sure if these can be fitted to the original. These are a pig to repair but the only damage to mine was on a grass outlanding after the RAM flamed out., since then they have been fine, no cracking or other damage. I wouldn't bother to replace them particularly if you use trailing link struts.

I swapped the BVM main gear struts for JetA1 trailing link gears on my XL which worked great (I used to fly off grass for which they are ideally suited) until the springs fatigued, I then went through 6 nose flex plates at a meeting in NZ until we repaired the springs, I guess Roger remembers that with a wry smile ! Because the springs had weakened they compressed fully on landing, the nose gear then touched and we got a divergent bounce ! Since fixing the springs, no problems !

Other than that both of my Bobcats are standard and have given, and continue to give, superb service. You WILL enjoy it. Mine will be flying again next weekend.

Regards,

David.

roger.alli

Hi Cody, David ,

David, I am expecting great things from my Bobcat. After all I know that you consider them the “go to” model when you just want to fly for fun..

I don’t think it would be feasible or worth it to retro fit the flex plate system to the main gear. The existing ply UC mount plate is quite substantial and would require major surgery to remove. Pic below. Like David I will be using trailing link main gear which I understand is a bit more forgiving then the Duro struts.

I do suggest that you keep the C/F moulded plastic nose flex plates/arms as standard. I have used this exact system on a Balsa Bandit and it works very well. The arms do break if you bounce hard on the nose or run through a big pot hole, but in my opinion this is better than damaging the internal structure. I know some modellers have fitted unbreakable aluminium flex arms, but to me this defeats the purpose. They are a sacrificial component and you should keep a few pairs as spare in your flight box, they only cost $8 a pair. (can often sell them at a profit though eh David.. )They are easily replaced at the field.

Roger

Grodus

Ok, Great. Sounds like I dont need to worry about the flex plates on the mains. Question, did you guys get you mains to completely retract with trailing link struts? I have some for mine but they were prevented for retracting by the wing tube so I went back with the wire struts.

David Gladwin

Grodus, the trailing link struts do not fully retract because of the wing tube, its absolutely no problem. The wire struts are not really up to the job, and were soon discontinued in original kits. There is absolutely nothing wrong with BVM struts, particularly if you fly of smooth hard surfaces, in fact they work and last very well, but I feel the trailing link gear with its rather longer stroke is better for less than smooth grass strips , as I used to fly off in Australia. I think the hammering they got on my local grass strip was the cause of the spring fatigue, but replacement springs are cheap and quite easy to replace.

The nose strut on my smaller Bobcat IS wire and seems fine, but not for the mains.

Roger, after my flexplate breaking session in New Zealand, I bought half a dozen replacement sets, just to be on the safe side. Guess what, not a single breakage since we stiffened up the strut springs !! ( Psssst, wanna buy some, cheap, reduction for bulk ??)

Do let me know how you and Rick get on with your BobCats, (and your F100) and don't forget my invite to UK for jetPower !!

Regards,

David.

roger.alli

I also found the trailing link struts fouled the rear tube. In order to ensure they lock up, I have installed a 1/16 ply packed under the retract unit. They still sit proud of the wing a bit though.. ( Of course this is not flight tested yet)..

Agree with David re the BVM Duro struts, I have had no problems with these on both my Bandits, on grass of tarmack.

Will stay in touch re my Hun.. It is due back on the bench as soon as this Bobcat is done..

Roger