Dumas Bearcat....

[KSU Flyer]

Thought I'd post a quick pic of my Dumas Bearcat conversion, inspired of course by Tom Hunt (guy who wrote an article about this conversion for RC Microflight). I've decided to do a few things different from Tom though....

My plane will utilize a:
GWS DXA power system
2 Hitec HS-50 servos
GWS reciever
Castle Creations Pixie 7P speed control
(a great little programmable speed control)

I don't have an exact AUW right now, but I'm positive she'll weigh in around 8oz.
(if you're wondering the Dumas Bearcat has about 170 sq. in. of wing area)

Here's a pic....

-Mike

[KSU Flyer]

another pic...

[CalmAir]

Looks great Mike. That one ought to be a handful! What did you cover it with?

Dale

[2NG]

Beauty, I love it:) Who makes this kit ?

[SteveH]

Real nice!!!

[KSU Flyer]

First of all, thanks for the complements guys....

Calmair,

The covering is Solite/Nelson litefilm, I love this stuff. I hope it flys a little more sporty than the stuff I'm currently flying.

2NG,

Dumas makes the kit, it is originally a 30" wing span rubber band free flight kit.

-Mike

[Richard Miller]

The picture evokes a memory. The Bearcat arrived at our field after the war had ended, but I guess it had been in the pipeline. We watched the C.O. taxi the first one out to the end of the runway, accelerate past us, pull up and disappear going vertically. That sort of thing kind of makes an impression on you.

-Richard

[KSU Flyer]

Richard,

I'm glad my pic got you thinking about the full scale Bearcat...
I hope my version has the same vertical performance you described, but somehow I doubt it.;)

-Mike

[KSU Flyer]

It's pretty much done.... I plan to test fly it soon.

[2NG]

Hi Mike,

I just saw your pics. over in EZONE... Your plane is sweet, and like Dreamer said, I too am going to getting one of these baby's!

How long t'll the initial flight report? I can wait:) Did you in anyway, reinforced or modified any thing?

genovia

[KSU Flyer]

Thanks 2NG, I like it too!:D

There is definitely some modification required due to the whole conversion process. If the weather cooperates I'll be flying it tonight! I'm pretty excited....


-Mike

[KSU Flyer]

I posted this in another forum, so if you visit both, I'm sorry for the duplicate posts. Another thing I want to add before anyone replies is that I built the Bearcat wing with the stock diehedral, which has each wing tip elevated 2". The wing span is 30" with about a 4.5" flat center section.

Feel free to jump in at any time Dave...


Alright guys I want your opinion of what I should do here. I'm going to describe the behavior of the Bearcat and see what you think I should do to make it fly better.


1st attempt:

First of all my flying spot has a nice concrete parking lot surrounded by grass.

I eased into the throttle and the Bearcat quickly picked up some speed, I then applied some elevator and it rose quite nicely off the ground. I gave it some left rudder to begin to turn and I immedi ately noticed that it liked to stay in the left turn. I gave it some right, then full right, and it started to come out, but I got scared and cut the throttle. About then it touched down just in time on it's wheels and rolled out. whew! almost really bad.

2nd attempt:

I thought I would increase the rudder throw to max to see if I just needed more throw. This time I decided to make a right turn after I got enough altitude and made the turn much wider. Great a successful turn. So on the next turn I performed another right turn (slightly more aggresive) and immediately noticed that it liked to stay in the right turn as well. I applied some left rudder to counteract the right turn. This time I pretty much had the same response as the first flight and so I cut the throttle and it sort of hit wing tip first and then rolled out on its wheels. whew again, only this time I sorta scratched up my pretty covering job

3rd and last attempt of the night:

Frustrated and puzzled I thought I'd try one more, you know, the feeling where you just can't leave the damn thing alone. I took off, and it rose off the ground just perfect, then I applied some left rudder and sure enough same thing only this time I wasn't so lucky. I hit pretty hard and cracked only a few sticks so I had to quit for the night. I'll fix it up and try it again.
At this point I'm pretty disappointed and confused, but by no means ready to give up. I'm like my dad, I'll tear it up before I make a wall hanger out of it!

Summary:

I'm starting to think I need more rudder area. I put the stock amount of dihedral in it, so I don't think it's and issue of not enough, maybe too much?
I hope a few of you guys have a recommendation. BTW, my friend managed to get an in flight pic, so I'll post it. Like I said, if the plane never had to turn it would be the best flying plane in my fleet.

[Dave Robelen]

Hi Mike,
You can increase the rudder, but the effect will be somewhat like a band-aid. For a low wing plane with high side area and a tall rudder, that dihedral is on the low side. The problem with the rudder is basically it is like a vertical aileron. When you apply say, left rudder, the tall rudder is also giving a right roll force that cancels a lot of the roll from yaw. Look at it from the rear with the rudder deflected and you will se what I mean. Adding more rudder will add to this effect while it increases the yaw force. The por thing really needs ailerons like the full scale for solid control.
Regards, Dave

[KSU Flyer]

Thanks for the reply Dave...

You're absolutely right, I wish I would have just put some ailerons on it in the first place. I've learned a pretty valuable lesson here. After flying the Bearcat and then taking a look at what you and others have mentioned makes perfect sense. So anyway, I've already made the decision to put ailerons in, which unfortunately means quasi-major-surgery. I went to the local hobby shop last night and picked up a new servo, some of Sullivan's awsome 1/32" flex cable, so let the surgery begin. I also contacted Dumas so I can buy some new decals for the wing. I still have a very good feel about this little warbird, and I plan to keep the rudder, so I'll have a full house Bearcat that I think will end up at around 8.5 oz.

-Mike

[KSU Flyer]

Welp, the subject says it all. What a great flying little plane! The plane is now a full house warbird that has absolutely no bad flying characteristics whatsoever. I'm attaching some pics that my girlfriend took just a few minutes ago. The pics show just how stable it is, it's like it flies on rails. I didn't get after it too much as I wanted to have it for at least one day.

I took it up 3 times and each time it just got better.

1st flight was with a 10x4.7 GWS prop and a 8.4VNiMH. It flew good, but I wondered if the 9x7 would make it better even though this fat little warbird has a big round cowl.

2nd flight was with a 9x7 GWS prop and a 8.4V NiMH battery and I noticed it had quite a bit more power immediately. Basically it just screamed off of the runway.

3rd flight (last of the day) I was running a 9x7 GWS prop and a 9.6V NiMH battery....As you can imagine it was pretty DAMN fast! I had to throttle it back pretty good for my girlfriend to even have a chance to get a pic with my digital camera.

I'm going to try to get some flight video up on my website soon, but for now I'll post some stills

-Mike

[KSU Flyer]

another pic...

[CalmAir]

Hey KSU,

Congrats on working the kinks out of it. Sure looks good in the air!

Dale

[FLB]

Hi KSU,

Very nice work and pictures...

FLB

[KSU Flyer]

Thanks Dale and FLB,

Sometimes it's tough to want to continue to tinker with a project when it doesn't start out so go, but in this case the extra time and work has paid off. I plan to get some video of it really soon, so you guys won't have to take my word for it, but this is a really nice flying plane. I would recommend converting the Dumas Bearcat and possibly other Dumas 30" models as maybe your second or third balsa built airplane.

I almost forgot, I can't quite take the credit for the photos, that was my girlfriend. Not a bad job ehh?

Thanks Again

-Mike

[Buddly6]

Haha, looks great. Next person to do this- take out the rudder and add RETRACTS!

[KSU Flyer]

Thanks Buddly!

I've been thinking the same thing. I'm considering doing another Dumas conversion and I'll probably combine the rudder and ailerons, and put some retracts in too.

-Mike

[micro_man]

Hey, I found a place that sells a conversion to go over the regular bearcat conversion. It turns it into a rare bear reno racer. you get the lower cockpit and shorter wings and decals and stuff check it out here http://home.fuse.net/ryan/rarebear.htm

[KSU Flyer]

micro_man,

I think you're confused about the Bearcat conversion. My Bearcat is a converted Dumas free flight rubber model and is not related to the Hobby Lobby Rare bear. That's alright though, because the Rarebear is pretty cool too.

[KSU Flyer]

Hi all,

I posted some video of my converted Dumas Bearcat on www.silentflightonline.com
You can go to the site and click on imagebase, then Parkflyer-Inflight Photo/Video, you can sort through the files until you find my Bearcat or click on this link to download it immediately from silentflightonline....

Bearcat video (http://www.silentflightonline.com/Site/Members/ImageBase/Images/724.wmv)

-Mike

[sootall]

How did you do the the ailrons on your plane I was looking at the kit and when I saw your plane I looked a little more.. can you give me so advice on how you went about doing the RC conversion....

I would love to post your story on my website...

http://www.sdparkflyers.com


thanks in advance

Robert Webmaster sdparkflyers.com

[KSU Flyer]

I’m glad my little Dumas Bearcat got you to consider this conversion for yourself. This fat little warbird has become the favorite plane in my fleet. If you decide to do one of these, I don’t think you’ll be disappointed. Just make sure you put ailerons on it as my original version only had rudder and had problems. Be sure to read this whole thread and the free article by Tom Hunt on www.rcmicroflight.com and I think you’ll have a good idea of what you need to make this work. But more specifically, be sure to replace some of extremely light/fragile 1/16” balsa stringers with either some harder balsa or light bass/spruce. Be sure to add some 1/32” balsa shear webs between the top and bottom spars in the wing. I’ll post some pictures of how I control my ailerons. I’ve used this method on more than one parkflyer and have yet to experience any problems. All you have to do is get some 1/32” Sullivan Gold-n-Flex control cables and you’ll be set. I’ll post a pic on how I mounted the GWS DX-A. If you look really close at a GWS DX-A you’ll see that it can be mounted with 3 small screws in lieu of the “slide over the stick” method. In my opinion using the mounting screw method was much easier for this type of plane. My plane is full house, i.e. throttle, rudder, ailerons, and elevator, and still has plenty of power, so don’t be afraid to do this on yours too. Be sure to take a look at the link to flight video in this thread, I think you’ll like the performance you see. I fell in love with this plane when I got comfortable enough to start doing some low quasi-high speed passes. In hind sight I would have put the GWS retracts in it too, but that’s for my next conversion project. I’ve got a Herr Engineering 30” Corsair in the works that I’ll try to put retracts in.

As far as posting a story of how I went through this on your website…
I’m afraid I didn’t do a very good job taking step by step pictures of my progress and in all actuality I pretty much built the plane box stock besides the items mentioned above.
I think you would have a much better article if you go through this process yourself and document it as you go. In my opinion you’ll come out with a better article that people will enjoy reading and most importantly an awesome little warbird.

[KSU Flyer]

pic of motor mount...

[KSU Flyer]

OK, I tried to get the pic of the aileron cable routing posted...I can't get the file size small enough to post on this web forum. There is another popular electric forum and if you do a search for Dumas Bearcat you'll find the pic. sorry, but 60KB for a pic is too small

-Mike

[sootall]

I ordered my Bearcat yesterday so it will be my next project on my website thanks for all the info.. stay tunned for my report on how to build and fly the Bearcat comming soon... thanks

[KSU Flyer]

I'll look forward to your progress...Best of luck!

-Mike

[sootall]

quick question did you do the ailrons on your Bearcat like described in the article in micro flyers, I saw a post and you had said something about ez-bend rods or something is that how you did your bearcat... I have kinda a idea of how it is done you snake tubes threw each wing and bend it so it comes out under the botom of the ailron and attach it to the ailron with a small arm.. then mount your servo in the middle of the wing and use a linkage setup to controll your surfaces...

[KSU Flyer]

I think the 1st post on this page explains my aileron setup pretty well...take another look at it

-Mike

[468/f]

Hi Mike,

I just got here. I really did enjoy reading the thread. You produced a nice plane. Your work makes me think I might like to try it sometime.

The video was the trick! Really nice!

Thanks,

Roger