doxilia

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The Webra 2 ccm (.12) ABC RE Speedy (#1008) - a ducted fan engine:

I caught a glimpse of this little jewel on RCU a few months ago and immediately gravitated toward it. I contacted the seller but eventually the communication vanished into thin air. A few weeks ago, Isaw it again with some new pictures and Irealized it had to be the same beauty. This time around com didn't break down and it finally arrived at my door step today. I unwrapped all the goodies that came with it from the shoe box, and extracted the engine and carb from the box - both were extremely tight - oops! I immediately thought new bearings and cross your fingers on the carb. I went to work on it and slowly but surely after cleaning, lubricating and re-assembly she's as good as new. A couple of runs will eventually tell how well the front bearings are going to hold up.

The 0 degree header and 10" Macs straight tuned pipe are definitely designed for DF applications. If I could somehow retrofit the header to angle it at 10-15 degrees or find a suitable fuse top header, perhaps add a muffled pipe then we'd be ready for some serious planning. So, with that objective in mind, the simple question is:

What little pattern ship would you build for it? All suggestions and recommendations most welcome!

David.

dhal22

in all seriousness what size of pattern plane would this engine be applicable for?  a propped speed plane would be a great fit i bet.

doxilia

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Now we're talking... seriousness is the word I'm thinking of.

David, have you seen Mark's mini pattern creations over in RCG? He's scratched 50% Curare's and an EU-1A which look like little works of art! Those are electric powered which makes things a little easier - no exhaust to deal with. However... I've just been taking a look at these plans (save as .pdf).

I'm not sure if Walter would consider the PP 15 a pattern plane or a speed sport plane but whatever the case, the header and pipe that Ihave would actually fit right through the fuse. Question is, whether that will melt everything else inside!?

A 2-3 oz tank under the header and glassed pipe compartment with cooling slots along the top. The tail servos could go behind F3, the aileron servo is fine mounted inverted, the battery could go under the tank (I think) and the Rx in the front part of the belly pan. Doable, sensible?Dunno.

David.

rainedave

My Feedback: (1)

What a beautiful engine.

A while back I scaled the Brushfire plans down to 38" but never started building one. If you can find or make a 15° header it would be a good choice.

Right click and save as brushfire-38.pdf

David

alcarafa

Why not the picorare ?  ...with that kind of engine woooow could be a lil missile !!!!

doxilia

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David,

thanks for the great suggestion and plan. 38" is exactly where my thoughts were - something in the 30 oz range AUW. Iwasn't familiar with the Brushfire but Ireally like its wing and stab planform with its blazing sweep. The build sure would be intense at any scale given the numerous details.

I've been measuring things up on the plan left, right and center and Ithink it just might work with the engine mounted inverted and a few minor modifications. The header (at its current full length) would end just aft of the forward fuse/wing junction which Iwould move back by building the junction vertically rather than at a tilt. The former about the wing LE would be made out of lite ply and extended further down to simplify the wing mount via two dowels in the front. This would also leave the header coupler protruding through the doubler to allow the pipe to be jointed on mounting the wing. The pipe would be permanently installed in the wing belly pan by carving a recess into the wing rear portion for the girth of the pipe. Exhaust would be diverted downward just forward of the rear wing mounting bolts. The only tricky aspect would be the joining of the pipe to the coupler as access to the coupler clamp would be limited. A solution would have to be found.

I would build it either without LGor with fixed gear and light wheels as I'd like to keep it simple - not too many servos. While my idea was to use 4 servos total, the model calls for separate aileron servos particularly if one builds the wing as shown with flaps. The core concept of the wing is brilliant and I thought about exactly doing that on my next < 40" foam core model. I think a 2 or 4 oz tank could be located on a plate just above the header leaving the wing center undisturbed except for the flap servo. A simple 1/2A nose gear bearing could be mounted to the right side of the header (Ithink).

With an inverted engine a FGcowl would have to be made - Ican't see any way of gaining access to the engine with a fixed wood cowl (unless it's removable of course...) The canopy and turtle deck to my mind would also have to be carved out of foam and laminated with 1/32 balsa - or, done with formers and sheeting. I'm not big on clear canopies so Isee no reason to aim for one. Instead, I foresee the canopy as a removable hatch giving access to the tank and part of the radio compartment (battery/Rx).

Mmm... another option would be to make the nose bottom (gear) area removable to allow connection to the header. In this case the coupler would be fixed permanently to the pipe and it would be inserted though an opening in the fore fuse/wing junction. Yes, this sounds easier than making the belly pan removable. A third, and possibly easiest option would be to make a tunnel in the belly pan for an exposed tuned pipe. In this case gear would be mandatory.

Perhaps one more project to add to the agenda... A flying stab - now that would be cool!

David, a question, what's the full size span of the model or otherwise put, to what scale was this plan reduced? This would help to scale all the wood appropriately.

David.

doxilia

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Rafa,

I'm glad you caught this thread. I thought you might enjoy seeing that little engine. Iassume the pipe is the same as the one you used on your Pico and Magnum 15, right? It's an unmuffled straight 10" pipe.

Well, the first thing Idid was to unroll the Pico plans but with the header Ihave it just wasn't going to work nicely. The only reasonable thing to do was to source a fuse top header, which would have to be custom made and likely expensive, and mount the engine normally on its side with the pipe down the side of the fuse. Very doable but in the absence of that header...

On the other hand, I may have located a side exhaust muffler for this engine (cool thing brings the exhaust from the back out to the side) but that would defeat the whole ingenuity of the project and the revving of this little speed deamon - and that's why I bought the gem!

However, if Ibuilt the Pico with Illusion mods... now there's another idea. The arragement would be very similar to the Brushfire. The build would also be much simpler. I'll have to unroll the plan again...

David.

P.S. How're your projects coming along?

alcarafa

David projects are going well, Kaos .15 is done and flying quite well altough not as good as deceased picorare , I finally found the problem on my DX7 it was an output power problem, not the recievers.

I have send the radio to horizon and hope they can fix the problem, it's sad but dont trust DX7 anymore, I  have seen other  pilots here having problems with theirs also.

Im thinking on moving to airtronics 2.4 ghz , have read good comments about those.

The other plane ( you know wich one ) is almost done and hope it will end well under suggested weight, I build some parts from blue core and it feels very light, have a new electric engine for it  and also another NIB magnum 15, only thingh that keeps me from finishing it is retracts, have never installed one before so im studing well, how to do it right.

Let us know your final choice for that beauty you just got.

doxilia

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With a bit of Raindave's help, I was able to locate 4 pictures of completed Brushfire's. The first three pics are of the first prototype built by Ken Bonnema himself. I also believe that the pilot in the pictures is Steve Rojecki.

David.

doxilia

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Attached are the (PDF) plans of the 40" (~61% scale) span reduced version which are more appropriate for the Webra 12. Full size plan (first attachment) as well as letter sized tiled plan (second attachment). Save as Brushfire-10.pdf and Brushfire-10-Tiled.pdf.

David.

doxilia

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Ken,

I hope you catch this thread. Attached are a couple of planning snaps on my tiled plan printout. I hope you don't mind my uploading the reduced plan to the thread (please let me know if I should remove it).

As can be seen from the pics, the FW would have to be moved back one thickness (1/8") to allow the engine to fit. Who'd think a .12 would need space to fit!?

Attached are also the resulting specs (jpg &pdf).

David.

doxilia

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Rafa,

sorry to hear about your Spektrum troubles. Ihad similar ones with a beautiful JRCentury 7 that was my prized jewel (20 years ago). Despite it having brought down two models, I still held on to it. Iadded a Spektrum module to it but perhaps that's not the best idea. I'd also have to send it to Horizon for some work before putting it back into action.

I'm sure you'll have fun with that electric model you're building.

On the other hand "Kaos .15 is done and flying quite well altough not as good as deceased Picorare" might also apply to said model...

It's looking like convergence on the Brushfire is happening. I'm hoping that Ken Bonnema, the designer, might offer some insight into a few questions I had. Isn't RCU great!?

BTW, the Brushfire would make an excellent electric conversion! (it's terrible, every small model that catches my attention now, has to be duplicated in both glow and electric... I'll have to make some choices).

David.

alcarafa

Brushfire ? good desicion David sure you have plenty of questions about the model [&:], regarding small pattern models I think I have the same problem, since I get those electric engines I feel more confident with performance, there are no surprise's ( dead stick, carburation, hotshot etc ) with them, but u cant replace the smell of nitro burning  !

Im sure you ' ll keep us informed on this new project, but please finish the old ones first   !!!!!

doxilia

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In the interest of continuity of this thread, I'm going to repost a recent exchange on another thread with Ken Bonnema on the Brushfire.

Posted by myself:

Ken,

...

Speaking of looking forward, thanks to you and Raindave's suggestion, I've pretty much decided to build a 40" span Brushfire around a little Webra 12 REjewel that I picked up recently. Ithink I can make it work with the engine inverted and the header running in the nose gear retract bay (no retracts on this one) and out through the forward wing belly pan former. The 10" pipe would run under the wing and end just aft of the rear pan former where the exhaust would be diverted downward. Unfortunately the belly pan would be built as a tunnel rather than keeping the nice round contour of the original fuse bottom... some compromises. I think the pipe would be concealed for the most part though.

If you have any suggestions on such a project they would be very much appreciated. It would also be great to read the original MB article if you happen to have it.

I do have a few questions if Imay:

[*]the fuse side view shows 3/4 sq (3/8" sq at 60% scale) along the bottom and along the canopy base. The section views however show a round profile to the fuse as if triangle stock was used rather than square stock. I though about using tri stock but it would provide little support for the "strip formers" at the base. Am Imisinterpreting something or do you think either one would work?[*]The 3/8" ply firewall is shown to be cut with round contours all around. How does the square stock in the retract bay intersect F1? Does one shape it to contour around the former? Likewise for the square stock beneath the canopy at the F1 junction? Do you think that cutting F1 with square angles at these intersections and providing a square slot for the stock to enter would work equally well? I'm thinking of something analogous to the way spars enter notches in balsa ribs; the square stock would meet and join F1 flush with the front of it.[*]Did F4 interfere with the flap servo or were notches just cut into the base of the former to allow the pushrods to pass back to the torque rods? I was thinking of omitting F4 on my little version. I don't know whether it makes any sense to install flaps on a model this size (a wet AUW of 33 oz is my goal).[*]The 3/32"balsa flap ribs are marked F1 through F4 with F4 being the largest rib. The wing plan shows these ribs as running from root to tip on the flap F1-F4 which would produce a wider flap at the tip than the root. Does this make sense or should the ribs be inverted running F4-F1 root to tip (flap would taper in thickness toward the aileron junction)?[*]Any suggestions on how to secure the round aileron servo covers? Simple 4 screws or did you guys do something clever? I was thinking of mounting the micro servo's with foam tape to the covers.[*]I really like the wing and stab planform as well as the wing core design. It would be really cool to use a flying stab! Any suggestions on how to do this (what hardware) at this scale?Maybe it would be simpler to just use elevators and a fixed stab.[*]Was the height of the landing gear as shown suitable for an 11" prop? I'm able to get a 7" prop to swing clear on the reduced plans but would have to raise to allow an 8"prop. Do you foresee any problems with a higher stance?[*]Last ones: what was the wing span and weight of your first wood/foam model? Did your glass ones come out lighter or heavier?[/list]Thanks in advance for any help you can provide.

David.

doxilia

My Feedback: (3)

Posted by Ken in reply to my questions:

David,

I don't mind the plan being posted. The original plan from the MB article appears several places in RC Universe.

Now on to your questions: Wow, you're asking me to remember back 31 years for details of a one-off building project. I'll give it my best shot.

- Yes it was square stock, but it had to be carved on the outside and hollowed on the inside to the contours shown in the fuselage cross sections on the plans. I spot glued them on initially, then carved and sanded the outside. I then popped them loose and carved and gouged the inside so that about a 1/8 to 5/32 wall thickness resulted. Then they were glued back on permanently. It was never an easy airplane to build in the balsa version. You can use triangle stock, but you'll have to extend the fuselage sides up to the top of the canopy rails and down to the bottom of the lower rails or you'll have nothing to glue the triangle stock to. As I recall, I contoured the fusealge and canopy separately and finally glued them together only after sanding. If you don't do that, it's very hard to carve and sand the concave discontinuity between the fuse side angle and the canopy side angle (See Section B on the plans).

- Yes, everything was contoured to fit the around the firewall shape shown (See Half Section A on the plans). I believe the firewall was glued to the flat fuselage sides first. Then the 3/4 square was shaped as described above and glued to the fuse sides and the firewall. Finally, the top block and bottom sheet were shaped and glued to the fuselage and firewall. You can put square or triangular notches in the firewall, but make sure you have plywood firewall wherever a motor mount bolt goes.

- I think I cut away the lower cross member of F4 to make room for the flap linkage.

-The flaps are a constant chord, but the wing is highly tapered. This makes the inboard end of each flap a smaller percentage of the local wing chord and the outboard end of each flap a larger percentage of the local chord. The result is the outboard end of the flap is thicker than the inboard end. The plans are correct - the deepest rib goes outboard.

- Our aileron well covers were Trim Monokote. The servos were mounted to a plywood floor in the well.

- The first Brushfire had a flying stab using a Giessendanner (sp?) mechanism. The nylon control arm that came with it didn't fit inside the narrow fuselage at that location. So we drilled a hole for a threaded rod control arm in the square aluminum bar that was the spar for the two stab halves. It worked great until the stab came off in flight and totaled the airplane. The aluminum bar broke right at the small hole we drilled. You're never so stupid as when you're being smart! I haven't been following the hobby as of the last 20 years and have no idea what kind of flying stab mechanisms are available these days. Can someone else help out here?

- Yes, we ran 11 or 11 1/2 inch props. The Brushfire was very solid on its gear. You should have no trouble lengthening it some as long as the wire diameter isn't too flimsy..

- Balsa Brushfires ranged from 8 1/4 to over 11 pounds. It all depended on how much hollowing you did, whether the wing was built up or foam, and if it was foam, whether or not you you included the lightening holes in the cores. Fiberglass versions with cut out foam wing cores could come in at less than 9 pounds. The span was 65 inches.

Good luck with your project. That engine and the size you've settled on should be a show stopper.

Ken

doxilia

My Feedback: (3)

Posted in reply to Ken's detailed answers and suggestions:

Ken,

your reply and answers to my many questions are invaluable. Many thanks for taking the time to go back 31 years in cadid detail!

Ithink Ican see a little clearer now on how to go about things on the reduced scale version.

I'll be sure to inform you of the results of my project when the time comes. Hopefully, I'll manage to get a build thread in.

Best regards, David.

doxilia

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An electric Brushfire 10 (I'll stick to calling it a 10 this time and not a 15) with retracts would be wonderful! In several respects it would be easier to build than the glow version.

I will bring the project to life later when, as you say, other projects are wrapped up - the wrapping will all happen this summer (some of it is already happening!)

The inspiration and planning of projects in this hobby is one third of the fun for me - especially scratch built projects!

By the way, unless better ones come along, I've already chosen radio gear for this model: Futaba 3114's on a Spektrum Rx

At 24 oz of torque, .09 transit, 7.8g, small dimensions and an excellent price, they sound like the ideal choice for models of this size! Perhaps not as good as the Hitec HS-65's but considerably better than the HS-55's. It's been a while since I've used Futaba servos.

David.

ccp10

David,

In post #10 you list as attachments, the full size plan and from what I gather is a 61% tiled plan. Is this correct? I downloaded and printed out the tiled version. This is what I used to start my build with. You mention here and in the Pico thread a 40 inch version. This tiled version only has a 38" span. Did I miss something?
Anyway as you can see from the picture It's comming along. I think it's way to small for the Magnum 15XL and Macs pipe I planed on though. Auw is 19.5 oz as you see it in the pic. this is with a built up wing. I expect this is as far as i'll take this one, cause I think it needs to be a little larger.
Good luck with the Pico!

chuck

doxilia

My Feedback: (3)

Chuck,

what a beautiful rendition of the little Brushfire! I'm sure Ken will be duly impressed (as am I!). I hope he's subscribed to this thread.

Your description of the plans in post #10 is correct. I produced the tiled version so that I could print and assemble at home. Attached is a (poor) snap of my tiled plan. You can see that it's half span is barely shy of 20" - this is due to the tiling and excess cutting and assembly process. If the wing came in at 38" span (actually 38.4"), I have the feeling it is due to your printer scaling down letter size printouts to 96%. This is pretty common and is done to ensure content is kept within margins - my HP laser printer (on which the plans shown were printed) does this by default. In order to print to scale I have to tell it to scale to none. Do you think this is what might have happened?

That aside, at 40", I think a 15 would be at the upper end of the desired power (perhaps a K&B 18 tops). I really custom tailored the plans to fit the Webra 12 with pipe as shown higher up in the thread. At 38" (closer to Rainedave's original scaling), we're really talking about a Brushfire 10.

With that said... you absolutely must finish that jewel! At 38.5", she'd be ideally suited for an OS 10 FSR, a ST X11 or similar. You could put a 2.5cc macs pipe off the side of any of these engines but it probably would be just fine an ounce or so lighter without the pipe and a muffler. Alternatively, you could venture into the wild and bolt an outrunner on to her, forget the landing gear and go have fun at your local high school!

If you're really set on building a 40-42" span version (42" would be better for a Mag 15), I'd absolutely love to finish her! She looks like a diamond in the rough to my eyes! I could see if the Webra 12 fits but I think at that scale, I'd really be inclined to putting the other Pico motor I picked up.

I could send her back to you with a 1/2 page "how to fly a 10 karat electric Brushfire" instruction sheet. But you probably wouldn't need it...

Man... nice job! Does the entire foam deck come off? Looks like the wing is permanently attached - make's sense. All access must be through the canopy. It also looks like you brought the fuse sides down to the bottom plan line and used tri stock for the joint. That's what I planned to do too. They're nice plans.

David.

P.S. I re-uploaded the plans in post #10 as files with PDF extensions. No need to rename extensions any more as PDF is now supported on our forum.

ccp10

David,

My bad on the plans. I took the first attachment up to Staples and got two copies of the 40" plans. Now to order up some wood and whittle out another one. The first was a good learning tool for things not to do!
Believe me when I say, you don't want this one. The picture looks okay, but you can't see all the problems with it. The wing has a little twist in the right half, kind of like washout. Must have happened when I sheeted the top, as the wing was built upside down flat on the plans.
The fuse is a little banana shaped too. One side curved a little more then the other. I also added some anhedral to the stab. Looks like it could use a tad more. Yes, the entire canopy is removable for access to radio and fuel tank.
The fuse sides do come down to the bottom and have triangle stock on the inside. The bottom sheeting has not been installed yet. All bulkheads and firewall were made a quarter inch wider.
Anyway, lots of lessons learned and i'll be starting #2 this week.

Thanks for the kind words.

Chuck

roncoleman

My Feedback: (14)

Chuck

Love your little Brushfire.

Ron

turbo.gst

My Feedback: (8)

ccp10,

That little Brushfire looks good. What wing area and weight are you at? Makes me want to get out the foam cutter. Think of those little imperfections as little speed bumps. My second is always the better plane, but I try to learn all I can from the prototype. Great Job!

turbo

doxilia

My Feedback: (3)

Chuck,

how's #2 coming along? Plans bumped to 40"?

David.

ccp10

David,

After further consideration, I enlarged the plan 5% to give me a 42" wingspan. I just completed sheeting the bottom of the wing. Takes a little longer when you have to custom make each rib! I'm already at 5.5oz. Seems to me, if I remember right the 38" wing came in at 6.5 oz. Hope I'm not building a brick! Should have the wing done this week sometime.

Chuck

doxilia

My Feedback: (3)

Chuck,

good call. 2" of additional span sounds just perfect for a 15. I was wondering about those ribs but it sounds like it might be less work in the end than coring a foam wing. The top wing sheeting shouldn't have it tipping the scale at more the 6.5 oz like your previous one.

I actually just started planning out another small model (see my latest post in the Tsunami thread) for an identical 300W motor that I picked up (in theory as a spare...). I went for 43-1/4" span but the design has flat wide wing tips. The effective lift span is 40". It also has 310 squares compared to the Pico's 270.

I plan to hollow out the wood as much as I can without compromising strength. One thing that I was considering is producing oval shaped openings in the LE sheeting in between the spaced out outer ribs. This removes a fair amount of material. If done properly, it shouldn't weaken the structure significantly once covered. Of course, the model doesn't need to stand up to vibration. Someone built a full scale 58.5" span model to 3.5 lbs AUW so I'm sure it should be doable to build a 75% scale to < 2lbs AUW.

In any event, depending on your thoughts and outcome for the 42" Brushfire, I think I might go with that size too for the Webra 12 as I'd like to use a muffled pipe as opposed to the open pipe which is 2" shorter. The longer fuse should help to accommodate the longer pipe.

If you made tracings for the ribs, please preserve them! I sure could use them! Someone has to do the heavy lifting...

I look forward to some pics!

David.