combatpigg

My Feedback: (3)

A lot of those engine were fried flying AMA combat, pylon racing and sport flying with speed props once I got interested in RC Speed.
The last casualty was a very nice VA running on crank case pressure...the big end of the rod failed at 100 mph. No warning, no lean runs, plenty of oil...just simple fatigue of a weak part.
I like the proportions of the Toucan and would like to see you get a lot of solid data before shrinking the wing. It might turn out to be worth building a second wing if you are curious enough and inspired enough to improve on the original..

Pond Skipper

Per Mike,118 sq in or 108 sq in depending on what you read.
Prolly 118.AUW 9.4-9.5oz, we'll soon see = 11.6 oz/sq ft at 118 squares

After flying it Mike is seeing a floater on landings thus more wing than needed flying for speed.

From the site.Details: Wingspan 30 in Wing Area 118 sq in Wing loading 15.9 oz/sq ft Airfoil MH42 Mod Length 23.5 in Weight 13 oz RTF Controls Ail-Ele-Throttle Speed 400 - 6V motor and 10 x 500 AR cells,

Site says it has been recorded going 180mph with brushless so .09 on 6P / 29k / 165 mph would be nice.

This thing was made when lipo wasn't or may not still be allowed in the area where the designer races.
10 AR cells do weigh more than lipo and for sure more than a 1/2A set up.

30in span could do with a .09 per that chart I posted.


Year 2014 General Rule of Thumb:
Eng. / Span
.049 - 18 to 28in
.09 - 24 to 32in

Pond Skipper

The wing tips are well made for speed reducing major tip drag at the speeds your flying, would be well worth reconstructing if you reduce the span.

The Skorch is at 88sq. / 28in span I will be just under 11oz RTF so should be reasonable on landings.

MJD

My Feedback: (1)

Bear in mind the wing is fairly stiff composite construction and a 7.6:1 aspect ratio - higher than typical sport 1/2A models, so the span will naturally fall a little outside the rules of thumb. Average chord 3.93". But I also figure out I am better off with a precisely molded MH-43 airfoil than a TLAR sheet wing too. So far the performance bears that out.

I already asked about buying a wing only - nope, can't - exactly because I don't want to chop the original.

Yuck - 10 x 500 AR cells = 180g battery pack!

MJD

My Feedback: (1)

At the low lift coefficient with such a light model and being only concerned with straight line speed - is the induced drag reduction going to outweigh the friction and form drag? Don't see them on any F3 speed models. Without the precision of the CNC-mold tips, I am not entirely convinced adding them post-chopping will help. I'm of the opinion that winglets, elliptical tips, etc. are a waste of time and could even be a detriment unless they are designed and executed with a certain minimum level of precision that I am not sure is attainable by hand.

combatpigg

My Feedback: (3)

The guys who are involved with pylon racing and Euro RC Speed would have undoubtedly done side by side comparisons with equal power.
Both you and I have flown deltas with and without fancy wing tip treatment on the same power. I never had any "Eureka Momements"...but like you say the perfect tip design needs to be formed scientifically.

MJD

My Feedback: (1)

Yeah, I think it is not a big deal to put tip fins on at zero degrees, or even with a hair of toe in, and they work great - without any or most of us ever knowing if there are any other tangible benefits beyond yaw stability. Certainly no great aerodynamic risks beyond getting them on pretty straight and the right size and behind the CG not ahead.. etc. My biggest fear is snapping them off from hangar rash. Matter of fact.. my buddy bumped into the prototype (my avatar) whose fins were so far in excellent shape and had survived cartwheels.. and it fell to the floor and snapped one in half (you're cut off Danny, beer all gone now). But it was a 5 minute fix with epoxy and clothspins so who cares.

But to build beneficial tiplets/upswept tapered tips, at least as far as I think, takes a bit more science and a lot less SWAG to realize a tangible gain - as opposed to looking cool and not working worse than the regular wing. Perhaps it is true that it is easy to get no gains, and hard to get much by guessing? I dunno.. but the little I've read on tip design tends to point out that they are of questionable value beyond bling if they are designed by any other means than with some geek knowledge. I go back to years of competition rocketry (I did pretty well at that back in them days) where there were some pretty smart folks - MIT aero grads and all that - who all had come to the conclusion that trying to get drag reductions on rocket fins with fancy planforms was pretty fruitless - because among other factors generally once you get down to a small chord, the airfoil starts to resemble a 2x6 with sanded corners. The general consensus was that you were better off with square cut tips or simply rounded (i.e. radiused along the top and bottom edges of the tip) because you could actually make a good facsimile of what you intended to make. Details aside, the general philosophy rang true with me and still does. Bottom line is I'd probably not try anything cute on the tips, just go with what I know. With CAD and CNC mold cutting, things are a whole nuther matter.

combatpigg

My Feedback: (3)

I don't think you can go wrong with rounding the leading edge of the wing at the tips with a generous radius, instead of leaving a sharp corner. High Plains mentioned that the lowest drag wing tips have more span at the TE than at the LE. The term for that feature was "Advancing"..if I remember correctly.
So, the swoopy shapes that look good to many of us are probably pretty good to go with..
Too bad you weren't here today. It hit 55 degrees, was calm and overcast most of the day.

MJD

My Feedback: (1)

I should really read up on how to make better wing tips. I tend to go with what I know (a cute phrase that certainly suggests a degree of apathy). The flow does tend to go spanwise a bit, doesn't it (?) so the longer span comment at the TE makes sense.. voila yer raked tip. Such effects are reduced at lower lift coefficients aren't they?

Pond Skipper

Tip vortices are dramatically reduced from dragging boat chains on each tip to dragging some dog chains = )

Pond Skipper

Modern big Jets go with vertical turned up tips as it reduces stress on the tips yet still improves duration yaw stability is just a plus. Fuel economy allowing lower power levels for the same speed. My office is inline with the airport glide path, when the older planes fly over about 10 seconds later swirling high speed loud winds knock the tops of the trees no bird would survive the tremendous power of these vortices is enough to rip your head off. Yet when a modern jet goes over I hardly hear anything and no effect on the tree tops.

MJD

My Feedback: (1)

I'm with you, I appreciate their benefits. But at this wing loading and low lift coefficient I think the losses from induced drag are diddly-squat in comparison to all other forms. At this scale I still think - perhaps wrongly - the wingtips do a large chunk of their drag-saving work at high g's versus straight and level. Oh I dunno, I'm not there yet, sounds like something to think about for a while.

MJD

My Feedback: (1)

Found another bin with an 8" stack of 60's magazines. Hoped to find the rolled fuselage article but didn't.. sigh.

But.. lots of other tidbits. In the August '64 RCM, page 6-7 have a two page announcement, Dale Nutter had just "shattered" the magic minute in pylon. Sidewinder delta, 745 sq in, 2lb 12oz, powered by a Veco .19 on an 8-6 and Veco #2 fuel whatever that was. These days, specs like that would have me wondering if the thing was capable of climbing under its own power. I wonder how long the course was.. I'm guessing they flew about 75mph back then, 10 laps in one minute is about 1-1/4 miles (2km but don't think AMA used much metric then) so 1/8 mile per lap or so?

Also, an ground breaking announcement from RCM, the introduction of Monokote. Owen Kampen's Skampy (Dec '67), a bipe that looks like most bipes I've drawn and said "yeah, like that" (Hobo).. all kinds of interesting stuff to read about.

I got my new monthly edition of Endless Quad-Rotors a few days ago. I noticed there was a typo on the front cover, it said Model Airplane News.

Pond Skipper

Based on your feelings I would say the best thing to do is not touch the wing and be happy as it is.

aspeed

To fly a pylon racer in 1964 would be a feat itself. Reed radios or whatever they used. Escapements that were wound up rubber bands were not that much earlier than that. I have been going through stacks of magazines lately too. Just got in trouble, and had to put them back on the shelf. Christmas decorations seem to have some kind of priority on the coffee table. Anyway, we found that a small speed plane would just fly at a higher angle of attack, and have just as much drag as a slightly larger one that flies flatter. Of course being lighter and smaller would be a bonus. Our 1/2A's were about 45 sq. in. but some were less than 20 in the earlier days. That was control line, and roll control was not a factor.

combatpigg

My Feedback: (3)

At some point in time the AMA rules banned deltas. AFAIK, this rule was in effect before radios came with elevon mixing. I never have heard the explanation why deltas were banned.
It usually takes something pretty drastic to happen to get the AMA to take an action like that.
For some reason, the .19s were popular before I got into the hobby. Many an old kit I've seen included them in the size range. I've only seen one .19 running and it was a VECO with no muffler, just a moving baffle in the exhaust port.

MJD

My Feedback: (1)

Well, if I could get a second wing more easily.. i.e. for less than the cost of a new aircraft.. it would be fun to experiment. I have the remnants of a buddy's Sunracer.. there is almost enough of the middle of each wing left to make an .049 speed wing. The LE is crunched up a bit on one near the new "root", but I could likely repair it well enough.

I'm almost back on line with the laser cutter. One thing I tried in a brief experiment before I got it all buggered up for a while, was cutting a formica root and tip template for an SWR wing with some thinned section as an experiment. I glued these to the root and tip of a balsa blank and used a sanding block to sand a solid panel to shape from light balsa. Worked really well.. vacuum bagged with a really light glass skin and the requisite reinforcements on LE/TE/Tip as required, might be a good way to crank out a reasonably well profiled wing. That's if I don't figure out a cheaper way to buy hotsy totsy electric pylon racer parts first.

So yeah, in retrospect the Boomerang is a great choice and its clean lines may get me quicker than I hoped, or not. So far my reaction is that this is going to be a fun model and might have a good life span. But now I need to find the equivalent in about 75-80% the wing area and really clean molded wings. Now I have a better feel for what amount of wing is required with this type of construction and the resulting flying weight.

I'm not trying to poo poo raked and cresent tips.. I just don't know the rules to make them effective. Funny.. minutes ago I was staring at the wing panel of a high tech Ukranian made glider with film covered wing. Lo and behold, the last two ribs at the tip fan out at the trailing edge to form a few degrees rake. The tip TE is maybe 20cm span, the LE a large arc from the last rib LE. That was easy..

MJD

My Feedback: (1)

Oh for sure - I don't think I'd want to go any faster than that! Interesting to see how it has evolved is really what I'm getting at.

I agree that the lighter wing loading is a benefit - the goal is to get as close as you can to the wing's ideal AoA. On this model, at top speed and with the low flight weight, I even wonder if it could be below that figure, rather than closer to it than a heavier one. I could make the effort to check I guess but not tonight.. yawn. Been cleaning the deepest bowels of the workshop after pulling two Windstar loads of kits and airframes out to storage at the hangar. I am now in the process of removing 2, maybe three tiles from the sliding tile puzzle my shop turned into with crap overload. I'll keep all inactive aircraft, down the road projects, and.. well.. crap out there and get it when I need it. Hooray.. room to tidy, then to work. Found the mouse entrance too... saw it pop out as I happened to be looking.. guess where the traps are going now.

MJD

My Feedback: (1)

Actually, there is enough room for an HS-35 or HS-45 plus a Perry IMC. An HS-35 plus the valve weighs all of 10 grams. There is lots of space under the wing LE. 10 grams = 1.4 Dubro stick-on weights, and won't make the slightest bit of difference to the performance. I think that would be an obvious upgrade.

This would cinch the decision to run crankcase pressure and a 1oz (light) tank. Actually a 20cc film can without the waste I seem to perpetrate with a bladder, might be enough run time.

combatpigg

My Feedback: (3)

If you can make a religious habit out of rigging up that system it'll become second nature to you and you'll eliminate bad runs that are your fault and not the engine's. Would you need to place it behind the fuel tank...?
I shouldn't make it sound like I've ever gone this extra mile yet, but I intend to do so.
I enjoy being out there on a cold sunny day getting some air time, but struggling with a bladder has been a pain. I look forward to getting everything converted to CCP and just use latex tubing for slingshots.

MJD

My Feedback: (1)

I could put it in front of the bladder, but I also want to avoid putting the servo up near the vibration source. The distances are short enough, and I do have adjustability, so with adequate pressure I think it should be fine plumbing the valve from the LE to the engine. So far that is my way of thinking on the layout anyway.. I could be talked out of it for the right reasons.

MJD

My Feedback: (1)

Or chop the wings down then send them to you for magic tips..

I put up a wanted ad for orphaned wings or wings with tip/root damage from small CNC-molded lekkie pylon racers.. from whence I could cut a pair of panels for an 18-20" wing.

combatpigg

My Feedback: (3)

I'd try to place the fuel valve and servo where you can easily service it, or on a detachable mount pad if it's buried in the nose of the fuselage. I think the air pressure in the system will push all the fuel that's in an extra long run of fuel line at the same rate until it's more or less bone dry. I figure you'll get steady runs just as long as there isn't any foaming in the tank.

MJD

My Feedback: (1)

Yup - I had it in mind to mount them together on a small plate of 1/16" ply or the like and Velcro the assembly to the fuse floor under the wing LE, I need access to the tank through there.

combatpigg

My Feedback: (3)

If all you want to do is shut off the fuel supply, the wire hook that pulls the fuel line back into a hole in the firewall is easy and effective, but it would take more effort than turning the barrel valve.