duaneh's 2023 CEF Run What Ya Brung Unlimited Speed Contest Build Log

It was a close decision, Jim. Here is the runner-up. Warren Pietsch's restoration of Jimmy Stewart's P-51C Thunderbird. I am going to build this someday, but it may not be as a CL model.

Basic frame-up is done. I still need to install the controls and cover the model.
The offset engine is less than ideal from a flying standpoint, but it works and looks so much better to preserve the fuse nose shape.

The piece of 1/4 ply inset in the fuse is the hardpoint to prevent rotation of the LG wire.
This is the first time I have used a one-sided elevator. It hardly seems like enough, but we'll see.

Wow! NIce.

I see a bit of Dago Red there.



My son has the R/C version. It got a bit crushed up while traveling in his '65 Mustang on it's way in a carrier from Denver to WV.

Yes, I believe Dago Red, Strega, VooDoo, and Miss Ashley II all had the same canopy system.

That's too bad about your son's Dago Red. How's the Mustang... err, uh.. Ford, I mean?

duaneh wrote:Yes, I believe Dago Red, Strega, VooDoo, and Miss Ashley II all had the same canopy system.

That's too bad about your son's Dago Red. How's the Mustang... err, uh.. Ford, I mean?

Old story here, but yes covered transporter stalled on the highway and got rear-ended by a Semi.  He thought it safest to ship here in the cars rather than risk the mail.  .






With my 50+ year old Enya .29 powered Sterling Fledgling

Ouch!! Man, that's terrible. The last thing you would expect to happen.

Taking a little time-out from building to select an engine. I know I want a horseshoe backplate configuration, but there are still lots of choices to make. I have these 4 on hand.
Top left is an Estes-era sure start with  a slit cylinder. Top right has a bottom end of the same pedigree, and a top end from an unknown Cox plastic with a stepped wall dual port cylinder.
Bottom left is a product engine with a thin wall single port cylinder, and a fine thread needle. Bottom right is a product engine with a thick wall single port cylinder, and also a fine thread needle.

I haven't run any of these. The slit cyl. engine shows no sign of having ever been run. The 2 gray backplates have stainless reeds, while both of the bottom 2 have their original copper star reeds. I could use any of these, or I could swap parts around to come up with a different, hopefully better, combination. I need to run all these on the stand to see what I have to work with.

Enviable briar patch to be thrown into Duane.  As you mentioned, mix and match, tach and select the best runner.

2 on the right i would think bee ur better runners , tach them and the SS reeds are well stiff and want work as good as a Mylar one will , stars are OK but old most times . I have made plenty from the plastic ? cover page of notebooks and work well 0.005 "i think is what your looking for in thickness , all the ones i have bought are this thickness ( If you don't have fresh stock)  Is it erg. tank or pressure / and what prop ? you mat want to read this >> https://www.coxengineforum.com/t12316-reeds?highlight=making+reeds

Well, I ran the 4 engines posted above, and got some unexpected results. I have to admit I have never tached a Cox engine before. Just tuned them by ear, and flew. I was expecting more RPM, after reading other members' reports here.
I used a Cox gray 6x3 prop and Fitz 24% fuel.

The surprise winner was the slit cyl. Sure Start, at 12,800
The red back engine with single port thick wall cyl. turned 12,500
The product engine with a 2-port cyl. went 12,000
The white back engine with thin wall cyl. ran 11,500

Are these typical numbers? I got all these engines second hand, and know nothing of their history, so we shouldn't read too much into my results. Still, they all seemed to run happily, with no obvious issues.

I wish I could find my tached pictures Duane, but I can't.  I purged many a year ago when Microsoft was bugging me about paying for more storage.  

As I recall they were running in the 15's, disappointing as some here were telling something in the 20's. (probably TD's) I was running Cox 25 and 35% and 5/3's.  

Bob

Duaneh I believe a 6x3 is overpropping these reedies. With dual port cylinders these reedies have their sweet spot at around 16k or higher, that is achievable with a 5x3 prop. (Except for the venturi diameter, a dual port product engine is similar to the Black Widow..refer to the Performance page on Martin Hepperle's Aerotools site with performance curves of most COX engines https://www.mh-aerotools.de/airfoils/cox_frameset.htm)

A high compression COX head would help crank the speed even higher, and a Kamtechnik, or Galbreath head with turbo plugs will make wonders. I suggest you check if the reed valves close well, and if the cylinder/piston fit is good for a strong compression.
Just my 10cents..

 

I reliably get 18.5 to 19k rpm out of several of my reedy cox 049 engines. they are a product crankcase, gray horseshoe backpkate and external tank. mylar reed, killer bee crank, TD cilynder standard cox glow head with 1 gasket, 5 x 3 prop, 25% nitro, 20% castor, 55% methanol and no friction starter spring. tried a Cox TD head and no extra rpm but it needled easier.

I agree with Andras that a kamtecknic head and turbo plug would increase the revs. I have used them and Im sure they increased the RPM but I havnt tachd them. the above config i have tachd many times and fly them regularly.

It really depends on what your trying to do. I see mouse racing setups and unless you actually tried mouse racing, it's not about top speed. Mouse racers are trying to obtain the most laps in the most economical way. Therefore, going fast and having to make multiple pit stops not too mention having your plane on the ground isn't efficient. Many times the pilot with the most average speed generally comes out on top.  In addition, the key to mouse racing is being able to start the engine quickly and reliably. As with any engine, if the needle is on the lean side, it's not going to want to restart due to heat soaking. Having a highly modified engine can result in running backwards consistently and erratic needle settings.

           If your trying to go fast, your not going to want a high compression head. Your going to want to pump a lot of nitro to the engine and having high compression will hurt your performance rather than work with you. You want a lot of pitch. You need the nitro to ramp up the rpm's to drive that pitch. You need to find that balance of decent rpm's and pitch. Even a 5" diameter prop could result in being  too large. Having around a 4" prop with high pitch 5 and up will yield decent speed. However, the days of having a wide availability of propellers are gone. 1/2A Nut Brad has reworked many props such as APC's. He's posted in regards to the subject many times and this is where one should be looking to go fast.

Great information, guys, thanks!

Now I know what RPM to look for, and some ideas for how to get there.
Yabby, thanks for the detailed setup information. I can duplicate everything listed except for the Killer Bee crank.
I'll report back with more results.

OK, re-ran the red backplate engine using a 5x3 prop, and with a mylar reed and TeeDee piston/cyl. installed. This time it turned 15,400.

Also re-ran the gray backplate engine with the 2 port cyl. No changes except used a 5x3 prop. Got 14,900

It looks to me like the biggest RPM gain comes from the smaller prop. Based on these results, I will go ahead and install the red backplate engine on the airplane. It is finished otherwise. Heck, the red will fit nicely with the airplane's color scheme.

duaneh wrote:OK, re-ran the red backplate engine using a 5x3 prop, and with a mylar reed and TeeDee piston/cyl. installed. This time it turned 15,400.

Also re-ran the gray backplate engine with the 2 port cyl. No changes except used a 5x3 prop. Got 14,900

It looks to me like the biggest RPM gain comes from the smaller prop. Based on these results, I will go ahead and install the red backplate engine on the airplane. It is finished otherwise. Heck, the red will fit nicely with the airplane's color scheme.

More in line with what I was seeing Duane. Same fuel I imagine?

Get you some of these props they sing !! > https://coxengines.ca/propellers/cox--049-propeller-yellow-4-5-x-4.html

Mounted the engine, and it looks like there is nothing else left to do. I'm calling this one done.
15-3/4 in. span, 51 sq. in. wing area, 5 oz. weight.




In order to reduce the offset thrust, I sank the engine into the fuse as far as I could while leaving access to the mounting screws.


The torsion wire gear follows standard RC practice. I will need a lot of flex since all landings will be on grass. The wire is retained in its groove only by clear silicone.


It's about the same size as my backup plane, Miss America.

Holy Cow man , that looks awesome . You got it done quick too ! Good work

Wow, quick is right. Like a dog with a bone. I picture you working on your Mustang at the same time that I'm gnawing on the Cox chainsaws. It's just not something that you can easily give up on.

Love the way you mounted the engine. Keeping that method in mind for my P-38. Got the wing done, but building the hollow log pod and twin booms has me scared off. But profiles..................

Well what you going to do now . lol WOW you can turn out some really nice models in a short amount of time   Cleaned on mine some yesterday and its got some fuel soaked ate one time /soft wood I need to deal with ? Maybe Just call it SHORT LIVED !