RE: CMP giant scale Zero build
 

24jul09

RE: CMP giant scale Zero build
 

Questions from cswann821

I have to say you've made a great thread on your zero build, and is helping me plan mine. I ended up getting the kit a couple weeks ago and am preparing for the build, through these readings. I am planning on useing a 3MM TOC 53 engine, which weighs about 3.6lbs bare engine weight. It should be here in setember.

None the less, I was wondering what size tires you ended up going with. In one post you mentioned 4.5" and 4". I've sized a pair of 3.25" that I had sitting around, and it seems these would leave just about 1/4" space when placed into the stock wheel pan. I've talked to CenturayJets, they have sent me great pics of the Retracts they make for this kit. They need to know what size tires I am going to use though. If you used the 4-4.5" did you have to mod or make a new wheel pan for them to lay in, when in the wing/ retracted? If so, how did you go about doing this? This will be the last step I do though, I want to make sure this thing fly's for me before I put a pair of CJ retracts in it, I'll most likely install the stock gear until I know she will fly and can afford the 380.00 for the gear. I'd like to be ready though.

- Did you end up haveing any issues/replaceing any stock hardware? if so, any suggestions on what stock hardware...not to use. I've read that some went with Robart hinges.

- I like your foaming suggestions, Do you believe makeing the wing a single piece is a must?
- Does foaming the engine block, add strength or lower vibration or perhaps increase it though????

After your flight, what did you think about the servos you used? Strong enouph? I was thinking of going with Hitecs 5645 . Do you think these will be fine?

With the Rudder/tail wheel servo moved up front, are you satisfied with the push rod you used? I've read that some have gone with a Pull-Pull system which I have never used, do you know if theres a differances in performance when useing the two styles? any suggestions here?



______________________________My answer_______________________________________


cswann821
Mine has a G-62 for power simply because I had it on the shelf. I’ne been running it with 20X12’s and am just not happy with the performance. I picked up a couple of 22X6-10’s last night and hope they will increase the vertical. I have 26 oz of lead shot mounted above the engine on a shelf I built specifically for it. I put both the E and R servos in the tail per the destructions. Big mistake! Over the winter I will move the E servos forward and loose 16oz of that nose wt. As for the size of the servos to use in post 28 I gave the minimums I would use. The way that is read is the number I gave is what you need to drive each surface, ie one aileron, one elevator, one rudder (the rudder on almost every model we fly will stall if given full through at full speed, it is important to your battery to understand that (simply don’t use full throw unless you are below 70mph). From E I used a Futaba 9202 for each elevator half. That gives me a 2 to 1 advantage in the most important control surface of the plane. I used a single futaba 9303 for rudder. Ailerons have airtrinics 94102 one per control. Flaps have futaba 3104 one per control surface.
Another guy in one of the clubs I belong to also has the CMP Zero and he mounted a G-38 and it flys much happier. He also used the H9 P-47 retracts and is happy with them, but the big difference is that he is pounds lighter than I and the plane seams to fly happier (just my observation).
Why foam? Save two paper towel roles foam one in the center then sword fight with the kids (give them the foamed one) see which one lasts longer. Without getting to technical foaming makes a mechanical structures exponentially stronger (but not as strong as solid wood), in effect creating an I beam with the stress bearing members on the out side and the thin web being replaced by foam.
Tires I have 4.5in, I arrived at this because I had 4.5 in tires. The reason they want to know is for the size of the yoke so if in dought tell them the bigger tire size, then you can always down size later if you want. The way I increased the size of the wheel well was to pull the covering up using scrap balsa to cut the wheel opening to the size I need it. Then folding the covering over the sheeting and ironing it to top and bottom. I don’t use the plastic cups, the full size had open wing bays there so why shouldn’t I. The stock gear is … well … c rap. I would be afraid of the damage it would do when it folds up. Mine did not see a gear retraction till flight 4 and the oleos will reduce the stress on the wing hard points tremendously.
I used the stock hinges, my concern is that they are made of a flexible self lubricating plastic so I am monitoring their coming unglued. I pull tested the robart hinges and these in the Me109 thread (completely subjective test) and the robarts came out the looser so the only advantage they have over these is they bond better.
I used wood dowels instead of the metal ones (was concerned with how long they would stay bonded) that came in the kit. For wing mounting I put a ply backer behind the glass they would go through (glass alone would cut through the wood in short order) and foamed between that and the firewall. The flaps are hinged in the center, that does not give enough throw. I plan to move the hinges to the bottom of the surface over the winter.
I would have loved to do a two peace wing! The problems where; holding the two wing halves together (easy), extra connectors, I’ve folded the wings of ARF’s I built stock and I was not overly trusting of the carbon fiber tube so I wanted to glass the wing joint’s
Only my tail wheel has a forward servo and a pushrod and that is because I lost the stuff they supplied to drive it. When I do the E I will probably use arrow shafts and two mid run braces.

I’ll post your Q’s and My A’s incase anyone else has the same concerns.

Joe

RE: CMP giant scale Zero build
 

So whats the census on keeping the wings seperate or expoxied together? I would love to keep them seperate if I can get support from those who are flying the Zero and believe its safe.

Any Ideas on where/ what kind of extra Connectors should be installed to give extra strengths in keepeing the halves together durring flight.

Also, What size / brand Prop is everyone likeing on this Bird?

Thanks, Chris</p>

RE: CMP giant scale Zero build
 

I started with a 20X10 (faster not a lot of vertical) and have gone to a 22X6-10 (a little slower but better vertical) on a G-62.

Last three landings have been wheels up because one gear is locking up. Initially it was the right gear and after some filing that came down the last time but the left gear hung up. I’ll find out next week. But I let the scuttle but at the field change my thinking on the third landing. The first two landings I always say fly the plane first, don’t concern yourself with anything but flying the plane unless you have time. In the last flight I tried to kill the engine to save the prop.. well I still broke the prop and split open the scoop on the bottom.

Joe

RE: CMP giant scale Zero build
 

Sorry to hear that Paladin. Whats going on with your retracts? None the less, at least it sounds like the Pilot still made it out alive, its better than a whole kamikaze ordeal.

RE: CMP giant scale Zero build
 

Thanks,

I'm getting quite frustrated with it! The first five flights they worked flawless. Then the right would not come down, and the left where nice and loose. After filing enough of the right cam away to give some play everything worked well in the shop and on the ground at the flying field. In the air the left one hung up? It was really loose in the work shop while I was working on the right and now its tight. Tonight I’m gona pull the struts and see if they are turning (more toe in). if anyone else has an idea what to check let me know I don’t want to belly land again! Three with a 21# monster is pushing my luck.

Joe

RE: CMP giant scale Zero build
 

I was talking with someone at the field today about retracts. Initially I am looking at dishing out the cost for a pair from Centuary Jets, which are made for the CMP Zero. The guy at the field mentioned though, that I should be sure to get pnuematics with a spring?? I don't remember exactly what he called them. But supposively if you run out of air pressure for what ever reason, the retracts are spring loaded and will automatically, due to the spring, pop into the down position. 

Seems like a smart investment to me. If anyone knows what these kind of retracts are called, who has them? I'd appreciate it.


Thanks

Chris.

Oh and Good luck Paladin!

RE: CMP giant scale Zero build
 

Well at the moment I should not be one to talk! But, 95% of my flights are off retracts I have one set of Spring-airs the rest have no spring. I fly 250 flights a summer and these are the first gear up landings in three years. Having said that spring airs have their place, not many people have my experience with fluid power. So they have their place, if you are new to retracts they are good. They will give you that little bit of buffer I do not have, or want.

If you want springs in the CJ’s tell Bruce He’ll put them in for you I’m sure. My problem is something is moving on me that is not supposed too.

Joe

RE: CMP giant scale Zero build
 

I've never seen Spring /air retracts... are they less scale or otherwise are the springs highly vissible? It just seems like a safety measure lots would want to have. Are there benifits and costs between Air / Air, and Air / Spring that I am not weighing in?


The Air / Springs are still technically Air/Air..with the springs that  just come into play when these systems fail right?</p>

RE: CMP giant scale Zero build
 

Check out http://www.retracts.com/ They look just like Robarts but are much better quality and durability. I have used Spring Air units for more than twenty years with no problems and great service. They are good enough that Robart, and other companies, has started to copy them and offer air up/spring down gear. I agree with paladin that, properly set up, it doesn't matter what kind of retract you use. I have, however, had a safety wired hose pop off due to Texas heat (not over pressurization). Saved a belly landing on a very high dollar airplane by having Spring Airs installed. Just one more level of protection. Prices are better than most air powered retracts as the Spring Airs come with air tank, hose, fill unit, and up/down valve. Nothing extra to buy except a servo to operate the valve.

And to answer your other question: No, the Spring Airs are air up and spring down.

Just my .99 cents...

RE: CMP giant scale Zero build
 

Hey Paladin,

                    Is their a template, method to getting the correct angle easily for that forward rack on your gear? That has to help landings alot, rather than the gear being straight down. What is that angle anyways?

Bruce from Centuryjets got back to me... They don't do "spring-Downs" and stated a some reasons on how they could fail. I'm still interested in their retracts none the less, it seems everyone agrees that centuryJ- is quality and the fact that they have retracts designed for the zero makes them a seller in my mind.

Has anyone Heard anything /news on the "Tam Jet Landing gear Fail Safe" Sold by Robart? I'd dish out 100 bucks if they were proven to work by others who have used them.. http://www.robart.com/air_systems/access.aspx (scroll down the page)

Retracts.com does have good prices... I'd want what.. 1/2" struts. I'll need to see if their are any more reviews on these guys first though.

Thanks guys!!

RE: CMP giant scale Zero build
 

Chris, my retracts started life as CJ fw190 retracts. I replaced the cams, shortened the struts and shortened the mounting ears. So my angle will not work for you. Once you have the gear measure the length of the strut ( from center of wheel axle to where it intersects the wing skin) this is the long edge of a right triangle. Measure from the center of the gear mounting blocks to the leading edge, the second leg of the triangle. The hypotenuse is perpendicular to the cord of the wing. The angle of the mounting blocks is tan of short side /long side. I leave the back block where it is and move the front one into the wing to that angle. Or put shims under the back mount.

My wheel axle is under the LE of the wing.

As for that gadget, it and the springs are just gadgets, proof that ignorance cost $$$$$. Its much, much cheaper to find someone who uses air retracts without errors and pick there brains, have them check your setup.

Having said all that the other CMP Zero in my club uses Easy Tiger retracts.
http://easytigermodels.com/index.php...products_id=31

Spring air is the best made retract that we have talked about so far.

Joe

RE: CMP giant scale Zero build
 

I Got the picture Paladin... Goodold fashion.... soa-cah-TOA.

I drew up a picture of what I believe you said... I could be totally off. Please excuse the dimesions/scale... I just used windows Paint really quick
http://i419.photobucket.com/albums/p...ehowtofind.jpg



So am I getting your input correct, your saying that spring airs from retracts.com are better quality than Centuary? I only ask because it seems you know something and more about retracts. If you and others seem to have this verdict, I wouldn't mind saveing a bunch on the spring actions. I'll be MODing the wing anyways to get that angle. I just want to be sure that they are built well.... built to last. I'll need to call them to find out which series/pair I would need to use on a 20 lb bird.

RE: CMP giant scale Zero build
 

Of course the picture didnt come out the size I wanted... Angles are just Tangent (short length / long length). I had the short length colored green (length from middle center of gear mounting blocks out to leading edge, and the long colored red in the picture (lenght from center of axle to where the strut intersect wing skin).... hard to see though.

RE: CMP giant scale Zero build
 

Hey guys this has been talked about elsewhere on this site. Check out the sierra retracts....far more scale than anything else! Scroll to the top of the page on the link for pix.
http://www.rcuniverse.com/forum/m_77...tm.htm#7787299

RE: CMP giant scale Zero build
 

Chris, this diagram should clear it up for you. The red triangle is the strut length measurement, the distance from strut to LE, and the line drawn perpendicular to the cord (LE) intersecting the two previous lines forming the red triangle. The blue line perpendicular to LE thus parallel to the cord forms a smaller triangle where the angles are =. Giving the angle in relationship to the cord.

I’ve never seen spring airs on a 20# plane so you need to get someone else to tell you that is ok. I know their 1.2 4c sizes are good. I also know the hole in the wing for the retracts is very small in the CMP Zero and Spring Airs may need to be trimmed to fit.

Joe

RE: CMP giant scale Zero build
 

Thanks again for clarifying that Paladin. I got it.

Aluminum overcast - I've read that page and am talking with centuryJets. The Sierras are a fortune, Robart left a message saying they don't have gear to support a 20lb, at least a spring up type.

Gonna give Retracts.com a call before I decide.

If I can get a good pair of spring ups, I think i'll go with them. Otherwise i'll be going with centuray Jets.

Chris

RE: CMP giant scale Zero build
 

I have used the 700 series Spring Air retracts on a number of over 20lb aircraft, including turbines, with no trouble what so ever. I use a 1/2" strut with the retract unit, either Robart or Spring Air. Robart look a bit more scale but the Spring Air struts work just fine.

RE: CMP giant scale Zero build
 

I kept saying spring ups.... I mean spring downs... you guys get it.

RE: CMP giant scale Zero build
 

Hey guys, I have tried many props on the G62. If you put a Zinger 20-8-14 on it will set sail and still have great vertical. Your trial and error will be over. Kevin.

RE: CMP giant scale Zero build
 

Thanks Kevin!
I just so happen to need to put an order in. thier like potato chips nobody can break just one.

Joe

RE: CMP giant scale Zero build
 

Thanks Crash,

Now that you mentioned props and the G62.... I was thinking of puting my engine order in at the end of the week or monday at the latest. I'll be happy to finalize and jump over thispart of the build. I'm Just waiting for a check to clear. Anyways After debateing the old engine debate, DL..Zenoa, CRRC, ect ect. My heart was content on the TOC 53 from wildhare http://www.wildharerc.com/products/engines/index.html, http://tech.flygsw.org/3mm_review.htmdue tosomeone pointing out that I should byan engine not just based on Brand... But also something that fit the application it would be used for.ie, warbird with ashort nose.Sothe TOC 53has good reviews through out the popularbig forums, itFitsthis warbird haveing a side mounted carb, competitive power against other major brands,and at anmore affordibleprice.

I didn't really look into the G62, just thinking it was to much power, although mentioned it wasn'tstrongly recommended when I was asking about engines about a month ago.
Paladin, you mentioned you weren't happy with it's performance. Was this a remark about the engine itself, or the prop you were useing.

I want to get the engine as soon as I can, so I can get the Cowl / nose finished and engine mounted. Then I'll be talking to J-tech most likely to have a custom muffler made. But can only bedone after theyknow how much room they have to work with.The clubs field which is close to me has a strict sound Db ordinance now, due to a particular residant complaining. We don't want the field shut down by the county which has a noise ordinance itself. Anyways to avoid haveing to drive a ways farther to another field... I'm going to have to look into good mufflers to make the engine wisper while keeping a good scale look, and with the fewest amount of cowl cutting as possible.

Has anyone heard a Wrap around Pitts muffler, Bisson makes one I belive. I'd like to know how quit / well they are / perform. May go with it if I don't do the custom build muffler.

Would be nice to see a usuable scale exhuast on this Zero too. But I if there were one.... it probably wouldn't be quit.

Chris

RE: CMP giant scale Zero build
 

my G-62 is still spitting fuel out the carb. once everything else is good i'll work on that. that will improve the vertical even more. I added 26 ounces of wt to the nose with that engine. with the E and R servos moved forward this would reduce to 2oz and its a pound and 1/2 lighter.

my clubs have 98 and 95 db limits they both accept the slimline 2100 turning a 20x10 zinger. that is also why it is so rich, when i lean it out the 95 db club wont allow it any longer.

Joe

RE: CMP giant scale Zero build
 

It will spin a 20-8-14 about 6900 to 7000 and it will fly my large Warbirds with authority. If you ever go to You Tube type in onlywarbirds in the search and it will go to my page, many videos with G62 will show you what it can do. Good Luck, Kevin.

RE: CMP giant scale Zero build
 

Hey Thanks I'll check it out. But Now I'm kinda torn between the G62 and the TOC 53. http://www.rcgroups.com/forums/showthread.php?t=953573
I've only seen great reviews for this engine(TOC). But now for about the same price minus an ignition but with more power I can get the G62, which is being used in many other warbirds.

My only big issue is that it's freakin ugly!! lol...... How does it sound?? Howconsumeing is it to get this engine tuned and setup to run like it should? The deal breaker thoughis if it's loud. With my clubs Db requirements the more powerful G62 will be more of a pain to quit down i would think. Will I have to cut the cowl to expose the carb/or anywhere else for a fit? I know B&amp;B has a MOD to bring the g62 carb 1/2" closer which could help.

Paladin, was the install easy in the zero's Cowl? any room in their left? The best Combo Package/price I've seen for the G62 is here...http://www.bhhanson.com/ . Seen any better anyone?

I was also wondering if you guys know if there is enouph clearance between the engine,mount, and firewall to fit an inverted wrap around pits all within the cowl. I heard that The Pitts that Bisson makes is nice and quet??


As far as retracts go, It looks like the 400series from spring air/retracts.com can handle 20-30lbs http://retracts.com/ComingSoon.htm, Do I want the 90 or 85 degree system for 220.00? http://retracts.com/Retrax_400.htm.Then another 90bucksfor struts. Theres isn't the best, anyoneknow who sells some more scale looking1/2"ers? The retracts have a 1" profile which should be good for the zero install I hope


Finally, what size (mm) spinner are you useing. I found a thread which gave a page for scale zero spinners . I was thinking of going with the 89mm olive drab color.(bottom of page) http://ecsvr.com/abm/ShopDisplayproducts.asp?Search=Yes. Although I was told in the thread that 100mm would be scale when flying the 82" cmp zero.

http://www.rcuniverse.com/forum/m_87...tm.htm#9037133

Chris.