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CMP giant scale Zero build

Old 12-25-2006, 11:38 PM
  #1  
paladin
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Default CMP giant scale Zero build

Well I bought this kit back in April or March the first one came with a hole in the wing. By the time I get the replacement it was May and the flying season. I tried to skip posting it and just build but that did not work so I’m restarting the build now.

This is the CMP Giant scale Zero, see it at:

http://ak-models.com/mm5/merchant.mv...de=CMPWarBirds

I’ve included a number of pic’s to show present progress so I can get right to the build.

I’m presently looking at adding retracts, you will notice the sweep forward by the strut as it fits into the wing. It came with a 3 inch dia. Wheel and 3.75in opening in the wing for it. If I measure from the back of the wheel opening in the wing to the sheer webbing on the main spars I find 1.375in.. So my scale calculations assuming this is a A6M5 tell me I should fit a 4.5in wheel. With the available space between the aft wheel opening and shear webbing I should be able to do the 4.5in wheel.

I also took some very poor pic’s of the mounting rails. It looks like those rails are made of pine or a light hardwood so I’m probably going to remove them and reposition them as well as the routing of the strut.

Joe
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Old 12-26-2006, 01:33 AM
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Default RE: CMP giant scale Zero build

I'll be watching along on this, looks like a nice kit ..like to see how they build... Have you chosen your retract system yet?
Old 12-26-2006, 06:37 AM
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Default RE: CMP giant scale Zero build

Joe , agree on the rails , I usually beef up that area with hardwood then Dremil away areas that allow the gear to fit then reinforce with glass .
Plane looks very clean , ice lines , flaps look large enought to be effective (unlike the tiny ones on the CMP spitFire )
Old 12-26-2006, 08:55 PM
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Default RE: CMP giant scale Zero build

Well. I'm planning to use a set of CJM I bought many years ago for my platt Focke wulf. Well to make a long story short, I'm a mechanical engineer and work on planes every day, so I sort of know what I'm doing. I had some problems with the gear, so I ordered parts from Bruce but they took to long so I picked up a set of platts in the meantime and they went in to the FW. now I've had these retracts lying around the shop for some time when this plane came on the market, the plane cost considerably less than the CJ retracts but its a chance to use them. So a little $ at the local Model shop and I have what is in the picture below.

For those that do not know how to take OLEO’s apart, at least CJ OLEO’s here we go. #5 is the strut as it comes from CJ, #4 is the strut with the roll pin removed and the strut to retract adapter removed. You can see the spring sticking out the top. I went to the local machine shop and had new adapters #2 made to allow the strut to come out of the retract straight no bending forward. This will allow me to position the retract mechanism for best fit in the wing. Now because I’m using the left over FW struts I will have to adjust its length and the length of the spring but I’ll deal with that as it comes up in the build.

At this point my plan is to remove all the factory supports, install maple retract bearing blocks, dremel holes in the existing support ribs, adding a ply doubler where possible. While doing this I will turn the mounts to give me the forward rake I want, push them as far into the wing as I can, and angle the strut out.

Joe
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Old 12-27-2006, 09:31 AM
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Default RE: CMP giant scale Zero build

Need to keep an eye on this one. Rich
Old 12-30-2006, 08:24 PM
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Default RE: CMP giant scale Zero build

I am currently flying one of these ,great flying plane, saito 150, semi scale exhaust ,plane built well flys great .One warning you will not be happy with century jet retracts I have a set of centurion's inserts bend every landing no matter how good of landing have. modified main part of retract to remove slop had new inserts machined to except robostruts My friend is builing one after flying mine removed his century retracts made mods to main part installed robostruts . just my opinion!
Old 12-30-2006, 09:55 PM
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Default RE: CMP giant scale Zero build

Cj replaced all the struts after 2005 , ask them if you have an old pair
Old 12-31-2006, 01:47 AM
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Default RE: CMP giant scale Zero build

Tofly, I will replace with robo's when the time comes. How much wt did you add to the nose?

The next installment is removal of the landing gear mounts from the wing. I use the pair of pliers shown in the first photo to grip the mounts and bend them until I hear the factory glue bond snap. Then reverse the direction of the pliers till I heard it break in that direction. Doing this on both ends until I can pull the free end out, then remove the rail. I left the aft rails in because I thought they could take the stress but the more I think about it the more I realize the week point is the adhesive so I’ll probly remove the backs and re-glue with epoxy.

Next I take some rough measurements with the retract to see how things will have to fit. Then will use the removed part as a template to make the replacements out of maple. Now the front ones at least I will make the hole in the ribs large enough to fit the entire maple block not the little tab shown in the pictures, the aft ones will look identical. More importantly though I will move the front mount in to the wing and turn it slightly and turn the aft slightly. This will put a forward rake on the gear when they deploy and keep the mounts flat to the retract ears.

Lastly if you do not know how to take the CJ retract cylinder apart I’ve provided pictures of the parts. The outer cylinder wall unscrews from the hub, to not destroy the outer cylinder wall you need to grip it at the barb end. Any access pressure there or trying to grip it on the center will permanently deform it. I have leaks in mine and there is so much petroleum jelly that the conditioning oils were not working so I needed to wipe them down, then lube them up with the good stuff. I have a piston leak in one and a hub leak in the other.

Joe
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Old 12-31-2006, 01:52 AM
  #9  
paladin
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Default RE: CMP giant scale Zero build

more pics
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Old 12-31-2006, 01:56 AM
  #10  
paladin
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Default RE: CMP giant scale Zero build

more pic's
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Old 12-31-2006, 06:10 PM
  #11  
paladin
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Default RE: CMP giant scale Zero build

I had about a hour today to play and I had enough time to remove the aft retract support and wrestle the computer from my kids. The mounts came out almost to easy. Tomorrow I’ll see how well the glue the manufacturers used will hold the cross braces. So far the glue used is very brittle. That along with the flexibility of the wood used is not good. The prognosis is it would take 10-20 flights to free up the glue then only the dovetailing of the wood is holding the parts together. Nothing a little fiberglass can’t handle.

Joe
Old 12-31-2006, 06:56 PM
  #12  
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Default RE: CMP giant scale Zero build

what scale size is yourn plane? i got an zero but its electric. i would like to get a big gas version of it.
Old 01-01-2007, 07:38 PM
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paladin
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Default RE: CMP giant scale Zero build

Ponochoyo, all the stats are here.

http://ak-models.com/mm5/merchant.mv...de=CMPWarBirds


Joe
Old 01-06-2007, 11:27 PM
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paladin
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Default RE: CMP giant scale Zero build

I epoxyed in the aft suports just as they came out. to follow are pic's of the notches for the new forward rail and the forward rail inplace before I epoxy in in place.

Joe
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Old 01-12-2007, 09:46 AM
  #15  
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Default RE: CMP giant scale Zero build

Hi there,

I am watching this thread with interest, its going to be a great flier when its finished.

Interesting comments about Century Jet retract, I thought that they were the 'world wide bees knees', in fact this is the first time that I have heard anything less than complimentary!

Did you pick out and engine yet?? nice clean petrol would be nice??

Good luck & keep posting

regards,
stu k
Old 01-12-2007, 08:26 PM
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Default RE: CMP giant scale Zero build

Stu, I have three engines that will fit this model:
Saito 1.5
Magnum 41 (USA 2.5)
Zenoah G-62

I’ve ruled out the saito because I’ve been told it will muck up the paint. The 41 is the presently leading candidate after hearing what
Fofly had to say, and assuming I will need some nose weight. The G-62 will make it hum but not leave much cowl. I’m looking for all the 1nput I can get here to help make up my mind.

As for CJ retracts I have 7 pair Rhom-Air, 3 pair Spring Air, and three pair CJ. Every spring I add 2 or 3 drops of AC leak stop to each set and have never had a problem. I have one set of CJ’s that have 250 flights on them with no problems. Well except when the OLEO strut adapter breaks about every 100 flights. Getting the part from the local tool & model shop was much more timely.

My son Bought retracts for a flop tite P-40 and both cylinders leak still.

I bought the FW retracts and the deployed side does not have a over center lock so under side load the cylinder while amplified by the inclined plane must resist the load. After sending Bruce drawings on how to fix it on two occasions I never got a response. So back to the local tool and modeling shop and you have seen the pictures.

Joe
Old 01-13-2007, 07:22 PM
  #17  
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Default RE: CMP giant scale Zero build

I’ve reinstalled the front LG mounts 3/8 of an inch further into the wing, then plugged the holes that made in the ribs with scrap peaces of hard wood. You will see that one of the holes is not plugged yet.

I use a ruler under the strut (that will be shortened later) to decide the size tire I can use. In order to use a 4.5 in wheel I would need to further cut away LG mount to allow the system to rotate to that point. So after verifying that the other wing will fit a 4 in wheel, will do just fine and be an inch above what came with the kit..

Last picture shows the forward rack of the gear with the new front LG mount location.

Joe
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Old 01-13-2007, 08:07 PM
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Default RE: CMP giant scale Zero build

Nice job , that is a very difficult angle to get correct !!!
Old 01-15-2007, 08:43 PM
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paladin
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Default RE: CMP giant scale Zero build

To those of you that have already flown this plane did you do anything different than what the plans call for on the wing tubes?

I’ve never done a wing tube before and my background tells me that the materials and mechanisms are ok. Assuming no flaws. I normally look for a 20G wing (+&-) and not knowing how the mechanism is put together inside the wing makes me think I should do something extra. For the tail assembly I’m leaning towards installing a dowel in the rod, I’ll probably PFM, or R6000 it in which will hold to aluminum better than epoxy. For the main wing I’m toying with making an I beam inside the tube then expanded bead foaming it in place for the main spar tube. The other option and one I know will work is to peal the bottom covering back on the wing and put a 3-4inch wide strip of glass over the center section.

Having had a GP Stuka that the wings folded on I’m leaning towards being really cautious. So I’m probably going to foam the tubes and glass the wing.

What have you guy’s seen does your wing flex if you do the nee at center section and hands at tips test is the most flex at the center section?

How has the covering held up on the wing? Is it a one or two summer cover job? Or did it hold up well this summer?

Joe

Old 01-16-2007, 01:23 PM
  #20  
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Default RE: CMP giant scale Zero build

I have the 80" WM Zero which is a great flyer. I assume these are simular however yours seems to have better outline and detailing. I used the standard aluminum tube "as is" and have had no problem. A solid dowel at the tail would give additional tap depth for screw which holds stabs in place. Personaly I believe the wing tube as is will work just fine but heck the I beam is a great idea and the weight won't hurt this planes flying one bit.
I did epoxy my tube into wing for a perm. one piece wing, same at tail and I would not do it again - I think I would prefer the seperate halves for easier transport.
Old 01-26-2007, 05:45 PM
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Default RE: CMP giant scale Zero build

Last night I screwed down the mechanisms and everything sat flat on the LG rails (that’s unusual). I then worked the mechanisms with a screw driver to check for bind points and found non. So now it is onto sizing the strut legs.
To take the OLEO apart find the roll pin holding the OLEO strut end/mechanism adapter in place. It must be driven out with a blunt tool, I usually cut a piece of CRS (cold rolled steel) that is smaller than the roll pin but bigger than the hole in the pin (I used 3/64 round }. Well in my case I’m not keeping anything from this joint but the roll pin so damage to the hole is OK. When removing a role pin you plan to replace later keep in mind that the adapter is usually aluminum on GS OLEO’s and can be marred badly if you are not careful.
Put the strut end in a vise so that it is holding the strut to the end cap. The strut end is under pressure from the spring and once the vice is released the end cap may be launched so plan for this. Once the role pin is out and the parts are out of the vise the ends of the stainless steel strut are sometimes folded over the end cap and must be removed with a dremel cutting wheel. Once this is done the strut will come apart. I had to do this so I put a tie rap through the roll pin hole.
In my case I’m going to shorten the strut so the first thing I will do is down where the strut telescopes into its self I’m going to rap masking tape to prevent from getting a bad measurement.
Mark on the tire axle where the tire ends then remove the tires and axils. Bend the axles so the tire will look correct on the strut as close to the tire line as possible. Grind a good flat on the axial for the set screw. Reassemble using 1/4 in ID washers to act as spacers between to wheel and the strut. Well the local hobby shop only had a 3.75in so that is what I will use. I want to set the wheel so that the closest part of it is flush with the old wheel opening then move the wheel away from that edge so it looks like it can clear the edge with a good margin. Mark the strut where it goes into the mechanism. Then do this for the other side also.
Once everything is marked and double checked cut the strut to length. Then take the discard piece and use it to mark how much spring to cut off. Springs are a funny animal, I’m not going to bore you with spring rate and compressed length. The easy method is to cut off as much spring as I cut off the strut.. Once the discarded portion is removed the bottom wind needs to be shaped to eliminate ant sharp edges.
Once the spring and new end are in place, clamp the mechanism end of the strut in a vice to hold everthing together. Drill the hole for the roll pin (same size as it came out of, 0.125) and drive the roll pin into it
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Old 02-04-2007, 12:35 PM
  #22  
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Default RE: CMP giant scale Zero build

Have you been working on the zero lately? Just wondered as it had dropped off the main page.. Looking forward to seeing it come along..
Old 02-04-2007, 08:11 PM
  #23  
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Default RE: CMP giant scale Zero build

Sorry for the delay, Everyone in the house is sick. But I did get a little done I opened up the wing to let the wheels retract. To do this I lifted the covering with a putty knife and cut the wood away. With a gas engine up front I really don’t need to do this but I wanted to give it a try. Next I need to add some supports on the top surface of the wing so I can cut back the ribs there to get the wheels a little further into the wing.

Lastly I needed to foam the area between the forward LG mount and the LE. The reason for this is to add some surface area to the joints up front. If we look at the stress in our LG mounts while the stress on both is = the aft LG brace is loaded in compression, and the forward LG mount is loaded in Tension. While the stress is = the reaction of most materials to then is quite different. Most materials are twice as strong in compression as in tension. To make our case even worse we use an adhesive to hold the LG mounts in place so any motion allowed in the rails allows them to slowly degrade to a final failure. I’m sure we all have our stories of a picture perfect landing when the gear broke out. That was caused by motion in the system. So I use the foam to hold everything in the forward LG mounts together. More importantly if I have a bad landing the foam will break away from the mounts and the motion will cause foam dust which I will pick up of the floor of the van if I don’t pick it up by looking for it directly after the bad landing. Some times I’m just not sure so I pull the mechanisms out and hit all the seams (epoxy & foam with thin CA.

Anyway I’ve included a picture of the holes I use to put the foam in. I’m showing the one that did not have foam over flowing out that hole. If you decide to do this to your plane the first few times you use this stuff use two holes one for pouring and one for overflow. I used one hole because I know I have to keep this hole free/open. If it should plug pressure will build as the foam is expanding and blow the wing apart.

Joe
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Old 02-13-2007, 09:00 PM
  #24  
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Default RE: CMP giant scale Zero build

Over the past week I have been preparing the wings for joining. I’m a bit anxious because I’ve never put together one of these wing tube guy’s before. So I foamed the tubes by taping one end shut and pouring the foam in the other end and waiting for it to expand. I do this buy pouring in just under what I think will do the trick into all three tubes then let it expand and they all did not over flow with the first fill. Then I mix up more and top them off one at a time, letting any excess drip on the floor. Don’t get this stuff on your cloths it sticks like glue. I’ve included a couple of pictures of each tube directly after the foam hardens, and then again after the foam has been trimmed.

Next I pealed the covering up where I plan to glass. If I included that pic you can see which side I worked first. I started by lifting the covering that had been bent over the center section with a x-acto knife. This lead to many unintended cuts and other damage to the covering. So I switched to a putty knife, one I use for grouting in windows (is grouting what it’s called), about an inch wide and it worked much better. Then I made a 1.5-2 in span wise cut on either end of the covering where I plan to stop the glass. This would allow me enough free play in the covering to push the putty knife under and free up the covering in the area where I plan to peal it back.

I need to be able to run the A, F servo extensions so I ran string or wires. I use Airtronics 731 servos of early 90’s vintage in the ailerons so that I can cut the leads and run one wire from left to right A. Then strip the part of that wire closest to the center and attach one connector there. The age of the servo is very important here because some time in the mid 90 everyone cost reduced there servos and removed the terminating resisters. This is something I was told by an EE and it seams to hold true so I continue to do it. Anyway the purpose of a terminating resister (TR) is to eat up the extra charge in the signal line that the transistor does not use. Without it the unused charge bounces back down the line and is eaten up by the of the other servo’s TR or the RX’s TR. In the mid 90 all the manufacturers decided redundant TR’s were to costly and removed them from the Servo’s. That works fine until you put a Y harness in. With a Y the excess signal has a choice to go to the RX or the other servo thus causing those jitters we sometime see in long Y’ed runs. Again I’m just repeating something told me by someone who would know what they are talking about and really am not qualified to offer any advice or opinions. All I know is that by buying a buffered Y when this does happen, it eliminates the problem and the EE took one of them apart and verified that they were terminating the signal line.

The flap servos I’ve used are new and in the 125-175 in-oz range and I don’t have the servo stall calculation handy but for flaps I usually pick the servo to stall at 45degrees at twenty MPH below max. speed If there is any interest I can go into how this was done but I’m going to leave this here for now. So I may need a buffered Y for the flaps, only time will tell.

Lastly I fit the tubes in the wing and joined them as a trial fit. I was very happy with the tightness of the fit, and the lack of flexibility once everything was joined without glue. There is a stop at the bottom of each tube in the wing so I’m supposing that a two peace wing could be done. But not with my lack of experience here.

Joe
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Old 02-18-2007, 01:58 PM
  #25  
paladin
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Default RE: CMP giant scale Zero build

Epoxied the wings together then glassed it I used 2oz on the wood cut 1.5in wide then 2 sheets of 3/4oz 2in wide on top of that. Balsa rite on that then iron the covering back down. If the covering does not last I’ll go back and put two layers of 2oz 5 in wide against the wood, and two layers ¾ oz 6in wide. The 3/4oz provides a smoother surface for reattaching the covering.

I removed the covers for the aileron servo’s. cut the male connector off it. Strung the red, black, and yellow wire through the wing past the center section and over to the other servo. Tin all the leads and soldier them up, so the servo’s are now connected together by the RBY wire. At the center section I strip back the insulation without cutting the wire, tin it then attach a male lead.

Now I’m getting the air components together, checking them for holding air before I install them.

Joe
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