aeroboy1293

I just need a little re-assurance on the wing retention system used by CMPro on their 1.40 size yak54.
I do not own this model but a close friend of mine has just purchased one as his first real aerobat.
It appears that the wing is retained by 2 screw in hooks in either wing panel then SPRINGS connecting the two panels through the fuz.
That to me does not look like a solid form of wing retention for a 72" span aerobat with a rather large motor installed.
Is there anyone out there who has one of these models or know someone who has one and can comment on this form of wing retention??
I am not saying anything bad about CMPro and their models it's just that I have not heard of this particular form of wing retention before.

greyfoxx

Airboy -

I'm in the finishing stages (mounting and cutting access holes in the cowl) of this same model and while I cannot give you any first hand experience on this model and the attachment of the wings. Following are some thoughts on this matter (CMP Yak 54-140) that Mark Davis shared with me. I have not decided upon the means of attachment I will use, but I believe CMP isn't the only mfg. that uses this method. There are other forums out there on this model, and most of them use the CMP method without any problem. However, I kind of like the means Mark used on his model for more reasons than just the wing attachment, (and it is far, far superior and a great method for all models with detachable wings) as you don't have to remove the canopy. I also have modified the means of attaching the canopy and hatch that the canopy attaches to. It does not require removing 6 screws that attach the canopy to the hatch and in turn the hatch to the fuselage. It's relative simple and does not require the purchasing of any additional materials to speak of. You might want to share this with your friend, as food for thought!!! And if he's interested in the way I chose to attach my canopy, just let me know either through this forum or by e-mail at [email protected]. I really like the following idea that Mark proposes!!!

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Phillip; First of all just want to say hello. Glad you are able to use some of the info I provided re the Yak.

One of the most critical items to make this plane fly comfortably is the CG. The suggested CG provided by CMPro have to be viewed only as a guide. There is no way on earth this plane will fly with a suggested CG going back to 152mm. It would go into a snap spin as soon as you left the ground!

I set up my CG at 130mm at fuselage and then added a big blob of plastacine (about 200 grammes) and flew it with good results. All up my Yak weighs 6kg (13.2lb). It is a heavy model.

It suffers from the same problem that most war-birds suffer from; short nose with long tails!!

In regard to the wings, I opted for a screw for securing as it provides a quicker way of setting up at field. You don’t need to remove the canopy and pan to secure with the bolts and springs.

Method of securing wings.

1. With the wing tube in the fuselage, ensure it is evenly spaced either
side.
2. Measure length from the side of the fuselage.
3. Hold wing under tube but mated up to fuselage.
4. Mark out on wing the location of the wing tube. Use a square
so you get the actual width of the tube marked on wing surface. Mark out the extremity of the tube.
5. Mark a point about 12mm or half an inch in from the end of
the tube location on the wing.
6. Cut a block of hardwood or hardwood dowel the same diameter of
the tube. Epoxy this in the end of the tube.
7. Drill a hole and put a self tapper through the fiberglass
tube into the aluminum tube inside the fuselage. This secures the wing tube and stops it from spinning around.
8. After the epoxy used for step 6 has cured, slide wings over
tubes and make sure they fit tight up against the fuselage. I had to lightly file the end of the tubes for a good fit.
9. Slide wings on and have them well butted up against the
fuselage. Get someone to help and hold them up tight. Drill two holes through the wings into the inner wing tube at the points marked as in step 5.
10. Remove wings. The holes should be through the aluminum tube into the hardwood block.
11. Mix up some micro-balloons and epoxy to a thick paste. Start squeezing it through the holes drilled in the wings to make a filler between the wing sheeting and the inner fiberglass tubes. You need to
squeeze in a fair bit to get it to form a filler.
12. Slide wings on and then using a 1.5 inch long self tapper,
about 8 gage, Screw down into aluminum wing tube. Oh, lubricate screw with some Vaseline or similar so it comes out after epoxy cures.
13. After epoxy cures, undo screws and remove wings. They might
stick if some of the epoxy has seeped between the inner tubes but it will come off with a little encouragement.

That is basically it for the wings. It is a secure way of holding on wings. This technique is used by others at my club with no problems.
Used for aerobatic and scale aircraft. You can do the same for the tail surfaces. I note that some manufactures use this technique for some tail planes on large scale aerobatic aircraft so must be good.

Have the aileron extension leads from the receiver sticking out the fuselage and put a small piece of balsa over hole to stop them going back into fuselage. Just need to slide wings on, plug in servos and secure wings. You are ready to fly. A good tip is to fit some large dark colored diamond shapes to bottom wing for orientation when flying.
It is great when you turn up to the field, unpack, connect wings, fuel up and are ready to fly in 5 minutes!!

Regards
Mark

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And always remember, "Experience is a hard teacher. She always gives the test first, and the lesson sometime later!"

Phillip

aeroboy1293

Thankyou for the very helpful advice on wing retention, I shall pass it on my friend Thursday afternoon.
I have no doubt that he will be interested in the canopy retention also. I'll e-mail you as soon as I have heard from him.

Regards
James.

p.s any thoughts on suitable servos, The retailer who sold him the kit said that Futaba S3003 standard non ball race 3kg/cm servos would be ok .
I however think that at the very minimum 6+ kg/cm should be used and preferably digital, that said I fly a 50cc Wildhare Extra300S with JR 8711 25kg/cm on all surfaces.

greyfoxx

Aerobody 1293 -

I think the Futaba S 3003's would be a little lacking for this plane, at best the minimum'; I'm using Hi-Tek HS475 HB Servos for the ailerons, Futaba S3010 Servos for the Push-pull Rudder and Elevator, and Futaba S3004 for the Throttle. These servos provide more than the minimum recommended using 4.8 volts, and I'm hooked up to a 2,000mh/6volt battery, so I they should be strong enough for anything but 3D, and I'm told that this airplane is too heavy for 3D. One also might notice that the ailerons do not run all the way up to the fuselage which takes away most of any prop wash coming over them. We'll see!!!

Another word of recommendation is in regard to the tail heavy tendencies of this model. When looking at a full-scale Yak 54, you will notice that the back of the prop is a considerable distance from the cowl. (if the enclosed side-view photo does not come through, send me an e-mail at greyfoxx@bellsouth and I'll e-mail it to you). I would recommend (bearing in mind that I have not flown mine yet) locating the engine as far forward as the mounts will allow. I have mine located so that the backplate for the spinner will be a full 1 inch forward of the cowl. Locating the engine so, will allow your friend to use the weight of the engine to its full advantage to alleviate the tail heavy tendency. Also consider locating the battery pack and throttle servo forward of the firewall as well, and if more weight is needed, use spinner weights. These should minimize adding 'dead weight' to the airplane, and the spinner weights (if needed) will be far enough forward that not nearly so much weight will be needed. I have read and chatted with some who have built this model that have had to add almost 16 ounces of 'dead weight' to the nose of the airplane, at the firewall, pushing the total all-up weight to 14 pounds or more. I've checked mine at this point and it all comes in at 12.5 pounds. I have not balanced it latterally yet, nor have I balanced it for the center of gravity. And that's another thing to consider. The mfg. sent two different balance points with mine. I've read and chatted with some who have used both, the more forward range, and those who have used the more rearward range. Most say use the forward range (perhaps the most rearward point within the forward range) as the rearward range will cause a snap roll on take off. Flying 50 cc gas as you do, you can help him with that, but there is loads of information out there on this airplane, and most say it's a good flying aerobatic plane, just not suitable for 3D.

Sorry, but I've been unable to attach the photo of the full scale Yak 54 in profile. Send me an e-mail to [email protected], and I'll send you a copy of the photo.

I hope some of this helps your friend. Bear in mind, I have "NOT" flown my model, so some of the information comes from others experiences with this model. When she flies, I'll try to get with you and let you know how it went. I build slow, and I've still got to mount the fuel system and receiver, and cut out the cowl for the pitts style muffler exhaust tubes, run the engine (OS 160 FX with a Perry Pump) before remounting it on the air frame, balance the plane, and set up the radio endpoints, expo, etc. I hope it will be ready in the next two or three weeks. This will depend largely on the amount of time I can devote to the project due to my mother having some health issues, and my 11 year old grandson beginning his Jr. Dragster drag racing season, but I think that is a realistic time frame.

My next project is a Great Planes (noticed you fly a Goldberg) Ultimate 160 with a 45 cc Copperhead Aviation Venom gas engine. This will be my first experience with gas. Wish me luck. I've been told once I go to gas, I'll never want to go back to glow!!! LOL!

And above all, don't forget that "Experience is a hard teacher. She gives the test first, and the lesson sometime latter!"

Phillip

greyfoxx

James - I finally figured out how to attach a photo. Duh, just read the directions at the bottom of the new post! LOL! Attached, you will find a copy of the photo of a full scale Yak 54 showing how far forward of the cowl the prop is mounted. An excellent way for us to avoid or minimize the amount of weight we have to put forward of the firewall to get the CMP Yak to balance. You might want to share this with your friend that is building this model.

"Experience is a hard teacher. She always gives the test first, and the lesson sometime later!"

Phillip