HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old May 03, 2007, 07:05 PM
SAC 380th Bomb Wing (FMS)
ruffnite's Avatar
Harrisburg, Pa.
Joined May 2007
38 Posts
Build Log
Guillows Cessna 172 Skyhawk my first RC kit

When I was 16 (1984) my dad got me my first RC plane for Christmas. I canít remember who made it but it was the chipmunk. It had an electric motor long before speed controllers and the only way they measured the size was saying it spun at 1200 RPMs. It was a foam plane but the foam was very brittle. It was a 2 channel and to say it was grossly under powered would be the biggest understatement.

I waited all winter for the upstate N.Y. weather to turn to spring (somewhere around July. Lol) to finally get this baby in the air. The day came. I went to the local clubís flying field, and badda bing their was a member there flying. With a world of convincing that life as he knew wasnít going to change because there was an electric on the field I talked him into helping me fly. He took it up for its madden flight I think the battery lasted about 5 minutes. I could see he was really struggling to keep it airborne, but he did and brought it in for a landing. Next it was my turn. We recharged the battery and he took it up again. At a safe altitude he handed me my brand new Futaba 4 channel radio, and in the next 20 seconds the yellow Chipmunk was history. I was heart broken. I figured their couldnít be a way I would ever be able to learn to fly with electricís being so new and under powered, and fuel being so expensive for a 16 yr old.

2005 brought a different light when I bought my first hobby zone. The day I went out for the first time I was alone it was 0600 so the wind was nil and I flew, Sun of a gun I flew. I must have been a sight all alone in the middle of the field dancing like an idiot. I was flying. Since then I have moved up threw the steps and can comfortably fly a 4 channel low wing, but still all of my planes are RTF or ARF. So this is the thread Iím starting of my first scale kit.

I have read so many threads of the guys that are building for the first or second times and Iím amazed of the helpful tips and hints and even joking around the more experienced fliers provide. Thatís how I came to the conclusion to post my progress. I truly hope you guys enjoy and have some tips and comments for me as we go. Oh, also my entries wonít be as long winded and just shoot me now dramatic as this. Lol

The plane I chose to be my first is the Guillows Cessna 172 skyhawk. I chose this plane because of the big 1/12 scale, it being a top wing aircraft, and knowing Guillows uses Balsa and good plans for everything if I break a part or need to modify it would be simple. Also I didnít know where to look for kits that where meant to be RC planes. Now I have sites that seem to find me. Anyway here we go. Again please help if you have suggestions.



[IMG]1[/IMG]
ruffnite is offline Find More Posts by ruffnite
Last edited by ruffnite; May 05, 2007 at 11:05 AM.
Reply With Quote
Sign up now
to remove ads between posts
Old May 03, 2007, 07:40 PM
Registered User
Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,205 Posts
Quote:
Originally Posted by ruffnite
The plane I chose to be my first is the Guillows Cessna 172 skyhawk. I chose this plane because of the big 1/12 scale, it being a top wing aircraft, and knowing Guillows uses Balsa and good plans for everything if I break a part or need to modify it would be simple. Also I didnít know where to look for kits that where meant to be RC planes. Now I have sites that seem to find me. Anyway here we go. Again please help if you have suggestions.
[IMG]1[/IMG]
The most important thing will be to build it LIGHT. Those Guillows kits have a LOT of excess (and poor quality/heavy) balsa, so you will need to leave out any extraneous material and trim and sand what you must use. If you can get the whole plane (with ALL the gear in it) down to 10oz-12oz you may be okay. That will mean a 20g brushless motor, a light Lipoly pack, 6g servos and a tiny Rx and ESC. Cover it with nothing heavier than SoLite (0.6g/sq.yd).

I have a 36" Herr Starlight and have struggled to keep it down to 5oz (120g) AUW by using a 12g motor and gearbox, 2g carbon fiber prop and 2s 340 Lipo.
Dr Kiwi is offline Find More Posts by Dr Kiwi
Reply With Quote
Old May 03, 2007, 07:40 PM
SAC 380th Bomb Wing (FMS)
ruffnite's Avatar
Harrisburg, Pa.
Joined May 2007
38 Posts
As I opened the kit my first big problem was starring me right in the face. The 172 has its wing mounted above the cockpit. Guillows solution to this was to vacuform the cockpit windscreen and the wing out of nylon. Could be a problem later, but Iíll deal with it as I go.

Iím not sure what motor I will use yet so I figured that I would build the strongest and lightest plane I can. Then I will weigh it and match a motor to my needs. Looking at the info I see on line, there are some pretty powerful motors that weigh next to nothing so Iím sure ill find one to work. Keeping to the plan to make it strong I decided early on that o would cover the wing in 1/32 basswood and the fuselage in 1/32 balsawood. Itís light and should be strong enough. Also I like the look of a smooth surface rather than tissue over spars, and besides if I cant keep the weight down and it never leaves the ground it will make a nice static model.

I started with the wing. I beefed up the center wing with 3/32 basswood for the wingroot and to house the aileron servo. I also eliminated all the 1/16th spars. The basswood covering will be a lot stronger and well lets cut as much weigh from the start. I already added a lot with the wing root.

After I laid out the wing I needed to decide the direction to take with the aileron servo. It would be easier to run two servos with a y connector but it would add more weight and besides being a scale plastic builder from way back with IPMS scale detail has always been a stickler with me. Not sure how to scale the skyhawk will be but Iím sure 2 servoís hanging from the under wing wasnít in the blue printsÖlol I went with 1 servo in the middle and I ran 2 short brass tube bent to fit. The guide piano wire move like silk in the tubes. I like the way it worked out.


[IMG]1[/IMG] [IMG]2[/IMG] [IMG]3[/IMG]
ruffnite is offline Find More Posts by ruffnite
Reply With Quote
Old May 03, 2007, 08:03 PM
SAC 380th Bomb Wing (FMS)
ruffnite's Avatar
Harrisburg, Pa.
Joined May 2007
38 Posts
Since I started reading all the threads on the site I can say the one thing I see the most is ďkeep the weight downĒ Iím beginning to think thereís something to thatÖlol .
At this point my wing is cover with the basswood. With the servo and push rods in place (minus the ailerons them selves. Iím sitting at just under 2 oz.) I certainly wonít make the weight that dr. kiwi mentioned, but I set a goal of under 16-oz. for the whole plane With all electronics. I am concerned it will be too heavy, but with a big enough motor I might get lucky. These are the things I hope I can solve with input.
At this time I am pretty far along, as you will see with my posts. I just keep my fingers crossed.
ruffnite is offline Find More Posts by ruffnite
Reply With Quote
Old May 03, 2007, 08:06 PM
Registered User
Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,205 Posts
Looking very nice. Getting plenty of power from a small motor isn't hard these days, but you will need to keep an eye on the wing-loading. What is the wing chord (?6") - that means you only have about 1.5 sq.ft of wing area so even 10oz is 7oz/sq.ft. At 16oz you are at ~10.7oz/sq.ft - so it will need to fly fast to stay aloft.
Dr Kiwi is offline Find More Posts by Dr Kiwi
Last edited by Dr Kiwi; May 04, 2007 at 08:26 AM.
Reply With Quote
Old May 03, 2007, 08:21 PM
SAC 380th Bomb Wing (FMS)
ruffnite's Avatar
Harrisburg, Pa.
Joined May 2007
38 Posts
im glad you brought that up. being new and one of the thing i REALLY need to know is how do i figure out wing load? Can you explane or is thier a site to help me with the formula?
again i love this site, one of the biggest questions i had (wing load) is being adressed in the first hour of posting. thank you for the time your giving me.
ruffnite is offline Find More Posts by ruffnite
Reply With Quote
Old May 04, 2007, 05:42 AM
SAC 380th Bomb Wing (FMS)
ruffnite's Avatar
Harrisburg, Pa.
Joined May 2007
38 Posts
and the hits keep comming

It is time to set up the dihedral. I took my time on this step. In the plans it looks like the 1/16th balsa strips absorb most of the stress on the wing where the dihedral joint is. I remade the wings structural parts of 1/16th basswood for strength and Iím counting on the 1/32 covering for the bulk of the strength Iím need. I used spare balsa to prop the ends of my wing to the recommended dihedral. (I canít remember the percent at the moment but when I goto the shop today ill get it and update).
This step took some time. Being I didnít use 2/3rd of the wood recommended I really wanted to make sure the wing didnít warp at all during the gluing process. I pined everything I could see.


I couldnít wait to start to cover the wing. Again I used 1/32 basswood. I figured the flexibility would make it easy, I just didnít know how well it would work. I was very happy. I started on the top in the center and worked out. I was real careful to go slow on the gluing. I didnít want the wing to warp the slightest little bit.
I love how the wing looks when youíre covering it and before you sand. You can just see the finished product in your head. I used ĺ x ĺ square balsa wood for the leading edge and sanded to the shape I needed as you can see in the pictures below. You can also see where the brass tubing exits the wing for the ailerons. I donít have the push rods hooked up yet but you can see the lay out with the servo in place.

The last few pictures are of the completed wing minus the ailerons. Now that I see the pictures ill try to get some better ones of the wing sanded. I need to take some of the fuselage now that it is covered.

Till next time. Happy building and flying.





[IMG]4[/IMG] [IMG]5[/IMG] [IMG]6[/IMG] [IMG]7[/IMG] [IMG]8[/IMG] [IMG]9[/IMG] [IMG]10[/IMG]
ruffnite is offline Find More Posts by ruffnite
Reply With Quote
Old May 04, 2007, 08:25 AM
Registered User
Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,205 Posts
Here is a link I found (with a sad ending!) - this guys plane came out at 13oz (or was it 15oz) and he found it had to fly pretty fast.

http://boiserc.com/forum/viewtopic.p...516852d9cb8552

Wing loading is simply weight divided by wing area. Assuming 6" chord, your wing is 36" x 6" = 216 sq. in = 1.5 sq.ft. 16oz AUW gives you 10.67 oz/sq.ft.
Dr Kiwi is offline Find More Posts by Dr Kiwi
Reply With Quote
Old May 04, 2007, 09:04 AM
SAC 380th Bomb Wing (FMS)
ruffnite's Avatar
Harrisburg, Pa.
Joined May 2007
38 Posts
great. im going to run some numbers and practice. great link. thnx so much. i may not want to hear the answer, but do you think im heading in the right direction so far? assuming i can put it on a diet?
ruffnite is offline Find More Posts by ruffnite
Reply With Quote
Old May 05, 2007, 08:07 AM
SAC 380th Bomb Wing (FMS)
ruffnite's Avatar
Harrisburg, Pa.
Joined May 2007
38 Posts
First thank you Mr. Kiwi for the time and info. So far like most that are new to the hobby Iím figuring it out as I go. Its amazing the things you can learn when you just ask.lol
Well thereís 1 thing I know for sure. I know that this plane will fly. Even if itís four and a half feet strait down it will be airborne. Lol. Now my goal is to see what I can learn from building it and so far I know at least twice as much as I did when I started. Oh yea and maybe see it fly a little farther that four and a half feet. hehehe.


Time for the fuselage. Still wanting to keep it light but strong I decided to wrap this with 1/32 balsa wood this time. After the wing I discovered just wrapping it made it so much stronger than the bare frame. I figured balsa should be fine and itís so much easier to bent and lighter than the basswood. I found that I need to be careful sanding it. It can get real thin real fast. Still didnít have any blowouts. I also replaced the side keels the kit provided with ones I cut of basswood, adding More strength


[IMG]1[/IMG] [IMG]2[/IMG] [IMG]3[/IMG]





I beefed up the area were the main gear would be and the under side of the forward fuselage. I than began to wrap the frame. The balsa was a good idea. It covered very easily. On the aft sections where the bends were very tight I just soaked the balsa for a few minutes and it seemed to just droop over the frame on its own. I was also amazed that I could ca the balsa while it was still damp. I left the top aft open for ease of installing the flight controls. After sanding and filling and sanding I think it turned out very nice. I used a set of hobbyzone landing gear for the main gear. The less I have to bend and fit the straighter and better fitting things seem to be. haha




[IMG]4[/IMG] [IMG]5[/IMG] [IMG]6[/IMG] [IMG]7[/IMG]
ruffnite is offline Find More Posts by ruffnite
Reply With Quote
Old May 06, 2007, 04:46 PM
SAC 380th Bomb Wing (FMS)
ruffnite's Avatar
Harrisburg, Pa.
Joined May 2007
38 Posts
Hey all, well this post will catch you up to where I am. Which brings us to the problem I mentioned in the first post I made. The cockpit!!!!

I finished the rudder and the elevator using 1/32 basswood sandwiched between 1/32 balsa wood this gave it strength and by using the balsa on either side of the bass it lightened it up. Youíll notice I have the hinges installed on the elevator but not the rudder. Just didnít get to it yet, but the notches are cut.


I dry fitted all the parts as you can see in the photos. I couldnít wait till I got to this step. Makes it feel like Iím actually building something. Lol. At this point I weighed the plane and with all the electronics, 3 Futaba s3103 servoís, a Futaba r114f Rx, all the posh rods, minus the control surfaces, motor, and controller. I weigh in at 9.25 oz. Its gonna be close I hope I can make it fly.


Now my problem, I didnít think ahead or maybe I did and thought a solution would present itís self before I got to this point. By covering my wing with basswood I changed the measurements and now the wing doesnít fit anywhere close in the cockpit vacuformed vinyl. What to do? I started to cut the vinyl to fit the wing, but in doing so I took all the strength away. So the question is, keep cutting and reinforce, or scratch build? If scratch build I canít figure a good way of doing it. Anyway look at the pictures and see what I mean, and please give me what ever you can come up with. This is where being in a club helps. Lol.



[IMG]1[/IMG] [IMG]2[/IMG] [IMG]3[/IMG]


[IMG]4[/IMG] [IMG]5[/IMG] [IMG]6[/IMG]


[IMG]7[/IMG] [IMG]8[/IMG]
ruffnite is offline Find More Posts by ruffnite
Reply With Quote
Old May 07, 2007, 01:25 AM
Registered User
Joined Aug 2004
831 Posts
It's looking good. I don't know about the beginners fly ability with the basswood sheeting, however it will be a tough plane. Ailerons on that plane will be very helpful. It will be a bit of a hot rod. Since you're part of a club, have them help you on the flight, it will be pretty tough to fly at launch with the speed you'll be getting with that model. Once it's in the air, the model will be just fine, for the most part. Find tall grass to launch and land in, like 3 feet tall grass. Not to be a fortune cookie... there is a great future headed your way! Very few modelers start of building planes these days, and you started off with a fairly complex one, and you're taking it without sweat, and you're building quickly. This is VERY good, for as un-recommendable this plane is, I think you've got an unusual edge above others.
Accu157 is offline Find More Posts by Accu157
Reply With Quote
Old May 07, 2007, 02:49 AM
Registered User
Kill Devil Hills, NC
Joined Jun 2002
179 Posts
Quote:
Now my problem, I didnít think ahead or maybe I did and thought a solution would present itís self before I got to this point. By covering my wing with basswood I changed the measurements and now the wing doesnít fit anywhere close in the cockpit vacuformed vinyl. What to do? I started to cut the vinyl to fit the wing, but in doing so I took all the strength away. So the question is, keep cutting and reinforce, or scratch build? If scratch build I canít figure a good way of doing it. Anyway look at the pictures and see what I mean, and please give me what ever you can come up with. This is where being in a club helps. Lol.
My 1st suggestion is to contact Guillow's for a replacement molded canopy.
While this is taking place, I'll post later on my recommendations of how to treat the problem, along with some weight-saving tips both on this model as well as others to come. This should include improvements in wood selection, the use of lightning holes, lighter servos and more.

Virg.
Virgil Kee is offline Find More Posts by Virgil Kee
Reply With Quote
Old May 07, 2007, 11:09 AM
MPP
In Unusual Attitude Recovery
MPP's Avatar
Danbury CT (DXR)
Joined Oct 2005
2,152 Posts
Hey Ruffnight,

You have to check out this thread. It is a masterpiece and you can get an idea of how it flyís. Keep it light as this one is 10 Oz. and flyís very well. You have a nice build. If your weight gets too high you might consider shedding some of that sheeting (especially the tail area) and go with Solight covering. I know it would be hard to do especially after all that great work you have done. Good luck these kits do fly.

Cheers,

Mark

http://www.rcgroups.com/forums/showt...ghlight=cessna
MPP is offline Find More Posts by MPP
Reply With Quote
Old May 07, 2007, 06:22 PM
Registered User
Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,205 Posts
What size motor are you thinking of putting on this? Did your estimated weight posted earlier (9.25oz without certain things) include the battery pack?
Dr Kiwi is offline Find More Posts by Dr Kiwi
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
GUILLOW'S CESSNA 172 SKYHAWK conversion to electric. reznikvova Parkflyers 25 May 03, 2008 12:56 AM
Guillows Cessna 172 w/ pictures... Propjob81 Parkflyers 25 May 25, 2004 10:14 PM
Cessna 172 Skyhawk 3-views? Gordon Scale Kit/Scratch Built 10 Nov 17, 2003 11:24 PM
Cessna 172 Skyhawk Grave Digger Scale Kit/Scratch Built 0 May 08, 2003 06:38 AM
WOW! - Got to see my first RC Turbine Jet. mrebman Electric Plane Talk 24 Sep 28, 2001 12:01 AM