cabinetmaker

This is my first airplane Build. I only have about $65 in it.
Made it from leftover materials from my cabinet shop, white pine, birch, basswood. No plans. Scratch built.
Specs:
Wing Span 98"
Length 74"
Weight 15.5#
25cc weedeater
16x8 prop
Will take suggestions or answer questions.
HAve no clue about what kind of skin or servos to get for it.

FlyerInOKC

My Feedback: (6)

No laughter here it looks a lot better than my first build! Since it is a first build you might try a covering like Monokote or Ultracote. Their are a number of resources on the web with how-to information or you can purchase Fay Tilley's book on the subject. I consider it a must read on polyester coverings. Both Monokote and Ultracote have on tutorials and their is an excellent one on RC Universe as well. If you have a local hobby shop near by you could take it in. They can look it over and make suggestions on servo etc. or check with a local club. Having someone actually see it in the flesh is a good idea they may catch little mistakes that you might have overlooked. I have been building and flying for years but I still do it during construction and after the airplane is built I turn it over to the old hands at the local club for inspection. I also have a local well known contest flier pilot it for the maiden flight and critique it. I get to take the pictures and it has saved me a crash or two. I don't build in this large a scale so I won't make suggestions on something when I don't have first hand experience.

speed lover

That's a nice plane you have built. Sounds light at 15.5lbs should fly really nice. I'm going to build my 72" Sportster kit very soon. It uses standard servos but I think you are running the limits as it weighs around 11lbs I will be using 12.5Kg servos metal geared but this is because it is quite a fast plane and I will be throwing it around a lot. I will probably use one Sanox for the rudder 1 for the elevator and probably around an 8kg servo in aech side of the wing for the ailerons.

Props4ever

Sure is very nice plane, as for starter you aced it it with good numbers i'd say.
It looks pretty good and solid also, you may want to go Hitec HS-645MG servos all around except for throttle, you can use standard there. I would also recommend using plastic covering as Ultracote or Monocote as they are easiest to cover a plane with and they have numerous different colors to chose from, being opaque to metallic types. Also it would be good ides to find a local club and take it to them for check out, i would say do it now before you cover it, this way if anything needs to be fixed as incidence or and structural part, it will easy to do now then after covering it up.

Keep us posted on your progress with it, hope you will have it flying soon!...

BMatthews

Can you let us know what the area of the entire horizontal tail is in terms of % of the wing area? The tail looks a little bit small to my eyes but it's not by much and it may be due to the camera perspective. And as always the elevator and aileron areas are to be included in the surface area of these two items.

Other than this small niggling detail and a general observation that the fuselage is a bit "wedgy" lookng the design looks fantastic. And when I take into account that this is your first design then all my criticisms other than maybe the tail area issue pale.

A very hearty well done. In this age of ARF'dom it's nice to see a few folks that don't march to the beat of the ARF drummer.

cabinetmaker

Thanks alot. I will get those specs posted. I went and bought my radio and servos yesterday at Hodges Hobbies.
RAdio- Spektrum DX 7 with 4 servos
Standard servo for throttle
Monokote for Skin.

BMatthews

Just noticed in the third picture a glimpse of the landing gear setup. Are you using plywood for the landing gear struts? That and the long unsupported length of wire between the end of the strut and the wheel is nasty as well. Post some pics of that area for clarification please.

Props4ever

Good eye Bruce,

Yep looks weird set up of the landing gear for sure. He would be better of getting aluminum landing gear with 4" wheels would be idea his his airplane, i think i have large enough aluminum landing gear that would work for him. I may have wheels also but have to check first if he is interested.

cabinetmaker

Your right it is a weird setup. I had a harder time coming up with an idea for the landing gear than I had building the whole plane. Trying to keep the store bought items on the plane to a minimum. I wanted to find some spring steel to fabricate the gear out of but I was afraid it would end up being too heavy. Right now it is 1/2" plywood with a 3/8" fiberglass rod for an axle. It is alot stronger than it looks, I have dropped the whole plane on the ground a couple of times just testing it out, it has some spring to it, which is what I was looking for. I am about to rework the rear wheel. I will post some progress pics soon.

shootnstarz

Yep, building planes in my cabinet shop too as there is no call for cabinets these days. Amazing the framing came out so light with the wood you used. I'd certainly rework the main landing gear but I think you should leave the stereo cabinet caster tailwheel, it adds a lot of character.

Rick

BMatthews

Hmmmm.... I'm a touch worried about the wing spar setup as well. Although you used decent sized stock for the spars you haven't used it in the best possible way. By placing the wood in a vertical manner like you have all the stress is focused on the outer 1/2 of the spar wood. Also the spars are working as three separate small spars instead of locking them together to form a mutually supportive spar system.

An example of a more "system" design would be to have used two of your spar pieces only. Laid on the flat with one on the bottom and the second on the upper surface. Then lock the two spars together with front and back vertical grain webs to form a box structure. Alternately vertical grain center webs would combine wiht the upper and lower spars to form an "I" beam structure. By locking the upper and lower spars together you get the most out of the cross section of the wood. Such a structure goes far beyond the sum of the elements in terms of stiffness and strength.

Keep it in mind for next time.

And I'd like to also add that you did a great job on keeping the overall weight down. 15 lbs for that size is excellent. At least I'm assuming that it's 15 lbs WITH the engine already onboard. If not then the wing loading is climbing too fast.

I think you'll have trouble with the landing gear. That flex you talked about is great for landing shock but the axle is also going to flex back and forth and make for some serious tracking issues on takeoff and landing.

Look up some landing gears used on old World War One biplanes. They use two V main legs with an axle supported in a slot at the apex. In their case rubber shock cords provided some shock absorbing and the slot the axle moves up and down in provides the travel direction control. You may want to duplicate that sort of setup but using some big #64 rubber bands with multiple overwraps to achieve the amount of flex you want. It would be a lot better than the uncontrolled flexibility you have in the present setup. I think you're also underestimating the power of a hard "arrival". I can see where you could easily hit with enough force to flex the axle as presently installed to the point that the lower end of the legs would dig in and trip the model.

cabinetmaker

Thanks guys, I will be taking your suggestions seriously. I will be changing the gear. I will be looking for someone to maiden it this week. It does great at high speed taxi, a little bouncy at lower speeds. Here are some pics.
Having trouble with pics. Try later....

cabinetmaker

I was amazed too, I thought I would end up too heavy. That 1/4" birch plywood stays pretty rigid after it has been riddled with holes. I also found that the white pine is lighter than basswood. Sorry about the tailwheel I have changed it. It is now attached to the rudder so I can steer.

Sandmann_AU

Perhaps not the prettiest plane I've ever seen, but certainly a LONG shot better than I could build, specially from left-over bits and pieces! Well done.

iiiat

Hey Cabinetmaker,
Very cool project for your first plane. Bravo!
I do have an observation. In your last photo, there seems to be very large gaps between the elevator and stab, and between the rudder and vertical fin. FYI, these large gaps will reduce the effectiveness of those control surfaces a great deal. These gaps could be sealed with some clear packing tape or even some monocote. Anyway, I'm sure whomever is going to maiden the plane for you will check it over and make a few suggestions.

Good luck!
Tom

dhal22

definitely have to seal the gaps.

cabinetmaker

Yea, the gaps were tight when I had it in the bones, then the guy at the hobby shop suggested those hinge pins, and I think they were the biggest ones you can buy. Do you have to put the tape on with some "slack" in it so the surfaces can move?

carlgrover

That plane looks fantastic. When I saw it, I immediately said to myself, "that needs to be finished out like a Russian Bomber" Did you dovetail any of the joints? ha ha. When I'm not building airplanes, I build furniture.

BMatthews

Dovetail joints in a model airplane.... Oooooooo that would be cool....

Now which parts should the wedged mortise and tenon joints be used for?


Another woodworker here

cabinetmaker

cabinetmaker








Well guys, I could not wait any longer I trained up on my flight simulator for a couple of days, put the third set of landing gear on the plane and maidened it Sunday. Sorry to those who wanted to see a video, I didnt want to create a bunch of hype about it, also thought it would make me too nervous. The plane survived! And I learned alot. The plane got off the groung pretty quick, but wanted to roll left, I found out later that I needed to increase the angle of attack on the left wing to counter the motor torque, I also learned that I will need to move the wings forward a little, it seemed to be nose heavy. The landing was rough, well what I could see of it was anyway, it went over a small hill out of sight before it touched down. It made a loud crashing sound but when I walked up to it everything was fine, except for the prop, it obviously nosed over. The main landing gear was sprawled out a little so I guesss it hit pretty hard. No folding of the wings or anything. I will be doing some adjustments to it and try to get it in the air again soon. I will be sure to video next time. Hopefully it will end up in one piece again.
Thanks for all the great info, it really made a difference!

Sandmann_AU

Sounds like you did well. Rather than changing the AOA of one wing, perhaps it'd be easier to angle the motor to the right a few degrees?

cabinetmaker

Would that stp the plane from rolling to the left? I was having to give it full right aileron to keep it level.

MasterAlex

Hey cabinetmaker, check out the article on How to Install Robart Hingepoints [link=http://www.rcuniverse.com/magazine/article_display.cfm?article_id=269]here[/link]; this will help you the next time you attempt to use HingePoints. There's a video over there too.

-MA

cabinetmaker

Great video, I knew something wasnt right when I was putting those hinges in, the hinge gets larger than the barbs up towards the pin, didnt realize you were to bury the hinge up to the pin. Too late now for that plane, I will know better next time. Thanks.

Sandmann_AU

Yep, assuming the plane's built straight it'll work just fine. The plane wants to roll left due to the torque of the engine (which is why Sopwith camels would turn so hard in one direction but not the other). The prop is "rolling to the right", so the engine (and the attached fuselage) wants to "roll to the left" - the same way as a helicopter'll spin out of control if it loses its tail rotor. If you have a look at just about all commercially produced single-engined models the firewall's canted off to the right by about 2-3 degrees, and sometimes 1-2 degrees down as well to stop the plane's tendency to balloon when you hit the throttle. On a typical twin-engined plane the right firewall's canted about 5 degrees right, and the left one about 2-3 degrees left to help with control in single engine flame-outs.

Changing the AOA will work, but it'll work all the time regardless of throttle position which means at low speed the left wing would want to stall before the right wing. To make sure it's rolling from torque rather than a twisted wing get it up high and then cut the throttle and let it glide - if it's built straight the tendency to roll left should disappear.