Model Boat Mayhem

Mess Deck: General Section => Other Hobbies and Interests => Topic started by: Andy M on May 14, 2020, 05:35:35 PM

Title: Experimental canard
Post by: Andy M on May 14, 2020, 05:35:35 PM
Here is my experimental canard, I say experimental as it is based on a plan, but I have changed it so much that it didnt fly to start with, my main wing has a lot of undercamber, and depron is pretty springy, so getting it to stay undercambered, even with ribs, is impossible unless you mould in the curve, some people use heated sheets of metal to reshape depron, but I use my fingers to gently form it into curves, I hadnt done this enough it turns out, as the wings pulled into a weird shape. The tip were angled up over 10 degrees so that wasnt helping it fly at all. I have worked some more on the wing, trying to get it totally flat on the bottom, its getting close but I will keep at it till I am happy with it. My main wing is made to fold in half,  the bit of masking tape holds the top of the wing halves together with strength to spare. The lower part of the fin fits in between the wing halves aft of the masking tape. Rubber bands hold the main wing and canard on. The fuselage splits in two just in front of the cockpit, it is held together with a strip of sellotape down one side, underneath and up the other side to just short of the red painted area. This has proved to be more than plenty, surviving many crashes so far during testing. The little Wltoys F949 receiver board is 25mm x 28mm and has speed control and 2 tiny servos with a socket for another servo. It works with my flysky fs-i6x transmitter, giving full mixing capabilities. I am definately going to get at least one more of these boards as soon as finances are better. My canard is powered by a single syma x7 quad motor, the same as I have in my syma powered kyosho minium plane. The canard's wing is shorter span than the minium but the whole plane is considerably bigger, I was worried it was going to be underpowered but it seems ok, it flies, just not that well yet, once (if?) I get the rest of the plane dialled in, I think it will be perfect.
 When I started making this plane, about 2 years ago, I was going to use 2 motors, I even cut motor pod ribs out and mounted the motors on them. I had drawn a small sketch of how I wanted my fuselage to look, and had a card cutout of the planform, just to see the proportions. The project stalled due to my racetrack, race cars, racing and loads of other stuff. It was only when I got the tiny board that I dug it out of storage and got it started again. It has turned out pretty much like I sketched it originally, a little bit narrower and slightly shallower fuselage to try and give the tiny motor a chance. Seems to cope, got about 25g of thrust max. Plane weighs in around 100g so its doing well to fly that much.
 The original plane uses 3 motors, each with their own plug, geared to a single prop, the board only has one socket so myself and my friend wondered if only one was plugged in at a time? Seems obvious but I found a 3 into one motor wire in the spare parts listing, but the 3 motors driving one prop will be running lower amps than 3 motors driving a prop each, I would imagine? Anyway, I made up a 2 into one lead, and worked up the courage to try 2 motors at once. Hesitated a bit in case this was going to be my board getting fried, then went for it, it worked! Yeehah. Basically, I can double the power now for a few grams extra motor pod weight. It was a relief to not fry the board, obviously. My friend has 4 of the boards but he wasnt up for sacrificing one to find out if 2 motors would work ok. Ah well, somebody has to just go for it sometimes. Lol.
 The plane, once broken down and wing folded, fits in an 18 x 7 x 3 and a half inch box, to fit in my rucksack. It takes a few minutes to assemble it at the flying area.
Title: Re: Experimental canard
Post by: Andy M on May 14, 2020, 05:45:20 PM
Its hard to imagine how small the gear teeth in these servos must be,I hope I never have to open them up for any reason!
Title: Re: Experimental canard
Post by: Andy M on May 16, 2020, 05:02:14 PM
A few measurements of the wltoys F949 servos on the board.
Title: Re: Experimental canard
Post by: Andy M on May 16, 2020, 08:23:27 PM
I can report a partial success,after some more work on the wing, it's now pretty flat on the bottom. And the plane now flies well in a straight line, nice and slow as I had hoped. But...... I just cant get it to turn. I made the aileron/elevators quite small as I didn't want to overload the servos, but I will be making much bigger ones to see if that will turn it. If that doesnt work, I already made arrangements for elevons on the canard, these were taped top and bottom to hold their position, removing the bottom bits of tape would let me fold them back and finish my taped hinge, a couple of ice cream tub horns and move the board into the front section. I think bigger ailerons will cure it though.
I must add that the plan that I loosely based it on is actually a free flight design. Maybe this is why its so stable in a straight line.
Anyway, I count this as a success and l just have to work on turning it now. It seems to have enough power, not much in reserve tho. It is using the standard syma x7 quadcopter prop, which has gussets moulded on the back which must affect the output, also they are not the usual propeller type of shape. It works fine on my minium plane.
Once I get turnability, I will experiment with prop, but it was flying at the perfect speed earlier so might not need to change anything. It had a few flights into branches earlier and survived well, quite robust for mostly 2mm depron. The wing is 3mm with bamboo edges. It does only weigh about 4 ounces ready to fly, so that helps a lot for 'contact events' (crashes)
Title: Re: Experimental canard
Post by: JimG on May 16, 2020, 08:29:01 PM
Is there much dihedral on the wing? As a free flight design it would be using this for stability. If so then reduce the dihedral, this will make the ailerons more effective. As an alternative replace the aileron control with rudder as this will be more effective with free flight levels of dihedral.
Title: Re: Experimental canard
Post by: Andy M on May 16, 2020, 09:11:59 PM
Hi Jim, as its a swept wing, this gives the effect of dihedral but is totally flat, tip to tip. The elevons are definately too small. I know the servos can handle a bit extra, I put some stress on them when I was removing the wing and pushrods. I have attached a photo of the original aircraft I based it on.
Title: Re: Experimental canard
Post by: Andy M on May 17, 2020, 01:40:37 PM
I have made a bigger set of elevons, probably about 3 times the area of the original set. Hopefully these will give me enough to get the plane to turn. I still have the option of control from the canard foreplane, although these are even smaller, but should have more authority due to the long moment arm. Anyway, I will see how I get on with the larger elevons first, I am pretty sure they will do the trick. I did say its an experimental canard, I expected to have to do some experimentation.
Also shown is the plane dismantled and in its transport box.
Title: Re: Experimental canard
Post by: Andy M on May 17, 2020, 05:57:05 PM
Results of bigger elevons were mixed, it was responding better to elevator inputs but turning... It was opposite way round, and not from having the elevons moving the wrong way. On a left turn, the right aileron goes down, creating more drag than the effect of left aileron going up, turning it to the right. I did have to get used to flying it that way but it is slow and stable enough to make this easier. I managed a 30 second plus flight, it was windy as well. Its better than I was getting, I need to program in some differential now to sort out tbe drag issue, less down than up. Or I can rotate my servo arms forward, means a new set of pushrods, 10 minutes. Its definately getting better, so I am heading in the right direction. Its actually a graceful little plane, the deep undercambered surfaces slow things right up, the syma gearbox/motor and prop is pretty quiet.
Title: Re: Experimental canard
Post by: warspite on May 18, 2020, 09:19:33 AM
Is it because the air is flowing along the ailerons rather than over them as the wings are swept back
Title: Re: Experimental canard
Post by: Andy M on May 18, 2020, 11:42:35 AM
Hi, it could be partly to do with that, the ribs underneath will reduce the tendency for the air to spill out along the wing on the bottom side but there is nothing on top to prevent this.
As they still work fine as elevators, I am pretty sure the adverse yaw is due to the drag from the downward moving elevon. I will try differential next, it is programmable on my transmitter, just need to have a proper look in the settings. It is possible to do it with servo arm positions, I may try this first.
In some ways I dont like the finish of depron, compared to balsa for building, but it is easier to modify things. Also, it doesnt need any covering, sealing, fuelproofing or painting. Glow powered planes required that all surfaces were sealed before you fired up the oil generator. Modifications were more difficult once it was oily.
With depron, it can be modified easily. I will try the differential and see what happens, I know its pretty close. Tx programming would let me adjust it so that the down moving aileron moves just a little, or not at all, if I need to.
Title: Re: Experimental canard
Post by: Andy M on May 18, 2020, 04:27:01 PM
I just noticed the photo of it in the box shows it with the small ailerons still fitted.
Title: Re: Experimental canard
Post by: Andy M on May 22, 2020, 07:50:31 PM
I found this picture of a similar sized servo to the ones on the wltoys f949 board. It shows just how small the gears are.
Title: Re: Experimental canard
Post by: Andy M on June 01, 2020, 04:08:15 PM
Short video filmed while flying with one hand here
Title: Re: Experimental canard
Post by: Andy M on June 02, 2020, 03:41:48 PM
One of the F949 servos has failed, it was making a chattering sound then stopped completely. It was subjected to some hard landings with the bigger aileron's momentum probably contributing to the failure. The ailerons are very big for these servos so I am not really surprised, just a bit disappointed. I have had a good look to see if I could repair it but no success so far. It still has one working servo, and a socket for another to be added so I could get it back working but I dont know if it will have elevon mixing anymore, will need to get a servo to suit it before I can experiment with mixes. Anyway, here is what it looks like dismantled......the board is approx 25mm long.
Title: Re: Experimental canard
Post by: Andy M on June 06, 2020, 01:55:05 PM
Here is the motor from my dead servo, 8mm long, 4mm diameter and a 2mm diameter gear. Super fiddly and would be so easy to lose bits if not careful. I havent found any motors this size in my stock of bits, will have a look online later, not sure if the motor is the problem though.
Title: Re: Experimental canard
Post by: warspite on June 07, 2020, 11:31:42 AM
Looks a bit bigger than those used in mobile phones to vibrate
Title: Re: Experimental canard
Post by: Andy M on June 07, 2020, 12:05:58 PM
Hi Warspite, turns out they are pager/phone motors. Found 10 for 3 odds with free delivery. I may have one in an old phone, save me some cash. (that I dont have at the moment)
Title: Re: Experimental canard
Post by: Andy M on June 27, 2020, 11:59:49 AM
I decided to try one of my whizzy motors in the canard, as it might have been a shade underpowered, it is pretty big for a 7mm motor and gearbox. The whizzy motor should cure this, in the same gearbox. The power difference on the delta was a transformation, even a bit more on the canard would be good, I think it was close with the older quad motor. I dont have a spare F949 board, I am still waiting on 2 arriving in the post, hopefully soon...... I am going to try it with the tiny board and 7mm motor. If its still not enough power, I am going to try v262 quad gearbox unit, they are 7.4v so I need to use 9g servos and my standard flysky rx, along with my 10a esc. A 7.4 v e-cig cell is proposed for that, if I have to go that way. The weight would increase pretty dramatically I think, compared to all in one board and a single battery.
Title: Re: Experimental canard
Post by: warspite on June 27, 2020, 12:21:59 PM
I still have a couple of phone vibration motors, they look smaller than yours it is a pain to remove the counter weight, not much bigger than a 1 pence piece.
Title: Re: Experimental canard
Post by: Andy M on June 27, 2020, 03:26:14 PM
Hi Warspite, thanks for the offer, I will hold off for now, I have the board with the dead servo in my elmira motor glider, the dead servo is the elevator, my friend gave me a 1.7g servo that plugged into the rudder socket on board. This was then mixed till it thinks its the elevator servo! Perfect. I intend this set to stay in the Elmira for a good while, its just hotglued in a few small areas and easily picked off if needed.