Probably basics for some - RC Groups
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Oct 06, 2009, 11:26 AM
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Probably basics for some

Hello, I really would appreciate some input on some basics. I have just de-moulded my first composite fuse and thought it best to check with the boffins on certain build aspects before ploughing on and doing something that I might regret later. The plane is a scratch built (called Skyhook) with a bagged 2500mm wing. I used Drela airfoils - Ag35,36,37 and 38 for the tiplett. The new glass fuse is based on a balsa prototype which has flown well despite showing up some characteristics that have been adressed in the glass design. The pictures might help explain my questions.

1. I have formed a recessed access hatch at the tail end (this still needs to be cut out in the photos and I have made a moulded cover to close it). My origional thoughts were to use a bellcrank pivoting on the flying stab main connector rod. One arm of the bellcrank in line and connected to the control rod, the other arm connected to the minor stab connection pin to drive the movement. Would a bellcrank in the position of the access hatch like the BOT be a better option or is there a better way of doing it?

2. My prototype uses rubber bands to hold the main wing on. I intend to use small steel bolts - two at the back and one in the front on this new fuse. Is this my best option? I dont want to use dowels in the front due to the thin wing section. Any information on "favourite" fixing methods would help.

3. I am busy with a second (interchangeable) wing with ailerons and flaps. Is the RDS system worth the effort for a non-competition plane?

Any input would be greatly appreciated but will probably lead to more questions (you have been warned). I sorry for asking questions that have probably been asked many times but I have searched and havent found any decisive answers.

Happy flying
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Oct 06, 2009, 12:31 PM
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prodjx's Avatar
Nice looking fuse, I would go with a carbon push rod and a bell crank. The ARF BOT uses a servo in the tail. Bolt on wing would be the way to go. I too am a scratch builder. If you search for "Petrel finally molded" you'll find my build log photo's on how I did it. The Petrel is an African design that was published in a back issue of Sailplane @ Electric Modeler several year's ago,oh it's a 2m. Dave.

for Petrel finally molded in the search
Oct 06, 2009, 01:10 PM
agony sweetns the victory
atjurhs's Avatar
Mark, I'm also a scratch builder and find lots of enjoyment in doing so.

Great looking fuse!!! Very nice work!!!

Question 1: on a plane this size, I would run pushrods up to the cockpit and mount both tail servos there. has good wire pushrods (and cheap) for a plane this size. Buy the 3M long ones just to make sure you don't end up with pushrods that are too short.

Question 2: definitely bolt the wing down. I'd use something on the order of a metal 10-32 bolt near the spar to take the bulk of the forces, but you can get use a long nylon bolt (again in the back to keep the wing from pivoting. In the event of a cartwheel landing the nylon bolt may shear and thereby do less damage.

Question 3: RDS is not worth the effort IMO unless you were building a serious competition plane. Instead, get a set of servo-arm covers (once again, will have some) and the drag will be greatly reduced.

Welcome to the world of scratch building

Oct 06, 2009, 01:34 PM
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prodjx's Avatar
markles23, hey I just noticed the honey comb effect on the red trim, that's neat. Kind of remind's me of putting some 1/8 cell aluminum HC in front of my camera lenses, everything in the center of the photo was normal and as you went out from the center you would get the HC effect.
Oct 06, 2009, 10:58 PM
Thermal Naked!
Hossfly72's Avatar
I'll second the honeycomb effect on the tail! OUTSTANDING effect!

Get the weight out of the tail (just my opinion).
Definitely a bolt on wing and with your skills, you could whip out some servo covers in a heartbeat. By the way, I wonder how much shipping charges from South Africa would be when you feel like selling that beauty to me?

PS-- What's a Boffin?
Oct 07, 2009, 02:41 AM
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prodjx's Avatar
I think a boffin is an A/C maintenence kind of person.
Oct 07, 2009, 02:46 AM
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Phew! such a quick response - thank you. Skyhook is an own design and thats why I'm trying to make sure I havent overlooked the obvious. Infact the only plane Ive ever owned that I havent designed and built is the BOT ARF. By the way this fuse is 1250 long and out of the mould weighed 185g (about 6.5oz) - is that acceptable?

Anyway, you were all warned about more questions - give me a finger and I'll take your arm. Prodjx - the carbon push rod sounds good. I've only ever used Sullivan type inners and outers. Does one use an outer with the carbon rod? I was intending to put the servo up front but where would you put the bellcrank? Pivoting on the stab joiner rod or down in the access hatch as per a modified BOT. Had a look at your Petrel posts - well done.
Atjurhs - thanks. I'll probably go for carbon rather than wire. Your right - servo up front. I agree on the bolts - two in front or just one? Your thoughts on RDS were as mine.
Hossfly72 - thanks, a boffin is a scientifically minded person that knows a lot about a particular subject. I'll search for some sexy servo covers.

Happy flying

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