HK Spitfire balsa 1234mm CG?

Bobmic · December 21, 2012, 08:01:40 PM

I know that quite a few you guys have the Hobbyking Spitfire - I bought one and put it together but I have a couple of questions:
1. Can someone tell me what is the correct CG? The manual calls for 90mm but from what I read in the forum people are setting it to 75mm, I checked it for 75mm and a 4500mAh 3s and it looks like it needs additional nose weight.

2. Anyone cut an opening in the cowling behind the prop to allow air to cool the ESC?

Thank you
Bobby

battlestu · December 22, 2012, 12:48:45 PM

Hey Bobby I have my CG at 75mm. I was lucky i didn't need any nose weight since i replaced the stock motor mount with an aluminum one. I was also thinking of cutting a hole for air flow since I'll be adding a spinner this winter.

Wingnutz · December 22, 2012, 04:33:33 PM

Hi Bobmic,
My CG is set to about 75. I've cut an opening in the cowl behind the prop to let air over the ESC and I also cut holes in the bottom of the fuse behind the wing to allow some air to flow through the fuse. Try to miss the longerons/stringers if you do this. I also drilled out the exhaust stacks but I'm not convinced the small holes actually do much.
Like you I'm using 3S but only a 3300mah.
I built mine to handlaunch and belly land so it has no retracts, a folding prop and half-cone shaped cover over the aileron servos. Glen N has a variation of this model that uses a single aileron servo and it's a better choice for a belly lander.
I have limited experience compared to many who post here but I love this model!
I'm recovering from knee replacement surgery so I'll post some pictures when I can get down to the basement.

Ededge2002 · December 22, 2012, 05:02:50 PM

Hope the surgery went well wingnuts! Your determination will get you through. Your going to be much faster by spring!

Bobmic · December 22, 2012, 07:14:48 PM

Thank for the info. this is definately the best forum...

The only reasone for the large battery is the fact that I have these batteries for my 6s setups.
Greg - I remmrmber you told me about your problems with the motor mount and I did order an aluminum mount but did not use it as it required drilling the firewall and the one that came with the plane seems ok.
Wingnutz- good luck with the recovery!
Even though I installed electric retracts, based on what i have seen there ate slim chances I will be able to use them.
Not sure about the folding prop though - I didn't notice many who broke props on belly landing these planes and as far as I know the folding ones are less efficient than standard APC ( even though I am not sure how important will this be for this plane)
Which prop are you using?
Thank you,
Bobby

Wingnutz · December 24, 2012, 01:31:42 PM

Hi Bobmic, and other thread contributors,
Thanks for the words of encouragement Hopefully I will be faster next season and won't disrupt the flow of landings and take offs when I hobble out to launch or retrieve!
My prop is a 11x8 mounted on an oversized folding prop spinner so it actually comes out closer to 12x8. I'm using an HK 35/36 910kv PropDrive to spin it. If memory serves me well, I think that's producing around 350-375W which is a whole lot less than Simon's using a similar 1400kv motor and smaller prop. The model's not as fast as the other HK Spits at ROGO but it's certainly adequate if you like fly scale models in scale fashion. The combination of no retracts and moderate sized battery keeps the weight down coupled with the relatively big prop giving adequate aerobatic performance.
Just an interesting aside, to prove the aerobatic qualities of the model, the pilot figure decided to perform a torque roll out of the launcher's hand on maiden launch...quite exciting! I must remind the pilot figure not to enthusiastically increase throttle as the model leaves the launcher's hand.
The RCPFA (Radio Controlled Pilot Figures' Association) recently contacted me to remind me none of their members had yet been installed in the cockpit of this model and to protest the unfairness of blaming one their members for unsafe flying practices.
Busted! I will have to accept responsibility for this one ....AND immediately install a pilot figured who will from now on accept all responsibility for dumb-thumbing!

sihinch · December 24, 2012, 03:02:05 PM

From memory, mine was also 75mm for CoG. I use batteries from 3000mAh to 4000mAh, all 3S. And I am using the Turnigy 3536 1400kV motor with a 10x5 prop, I think, getting somewhere between 500 and 550 watts.

Love this plane, it flies great.

Speedy recovery Bill - the Parkzone Spitfire pilot fits nicely. He does need a seat though!!!!

Merry Christmas everyone!

Bobmic · January 01, 2013, 06:10:33 PM

Since there is probably no way that I will be able to land this plane on wheels I was wandering how can I make a cover for the aileron servos.
I was thinking of cutting a small plastic bottle but I am not sure how to attach it to the wing (beside just taping it and hoping the cover will stay).

Thank you,
Bobby

thehaze · January 01, 2013, 07:19:48 PM

What about attaching a fin made of balsa to the wing? Just make it larger than the servos arm.

Bobmic · January 01, 2013, 07:32:41 PM

Sounds intersting but how to attach the fin.

Bobmic · January 05, 2013, 07:15:54 PM

Flew the Spitfire again today, for four flights. It flew roughly ok but was wobbling a bit a slower speeds.
Was using a 10x4 with 1400kv motor powered by a 4400mAh 3s.
It's wobbling mainly in the roll axis and I noticed that during my last flight the wind was minimal and so was the wobbling.
Didn't plaid with the CG, it is currently at 75mm the one thing I don't know is how to hand launch it myself.
Gripping it from the button behind the wings feels a bit nose heavy and I am afraid to throw it into the ground instead of up. It is is easier to grip it from the top behind the cockpit and throw up but not sure about that.

Anyhow looks nice, even if it does not fly as I would like it too.

Wingnutz · January 06, 2013, 05:49:28 PM

I get the Black Widow to launch mine and he does a great job!
Promised I'd check CG on mine...75-77mm. That required a 3300 mah 3S shoved against the firewall and 1/2 oz of lead screwed inside the cowling. Screw heads are visible in one photo.
Also included some pics (complete with ROGO mud stains from belly landing) of how I'm trying to solve the aileron servo/linkage protection on belly landing thing without completely re-mounting the aileron servos and my attempts to keep things cool. Envy those who can get out there to fly...nothing beats a sunny calm day in the winter! (Okay, so not every winter day's sunny and calm!)

Bobmic · January 06, 2013, 06:57:24 PM

Where did you get the aileron servo covers? I am looking for a solution.

- As for the launch.... I need to know how to launch myself and will not have two hands for that

Thank you
Bobby

Ededge2002 · January 06, 2013, 07:06:04 PM

My guess is that servo cover is the plastic packaging from a spinner.

Wingnutz · January 06, 2013, 08:20:14 PM

Ed,
You may be right...it's Frankensteined blister packaging but I can't remember what was packaged!
Bob, I'm not sure what these things do to the model's aerodynamics but at least they don't mess up the scale appearance in the air. I may yet pull them off (scotch-taped on) and build some simulated rad shrouds shaped as skids and located to protect the aileron/servo linkage. Sheet pink foam would probably do..so what if it gets chewed up ...but haven't really looked at mounting problems.
I really don't want to go retracts on this model. IMHO Mustangs, Hurricanes and FW 190's are better candidates for retracts because of their wider tracks. My AUW is about 2.8 pounds. Some of the guys on the RCGroups thread are over six pounds! I'll fly her a few more times next season and decide if I'm gonna put her on a further diet.
I've really enjoyed this model!