Textanker

Howdy guys. I just maidened my GP Combat Spitfire this afternoon. Currently has an OS .25 in her and she flew great. A couple of notes:

- Currently running a 9-6 prop got me about 15k rpm at max
- Had to put the battery behind the servo compartment rear former to balance according to manual.
- Recommended throws with about 50% expo.
- 15% fuel
- Built with the landing gear, and added a small tail-wheel rig.

I only ran her at about 1/2 throttle for the whole flight and had plenty of fuel when I landed. I definitely need to reduce the expo, as she had a kind of mushy response. Had to add about 4 clicks of down, and about 3 clicks of right aileron (I think)No tip stalling on a high practice approach, but I landed her pretty quick.

I have the Corsair as well, but I haven't flown a lot for a while (Active Duty Army), so I feel like I am re-learning how to fly again.

Sooo, a successful first flight. I love these small planes because you can transport them assembled, pull them out of the car, crank em up and fly. The field is only about 2 miles away from my work, so I can fly at lunch.

Anyone who has experience with this plane, speak up and let us know!

BuzzRTC

Try removing the baffle from the muffler, and try a APC 9x4. You should be able to get 16,500-17,000 RPM without compromising the engine, and the plane will lift right out of your hand if you decide to hand launch. You'll find it loses less speed in tight maneuvers with that prop as well.

Disarray

I had to cut a hole in the fuse to get the battery far enough to the rear to balance mine as well. OS 25 on the front. Mine will tip stall something fierce at high speeds if I dial in too much elevator, so be careful not to use to much elevator coming out of a dive. Only other problem is half my covering is pealing off. A high rate snap roll looks cool with this plane.

Textanker

Thanks for the advice. I have started to advance the CG a little more. Now it sits just in front of the rear cabin former. I also removed the baffle from the muffler and am looking forward to a little more RPMs.

sheridan005

Hi

I too have purchased this Spitfire with .25 engine (Irvine). Did you use the standard (out-of-cowel) exhaust muffler? Do you know of an in-cowl muffler for such a small engine & model? The Irvine muffler ocer 100mm (~4inch) long with diameter 32mm (~1.2inch) or so. I would imagine such a lump would spoil the looks of the model?

Have only seen electric option in clips, photos and on the box! Hence I'm considering taking electric option.

I took a look at JustEngines (UK) but the only possible suitable one is too wide (i.e. out from the flange to cowl).

Alternative I suppose is to have smaller/neater muffler to replace original Irvine-supplied muffler.

Currently engine is inverted (and in-cowl) as recommended. But could mount sideways (cylinder head poking out should be better than 'huge' muffler??): would then need suitable muffler to sit in space below cylinder and in-cowl.


Also: shame there's no retracts for this model. Anyone tried adding simple, wire retracts (I did see a simple wire based kit, but no detail to assess).



Any feedback appreciated.
Happy New Year.

Textanker

First off, congrats on your purchase!

I did use the standard muffler with my OS .25. It works very well. I removed the baffle from the muffler and it added a couple of hundred rpm.

I just purchased a Slimline Pitts muffler, but I don't know if it will fit under the cowl. I would have to mount it sideways, and that really wouldn't help. The looks of the model are pretty nice, even with the muffler exposed. In flight, you really can't see it.

Retracts would be a bear. The wings are very thin. I would love to see someone try it, though.

Damn. Now I can't stop thinking about retracts!

sheridan005

Thanks. Do you have a photo of your spitfire? Seems to fly fast in elec config (saw vids on YouTube).

I am still considering side-ways mount with engine head protruding side of cowel (easy access!). Looking at Pitts style muffler too now - - awaiting info on BCMP1526 if I recall. End of muffler may protrude cowel (also) but not by much. Which slimline muffler did u purchase?

BuzzRTC

If you have an OS .25FX you don not want the 1526. James Bisson makes a pitts muffler exclusively for OS.25fx but doesnt show iton his website. These are the only mfflers I use for my scale WW2 birds. Excellent product. I was getting 17000 rpm out of the box with one of these and an APC 9x4 prop. The exhaust pipes can be cut to length so they just barely protrude from the bottom of the plane. This is a picture of my Yak3 with a Bisson setup and my Ki84 with the same.

sheridan005

BuzzRTC - thanks for info n pics. I am using an Irvine .25, but I will certainly check out the 'possible' alternatives you gave. Having seen your pictures, I think I will try for side mounting.

But Textanker - I would like to see pics of a Spitfire finished (to give me incentive to complete the model... after my Extra 300... and the DIY... and my homebrew PC... etc. !! )

(oh, and someone needs to invent a direct retractable, all-in-one, replacement for fixed wire undercarriage!?! Can't find on web)

Thanks again.

Textanker

I will post a photo as soon as I take one. I usually don't take pics of a plane until it has flown a few times (superstitious).

I got this one:

http://www3.towerhobbies.com/cgi-bin...?&I=LXFG82&P=7

sheridan005

Hi

I found an in-cowl muffler. Purchased from "Just Engines" of Scotland UK, but it's actually a modified BCM (Bisson Custom Mufflers - www.bissonmufflers.com) of Ontario, Canada...

It's not on Just Engines website, but I gather its a actually an "OS25" (exhaust bolt hole centres drilled & tapped to suit Irvine).

NOTES:

- the muffler inlet is at end of muffler can: end of can appears to just clear inside of cowl (TBC absolutely).

- I have added in the 'exhaust extension block' to place outlet pipes outside of cowl.

- Muffler+block is light - around half the weight of 'blimp' muffler


Some pics of muffler laying next 2fuz and cowl (have not started building really yet). Need to make sideways etc - will get back to you if there's any problems.

Regards

erh..not sure if the pics uploaded (if indeed that is what I am suppose to do)???

BuzzRTC

Sheridan,

I spoke to James Bisson last year and told him the location for that pressure nipple sucks. He has gone ahead and repositioned it so there wont be any chance of kinks. This is what he gave me:

Sorry for the poor quality. Its from my cell phone camera. The bolt holes on the .25FX measure 1-3/8" o/c. What do they measure for the Irvine?

As far as exhaust extensions, the Dubro exhaust deflectors fit fine on the tubes.

Dan

sheridan005

BuzzRTC

Yes, my muffler has press nipple at rear (old stock held in UK no doubt). I have 23mm clear to firewall so should be ok. Else I might reposition and plug existing... (like I need another project). Thanks for the pic.

Irvine exhaust port - hole spacing is 35mm (about 1.37 inch???).

Had wondered about 'silicon' exhaust extensions (rather than ext block), thanks for info. Their flexibility could improve/ease cutting of cowl and installation... won't know till I try though.

Will keep posted (timescale could be weeks or months !)

ejc34710

Heya fellas. After flying electrics only for a few years i decided to go glow and got the combat spitfire. Im definatly going to install a .25 w/ no landing gear. My question is this. How am i going to belly land with that engine running?! Do i have to wait for it to run out of gas or what? I could just cut the throttle on my electrics but im a little lost on this thing. Might sound like a dumb question to some of you, but im kinda scratchin my head on this one. I have experience with glow (used to race 1/10 nitro touring) but they stayed on the ground (most of the time neway) Thanks for any help fellas,

BuzzRTC

First off, MAAC combat regs require that glow egines have the ability to be cut while in flight. I assume AMAregs are the same. Set up your propeller so it is horizontal when the piston is at TDC, this way you'll save props on hard landings, then justkill the engine on your landing approach.

jib

You can set up the servo throw so that you can use your trim to shut the engine down in flight.  Keep the trim to the center to avoid an accident, then move it down to close off the carb.

Jack

Textanker

Just picked up a set of .25 sized retracts from Robart. Should be fun to install them and see if they work.

ejc34710

Ha, thanks for the advice! I was unaware you could shut em down like that. Makes sense about killing the engine with the trim. I thought about the retracts too but im kinda on a semi-tight budget and am itrying to get this and 2 other planes going. I just usually see a plane i like and buy it, then wait till i have the money to get the rest of the stuff to get it finished. Once i have the plane, i HAVE to finish it!! Thanks again very much much guys.. Happy flyin!

sheridan005

Textanker,
That link was to retracts for a heli... it will be interesting to see if you intend and manage to fit them to the spitfire. Keep us posted.
Handy tip about the horizontal prop at TDC/B - belly landing damage vs aesthetics... mmh. Still have yet to complete the model
Did wonder if cowlings could be added (some real spits had these under each wing) to assist belly lands or indeed hide/house retracts.
Probably not worth the hassle though.
Regards, Lee

BuzzRTC

Lee,

Dont sweat the belly landings. In all my combat experience, I have never seen any damage from belly landings, unless the plane really pancaked down.

If you are using the Bisson pitts exhaust though, you wanna make sure you trim those pipes to just a hair proud of the cowl. On hard landings with my mustang, I had left the pipes full length which extended about 1/2 outside the cowl, and I did tear one off. Mind you, the Mustang belly tends to make the plane drag its nose on landings.

ejc34710

hey fellas. I could use some help here. After finally gettin the mullah for my servos and rx pack and the rest of the stuff i needed, i ran into a problem. The CG is wayyyy off. I need 3oz of tail weight to balance this thing out. I thought about using a 2 cell lipo and adding tailweight to try to keep the weight down, but i dont know where to put the weight. I certainly dont want to put it on the outside of the fuse. I read that someone cut a hole in the rear of the fuse, wouldn't this reduce the strength of the fuse?? If i could get my nimh rx pack more towards the back i could probably get away with 1oz or less. I cant get any of the packs any farther back than where it says to put them in the manual. Im too paranoid to cut any holes in the fuse for fear ill ruin my plane. I dont have much experience with building as all i have bought to this point are ARFs. Guess my real question is how are you guys doing this? Where are you cutting the holes. Are you like cutting a square outta the rear bottom and regluing the piece back in or what. Im completly lost. What would you guys recommend i do? Use the lipo in the manuals location and add tailweight, or move the nihm to the tail of the plane. The nihm to the tail would probably be the lighter option as id probably need less than an ounce depending on how far i can get it back there. If i were to use a lipo, how do i get the volts to 4.8-6.0, a BEC like the Castle Creations one? Im leaning on cutting a square of the rear bottom fuse out (roughly a little larger than my rx) and securing the battery to the piece i cut out, the regluing it in. I've built 8 arfs and had no problem at all with 6 of them. the 2 i did have problems with have been Great Planes. They shoulda counted on this and made some sort of attempt to put something in the maual to help with this problem-and im using a lighter engine than the one they recommend (GMS .25). If someone could help me with this, id be GREATLY appreciative.

Oh, any of you guys hand launching this bird? I've hand launched all sort of planes but never any thing this heavy. Its got a 9x4 prop cause the GMS manual says nothin bout the 9x6. I've heard that it'll fly outta your hands with a 9x6, think it will be the same with a 9x4? I also have an 8x6. What would be best? 9x4, 8x6 as the manual for my GMS suggests, or would it be okay to use a 9x6? In advance, thank you thank you thank you.

BuzzRTC

With regards to the CG, what are you using for servos? What kind of engine are you using?
Easiest solution is to use the smaller nicad packs, or even aaa nicads and insert them behind the TE former in the fuse.

As far as hand launching, the smaller the pitch, the more adavntage you have. We exclusively use the MA 9x4 or the APC 9x4. The APC is a better prop but they are more brittle, so if you dont set up your prop to sit horizontally on a dead stick, the APCs tend to break easier. Either way, with a 9x4 prop, this plane will practically fly out of your hand.

ejc34710

Im using a GMS .25, hs-85s for ailerons, hs 82s for elevator and rudder, and a cirrus cs22 for throttle. They are all MG. I dealt with the CG the best i knew how. I put the rx pack (4.8 1500 spuare pack) behin the servo bay on the fuse floor by cutting a square out of the bottom of the fuse slightly larger than battery pack. Then i took scrap piece of lite ply and inserted 4 blind nuts and secured the battery to it with a rubber band and double-sided tape. I then inserted the piece of lite ply into the hole i cut on the bottom of the fuse and secured with four screws into the blind nuts. Then reinserted the fuse floor piece and screw it in with a couple small screws. Hope that wasnt too confusing. This moved the battery a ways back from the CG mark but i still had to add 1.5ounces of tailweight. Better than the 3.5 i woulda needed anyhow. Thanks for the info on the pitch sizing! Was unaware of that. Guess ill be using the 9x4 for first few flights, (its a wooden zinger), and switch to my 9x6 MA after i want some more speed and am a lil more comfortable. I hated having to cut a hole in this thing, but i didnt see any other way but to stick 3.5 ounces of lead weight way out n the rear.

BumRC

Just got one in. Has anyone mounted a .15 LA in this thing? I am aware that power will be low, but a .15 should have enough power to move it around, there are a few people who mounted .15 LAs in the GP P-51. I was just wondering what mods are required, I am already aware that the engine mounts are too far apart and I will need to drill new firewall holes in order to get them closer together. A friend and myself are considering using these things for friendly basic combat, nothing too fancy mind you, just chasing eachother around and occasionally clipping a ribbon.

Textanker

Why not use a .25LA and not move the engine mounts?