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Old Jan 23, 2013, 06:54 PM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
Joined Feb 2012
1,306 Posts
Quote:
Originally Posted by Dad_Roman View Post
My point exactly. Then you put it on a fighter airframe, high wing loading, low aspect ratio, etc, etc.

Dogfly...welcome to the group. All we are saying is that it is fairly marginal. Does the kit say ok?...yes. But notice its the absolute very BOTTOM of the recomendation.

It will fly it. Just going to be scale like, no R/C airplane yankin and bankin, long rollouts on take off, no floating in on final, no flyin on the prop, and (if) when the wing stalls, it dies.

I actually enjoy and appreciate a scale type of flying, but Im also very aware of the limitations of this in our sport. Most seem to enjoy the availablity of extra power our sport can (easily) provide us.

Nice combo, I wish you the best and it should be fine. Keep us apprised
Now, lighting off some methanol fuel W/CDI set-up W/some aggressive advance, it would spin a medium sized prop about like a GI 91 on GI.

About 20-25% MORE power than the FG14 in the same sized package..
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Old Jan 23, 2013, 07:01 PM
sKrude up, Rejected!
DogFly.'s Avatar
United States, CA, Santa Barbara
Joined Jun 2008
3,186 Posts
Quote:
Originally Posted by SrTelemaster View Post
Now, lighting off some methanol fuel W/CDI set-up W/some aggressive advance, it would spin a medium sized prop about like a GI 91 on GI.

About 20-25% MORE power than the FG14 in the same sized package..
I'll have to start a build when I get the kit,
right now I have to spend $2000 getting my truck fixed.
So I'm thinking 2-3 months.
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Old Jan 24, 2013, 12:11 AM
Talk soft, carry a big plane.
maxadventure's Avatar
northern colorado
Joined Jul 2007
230 Posts
Quote:
Originally Posted by DogFly. View Post
Dad_Roman,
If you look at the specs:
70-.91 4-stroke engine
The FG14 is an 82 if I've been learning right, so that's right between a 70 -91.
You missed the comment with the loss of power with a gas motor. That rating of .70-.91 is for a glow four stroke, the FG14 is gas, and as such it produces less power and will have more overhead weight, certainly with the recommended aluminum mount (over a kit included poly) and the ignition system/battery. Also, what is your local air density? Even at sea level the consensus is you won't have reserve power with that combo. The spit is classic for spinning on final with marginal power, trust me. I've done it many times in my kyosho spit, and I hope I've finally learned my lesson. (was electric, will be playing with YS .91 4 stroke on the latest rebuild)

Read the posts carefully, especially those like Dad_Roman and I TOBAR, who have provided some excellent un-biased advice over the years.

Love the engine, love the plane - best of luck if you go forward with it!
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Old Jan 24, 2013, 12:23 AM
sKrude up, Rejected!
DogFly.'s Avatar
United States, CA, Santa Barbara
Joined Jun 2008
3,186 Posts
Like I said in my first post, new to gas engines.
I'm trying to find the best airframe for this motor, would like to go with a spit,
what would you recomend?

How about this one:

http://ak-models.com/mm5/merchant.mv...egory_Code=CMP
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Last edited by DogFly.; Jan 24, 2013 at 12:30 AM. Reason: add plane model
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Old Jan 24, 2013, 12:58 AM
Hutch
hutchinstuff's Avatar
United States, Mt, Bozeman
Joined Jan 2012
323 Posts
Dad, I think I got the top end figured out... its too damn expensive to try to new stock! I've got two of em, so I'm hoping to get at least one of them in working order!
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Old Jan 24, 2013, 06:59 AM
Twistaholic AMA 134406
Dad_Roman's Avatar
USA, TX, Teague
Joined Jul 2007
5,691 Posts
Thats the spirit! Im one of those guys who would rather rebuild and bring the old back to life rather than buy new....thats just me....I get the greatest joy out of that.
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Old Jan 24, 2013, 08:44 AM
Talk soft, carry a big plane.
maxadventure's Avatar
northern colorado
Joined Jul 2007
230 Posts
Quote:
Originally Posted by DogFly. View Post
Like I said in my first post, new to gas engines.
I'm trying to find the best airframe for this motor, would like to go with a spit,
what would you recomend?

How about this one:

http://ak-models.com/mm5/merchant.mv...egory_Code=CMP
Not sure I can recommend something you would like, I would say something like this: http://www.rcgroups.com/forums/showthread.php?t=1783769
Personally would love to get my hands on an FG14 for my 1/6 L4.
One concern for these small engines is the prop clearance. By the time you find a small enough model for the power, they may not be able to swing the best prop. (currently have this issue with my L4 and a Saito 65, not sure how to fit the FG18 - but I still want to!) Keep in mind, I don't think anyone said don't do it, just be aware of the challenges and plan to meet them. Heck it would be awesome to hear how it worked great. I think we're just trying to point out the gotchas so you can make the best of it.

As far as your last link, as a small fiberglass pre-built, I'm guessing heavier than a balsa at this size - but I'd defer to those with more experience. You will want to be as light a wing loading as possible, like a larger scale but stripped down for weight savings. *shrug* it's really hard to find the perfect plane for an engine. I always seem to fall in love and get an engine, then start thinking about what to put it in. I have three engines needing projects right now sitting around from that same method! FG36 , FG20 (actually in a plane, I just don't like it!) & YS 1.10
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Old Jan 24, 2013, 08:55 AM
Talk soft, carry a big plane.
maxadventure's Avatar
northern colorado
Joined Jul 2007
230 Posts
Quote:
Originally Posted by SrTelemaster View Post
The gas makes 15% less power as a rule, so it would run more like a 70 glow 4-stroke..
Quote:
Originally Posted by Dad_Roman View Post
My point exactly. Then you put it on a fighter airframe, high wing loading, low aspect ratio, etc, etc.
Quote:
Originally Posted by DogFly. View Post
Dad_Roman,
If you look at the specs:
70-.91 4-stroke engine
The FG14 is an 82 if I've been learning right, so that's right between a 70 -91.
to help illustrate SrTellemaster's point - just for education, not trying to dissuade your project - take a look at what engines they recommend for this spit: http://www.troybuiltmodels.com/items...ITF-73FAF.html You'll see the two stoke gas (more power per cc) size is quite a bit larger than the glow 4 stroke. Of course it's all just general rules because different engines make different power at the same displacement and manufacture recommendations should always be taken with a grain of salt.

Heck, the right prop and a nice build may be great with your first kit choice. I'll stop going off on the subject, it's just that I've 'been there and done' that several times over the years.
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Old Jan 24, 2013, 09:56 AM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
Joined Feb 2012
1,306 Posts
A gas 4s 82 would be suitable for a 40 sized airframe. But a 40 sized airframe will be small when you try to house the ignition module, ignition battery, etc. It can be done on SOME 40 sized airframes, but it's shoehorn fit. The extra weight/bulk could be offset by the much smaller gas tank that would be required.

A 60 size would be better as far as room for components, but the FG82 would be very marginal for a 60 size.

For the life of me, I don't know why Saito bothered W/such a small engine for gas.

I think the bottom limit should be around 1.00 cu in (16cc) for 4s gas, 1.20 (20cc) would be more practical.
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Old Jan 24, 2013, 10:04 AM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
Joined Feb 2012
1,306 Posts
Quote:
Originally Posted by DogFly. View Post
Like I said in my first post, new to gas engines.
I'm trying to find the best airframe for this motor, would like to go with a spit,
what would you recomend?

How about this one:

http://ak-models.com/mm5/merchant.mv...egory_Code=CMP
IF you can shoehorn the FG82 ignition module into that small airframe, The FG14 will have ample power.
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Old Jan 24, 2013, 10:52 AM
Twistaholic AMA 134406
Dad_Roman's Avatar
USA, TX, Teague
Joined Jul 2007
5,691 Posts
That looks like a perfect match. Can anybody read the wing loading into english for me?
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Old Jan 24, 2013, 11:35 AM
I HATE GLOW PLUGS!
SrTelemaster's Avatar
United States, NY, St Lawrence
Joined Feb 2012
1,306 Posts
Quote:
Originally Posted by Dad_Roman View Post
That looks like a perfect match. Can anybody read the wing loading into english for me?
You can instal a gas tank about 1/2 the size of the original (sized for glow fuel) to make room for the ignition module. You will most likely have to shift the tank to the rear as the module sould br monted as far from the Rx as possible. On this small of a model fuel delivery should not be a problem, The clunk will still probably be about the same distance from the engine anyway.

Use a seperate battery pack for the ignition W/it's own switch/charging jack. You can use a NiMh 650Ma 4.8v pack if you remember to recharge after every other 10 minute flight. A 650ma pack should run the CDI for about 40 minutes max, 20 minutes run time betweenj charges gives you a safety margine.

For the throttle linkage utilize a nylon pushrod such as a Sullivan Goldenrod to minimize the chance of RF from the ingnition being conducted near any servos or the Rx.

It does look like a good match sizewise as long as eveyrthing fits into that small, narrow nose.

Something W/a "round engine" like a P-47,or Focke Wulf FW190A might make it a little easier to get all that equipment stuffed into the nose.

If the OP is not an experienced pilot, the narrow maingear on the Spitfire might be a bit challenging too. That would also make the P-47 or FW190 better choices.

My "English" wing loading calc comes out to 29.4oz per sq ft.

Does that sound reasonable? I used 3.937" per decimeter.
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Old Jan 24, 2013, 11:57 AM
Twistaholic AMA 134406
Dad_Roman's Avatar
USA, TX, Teague
Joined Jul 2007
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Im gonna say "yes". Thats pretty heavy but it sounds like exactly what a fighter airframe would be
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Old Jan 24, 2013, 01:09 PM
sKrude up, Rejected!
DogFly.'s Avatar
United States, CA, Santa Barbara
Joined Jun 2008
3,186 Posts
Hey guys,
Thank you all for helping educate me, with no experience with gas, it's better to ask people with the experience I lack.
I have been flying for some time, I may not be Top Gun, but I feel competent with my skills.
This seems to be an odd size engine, at least for what I was hoping to do with it.
Understanding that the engine is a little under powered for the TF Spit,
I thought the 2nd choice to be more of a usable size, however the weight was more because of the fuse being fiberglass.
Also, the nose being narrower, it would be harder to fit the module in.
So the idea of a FW190 or a P-47 sounds pretty good if the Spit won't have enough space for the gear I need to run.
I prefer the idea of a P-47 because of the wider wing chord, although the FW190 sure has a classic look to it.

Any suggestions guys?
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Old Jan 25, 2013, 12:17 AM
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DarZeelon's Avatar
Israel, Ramat HaSharon
Joined Nov 2003
1,170 Posts
Quote:
Originally Posted by SrTelemaster View Post

My "English" wing loading calc comes out to 29.4oz per sq ft.

Does that sound reasonable? I used 3.937" per decimeter.
It is not, Sr., as far as your conversion ratio goes; although you eventually did reach a right final result...


You seemingly used a length in inches of one tenth of one meter (one decimeter)...
It is an area ratio, not a length ratio!

One square foot is .3048 m by .3048 m.
A square decimeter is .10 m by .10 m.

So, a sq. ft. is 9.290304 sq. decimeter.

An ounce is 28.3495231 grams, so 81-90 grams in ounces is equal to 2.857-3.175.
So, the specified wing loading in imperial units, is 26.54 to 29.49 oz/sq. ft..
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