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Author Topic: Frog Chipmunk  (Read 5709 times)
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Yak 52
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« on: May 14, 2012, 07:26:35 PM »

Well since everyone seems to be building for the next years Nats, I thought I'd post something on my kit scale entry for last year that has become next year's entry  Roll Eyes

This is the Chipmunk from the deluxe series by Frog. It comes in at 21" but I seem to have built it a tiny bit smaller at 20.75". Not intentionally, I just printed off from Mike S's site and that's what I ended up with. I have had a few issues with the parts fit - most of it works ok but there are a few ribs that were short and the odd issue with oversize parts but that may be my printer.

I've built most of the fuselage and the wings just need joining together. The fuselage actually came out quite rigid but I decided to fit it in a 'strongback' jig to add the second sheet side. It actually worked very well.

There's a lot of wood in the old frog's so maybe not the best choice for kit scale but it has plenty of dihedral for a low winger. All the wood at this point is coming in at about 14g, not too bad considering but I have been trying to use light wood. I've made up some wheels from balsa too.


Jon
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Frog Chipmunk
Frog Chipmunk
Frog Chipmunk
Frog Chipmunk
Frog Chipmunk
Frog Chipmunk
« Last Edit: May 14, 2012, 07:45:58 PM by Yak52 » Logged
Phugoid
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« Reply #1 on: May 15, 2012, 04:28:07 AM »

Hi John,

Looking good, as I've said before it would be really nice to see you next year.

In the couple of years I've been there I don't think that ther has been an entry built from a FROG kit.....

You're not too far from Nottingham are you?  If not the indoor sessions set up by the Nottingham Club are great to get your model reasonably well trimmed before the day itself.....

Just make sure you don't get distracted by other builds! Grin

Andrew
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Pete Fardell
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« Reply #2 on: May 15, 2012, 05:41:22 AM »

I must admit I wasn't properly aware that Frog even did scale kits, so I just checked them out here http://www.houseoffrog.co.uk/senior_scale.htm
VERY nice models, Andrew! (especially that ultra cute bird dog). Hope we can see them in the flesh some time.
I'm really looking forward to seeing this Chippie take shape Jon. Looks very nice so far.
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Wout Moerman
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« Reply #3 on: May 15, 2012, 09:45:45 AM »

I have built the Bird Dog many years ago from rather heavy wood. It still is one of my best flyers.

Wout
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Phugoid
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« Reply #4 on: May 15, 2012, 10:47:47 AM »

I think I've seen yours Wout, It's an orange one isn't it?

The Bird dog flies pretty well and copes with pretty windy conditions, The Moth Minor hasn't flown too well, it needs a real dollop of noseweight to counter the all sheets surfaces so flies pretty fast.  I have the canopy for the Seamew, but I've not got round to building it yet.

The Chippie seems to have been designed by a different chap to all the others.....
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Yak 52
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« Reply #5 on: May 15, 2012, 12:38:35 PM »

About an hour to Nottingham for me... I would probably be able to do that actually - we don't seem to have any indoor sessions for a quite a while in P'boro. I'd certainly like to know what sessions there are up there. I've just started a thread: http://www.hippocketaeronautics.com/hpa_forum/index.php/topic,12002.0.html for that kind of thing, if you want to post dates there.

I think the Chippie will have the same nose weight issues - I might cut the tail pieces again from lighter wood. The plan for this one was drawn by Bill Knox. It's quite a nice model to do so far, the bits that I thought would be tricky - the wing root piece particularly - went ok. I have been struggling with the wing join/centre section. It's not quite clear on the plan where the joins are and whether it's a single dihedral break or a flat centre section (I think it's the former.) Fortunately it's all covered by the fuselage anyway!


Jon
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« Reply #6 on: August 12, 2012, 05:54:42 PM »

Yak and Phugoid, I apologize for intruding into foreign affairs, but it seems that either or both of you may have answers to some questions I have.

I'm well into a Frog Moth Minor build (covering at present) and in addition to the things you mentioned above, prop size, rubber size and number of strands are something on which I'd like an opinion. I'd also like a staring point for balancing based on your experiences. The Chipmunk is a very similar design and I figure flight characteristics should be about the same, but maybe not.

Anyway, after looking around a while, this thread looked like the most promising for finding some answers.

Thanks guys,
David

     
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Yak 52
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« Reply #7 on: August 12, 2012, 06:09:48 PM »

Hi David, feel free to ask away!

There is a picture of Andrew's Moth Minor on Mike Stuart's House of Frog Site. My Chipmunk is still at the bones stage so I have no concrete advice other than I will be looking at a 7" prop and something like two strands of 3/16 rubber for indoor, perhaps four strands of 1/8 if it's a bit heavy or for outdoors. Hopefully Andrew will chip in with some trimming tips...

I'm getting close to finishing the wood work, a few block bits to do but it's always worth a mock up shot  Smiley

Jon
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Re: Frog Chipmunk
« Last Edit: August 12, 2012, 06:23:43 PM by Yak52 » Logged
cd_webb
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« Reply #8 on: August 12, 2012, 06:18:16 PM »

Thanks, Jon. I blindly ordered 1/8 rubber, but an 8" prop. There are no indoor facilities anywhere near, so this one will be strictly for outdoors.

I'll be watching the Chipmunk, I've got these plans saved back too. Thanks for your reply!

David
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Yak 52
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« Reply #9 on: August 12, 2012, 06:20:54 PM »

I'm sure an 8 incher would be ok, you could always cut it down a bit if it's too hard to trim.... Andrew was flying his outdoors, I think he might have links for some video even.

It would be great to see some pics of yours if you're so inclined Smiley

Jon
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« Reply #10 on: August 12, 2012, 09:57:34 PM »

Weight, up to the point of covering, was 21 grams. That includes fuse, wing, fin, stab., and wire gear. Covering is going on dry, attached with glue stick. I've always used dope in the past, but like a lot of other folks, the memories the fumes bring back aren't worth upsetting the wife! I've built in 1/8" washout into each wingtip. I hope that is enough.

I think that if I'd known of the nose weight problem mentioned earlier, I would have stringered the turtledeck.

David
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Yak 52
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« Reply #11 on: August 13, 2012, 03:21:02 AM »

Very nice! A few people have built them with proper built up tail structures for the same reason. On my latest (Raven) I got away with it by using very light wood in the tail, in fact I might cut out the Chipmunk tail again from lighter still. Once it's covered it stiffens a lot more than I'd thought.

You might enjoy this thread on RCG: more Frogs including a couple of Moth Minors: http://www.rcgroups.com/forums/showthread.php?t=1401224

Jon
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Phugoid
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« Reply #12 on: August 13, 2012, 06:08:10 AM »

Hi,

Mine has a 7" peck prop the details are at the link below.  I had a few decent flights out of her (30s plus) but she flies fast and landings are hard.  Since I enjoy the building more than the flying (and have more opportunity for the former) she is retired to the display shelf before I had one too many hard landings.

http://www.houseoffrog.co.uk/senior_scale.htm
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Yak 52
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« Reply #13 on: March 07, 2013, 10:55:12 AM »

Been doing a bit more on this one seeing as its only six weeks to the Nats...  Undecided Just little jobs like the nose block and joining the wings.

I re-cut the tail and fin from lighter wood. The original was #7.9 from SAMS, the replacement #5.2 from my local model shop  Cool I've saved 0.9 g at the tail so I reckon about 3g if you include the neccessary nose weight. Worth having...


Jon
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Phugoid
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« Reply #14 on: March 07, 2013, 01:43:16 PM »

Are you going to tissue over the balsa tail to get colour?

The reason I ask is that if you use the dope and thinners method to do that on sheet surfaces you can sometimes end up with a heavier part from the lighter wood I always think.

I think that the lighter wood tends to be more porous, soaking up more dope.  I've no scientific evidence of this, at one point I was going to do some sort of test to prove it but never got round to it.....

Andrew
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« Reply #15 on: March 08, 2013, 04:39:18 AM »

Could you pre-shrink and dope the tissue before covering the light sheet, attaching only around the edges?
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Yak 52
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« Reply #16 on: March 08, 2013, 06:32:22 AM »

Are you going to tissue over the balsa tail to get colour?

Andrew, yes that's the plan. I've usually done dope 'n' thinners on past models but I haven't noticed the extra weight from absorbtion (perhaps I should have weighed before and after) I've certainly noticed it's true with glue joints so what you say makes sense. I might try glue stick instead.

Ian, I've found I get bubbly bits doing it that way and it looks pretty rough. Probably me though...
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« Reply #17 on: March 11, 2013, 04:21:17 PM »

I've added the nose block and spinner and I've been finishing the sanding of the cowl block. The spinner is a bit bigger than scale but I don't think it would cover the prop hub if it was any smaller. It's pretty close to what the plan shows. The nose block is removable and secured with a magnet.
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Re: Frog Chipmunk
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Re: Frog Chipmunk
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« Reply #18 on: March 11, 2013, 05:12:50 PM »

Very nice shaping Jon  Smiley ... forgive my memory, is this the only kit scale model you are building at the moment?
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Phugoid
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« Reply #19 on: March 11, 2013, 05:27:12 PM »

I Agree with Russ, top shaping on the nose block and spinner, it looks very neat indeed.  I don't think the spinner would be judged anyhow if that is your worry since the prop isn't (but then again I have been wrong on the rules before  Embarrassed)

I've plunged moulded mine since I realised that the space at the front is very useful for getting your first estimate of noseweight in, you can't get any further forward than that  Grin Wink

Andrew
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« Reply #20 on: March 11, 2013, 05:35:42 PM »

Looking good Jon, have you decided on colours yet?
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Yak 52
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« Reply #21 on: March 11, 2013, 06:48:38 PM »

Thanks guys. It will be finished as the Shuttleworth RCAF colours. Russ, yes this is my only Kit scale model, I was thinking of entering Open but I may not finish in time.

Jon
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« Reply #22 on: March 11, 2013, 07:09:49 PM »

Very nice Jon, nice flowing curves...
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« Reply #23 on: March 11, 2013, 07:33:01 PM »

Quote
I don't think the spinner would be judged anyhow if that is your worry since the prop isn't

Even if not included, I think things like this do influence how the judges gauge the overall craftsmanship.
I know that you have read the judges guide ... here they are encouraged to give some sort of initial 'order of merit'.
I think it's here where nice details have that vital first impression.

Jon,
Speaking openly, I do think the Chipmunk would perhaps suit kit scale more. Without modifications to the original, I think there would be a finite limit to the amount of static points it could glean ... even as well built as yours.
To completely contradict what I have just said, I would like to see just how a 'kit scale ready' model could do in the open event! .... thought about doing it with the triplane too  Roll Eyes It also might perform so well in the air that the static score is not as relevant.
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« Reply #24 on: March 12, 2013, 03:41:06 AM »

Jon, very nice Frog!
Makes me want to build more Frogs....

Your build looks very clean. The wheels and the spinner are just beautiful. Looking forward to see it flying.

Happy building Roman
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