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Author Topic: Consolidated PT-3 for Indoor Rubber  (Read 13710 times)
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Indoorflyer
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« Reply #250 on: February 12, 2019, 01:36:48 PM »

Well done Pete! That is a very good looking biplane--nicely detailed.
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MKelly
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« Reply #251 on: February 12, 2019, 02:01:37 PM »

That came out very nice Pete - best of luck for the trimming and hope to see video of it in the air at some point.

Mike
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ffscale
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« Reply #252 on: February 12, 2019, 03:27:37 PM »

Looks great Pete - that is a plane that ticks all my boxes!  Full of character and the detailing is impressive.

Fingers crossed for the trimming.

Mike S
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Graham Banham
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« Reply #253 on: February 12, 2019, 04:15:08 PM »

Looks great Pete: bags of character! If the engine isn't fixed perhaps remove it to avoid damage and ballast the model for some test glides outdoors weather permitting? Will at least get you a ballpark CG without a hard floor underneath it.
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TheLurker
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« Reply #254 on: February 12, 2019, 04:18:35 PM »

Cor.  Nice aeroplane Mister.
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GrahamKennedy
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« Reply #255 on: February 12, 2019, 04:42:45 PM »

It's definitely worth several looks!!

Perhaps see you at the Velodrome on March 16th. I've managed to get the day off...
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DHnut
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« Reply #256 on: February 12, 2019, 05:28:22 PM »

Pete,
         A facinating build with a very practical approach to all the difficult bits. I also like the way you have balanced the unknowns on the documentation front to achieve a reasonable solution that is difficult to challenge. Definitely top drawer.
Ricky 
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abl
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« Reply #257 on: February 12, 2019, 06:10:47 PM »

Nice aeroplane, Pete.
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Pete Fardell
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« Reply #258 on: February 12, 2019, 07:22:07 PM »

Thanks for all the kind words. Couple more pics.  It now has a prop assembly. Also remembered I’d made two little fuel caps a while back, so I stuck them on the centre section tanks. With no markings on the top wing I think a bit of detail helps up there.

Graham K- yes, really hope to see you at the Velodrome on March 16th for the NW Gala. Whether I fly this model though will depend on how the trimming session goes at the fun fly session there a week on Saturday!

Graham B- thanks; good idea to test glide for CG if I get a calm day. The engine is stuck on I’m afraid, but I could maybe band a bag around it so that if I knock bits off I at least won’t lose them. For the main trimming session at the ‘drome I shall go from the ground up (ie attempting to ROG from the off) as per my usual method. Less nerve wracking than chucking it into the floor I find!
Attached files Thumbnail(s):
Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
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danmellor
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« Reply #259 on: February 13, 2019, 02:46:10 AM »

Are you making Alfreton on the 23rd, Pete? Lovely model...

Cheers,

Dan.
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Pete Fardell
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« Reply #260 on: February 13, 2019, 07:48:16 AM »

Are you making Alfreton on the 23rd, Pete?
I’d like to, Dan, but unfortunately it’s the same day as the Manc Velodrome session. The Velodrome is a similar journey time for me but it’s a fair bit bigger than Alfreton. (Plus the walls are made of soft netting!)
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Gromit
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« Reply #261 on: February 13, 2019, 10:24:36 AM »

Many thanks for all the tyre info. That's a great story, PP.

I'm curious to know if these foamlike alternatives are significantly lighter than solid painted balsa. If they're not then I'll probably just turn balsa tyres as usual because it means I can make them an integral part of the rim and (if I make the spoked wheels my preferred way) I'll be on altogether more familiar ground. The downside to balsa tyres on indoor models is the 'clatter' on landing, but there are ways round that.


Not sure if I'm doing this reply correctly Pete being a novice at this HP game but my thoughts are don't worry about the weight of balsa in the wheels - the weight is in the right place for stability and probably means you can stay with scale dihedral

Doug
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Gromit
Pete Fardell
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« Reply #262 on: February 13, 2019, 01:57:16 PM »

Thanks, Doug. I think you're right about wheel weight aiding stability and, as you say, they're in just the right place. However, the dihedral is already slightly uptweaked, partly at the suggestion of Richard C to give it a better chance of turning within walls.
For tyres, I've come to the conclusion that unless you're worried about wear and tear (eg for a power model landing on tarmac) balsa is usually as good as anything.
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DHnut
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« Reply #263 on: February 13, 2019, 02:35:37 PM »

Pete,
       While I agree that heavy wheels are a positive in one sense they do however add to overall weight which is not so positive. To me the top priority is to reduce overall weight consistent with sufficient strength. I now as a matter of course use balsa wheels to reduce weight. The do scuff but a lick of paint soon fixes that. Your approach to testing is similar to that Walt Mooney advocated for his outdoor models on similar grounds. If you have to ROG in competition then is makes sense to find out what is needed to achieve that stage with the added bonus of minimising any damage. Have a great day at the velodrome.
Ricky 
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avrovulcan
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« Reply #264 on: February 14, 2019, 05:27:04 AM »

That looks great, amazing workmanship.
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Pete Fardell
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« Reply #265 on: February 16, 2019, 05:52:00 PM »

Thanks, Ricky and Caroline.

Does anyone have any thoughts on setting a likely CG on a biplane with staggered wings?
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Graham Banham
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« Reply #266 on: February 16, 2019, 07:18:04 PM »

Looking at the stagger i’d say roughly on the lower wing L/E.
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John Webster
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« Reply #267 on: February 17, 2019, 01:25:55 AM »

Measure from the nose to the 25% chord point on each wing, add the measurements and divide by 2. That should give a slightly nose heavy starting point.
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Graham Banham
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« Reply #268 on: February 17, 2019, 02:14:50 AM »

By my reckoning John’s method (or marking 25% chord on both wings and splitting the difference: same thing) gives a CG mid way between the bottom wing forward interplane strut point and the bottom wing LE. 25% could well be ok on a lightly loaded bipe with a big tail, but i reckon no further back than that: if if is, more negative on the tailplane until it stops pitching down with the CG at 25%.
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DavidJP
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« Reply #269 on: February 17, 2019, 05:07:55 AM »

Just seen this ......... that, Mr Fardell, is one damn fine model!

Must try then idea of OoG from the off ...... often though of it but not seen anyone do it so didn't!  But of course I don't get out much.
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Pete Fardell
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« Reply #270 on: February 17, 2019, 05:41:51 AM »

By my reckoning John’s method (or marking 25% chord on both wings and splitting the difference: same thing) gives a CG mid way between the bottom wing forward interplane strut point and the bottom wing LE. 25% could well be ok on a lightly loaded bipe with a big tail, but i reckon no further back than that: if if is, more negative on the tailplane until it stops pitching down with the CG at 25%.
Thank you both. The CG is almost there already so that's quite encouraging. The motor will put it back slightly further of course, so some nose weight will be needed.

Another worry is with my docs photos. On a PT-3, the two wires coming down from the cabane to the bottom wing do so in a V as both anchor near the rear cabane strut (see pic 1). On a PT-3A, however, one wire comes from near the front cabane strut and one from near the rear, so that they run down to the lower wing in parallel (see pic 2). This matters because it means I now know that my only decent plan view photos are of PT-3As (pics 4 and 5). The only vaguely 'above' shot I have of a PT-3 is very low res (pic 6).

So, I'm back to the issue of whether I can justify using PT-3A shots in my documentation. As mentioned before, there is also a difference with the rear turtle deck. I'm pretty sure the wing and tail outlines of the two types are the same, but when all is said and done they are technically two different aircraft and I'm not happy about submitting PT-3A photos.
(I do have published specs for the two types as well. All given dimensions are the same except that the PT-3A's length is 2 inches shorter. This might be due to it having a "Wright Model R-790-3" engine instead of the PT-3's boring old Wright Model R-790, but who knows!?)
Attached files Thumbnail(s):
Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
Re: Consolidated PT-3 for Indoor Rubber
« Last Edit: February 17, 2019, 05:54:13 AM by Pete Fardell » Logged
Graham Banham
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« Reply #271 on: February 17, 2019, 06:09:04 AM »

One question you need to ask: can you discern this rigging/ turtledeck difference in your plan view PT-3A photos when compared to your other PT-3 shots? If not, or you need a magnifying glass to do so, the 3 and 3a are clearly so similar overall that i would suggest you don’t have a problem. Use the 3 pix for the subject aircraft, and the 3a shots for plan view outlines.
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Pete Fardell
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« Reply #272 on: February 17, 2019, 07:46:08 AM »

One question you need to ask: can you discern this rigging/ turtledeck difference in your plan view PT-3A photos when compared to your other PT-3 shots?
Thanks Graham. You can discern the rigging difference in the plan view shots but only if you're looking for it as I was. In fact, both the plan view shots are labelled as PT-3s on the websites where I found them. I only know they're really 3As because I can see the rigging wires go to the front cabane. I very much doubt a judge would notice, but it doesn't quite seem honest to pass them off as PT-3s. I suppose it goes back to the question of whether PT-3s and PT-3As count as the same beast.
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Squirrelnet
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« Reply #273 on: February 17, 2019, 07:54:00 AM »

I'm pretty new to the scale scene and particularly presenting documentation but can't you use the pics but label them as as PT3a's stating the small differences as you have here ? They are relevant to your model minus the 'a' variant differences.
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Jack Plane
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« Reply #274 on: February 17, 2019, 07:55:42 AM »

I'd balance for 1/3rd back from the LE of the TOP wing only, then tweak it from there on.
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