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Author Topic: DPCM Sopwith Pup  (Read 3371 times)
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Squirrelnet
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« Reply #75 on: December 08, 2019, 12:49:35 PM »

The Pup is pretty much done now, apart from some minor bits like pilots step in the fuselage, pitot tube, possibly control lines but the next stage is definitely trimming. With that in mind I pessimistically  took some photos of it case it doesn't survive the experience  Huh

 Andy - I hope I'm in the ball park ? I have a 12" loop of 3/16" fitted as trimming motor which pulls it across the workshop floor with seemingly enough go and have balanced it out. It'll come as now surprise that it needed a lot of lead to get it to a CG at 30%. The cowling is now nearly as heavy as the rest of the airframe !!!

Anyway some numbers with the motor 51.5g which gives a wing loading of 8gm/dm2 which I think sounds OK. You guys will have a better idea than me
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Russ Lister
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« Reply #76 on: December 08, 2019, 01:37:03 PM »

Looks great, Chris  Smiley
If my calculations are good then that is about 0.51g per Sq.Inch? ... sounds good to me.
My DPCM Sopwith Triplane was about the same weight, but converted to CO2 later ... cruised around nicely (except for my Nats bogey with it)
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Jack Plane
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« Reply #77 on: December 09, 2019, 02:38:09 AM »

Weight sounds okay Chris - my CO2 Camel of same span was 46g/sqin... although ZK-AUD's rubber Camel was only about 3g...!  Shocked

Looks fab too - is it for Open Rubber?
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Squirrelnet
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« Reply #78 on: December 09, 2019, 02:50:47 AM »

That's good to hear Jon and Russ. Yes if I can successfully trim it it's for Open rubber or the new intermediate scale ... if it actually happens Huh

Any news out there on that from the STC Rules meeting, i thought we may have a decision by now
« Last Edit: December 09, 2019, 03:11:46 AM by Squirrelnet » Logged
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« Reply #79 on: December 09, 2019, 05:58:26 AM »

Yes if I can successfully trim it it's for Open rubber or the new intermediate scale ... if it actually happens Huh


I didn't realise that this was even a possibility for 2020 ... I am out of the loop. I would've thought that there would need to be a longer period of notice to give competitors chance to prepare models?
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Pete Fardell
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« Reply #80 on: December 09, 2019, 06:23:41 AM »

Yes if I can successfully trim it it's for Open rubber or the new intermediate scale ... if it actually happens Huh


I didn't realise that this was even a possibility for 2020 ... I am out of the loop. I would've thought that there would need to be a longer period of notice to give competitors chance to prepare models?

According to Andy Sephton's column in the recent BMFA News it is happening in 2020. I don't think there's really an issue with giving competitors time to prepare models. We can just enter the ones we've already got can't we, or finish a nearly finished one? Probably still time to make something new, given the requirements will be less stringent than Open Rubber. I agree- would be nice to see the rules up soon though.
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« Reply #81 on: December 09, 2019, 06:52:27 AM »

Pete,
Yes, to an extent ... I'll have to read up as I haven't got a clue what angle it will take.
I think it's more the static element I'm thinking of ...will it be a subtractive system like kit scale or an additive system like the open classes? Ie. Will there be penalties like kit scale? ... this would affect the preparation by a competitor.
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RalphS
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« Reply #82 on: December 09, 2019, 06:53:45 AM »

my CO2 Camel of same span was 46g/sqin

Flying it on the moon Jon?

Ralph
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Crabby
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« Reply #83 on: December 09, 2019, 08:09:26 AM »

Great piece of craftmanship Chris. Your work quality holds up to close scrutiny. You must have had your "bench dpi" set at "high definition"! Well done!
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« Reply #84 on: December 09, 2019, 10:32:28 AM »

Just a bit of news from the STC on 30th November meeting, as Chris asked for above.
Yes, we have discussed them and have the new rules pretty much sorted.
As the new PRO for the STC, I will be putting them up asap, not just when the new rulebook is available next year, so you have them earlier.

If you have not registered for notification on the Scale BMFA website - please do as you'll get an email to tell you there is some news. https://scale.bmfa.org
If you do facebook there is a new scale BMFA site for that too.  https://www.facebook.com/groups/2457811227878150
Lastly, if you want to be on the STC email list for scale, please email me with your permission to hold your data (for GDPR reasons). 
I need your name, BMFA no. email address, and what kind of scale your are interested in RC FF etc - plus if you are able to do any judging or helping.

Regards John M


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Jack Plane
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« Reply #85 on: December 09, 2019, 11:30:34 AM »

my CO2 Camel of same span was 46g/sqin

Flying it on the moon Jon?

Ralph

Since its no longer eligible for BMFA Kit Scale, I thought I'd try elsewhere...!  Grin
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Squirrelnet
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« Reply #86 on: December 09, 2019, 03:04:17 PM »

Quote
Just a bit of news from the STC on 30th November meeting, as Chris asked for above.
Yes, we have discussed them and have the new rules pretty much sorted.
As the new PRO for the STC, I will be putting them up asap, not just when the new rulebook is available next year, so you have them earlier.

 Thanks John that's a great idea

 I have signed up to the STC newsletter on the website, I'm also on Doug/Mike's FF Scale list as well so that should have it covered.
« Last Edit: December 09, 2019, 03:21:34 PM by Squirrelnet » Logged
Squirrelnet
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« Reply #87 on: December 09, 2019, 03:08:47 PM »

Thanks the kind comments Crabby  Grin
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Squirrelnet
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« Reply #88 on: January 05, 2020, 12:45:20 PM »

So finally I got to trim out the Pup today thanks to the OFFC meeting at Berinsfield nr Wallingford.

I'd already tried a test glide of some soft greenery, well brownery really , some old ferns on the common and ... yes you've guessed it needed more nose weight.

So armed with some extra plasticine on the cowling and a loop of 3/16" I tried some tentative ground runs in the hall at Berinsfield which proved that 3/16" is no where near enough power. Re engined with 4 strands of 1/8 and a few hundred turns, a gentle powered glide resulted from a hand launch along with a very tight left turn.

The rest of the session was spent adding more downthrust as the power increased, more noseweight and gently opening out the turn. The hall is quite small so opening up the turn is a risky business but the end flight resulted in a big cheesy grin. There's clearly not enough power for it to ROG with 4 strands of 1/8 but luckily John of Flitehook was there with his rubber supply and I have some .130" and some .150 to try again next weekend at the much larger hall at Bushfields at the PMFC Tony Beckett Tribute meeting

For those interested or contemplating building one I ended up adding another 5g's of nose weight and 1g of tip weight to the outside wing tip that brings the weight upto 54g + 5g of rubber which is a 2x loop of 1/8 and still not enough

 Chatting to Peter Smart about it, electrification maybe a better solution as I could achieve the cg without the xtra weight of the rubber motor but I'll keep going with rubber for now

I have some video of it too, along with some other models which I'll post here in a bit

Pic 1    More noseweight..

Pic 2   ..more tip weight

Pic 3 - Now around 6deg downthrust ( that's a guess)

Pic 4 - first mission complete :-)
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Re: DPCM Sopwith Pup
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« Reply #89 on: January 05, 2020, 12:51:43 PM »

I'm glad that some are flying! ... look forward to the video and hopefully seeing the model at Bushfield.
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Squirrelnet
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« Reply #90 on: January 05, 2020, 02:34:33 PM »

Here's the video https://youtu.be/SkPyCTiNzhA

The big thing that stands in relation to watching the video is the Pup's 'scale' landing... see attached photo
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Russ Lister
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« Reply #91 on: January 05, 2020, 04:35:50 PM »

It looks more than a little akin to trimming a model at Impington ... a bit marginal for anything of about 16" and above. I think things will be different when you can open that turn at Bushfield  Smiley
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« Reply #92 on: January 05, 2020, 05:59:44 PM »

Well done Chris getting this to fly in what looks like a pretty tight hall.  I agree with Russ that you will do better when you can open the turn out though that will probably bring back some stall.

If this is the 16" model then it is very comparable to my KK Camel.  You'll recall I predicted that you would need all of that down thrust so no surprises based on my experience with the Camel and also my VMC Tripe (the same).

I've found that it's a given that you will need a heap of lead in the nose with these,  so the key thing is to keep all weight,  and particularly tail weight,  to an absolute minimum to keep the AUW down once the inevitable pile of lead is added.

The Camel was built light and was about 20g before trimming but with the noseweight that ended up being necessary and the slightly heavier rubber it ended up being about 35g AUW including the rubber.  It flies superbly at that however.  Motor is 4 strands of 3/32

If you are at 60g AUW then I think that does present challenges.

For comparison my Avetek Tiger Moth which is a 21" model and fully detailed is just over 50g - I use 4 strands of 5/32 (stripped from 3/16) for outdoor and 4 strands of 1/8 for indoor.

Happy to share my thoughts on getting them lighter if that's of any interest
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Squirrelnet
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« Reply #93 on: January 06, 2020, 02:16:19 AM »

Thanks for the info Mike, much appreciated.

I'm still learning about how to build light for indoor flying so all thoughts are of interest.

Chris

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« Reply #94 on: January 06, 2020, 08:43:52 AM »

That is progressing well Chris - however as you mention you have already mastered scale landings Smiley Looks nice in flight.

John
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Jack Plane
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« Reply #95 on: January 07, 2020, 06:29:12 AM »

Thanks for the info Mike, much appreciated.

I'm still learning about how to build light for indoor flying so all thoughts are of interest.

Chris


Build lighter...  Grin
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« Reply #96 on: January 07, 2020, 09:16:52 AM »

Thanks for the info Mike, much appreciated.

I'm still learning about how to build light for indoor flying so all thoughts are of interest.
Build lighter...  Grin
Chris, the likely final weight weight is heavily influenced by your choice of subject, so the moment you picked a Pup for rubber, lead was going to be involved!
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piecost
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« Reply #97 on: January 07, 2020, 11:12:01 AM »

It is worth considering moving the motor peg forward a bay or two to just begind the lower wing. This may allow the noseweight to be reduced by a few grams.
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« Reply #98 on: January 07, 2020, 12:11:02 PM »

Echoes of my DPCM Sopwith Triplane ... Bill was right then and both he and Piecost are right now.
I managed to get a decent hand launch but as the trimming weight was added, the ability to hop off of the floor disappeared. More time and power might have found a sweet spot, but the CO2 conversion got it flying nicely. I have to admit that power is still an issue for a ROG.
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« Reply #99 on: January 07, 2020, 02:22:29 PM »

.... just to add ... your peg is further forward than mine was, so not as much of a problem.
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