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Author Topic: John Barker's Hepcat  (Read 7187 times)
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Crabby
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« Reply #125 on: May 18, 2017, 03:37:58 PM »

This is taking on an Aunt Essie Rhubarb pie dilemma, where she gave everyone the recipe last Thanksgiving, and is now snickering while everyone is scratching their heads.  I am in the nose bleed section watching you Brits noodle out the magic formulae!
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cvasecuk
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« Reply #126 on: May 18, 2017, 04:15:29 PM »

I don't like hooks etc on tailplanes; the poke holes in everything!
Ron
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gossie
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« Reply #127 on: May 18, 2017, 05:59:50 PM »

Ready to go but it crashed onto the scales at 65g. I have used good wood, mylar/tissue fuselage and have no idea how I could get that down to the under 50g quoted. We'll see


Looks great Bill.
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billdennis747
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« Reply #128 on: May 19, 2017, 03:28:43 PM »

I just took it to the local park. With the cg correct it needed 1/16 tail TE packing. I swung the whole tail a fraction to get a wide left turn - is there any practical difference between this and a fin tab? Then 1/16 noseblock packing gave a right turn on 50 hand winds, so that's trimmed then.
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« Reply #129 on: May 19, 2017, 04:19:04 PM »

For glide turn I prefer to keep the tailplane square and use a piece of 1/16 sq on one fin as a Gurney flap. Easily adjustable.
Ron
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Hepcat
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« Reply #130 on: May 19, 2017, 04:46:09 PM »

Bill,
What a delightfully light touch you scale builders do develop: you must be a WoW with the ladies.  Old 'Cat' is getting on a bit now (born 1945 but don't tell her I said so) but under your caressing touch she seems like a dimple cheeked debutant in #124.

I suppose offsetting the whole tail unit will give a millionth of a gram less drag but like you I don't think a strip or a tab or the offset will make any difference.  Just remember to glue some keys on when trimmed.

John
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skyrocket
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« Reply #131 on: May 22, 2017, 09:40:59 PM »

not to worry Bill...go with it but make sure it's straight...then you have a good starting point...it does require down and side thrust...I always build in down thrust to start out with and then mess around with side thrust...don't forget cg has a nasty way of changing all this and messes with yer head but that's why it's so much fun to wind this model up and fly it...all 3 of mine gave me so much fun it's a wonder why I fly anything else...the key to this model is, I think, the prop...the p/d worked out to 1.25 and just keeps pulling to the end of the run...I fold it on top of the fuselage so it doesn't flop out due to mis-siting of the screw...hasn't failed yet...
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billdennis747
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« Reply #132 on: October 16, 2017, 03:33:46 AM »

I took my Hepcat to its first contest yesterday. Three straightforward maxes and then a flyoff which went badly wrong after about 30 seconds when it turned into hammerhead stalls in a thermal. Down in a minute. I don't know what caused it. I very much doubt if anything moved because it was all in place when I got to it. All I can think of is a big rubber bunch at the back. I wound it badly and there were knots at the front but not enough to explain the big stall if something similar occurred at the back.
I like the Hepcat. I have always flown te Raff V and like it as it's easy to keep the weight down, but it's a fat thing and I wondered what less drag would do. Only when I built the Hepcat did I notice it was smaller but it makes no difference. But I need to solve that stall.
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skyrocket
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« Reply #133 on: October 16, 2017, 01:21:55 PM »

Yep, rubber bunches do that...my Hepcat is 3 years old and getting tatty but still produces maxes...I braid the motor even though it is a folder and everything seems to stay in place...two other models I fly are the Cherokee and the Elite Petrel...both max hounds and go up like rockets...but for looks, Hepcat has it in spades.
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billdennis747
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« Reply #134 on: October 16, 2017, 01:46:04 PM »

Hmmm. I had thought about it and convinced myself the tail must have jumped and given itself 1/8"  extra negative, which would explain the BIG stalls which developed  suddenly 30 seconds in. I've never suffered from big bunches and the motor is quite thin so I'm having second thoughts on that. For some reason I used a thin (2lb) fishing line for the DT line so maybe it allowed the tail to jump. It was gusty.
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skyrocket
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« Reply #135 on: October 16, 2017, 05:55:01 PM »

I use fly fishing line BACKING for all D/T lines...it doesn't stretch and is supple but feel it first because some of them on the market feel waxy and set in a kink...I haven't used mono in a long time and in the heat, it does stretch...I don't put the fuse at the back but instead I locate the fuse at the C/G and closer to me so I can light it easier and I try to keep whatever weight there is up front for a better nose moment for stall recovery...this is just a guess but it works for me...
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cvasecuk
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« Reply #136 on: October 17, 2017, 05:20:40 AM »

If the tailplane had ridden up over the stop it increases the incidence and the model would have been seriously under elevated. It would have been in a steep dive. It has happened to my Hepcat several times!!!
Ron
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billdennis747
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« Reply #137 on: October 17, 2017, 05:33:38 AM »

No, I suspect the back jumped up and the keying stop sat on top of the packing
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skyrocket
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« Reply #138 on: October 17, 2017, 05:30:12 PM »

bd747...yep, that's a common bugaboo...I usually build in 1 degree minus in the stab mount on the older models to stop having to add packing but it has a lot to do with CG location too, I think...the NACA 6409/RAF32/DAVIS type airfoils are strange beasts and you never know how much incidence is ever needed...
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skyrocket
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« Reply #139 on: January 03, 2019, 03:08:16 PM »

Hep Cat #5...this is the latest at 60 grams...yep, a little porkie...but it feels good and looks straight and I didn't pay particular attention to selecting wood...I did however matched wood to its use...I have seen the article in NFFS on it and I took exception to the wire hub and blades and stab fins so I build them to the Aero-Modeller plan...sorry John...the plan I drew and use is as close to the AM plan as I can get...
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