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 Post subject: hotliner question...
PostPosted: Tue Dec 17, 2013 4:28 am 
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Joined: Mon Jul 25, 2011 5:07 pm
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Location: West sussex, UK
Hi Gang,

I used to love my funjet 100mph flybys are cool, but after a while get boring.

I love my little E-hawk power glider.

there are a few compromises in the e hawk but the general shape and size is spot on, and a decent colour scheme may stop it dissapearing, converting the V tail to a traditional fin and stab will also aid in orientation.

I was thinking about adding a longer spar and a hot motor to it to make me a super cheap hotliner. running 3s 2200 pack with the only mods to the wing being adding a servo so each aileron has it's own servo.

The one I have flies nicely on a 3s 1000 and is pretty light even with a full house control setup.

my reasoning is I can blat arount at 100mph+ if I am in a hooligan mood, or I can speck it out and do some gliding with it if I am in a sedate mood. (I have lots of mood swings during a flight so having a multi role plane would be great)

so to my question, is a hotliner simply a stronger built stupidly overpowered glider or am I missing something?

I have no desire to spend $1000 dollars on an all composite thing of beauty I just want an everyday hack that can go fast or slow...

so your thoughts what would you add to the basic airframe (which probably isn't stressed for more than 5 g's) to mke there less chance of folding the thing up on the first full speed turn?

oh and for those not sure what an E-hawk 1500 is or looks like here is a link to the superbly cheap airframe
http://sussex-model-centre.co.uk/shopexd.asp?id=42574" onclick="window.open(this.href);return false;

And I have added some piccies of my current one below..

So to recap, mod the tail so it is a proper shape, strengthen the wing add a silly motor of 28mm diameter.
I'll be doing this from a new kit as they are only £40 to buy and the one I have has had a few eventful arrivals.

Cheers
Steve


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 Post subject: Re: hotliner question...
PostPosted: Tue Dec 17, 2013 8:22 am 
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Joined: Mon Jul 25, 2011 11:58 am
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Location: Austin, TX
stevec wrote:
so to my question, is a hotliner simply a stronger built stupidly overpowered glider or am I missing something?
Steve, that's a very accurate summary! :rolling

That little Hawk has all the basic DNA you need. The RG15 airfoil has a good speed range and the rest of the design already looks the part. Just build it with carbon-capped spars, consider fully sheeting the wing (for torsional rigidity) and make sure the tail surfaces are stiff enough not to twist / flutter. They look to be solid balsa, so I would recommend a spruce spar and fiberglass / resin over the balsa to make them strong enough.

Beyond that, metal gear servos would be my only other recommendation over the typical gear you'd use.

Keep us posted, that sounds fun. :)

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 Post subject: Re: hotliner question...
PostPosted: Tue Dec 17, 2013 8:53 am 
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Joined: Mon Jul 25, 2011 5:07 pm
Posts: 778
Location: West sussex, UK
sorry I am new to this, a spruce spar in the tail?

also how many watts per pound to get a nice fast plane, not wanting to break records but funjet speeds would be nice, my old funjet reportedly was equipped for 120mph, although personally I don't think it got anywhere close to that. 100 in a dive at full chat was probably just about possible.

I was thinking somewhere in the 300 w range? this is a light plane and comes in at about 1 1/2 lbs with the battery.

The other confusing things is do hotliners use standard folding props because the idea of spinning a 11x7 folding prop at 22000 rpm scares the crap out of me!

Cheers
Steve


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 Post subject: Re: hotliner question...
PostPosted: Tue Dec 17, 2013 9:51 am 
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Location: Austin, TX
If the tail is made from flat balsa, you'd simply slice out a section at about 25% chord and glue in a same-thickness slice of spruce. It just stiffens it up span-wise. The fiberglass cloth (ideally with the weave at a 45 degree bias) will give it torsional rigidity.

You're right, you don't want to spin a folder at those kinds of speeds, that's why hotliners use large diameter high pitch folding props and geared power systems. 200+ watts per pound will make it entertaining.

Here's the thing: You don't want to choose your power system with the idea of going fast with the motor ON, the motor is just for climb! All hotliners will over-run the prop and typically go faster with the motor off and prop folded.

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 Post subject: Re: hotliner question...
PostPosted: Tue Dec 17, 2013 10:14 am 
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Location: Houston, Texas
OK that is a cheap kit!

So why cant i find the same kits for sale in the US?

Chris i need your Google Fu!

I have a modified version of the 1400 E Hawk, although i haven't flown it yet, its still stuck in a bloody shipping container somewhere!!

Ben

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 Post subject: Re: hotliner question...
PostPosted: Tue Dec 17, 2013 11:53 am 
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Location: West sussex, UK
Do you want me to find out what shipping would be to the US? I would be happy to post to you mate.

Sent from my C6603 using Tapatalk


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 Post subject: Re: hotliner question...
PostPosted: Tue Dec 17, 2013 12:05 pm 
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Thanks for the offer but i have too much else going on at the moment

I don't need another project

BUT!

I may take you up on that offer sometime in the future!

Cheers

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Home of Burnt Wood RC The Splinter-T, Splinter-V Mini Multi's
Blade 450 Franken Heli
68" Velox Electric
TT eHawk 1400
K&A Models Mk 24 Spitfire
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 Post subject: Re: hotliner question...
PostPosted: Wed Dec 18, 2013 2:12 am 
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Location: West sussex, UK
JustPlaneChris wrote:
If the tail is made from flat balsa, you'd simply slice out a section at about 25% chord and glue in a same-thickness slice of spruce. It just stiffens it up span-wise. The fiberglass cloth (ideally with the weave at a 45 degree bias) will give it torsional rigidity.

You're right, you don't want to spin a folder at those kinds of speeds, that's why hotliners use large diameter high pitch folding props and geared power systems. 200+ watts per pound will make it entertaining.

Here's the thing: You don't want to choose your power system with the idea of going fast with the motor ON, the motor is just for climb! All hotliners will over-run the prop and typically go faster with the motor off and prop folded.



is gearing down necessary now with modern brushless motors or is it a way to get the torque up on a weak motor due to the narrow confines of the nose?

I will see if I can find a 28mm 300w motor with a KV of around 1500 does that sound like a good starting place? the motor KV and prop size is where I am struggling I am ok with the little inrunners running a 5x4 or similar I can see how that works, but what revs do you look for on a 12" folding prop?

cheers
Steve


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 Post subject: Re: hotliner question...
PostPosted: Wed Dec 18, 2013 8:49 am 
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stevec wrote:
is gearing down necessary now with modern brushless motors or is it a way to get the torque up on a weak motor due to the narrow confines of the nose?


It's a little of both, really. Outrunners are difficult to fit into the nose of a glider, and inrunners typically don't work well direct-drive with large props.

1500kv is pretty high for 3S on a glider. As an example of what I know for sure works, I'm using a JustGoFly 450XT (950kv) in a scratch built 1.5m "warmliner" of my own design.

http://www.justgofly.com/tech_450XT.htm

In fact, there is a picture of it on that site, and a short narrative I sent to Vinnie back when I first got it flying:

Saturday I flew with a gent who has an ArtHobby "Castor" 2 meter, which was powered by a Mega 16/15/4 with planetary gearbox ($$$). It's a slightly larger and heavier glider, but I could literally run circles around him. When he found out my power system only consumed 13.5 amps and the motor was only $51 (and no gearbox required), he just about fell over. :^)
Long story short: You can DEFINITELY recommend the 450XT and Aeronaut 10x8 folding prop combination for any glider in the 20-25 oz weight range. Heck, even at 30+ oz I suspect it would do fine, but at 23 oz it
will nearly go vertical. Great fun, and I couldn't be happier.


Image

So.... you'd want something 900kv or less. The power system in my Tiger hotliner is an outrunner + planetary gearbox.

http://www.modelmotors.cz/index.php?pag ... &line=GOLD

The motor is 1880kv, but with the gearbox (3.1:1) that gives you an effective kv of ~600. With that system on 3S, the Tiger swings a 14x12 prop and goes straight up with authority (~530 watts) in a 38 oz. / 1077 g airframe.

Sorry to ramble on, but sometimes other power systems and configurations will help figure out what you need. :)

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 Post subject: Re: hotliner question...
PostPosted: Wed Dec 18, 2013 1:56 pm 
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Location: West sussex, UK
Thanks Chris exactly what I was looking for. I'll get on the websites and find some bargains...

Sent from my C6603 using Tapatalk


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