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g-mosie
06-27-2007, 01:32 PM
I would really appreciate some assistance with my next project. I have been fortunate to acquire a completed airframe for a DH Mosquito, unsure of it's true pedigree, though it appears to have a lot in common with the Brian Taylor 83" model. The build quality really has to be seen to be appreciated, alas something I cannot reproduce. Looking at the model it is screaming out to be electrified. The prospect of running a twin IC fills me with dread and fear. This is the reason for my plea for assistance. I'm a complete rookie with regards to electrification and the more I research the more I'm confused.


Here are the details of the model

Similar to Brian Taylor design which is quoted for 40 - 70 4 Stroke IC
Wingspan = 83"
Wing area = 996 sq in
Target Wing Loading < 30oz/sq ft
Target weight not greater than 207oz
Current airframe weight including servos and radio gear 156oz

I want the model to fly realistically, which I appreciate will be at some speed, but not resemble a jet fighter dressed in world war II clothes

I just don't know where to start in terms of deciding what I need.??

What type of motors
What size of motors
To gear or not to gear
Batteries seem a no brainer Lipo I presume
Do I run the radio off the same batteries as the engines or do I run a separate flight pack
Should I take any special precautions with regard to interference

I would very much appreciate any assistance anyone can offer in solving this problem.

Johnr
06-27-2007, 02:47 PM
I have electrified the BT mosie but it was enlarged to 93". It has DC motors with gearboxes but you really need something like the AXI4130 16 outrunners (no gearboxes) with 15" x 10" APCe props although these motors might be a bit too big. Batteries - 2 5s3p Lipos at about 5ah (Thunderpower Extreme) and 77 amp Jeti speed controllers would work although this bundle will weigh more that the 51oz you allowed. Maybe 4s3p would be OK with smaller speed controllers. You also need to determine where the batteries will go, to not have to have to put lead up front to get the C of G right.

Suggest you work out the weight of all the components first to see if your wing loading is going to be too high. If the Mossie is heavy then you will need the additional power of the AXI4130/16. I use a separate flight pack for the receiver. Also check that the washout has been built into the wing or it could bite!

Hope this helps.

John

g-mosie
06-27-2007, 04:12 PM
Thx for the reply, though I have to confess when you start talking about 15 x 10 props your certainly challenging my comfort zone. My research so far has thrown up an account by Lars Baeter who electrified the BT Mosquito back in 2002. He reported success at that time using 2 X Plettenberg 290/20/8 motors geared 2.33:1 swinging 13 X 8 props. I'm hoping to beat his stated wing loading of 37oz/sq ft by some margin (an all up weight of 207 oz must be do-able). I'll certainly check for the washout and also dust off the hand written notes which came with the model regarding CofG. I would appreciate some confirmation of the suitability of this at a later date (No Plan with model).

Johnr
06-28-2007, 09:02 AM
You can reduce the size of the props by getting less winds on the motor but you will lose efficiency. If you have a fixed weight of plane then add to the it fixed weight of the motors and batteries to see what you might get. Alternative motors will not be much different. I know Lars and I nearly experienced the same interference problem on my Mossie. The answer is a ferrite ring on at least the speed controller servo lead.

John

Zephr77
07-17-2007, 10:24 AM
I am also looking at a similar project but am no where near as close have plans and moulds from Brian taylor and tailplane and rudder is built now the hard stuff starts will be interested to see how you get on and what you decide on for power etc?
My thought with engines is with such big spinners you want them to run very true is this possible with a outrunner???

Johnr
07-17-2007, 10:39 AM
Yes large spinners are not a problem. I vacuformed mine for the BT 81" Mosquito and the Hornet spinner is even bigger at over 5" diameter on an outrunner at 5000rpm.
John

Bill G
08-06-2007, 02:41 AM
How about this one?:Q
It will need some serious electrifying help too.
I picked it up for 20 bucks, and have just sort have been dabbling with it, a few minutes here and there. Had good success with other Cox and FZ jobs, and just had to have the Mosquito.

I guess the success will depend on how much loot I'm willing to put into it.

Bill

PETERRAKE
08-06-2007, 01:33 PM
Although not actually a Mossie, I was fortunate enough to watch the John Ranson Hornet flying yesterday. Being nosy, I got the full gen - 2x Hacker 60/24s motors, each running on 8x5000 mAh LiPos and swinging 20x13 props. All up weight is 27 lb. The only info I didn't get is how big it is, probably bigger than you are contemplating.
This is an absolutely stunning model, with sound system - both engine and machine-gun - retracts (naturally) and high level of detail.
Unfortunately, John over cooked a low (very low) pass and clipped one wingtip and prop, stopping that motor. No small tribute to his skill is the fact that he climbed the model away, completed the circuit and made a perfect landing. He was last seen with the cowl off, investigating why the motor stopped and how much it was going to cost to put right. Probably about what one of my models costs me.
Pete

Johnr
08-07-2007, 09:05 AM
Hi Pete,
Oops, you have slopes in Norfolk, not like in Suffolk. The ground came up again and clonked it! Luckily no damage and it flew again after about an hour. Did a small cockpit video which I will post.

No mechanical damage to the drive although the prop is a bit banana and needs replacing. David's theory is that the electronic rotational sequencing was put out between the ESC and the motor when it was stopped by terra firma and it could not 'couple' again until it was switched off then on again. We checked the rpms later and they were fine.

The only damage was the wing tip light edging and a rocket fin ripped off. I was very lucky to get away with that as the 1/4 scale Hornet at Cosford was pulped in very similar circumstances about a month a go. It spun in on climb out on one engine. That was a very high risk attempt to climb out and I should have shut the other engine down and put it into the weeds.

John

PETERRAKE
08-07-2007, 09:34 AM
John,
That's a relief mate, glad to hear it was nothing major. Sorry I missed the final flight of the day though, I was starting to cook in the heat so left early. Next thing I know you'll tell me the wind died right away and I could have flown.
Totally separate from the club, I'd like to extend a personal thanks for making my day. A super model, superbly flown (most of the time). Now perhaps they'll stop extracting the urine about me flying these strange, quiet models. Probably not though, all part of the fun.

Pete

Aussie E-Flite
08-07-2007, 09:50 AM
I've had my eye on this one for a little while now.

http://www.cmpairplane.com/warbird/Mosquito.html

Once I find a source for the retracts, it will be heading my way.

Planning on a pair of E-flite Power 25s, not sure about batteries and ESC just yet.

Johnr
08-08-2007, 09:06 AM
Hi Pete and all,
Thanks for those kind comments, glad you liked it. As you know, twins are especially good for electric power and that was the first single engined escapade with any of my twins, which amounts to 1 circuit in about 250 flights. That was quite enough however. I have put myself on a charge.

Here is that link from the last flight and it was still windy when I left. Note the windsock right at the end. What a super day though. Many thanks to Kings Lynnn Club.

http://www.youtube.com/watch?v=sI7hg7aYB_E

John