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Bleriot XI

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Birgir11/10/2015 20:51:47
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146 forum posts
61 photos

Hi everyone

I‘ve been building a Bleriot XI for the last few months. I’m using a plan by David Boddington of a 60” Bleriot. (**LINK**)

I’ve done some modifications to get closer to the plane Luis Bleriot flew over the Channel in 1909. For example split stabilizer and roof-like strut. Now, when the building is well on way, I’m having some doubts.

Firstly, I decided to use the SC30FS engine. The plan recommended a PAW 29 which is a diesel engine. The SC30FS is probably not a very powerful for a 60” model, but the original ANZANI was probably not that powerful either.

Secondly, it looks like I will have to put quite a lot of lead in the front, to get the CoG right. According to the plan CoG is about 10 cm from the LE of the wing which is 34 cm from LE to TE.

I would welcome any thoughts, ideas or suggestions that could help me along solving these problems.

Here is a video of the landing gear that I think is working quite well smiley

More pictures can be found at my web: http://flugmodel.weebly.com

Regards,
Birgir

Edited By Birgir on 11/10/2015 20:53:02

mightypeesh11/10/2015 21:57:59
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679 forum posts
892 photos

Superb bit of metal work there - she is going to look gorgeous! On the cg front you already know the problem is going to be getting it far enough up front and aside from squeezing electronics and fuel as far forwards as you can you will need to add lead - all I can say is fit and forget as you cannot fly without it! Did you make you own wheels too? looks great

Cheers, Simon

Birgir11/10/2015 22:53:06
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146 forum posts
61 photos

Thanks Simon

I found a thread at rcgroups.com, **LINK** that is very enlightening.

The CoG in my model is at present, i.e. without wings and covering (and lead),  at 48%. So, perhaps I can do with a little less lead than I feared.

B.

P.S Yes, the wheels are my own design http://flugmodel.weebly.com/teinahjoacutel.html blush

Edited By Birgir on 11/10/2015 22:54:24

Keith Simmons12/10/2015 09:28:03
445 forum posts
9 photos

Very interesting the video of the flight, the elevator was down so the cg was rearward so the plane needs a lifting tail . Or it did fly that that? Good luck with your project.

Birgir13/10/2015 18:28:34
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146 forum posts
61 photos

Thank you Keith

Now Luis has shown up. He‘s 56 grams, just behind the CoG angry

luis.jpg

I wonder if it would be clever to give the stabilizer a positive angel of attack?

B

Don Fry13/10/2015 19:08:06
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3820 forum posts
42 photos

No

J D 813/10/2015 19:36:59
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1227 forum posts
74 photos

Hi Birgir, I am slowly restoring an original 1970's Bleriot also from DB. Mine is somewhat larger at 90 inch span.

It was powered by a Webra 61 glow and I have recently obtained one that seems in good order. The next thing is an exhaust as I dont think it flew with one as original. That was ok then but not now.

Early aircraft tend to be somewhat one speed flyers due to the engine power available at the time and lifting tails helped them get airborne. However they can be a problem if you over power or dive the the aircraft to fast when the lifting tail can push the nose down even when you give up elevator a condition called tuck under. Cheers John.

J D 813/10/2015 19:39:13
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1227 forum posts
74 photos

Flambards Bleriot

Birgir14/10/2015 11:58:22
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146 forum posts
61 photos

Hi John

What an exciting project. I agree that a project like that should be enjoyed slowly, like eating a good dinner.

A lot of questions come into my mind. Do you know the weight of the airframe? Do you know if it was flown a lot with the 61 engine? Was it powerful enough?

And last but not least; have you tested where the CoG is?

B

PS. To Donald Fry - I agree

Roy Hill 314/10/2015 13:37:21
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134 forum posts
97 photos

Great project, John. If you have a look at my album, it makes my attempt look rather amateurish! Well done. Roy

Don Fry14/10/2015 14:55:46
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3820 forum posts
42 photos

My guess is that your modern 30 4 stroke won't be much different in power to the old 29 diesel. Prop the engine for power, not speed, i.e., a 4 inch pitch. Assuming it has a thin under cambered wing, all these things only fly straight and level at one speed, increase power and it goes up, at the same speed, decrease power, in goes down at the same speed. Trim it just above the stall and it will land, at the same speed. They can certainly get away with little power. If it were a similar size Junior 60, no on would comment or worry, about a 4st 30 up front. But it marches to a different drum to the modern designs. Just be patient on the take off run, it will take its time to get up. If you need nose lead, you need nose lead, but try to design its location as far forward as it can go. Take a deck chair on a calm day and enjoy relaxing flight. Stated CG sounds about right.

J D 814/10/2015 15:27:15
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1227 forum posts
74 photos

Hi B, Airframe weight with radio but no motor or battery is about 8lbs or 3630 grams.

It flew well with the Webra it being one of the most powerful engines available at the time. It was made by DB and team along another model and a full size ground running replica [ other aircraft both model and full size were built ] for use in filming the 70's TV series "Flambards" It can be seen flying on you tube, Look up Flambards song of Christina.

Model is of the later " two seat " Bleriot XI that was powered by a rotary engine and has a modern type elevator instead of the all moving tips of the channel crossing type.

Have not yet tested for CoG position.

Hi Roy, has yours flown yet? and if so how did it go?

Cheers John.

Edited By john davies 8 on 14/10/2015 15:28:16

Roy Hill 314/10/2015 19:25:31
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134 forum posts
97 photos

Yes John, Mine flew last year, albeit very briefly. It is only 3 channel, no wing-warp etc, therefore it was a bit like flying a barge! She is now a 'Hangar Queen'. Happy landings, Roy

Birgir15/10/2015 13:35:19
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146 forum posts
61 photos

Hi

This is a very interesting discussion and there are many good advice here.

John, if your model, without engine and battery, is 3.63 kilos it could be about 4 kilos dry weight with engine and battery.

My model is 1.55 kilos without wings and covering. If I use the ratio between wingspan.e. 60” to 90” I must keep mine below 2.66 kilos. Hopefully that gives me some margin for lead.

Is this way of thinking logical?

B

Don Fry15/10/2015 15:35:27
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3820 forum posts
42 photos

Birgir, what sort of airfoil has your machine got? The power required to lift weight on an under cambered wing is less than if the wing is flat bottomed..

Birgir15/10/2015 21:18:02
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146 forum posts
61 photos

If I understand this correctly the wing is under cambered.

So this is good news.

wing.jpg

But it might be a problem to cover an under cambered wing.
Does anyone have an experience of that?

B

J D 815/10/2015 22:19:42
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1227 forum posts
74 photos

Yes that is an under cambered wing,on my Bleriot the structure would have been coated with balsalock or similar PVA type glue then the nylon covering applied,once well dry it would have a coat of shrinking dope to tension it. Don't know how it is done with modern coverings.

Don Fry16/10/2015 06:59:05
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3820 forum posts
42 photos

Exactly the same, balsaloc to the spar, attach Solartex to spar, then rest of wing. Only watch for is when you shrink the fabric you do not pull the material off the spar by heating it accidentally. The fix is to pin a piece of heat insulator on the spar, over the fabric, to protect it. I would guess that you will be fine with your 30 FS up front.

Birgir18/10/2015 08:45:56
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146 forum posts
61 photos
Thanks for the advice
Im not sure that I can buy balsaloc in Iceland, but Im in Glasgow for today. Do you know of any modelshop in central Glasgow?
Don Fry18/10/2015 12:35:03
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3820 forum posts
42 photos

Don't know about Glasgow, but an alternative to balsaloc is to paint the spar with ordinary white pva wood glue, and let it dry. It will do the same job when the Solartex s heated onto it. Be aware however that while balsaloc melts every time you reheat it, pva melts and goes back once, on the second reheat, it loses its stickiness.

Edited By Donald Fry on 18/10/2015 12:35:46

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