Bleriot XI

[Birgir]

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



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

Regards,
Birgir

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

[mightypeesh]

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

[Birgir]

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

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

[Keith Simmons]

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.

[Birgir]

Thank you Keith

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

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

B

[Don Fry]

No

[J D 8 - Moderator]

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 8 - Moderator]

[Birgir]

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 3]

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

[Don Fry]

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 8 - Moderator]

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 3]

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

[Birgir]

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 Fry]

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..

[Birgir]

If I understand this correctly the wing is under cambered.

So this is good news.

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

B

[J D 8 - Moderator]

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 Fry]

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.

[Birgir]

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 Fry]

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

[Birgir]

Thanks for the advice.

The building is coming along nicely, enjoying every step of the way

http://flugmodel.weebly.com/bleriot-xi.html

Birgir

Edited By Birgir on 30/10/2015 19:45:45

Edited By Birgir on 30/10/2015 19:46:48

[Birgir]

Dear friends

Browsing the net about Bleriot XI rc model, I came across a text on Mick Reeves webpage that describes a 1/3 scale Bleriot XI model.

The main facts from that text is:

• Wingspan: 115”
• Weight of nose ballast: 4 kg
• Total weight of model: 14 kg
• The model flew.

My question is:
Can I downsize this information to my 60” wingspan model using the rate 60/115 assuming that my model could take 52% of the weight i.e. 7,3 kg (incl. 2 kg of ballast)?

At present it looks like my model will be 2.6 kg incl. 0.55 kg of ballast, a lot less than the calculation above.

Birgir

[Don Fry]

Stick to your weight projections. The larger plane has about four times the wing area, and should be about four times the weight. And it is.

[Birgir]

Thanks Donald, of course, it is the square area that counts

[kc]

Last month John mentioned his plane was from the Flambards TV series. The Flambard series is available on DVD if you want to see it all.

In my opinion Wings ( the BBC version ) was even better and of course also featured Boddos models. twice the price but possibly worth it. It's here

A WW1 airfield still exists in fairly original form at Stow Maries in south east Essex. It cannot be a coincidence that this is called Flambirds farm.