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May 22, 2016, 11:04 PM
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I might be in over my head with this. 161 inch ws Convair R3Y-1 Tradewind


So I haven't gotten close to starting this project (I only inserted some 3 views into Rhino). I was thinking about using Ivan P / Pat Tritle type constuction with balsa sheeting and glassing. I'm looking for a top speed of about 60-70 mph, but I have only a loose guestimate of the flying weight of over 25 lbs. I guess that I mostly need help with estimating the flying weight. I'm also curious about what size balsa (Or Basswood) sticks are used in the Ivan Pettigrew Martin Mars wing spar and fuselage box frame so that I can have a clearer frame of refrence.

Btw most of my previous builds were pat tritle kits and one RBC P80
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May 22, 2016, 11:24 PM
Ken Stuhr
You might consider building an Ivan flying boat just to get an idea of how to build lightly.

The wing on the Tradewind is very small relatively and will end up being very heavily loaded if you don't take every step to BUILD LIGHT. Sure, you can load enuf batteries and motors in to get off the water, maybe at that 60-70MPH number you mention, but it won't be very representative. There are better choices for aerobatics.

At the very least, get the plans for an Ivan plane and give them a good study! None of his planes approached 25 pounds. Good luck.
May 22, 2016, 11:51 PM
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Quote:
Originally Posted by flyboyken
You might consider building an Ivan flying boat just to get an idea of how to build lightly.

The wing on the Tradewind is very small relatively and will end up being very heavily loaded if you don't take every step to BUILD LIGHT. Sure, you can load enuf batteries and motors in to get off the water, maybe at that 60-70MPH number you mention, but it won't be very representative. There are better choices for aerobatics.

At the very least, get the plans for an Ivan plane and give them a good study! None of his planes approached 25 pounds. Good luck.
Ok, I might have been exagerating (in my mind) how heavy the plane would be (worst case senario). I guess I should aim for about under 20 lbs. Ivans's Beverly and Martin Mars weighed about 10 lbs for a 120 inch wing. The Tradewind's wing would be 160, almost 25% longer (but as you mentioned, it has a high aspect ratio). But I'm looking for about twice the speed of the Ivan Martin Mars because it is the real Tradewind's top speed is around 400 mph while the Mars is about 200, and I'm planning to do the R3Y in 1:11th scale, and the Mars is almost 1/2 that scale. My main goal is to create a scale speed that will match my other 1:11th scale planes. I suppose that I don't have to glass the whole plane, mostly the area that contacts the water.
May 23, 2016, 04:47 PM
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Airboatflyingshp's Avatar
Hi minimicrorc Ivans Sealand 480 probably has the finest wing of his semi scale models ..you might want to stretch it a little on this?............... but as for glassing yes only if you have to ,, look at Sopwith mikes Saro Princess or Barts Short C class ........... go through the BIMBOS thread and The Ivan thread set up by Luke... above all think like you are building a rubber powered stick balsa and very thin sheet covered model at the core.. or balsa reinforced air..
I say look at Sopwith mikes Princess and his web site as it has an even more complex multi curve hull...On his web site you will see the Saro Duchess fuselage he started .. you will see what I mean about the stick built core.

A great subject but you might want to consider also incorporating some of the originals lift enhancing devices... again see where Bart83 has Gone with his latest Dornier..
The Convair corp. built a very large scale model running some very non scale weed whacker motors it features in a PDF file.. I think theres a link in the waterplanes sticky ..but it might be too big to load here.
Last edited by Airboatflyingshp; May 23, 2016 at 04:57 PM.
May 23, 2016, 04:48 PM
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Airboatflyingshp's Avatar
I'm watching with interest
May 24, 2016, 01:58 AM
71% of the world is runway . .
Bart83's Avatar
Sounds like my kind of guy ! Ivan , Flyingboats , Rhino , it just doesnt get any better

Very nice subject en if you keep it light this is a perfect airplane. Small wing but long nose so you can get away with a very very small battery to get the cg right.
I suggest you purchase a set of plans from Ivan just to get familiar with his construction techniques.
For this build you will have to make concessions in scale to accomodate the boxframe fuselage.
My first design was an Empire flyingboat in an Ivan style construction. This also was my first effort in Rhino.
Will follow this thread with great interest.

Have fun !

Bart

May 24, 2016, 07:44 AM
Slip the surly bonds...
Sopwith Mike's Avatar
Hi minimicrorc,

Interesting project! I estimate you will have about 23 sq ft of wing area (13ft span x 2 ft root chord, guesstimate) so for a wing loading of 15 oz/sq ft, your plane could weigh about 20 lbs. I think this is achievable although you will have to be very weight concious, as all the posters have said. It's probably easier to make a realistic flying model at this size than at say 6ft span, where the wing would be just too small relative to the likely weight of the model. The heaviest component is the power wire...but very good luck with the model.

My only other comment is that even though the full size could reach 400 mph, the most enjoyment you will get from the plane is flying relatively slowly. 15 oz/sq ft will be fine for relaxed flying.

Mike
May 24, 2016, 10:54 AM
Registered User
Martin Irvine's Avatar
Don't forget the scaling effect on the wing loading. As the giant scale guys will attest, as the planes get larger, the wing loading can go up considerably and still fell like a much lighter loaded, but smaller, airplane.

I have a 10sq.ft 1/4 scale Nieuoport 17 with a 22oz./sq.ft wing loading that flies slowly and easily, much more like a 16 oz. loading on a 1/6 scale version.

A 12-13ft fuselage is not going to be light! Have a look at
http://www.ef-uk.net/data/wcl.htm
and play around. I'd guess that 32oz./sq.ft would be trivial for a 160" model - more like a glider.

What power are you shooting for?

Martin
May 24, 2016, 12:21 PM
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Thread OP
Quote:
Originally Posted by Martin Irvine
Don't forget the scaling effect on the wing loading. As the giant scale guys will attest, as the planes get larger, the wing loading can go up considerably and still fell like a much lighter loaded, but smaller, airplane.

I have a 10sq.ft 1/4 scale Nieuoport 17 with a 22oz./sq.ft wing loading that flies slowly and easily, much more like a 16 oz. loading on a 1/6 scale version.

A 12-13ft fuselage is not going to be light! Have a look at
http://www.ef-uk.net/data/wcl.htm
and play around. I'd guess that 32oz./sq.ft would be trivial for a 160" model - more like a glider.

What power are you shooting for?

Martin
I was thinking about the wingloading in a similar way. I do not want the plane to be too light because I would fly on the ocean when it is calm. The winds in the area tend to be from 10-15 mph, and a lighly loaded plane would not handle those conditions very well. The power system depends on the planned flying weight (which I unsure about) but I'm looked for a 1:1 thrust to weight ratio and a static pitch prop speed of about 55 mph. I'm not going to be flying at the speed for most of the flight but it is nice to have.
May 24, 2016, 12:26 PM
Registered User
Thread OP
Quote:
Originally Posted by Airboatflyingshp
Hi minimicrorc Ivans Sealand 480 probably has the finest wing of his semi scale models ..you might want to stretch it a little on this?............... but as for glassing yes only if you have to ,, look at Sopwith mikes Saro Princess or Barts Short C class ........... go through the BIMBOS thread and The Ivan thread set up by Luke... above all think like you are building a rubber powered stick balsa and very thin sheet covered model at the core.. or balsa reinforced air..
I say look at Sopwith mikes Princess and his web site as it has an even more complex multi curve hull...On his web site you will see the Saro Duchess fuselage he started .. you will see what I mean about the stick built core.

A great subject but you might want to consider also incorporating some of the originals lift enhancing devices... again see where Bart83 has Gone with his latest Dornier..
The Convair corp. built a very large scale model running some very non scale weed whacker motors it features in a PDF file.. I think theres a link in the waterplanes sticky ..but it might be too big to load here.
Alright, I am thinking of building his 480 Sealand,a and I do plan to incoperate flaps at the scale outline. I'm thinkng 40 degrees for the max throw.
May 24, 2016, 12:29 PM
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Thread OP
I will also do retractable landing gear so that I am not limited to flying off of water or long soft grass. I am going to do a bicycle landing gear setup similar to the B-47 with the outer smaller gear retracting into the wing floats
Last edited by minimicrorc; May 24, 2016 at 01:31 PM. Reason: spelling
May 24, 2016, 01:56 PM
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Thread OP
Thanks Matin Irvine for the link to the wcl (wing cubic loading) calculator. So the ivan 1/12 catalina 600 has a wcl of 5.1 while the full size pby catalina has a wcl of 16. The ratio of full size wcl to the 1/12 scale model wcl is 3.13. The wcl of the full size Trade wind at 100,000 lbs is 19.8. 19.8 divided by 3.13 give a wcl of the 1/11 tradewind of 6.3. I should be able to attain this number at 24lbs. So my goal is to complete the plane at 22-23 lbs. I can always add more batteries and increace cell count if I want a higher wing loading.
May 24, 2016, 03:59 PM
Registered User
Airboatflyingshp's Avatar
Ive just been chatting to David Plummer whose built a 7 foot span Boeing Searanger twin that has a proportionately longer but high aspect ratio wing he came in with finish wt of 11.5 pounds . ..he hasn't had a chance to test it yet.

Every model of this plane Ive seen that has struggled to get airborn and there's been a few is because of too higher wing loading/AUW .... aim to fly from ROW keep it as light as you can initially -waters sticky stuff and doesn't always want to behave scale.

The centerline UC and outriggers is a good way to go given a V hull form.. there are several large 10ft sunderlands and some others that use it , would you use the floats to house the outrigger wheels this aircraft has very robust v float mounts?
If you did the UC as plug in removable units you could save wt and simplify things a lot when it came to the tricky ROW bit .. just fit flush sealed covers, I think that's how one giant spruce goose was done but I will check.

Do you want any extra images or links pertaining to this version adding ..I assume you've already visited SeawingsUK ?

Clive
Last edited by Airboatflyingshp; May 24, 2016 at 06:18 PM.
May 26, 2016, 05:05 PM
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Airboatflyingshp's Avatar
link to the PDF on the Navy's flying midgets https://www.rcgroups.com/forums/show...&postcount=152
May 26, 2016, 05:47 PM
Registered User
Thread OP
Quote:
Originally Posted by Airboatflyingshp
link to the PDF on the Navy's flying midgets https://www.rcgroups.com/forums/show...&postcount=152
Very intesting read. Their planes were much heavier 90 lbs at the lightest


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