Bridi ESCAPE new build. any tricks or tips would be lovely !
02-22-2016, 04:51 AM
#152
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Yes, all of it. It's not rocket science. You just have to be careful with every aspect and keep weight in mind at all times during your planning and build.
Most classics are overbuilt by original design. Wood was cheap and 3/8" & 1/2" planks and blocks abounded. Stressed skin building and internal structure is the order of the day. Take a look at modern ARF designs and construction like those by SebArt and you'll see how lightness is achieved.
That said, the same "box" construction technique can mostly be still used but with a little re-engineering one can shed 1-3 lbs on some of these classics. The Bridi designs are among the easier to accept a diet.
I'll post some drawings later showing a "before and after" Bridi design where I estimate the model will go from the original 11.5 lbs to under 9 lbs (hopefully). It's a classic but a pretty large one (6' fuse) hence the high overall weight. At 9 lbs with light wings it will do quite well on many 61 RE engines but can also easily handle a RE 80-91 vintage engine (OPS, Picco, Rossi, Webra, OS). The fuse is the main component to receive the diet although every piece of wood is lightened wherever practical.
If you take a look at a current Curare build on the RCG Classic forum, you'll see how the redesigned model will have shed 1-1.5 lbs by the time it's finished. Even if one is not diligent with paint, one can loose that weight in the airframe alone sometimes.
David
Most classics are overbuilt by original design. Wood was cheap and 3/8" & 1/2" planks and blocks abounded. Stressed skin building and internal structure is the order of the day. Take a look at modern ARF designs and construction like those by SebArt and you'll see how lightness is achieved.
That said, the same "box" construction technique can mostly be still used but with a little re-engineering one can shed 1-3 lbs on some of these classics. The Bridi designs are among the easier to accept a diet.
I'll post some drawings later showing a "before and after" Bridi design where I estimate the model will go from the original 11.5 lbs to under 9 lbs (hopefully). It's a classic but a pretty large one (6' fuse) hence the high overall weight. At 9 lbs with light wings it will do quite well on many 61 RE engines but can also easily handle a RE 80-91 vintage engine (OPS, Picco, Rossi, Webra, OS). The fuse is the main component to receive the diet although every piece of wood is lightened wherever practical.
If you take a look at a current Curare build on the RCG Classic forum, you'll see how the redesigned model will have shed 1-1.5 lbs by the time it's finished. Even if one is not diligent with paint, one can loose that weight in the airframe alone sometimes.
David
Last edited by doxilia; 02-22-2016 at 04:59 AM.
02-22-2016, 05:02 AM
#153
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Would like to bulls build another escape, tipo, or eu1 next winter. This build was just to get my feet wet many years after not building. Would like to try a scratch build
02-22-2016, 08:47 AM
#154
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For simpler designs like many of the original BHE kits (XLT, Escape, Great Escape, Deception, Kaos', etc.), scratch building is a great option. Not only can one "thin out" all wood but one can also select it. In my experience, the 1980's kits, while wonderful at the time, used extremely dense/heavy wood. A 1/2" thick top kit plank would weigh twice as much as one chosen today and ~4 times more than using a 3/32" skinned top about curved formers.
Mark of CCK is soon to release a re-designed UFO kit which will likely be 1.5-2.0 lbs lighter than the 1980's 8.5 lb UFO's (much like my Mamma Mia which I'll post pictures of later). A model like that with its ~700 squares and a 55AX piped engine would fly very well. A light airframe also gives lots of latitude if a painted finish is desired.
David
Mark of CCK is soon to release a re-designed UFO kit which will likely be 1.5-2.0 lbs lighter than the 1980's 8.5 lb UFO's (much like my Mamma Mia which I'll post pictures of later). A model like that with its ~700 squares and a 55AX piped engine would fly very well. A light airframe also gives lots of latitude if a painted finish is desired.
David
02-22-2016, 06:33 PM
#155
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+1 For David's reply.
Having built several original Bridi wood kits back in the 'day' I will say that the price was certainly good. The wood quality was a bit inconsistent and you could have some pretty heavy wood. Why Joe felt the need to use 3/32 sheeting for the horizontal surfaces which was overkill even back then, but the airplanes built stock from his kits were pretty rugged. A fellow club member flew his UFO through another pattern ship which was destroyed; the UFO had a relatively small gash in the leading edge of one wing. Bridi fuselages were basically balsa baseball bats, but very easy to mass produce. I scratch built Deceptions and Dirty Birdies mostly sticking to the original plans (1/16" sheeting for the horizontal surfaces and contest balsa everywhere) and built a stock, fully painted Deception at a bit less than 8.5 pounds which fly great with a YS 60FR.
The quality of the current Bridi/Blue Jay kits is much better than the originals (IMHO) and they should build lighter, though not as light as the new redesigns.
Having built several original Bridi wood kits back in the 'day' I will say that the price was certainly good. The wood quality was a bit inconsistent and you could have some pretty heavy wood. Why Joe felt the need to use 3/32 sheeting for the horizontal surfaces which was overkill even back then, but the airplanes built stock from his kits were pretty rugged. A fellow club member flew his UFO through another pattern ship which was destroyed; the UFO had a relatively small gash in the leading edge of one wing. Bridi fuselages were basically balsa baseball bats, but very easy to mass produce. I scratch built Deceptions and Dirty Birdies mostly sticking to the original plans (1/16" sheeting for the horizontal surfaces and contest balsa everywhere) and built a stock, fully painted Deception at a bit less than 8.5 pounds which fly great with a YS 60FR.
The quality of the current Bridi/Blue Jay kits is much better than the originals (IMHO) and they should build lighter, though not as light as the new redesigns.
02-23-2016, 01:03 PM
#157
Wood selelction is always the difference in a light vs heavy model.
4 to 6 pound 1/16th on foam wings and tails keeps them at a great weight if one knows how to pick the wood. Straight, tight grain is used only so the glue used to bond it to the foam is not saturated into open grain and punk wood is the worst at doing this. Sealing grain with hair spray or sprayed dope is a popular technique. Read some threads from Kevin Gribben on sheeting the wings and see how he avoids heavy final weights by not using leading edge stock, etc.
Fuselages can be built very light by following the plans on the old designs and yet selecting 6lbs wood only and not accepting anything else. One often starts a lightweight build but then starts to accept one piece, then another of 8 lbs wood and then a 12 can't hurt just here, and then the whole structure ends up much heavier then planned, the builder wondering what happened. Be honest, do not accept a piece of wood that is more than 6 lbs density.
Tails typically weigh an effective ton when finished because the builder doesn't realize the moment arm of where it is mounted makes it the most critical structure of all weight wise. The stab, elevator, hinges, horns, cover and paint all cannot weigh more than say a theoretical 4 oz for a typical Classic Pattern model if you are hoping for a theoretical sub 8 pound model. The fin and rudder should weigh a theoretical 2 1/2 oz with hinges, horn, absolutely max, and these are hard numbers. One should just throw it away and start a new one if they are more than this. The reason is that if you build a theoretical half pound tail and glue it on and slather a big fillet in there you are going to have to add three times that on the nose to balance that weight and many cannot get them to balance on hardware, engine and tank alone. (I'm in the midst of building glass and foam kits so my component weights are becoming known but not hard weights so I used theoretical for an example.) Because of the tail's small size, one may think they are light enough, only the scale can give the true answer.
Next is finish. Film made models so much lighter by not piling on the pounds of the variable of paint, primer and glass. Not all painters are equal! On a balsa model a guy can thoroughly fuel proof his model with a layer of .5 oz glass on the nose back to the leading edge of the wing and then just film the whole of a typical Bridi design and it'll last forever with good sealing and maintenance. The weight will be very low and repeatable if light density balsa is used and use of film for covering will always be constant.
Reducing the sizes of the wood sides and top and bottom blocks is only a weight savings if the proper densities are used here again. Strict discipline in choosing wood, by weighing it at the hobby shop and then once the collection is at home weighing it before use is the only way to know you are building to weight. If one reduces a 1/2 inch side to 3/8's on a Bridi design and then uses a 8 lbs piece instead of a 6 lbs density piece, it weighs more. No savings.
Getting a Sig balsa wood density chart and translating the numbers to your favorite unit of measure and making a chart for the typical wood sizes in 4 to 8 pound density and then using that chart, with the scale you brought to the store, to buy your wood is very helpful. Well, it's the only way.
I'm kinda new to building R/C models but transfer my C/L Stunt building discipline from there to R/C as much as possible and see the ARF's I've bought being well built and lightweight in comparison to the homebuilts I've seen and actually bought from the era or even some modern builds of my friends because of the wood density and heavy finish problems and variables on the building board.
I've got a 10 1/2 pound Tiporare I fly regularly and it is balanced well so does OK, but just think of how it would fly 2 pounds lighter, or three! For those of you that have seen it, how many wheels has it spat off on take off and landings, and I can only imagine how much slower I could approach with a lighter model!
I have an ARF Tower Kaos 40 which has an OS 46 AX that weighs 5 pounds with stock muffler and heavy APC props and old fashioned Dubro Lo-Bounce chromies and it has been the best flying model I've ever had because of it's proper weight, it having been constructed commercially well weight wise. As I see guys fly models at the field I see the benefits of light weight models. I also see old pros flying light weight ARFs, this means to me that these are as close to on weight as they can build themselves. Emulate the ARFs is a good idea in many instances.
I'm trying to build sub 8 pound kits from RCAiir right now and wil be able to create a component chart for myself soon after completing a couple of models. The P7 and P8 and Mach 1 should be typical enough size wise to have a good idea. Now if I can just get myself to the building board.
Chris...
P.S. This C/L Stunt model is built of a foam wing triple cored and sheeted with 1/16th with leading and trailing edge stock and fairly large, hollowed wingtips with a weight box on the outboard and an adjustable leadout guide on the inboard wing. It's total area is 770 sq inches with a 60 inch span.
The tail is biult up of all sheet balsa and completely sheeted, the tiny fin is sheet.
The fuse is all balsa, 1/8th sides, 1/32nd ply doublers to the trailing edge, balsa blocks on top and bottom hollowed to less than 1/8th and the motor mounts are 1/2x3/8th's rock maple.
The typical component total for the engine/pipe/prop/spinner/tank/gear/wheels/pants/bellcranks/horns and hinges is 20 oz on average for this size model.
It has a Nelson .61 with a Precision Aero CF pipe and an Eather CF 13x3 3/4" prop, a Tru Turn 1 3/4" spinner and a homemade 7 oz tin Uniflow tank, CF wheelpants on 1/8 piano wire struts with DB foamy wheels and is painted with DuPont acrylic Lacquer (those were the days). It has about 500 flights on it and is 22 years old.
The total weight of this model is 64 oz. It's a lot of model, with a lot of hardware yet with ight weight wood and proper component weights it's right on target for it's size. I can only believe the same is the right way to go on the R/C Classic Pattern ships we're building.
4 to 6 pound 1/16th on foam wings and tails keeps them at a great weight if one knows how to pick the wood. Straight, tight grain is used only so the glue used to bond it to the foam is not saturated into open grain and punk wood is the worst at doing this. Sealing grain with hair spray or sprayed dope is a popular technique. Read some threads from Kevin Gribben on sheeting the wings and see how he avoids heavy final weights by not using leading edge stock, etc.
Fuselages can be built very light by following the plans on the old designs and yet selecting 6lbs wood only and not accepting anything else. One often starts a lightweight build but then starts to accept one piece, then another of 8 lbs wood and then a 12 can't hurt just here, and then the whole structure ends up much heavier then planned, the builder wondering what happened. Be honest, do not accept a piece of wood that is more than 6 lbs density.
Tails typically weigh an effective ton when finished because the builder doesn't realize the moment arm of where it is mounted makes it the most critical structure of all weight wise. The stab, elevator, hinges, horns, cover and paint all cannot weigh more than say a theoretical 4 oz for a typical Classic Pattern model if you are hoping for a theoretical sub 8 pound model. The fin and rudder should weigh a theoretical 2 1/2 oz with hinges, horn, absolutely max, and these are hard numbers. One should just throw it away and start a new one if they are more than this. The reason is that if you build a theoretical half pound tail and glue it on and slather a big fillet in there you are going to have to add three times that on the nose to balance that weight and many cannot get them to balance on hardware, engine and tank alone. (I'm in the midst of building glass and foam kits so my component weights are becoming known but not hard weights so I used theoretical for an example.) Because of the tail's small size, one may think they are light enough, only the scale can give the true answer.
Next is finish. Film made models so much lighter by not piling on the pounds of the variable of paint, primer and glass. Not all painters are equal! On a balsa model a guy can thoroughly fuel proof his model with a layer of .5 oz glass on the nose back to the leading edge of the wing and then just film the whole of a typical Bridi design and it'll last forever with good sealing and maintenance. The weight will be very low and repeatable if light density balsa is used and use of film for covering will always be constant.
Reducing the sizes of the wood sides and top and bottom blocks is only a weight savings if the proper densities are used here again. Strict discipline in choosing wood, by weighing it at the hobby shop and then once the collection is at home weighing it before use is the only way to know you are building to weight. If one reduces a 1/2 inch side to 3/8's on a Bridi design and then uses a 8 lbs piece instead of a 6 lbs density piece, it weighs more. No savings.
Getting a Sig balsa wood density chart and translating the numbers to your favorite unit of measure and making a chart for the typical wood sizes in 4 to 8 pound density and then using that chart, with the scale you brought to the store, to buy your wood is very helpful. Well, it's the only way.
I'm kinda new to building R/C models but transfer my C/L Stunt building discipline from there to R/C as much as possible and see the ARF's I've bought being well built and lightweight in comparison to the homebuilts I've seen and actually bought from the era or even some modern builds of my friends because of the wood density and heavy finish problems and variables on the building board.
I've got a 10 1/2 pound Tiporare I fly regularly and it is balanced well so does OK, but just think of how it would fly 2 pounds lighter, or three! For those of you that have seen it, how many wheels has it spat off on take off and landings, and I can only imagine how much slower I could approach with a lighter model!
I have an ARF Tower Kaos 40 which has an OS 46 AX that weighs 5 pounds with stock muffler and heavy APC props and old fashioned Dubro Lo-Bounce chromies and it has been the best flying model I've ever had because of it's proper weight, it having been constructed commercially well weight wise. As I see guys fly models at the field I see the benefits of light weight models. I also see old pros flying light weight ARFs, this means to me that these are as close to on weight as they can build themselves. Emulate the ARFs is a good idea in many instances.
I'm trying to build sub 8 pound kits from RCAiir right now and wil be able to create a component chart for myself soon after completing a couple of models. The P7 and P8 and Mach 1 should be typical enough size wise to have a good idea. Now if I can just get myself to the building board.
Chris...
P.S. This C/L Stunt model is built of a foam wing triple cored and sheeted with 1/16th with leading and trailing edge stock and fairly large, hollowed wingtips with a weight box on the outboard and an adjustable leadout guide on the inboard wing. It's total area is 770 sq inches with a 60 inch span.
The tail is biult up of all sheet balsa and completely sheeted, the tiny fin is sheet.
The fuse is all balsa, 1/8th sides, 1/32nd ply doublers to the trailing edge, balsa blocks on top and bottom hollowed to less than 1/8th and the motor mounts are 1/2x3/8th's rock maple.
The typical component total for the engine/pipe/prop/spinner/tank/gear/wheels/pants/bellcranks/horns and hinges is 20 oz on average for this size model.
It has a Nelson .61 with a Precision Aero CF pipe and an Eather CF 13x3 3/4" prop, a Tru Turn 1 3/4" spinner and a homemade 7 oz tin Uniflow tank, CF wheelpants on 1/8 piano wire struts with DB foamy wheels and is painted with DuPont acrylic Lacquer (those were the days). It has about 500 flights on it and is 22 years old.
The total weight of this model is 64 oz. It's a lot of model, with a lot of hardware yet with ight weight wood and proper component weights it's right on target for it's size. I can only believe the same is the right way to go on the R/C Classic Pattern ships we're building.
Last edited by stuntflyr; 02-23-2016 at 01:33 PM.
02-24-2016, 07:15 AM
#158
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All classics were were built like brick you know whats. They absorbed engine vibes since soft mounting had not been invented yet for toy planes. But they were overbuilt nevertheless.
Regardless, a screaming 60 might put out 3 horses while today's 1.60-1.85 cuin engines put out around 4 horses, yet still use 1/8" ply firewalls or balsa and carbon composites which are lighter than the plywood.
Removal of of the wing bay material is a good start. But you might want to remove the tops too. You can open bays in the fuse and stab also . Simply cover with light polyspan and paint. All total you might remove 12-16 ounces on this particular plane
I use a scale that weighs in grams and weigh every piece I put into a plane. You might consider getting one of these before starting your next plane. The real weight savings happen when making better choices from the start and understanding that practically every piece can be thinner. Thinner means you sacrifice some unnecessary strength which is a no brainer.
02-24-2016, 07:36 AM
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I understand your points on how to build my next plane. This was a kit and I wanted to build it. I didn't want to scratch a new plane yet. Yes I'm using prepainted fabric which is almost the same weight as the ultracote film. I'm only going to base and clear the orange this time. I got from 13 3/4 to 9 1/4 lbs so I'll be mid 10s by the time I'm covered. That's ok for me for this plane. All my ballast is gone. I look foreword to building another better next winter. My summer project I'll practice going light on might be a enlarged hot kanary with speed wings. I love my top flite kit version. I'm just getting back into building after many years
03-18-2016, 07:34 AM
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got it recovered in solartex and lightly painted. came out to little under 11lbs fully balanced and ready to go. lost 3 lbs. I'm happy with that. itll fly fine. ill try to build something lighter next winter when I have time to scratch build and redesign. now just waiting for weather to go fly
05-23-2016, 07:37 AM
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got a dozen flights on it so far. super fast. faster then I want. my drop pitch alittle. very smooth though ! lands fast but easy and floats for miles. been in touch with novarossi, my big carb engine is not sucking fuel as needed. tried a new carb and same. so now we are installing a backplate pump. also have a smaller carb to try also. runs like mad but surges abit once in the air
Last edited by nappyroots2182; 05-23-2016 at 03:23 PM.
05-23-2016, 04:38 PM
#163
That's a great looking model. Very nicely done. Dramatic weight loss. Love the look, glad to hear it's flying well. Good luck with the engine run and trimming.
Chris...
Chris...
06-27-2016, 08:05 AM
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engine fried. being rebuilt and got a custom carb to try and get some fuel to it better. this has been one cursed plane. still beating me up. but should be back in the air quick
