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Old Feb 22, 2013, 11:40 PM
gonzalo contreras
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Build Log
Super gryphon.

Hi slopers

In few days, june 1, conmemorates in Torrey Pines, the 3rd. annual Katie Martin tribute Fly in. Itīs the spark to beguin a special build log of one emblematic planes of Bob Martin.

I buy some years ago, a pristine fuse of the bird, and a plastic cabin. I havenīt the plans or instruction book,i make a mold of the fuse, but never build one of these, itīs because i havenīt info about the wings. Some days ago, i receive the info about the wings and itīs time to beguin step by step, the Super Gryphon. The first flight is projected to the June 1 in my club. Some pics of the SGryphon in action is mandatory this day.

I have the foams block to cut the wings, maybe some of the readers apport the root and tip airfoils.

Thanks a lot Eric ( Oldscooler ) for the info, and B. Martin too. Itīs my personal contribution to conmemorate the 3rd. Fly in from my country.

Regards.
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Old Feb 24, 2013, 01:17 PM
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Gonzalo,

This is great you are posting a Super Gryphon build log. I believe this is the first. If not, its good to see the SG get an up to date building treatment, I know you will share many details that will be very helpful to new SG builders. Cant wait to see the flying video...Thanks!

Eric
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Old Feb 26, 2013, 03:20 AM
gonzalo contreras
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wings and fuse.

Today i open the holes in the mold to prepare the wet seams service holes, now have 5 coats of wax and tomorrow i apply the PVA and the first coat of fiberglass

The block of foams are cutted too and are ready to receive the root and tip airfoil templates.

The contour of the fuse, have the half of the airfoil of the designer 30 years ago, but, itīs a big airfoil, not to race, itīs for planes with a slowly fly. I decide to change the airfoil for other with better performance. Iīm working on it now.

Cheers.
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Old Feb 27, 2013, 07:03 AM
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Nice work on the molds, I saw OldScooler past to you some info about the wing, for sure the original airfoil is pretty thick but for the wing size and root chord is "normal" in that plane. First at all, that plane need to be treaty like a plank and not like a normal sailplane, that mean if you change the airfoils need to make more changes for example in the fuselage. That plane is a plank and this kind of flying wings has many "singularities", for example you can use reflex airfoills or plank's dedicated airfoils for that task like the MH-32 MH-45, PW-75, E166, E186, SB97FW. The SG has a LOT of positive incidence and if you don't want to put you in the "plank's dark side" is preferable to maintain the original airfoil, if you has the turtle deck you can mount over the fuselage and draw the airfoil. The SG is not like the original Gryphon with simmetrical airfoil and 0 incidence, that allow to put the elevons on reflex position and in case of change the airfoil is a LOT LESS work.

At the end, a plane like the SG with 7,5 oz/Sq.in is not a quick plane is the same wing load of a Gentle Lady. The SG was designed for acro not for speed. If you change the airfoil, for example for a PW-75 or MH-45 (are very quick airfoil above all the PW-75) you need a LOT of work in the fuselage to put the wing saddle to 0 degrees but with that lot of area you don't go more quick unless you fly in a hurricane and full ballasted.

If you are thinking in airfoils like RG-14, RG-15 (SD7012) or similar forget it, this kind of profiles has a very negative Cmo compared with flying wings dedicated airfoils and you can finish with a bad experience.

If you want better performance look for airfoils like the E-166 or E-186 and check the Cmo to be in 0 or almost there and need to rework the fuselage, a plank with flying wing or plank dedicated airfoils have 0 degrees in the wing incidence, otherwise is very prone to tip stall because the lack of pitch stability and no wash out.

Look in the flying wing section some info from Peter Wicks to understand the principles for his airfoils (PW), as well look in the Martin Herpeler's site (MH airfoils) and in nurflugel.es links or write to Eduardo Núņez there or in miliamperios.com .... He only work with flying wings and planks and really knows about it

Keep working
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Old Feb 27, 2013, 10:15 AM
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If you change the wing and whatever else, then it wouldnt be a Super Gryphon anymore would it. Just go design and build a new plane but dont call it a Super Gryphon. My vote Gonzalo is to build it like original, like Bob Martin intended and be happy you have a true SG. This will make him and you very proud.

Eric
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Old Feb 27, 2013, 12:30 PM
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Quote:
Originally Posted by oldscooler View Post
My vote Gonzalo is to build it like original, like Bob Martin intended and be happy you have a true SG. This will make him and you very proud.
Second that vote, not always speed mean better performance some time speed hidden the joy of fly and to have a real jewel.

I make it the Mini KD for an "upgraded" version of the Katie II, now if I build my Katie II kit or prepare the wings and tail feathers for one of the two spares fuselages I will make it as Mr. Martin design, for that reason in your time we talk about the mods in the SR7 and Coyote, both of your planes flew extremely well but at the end you are not fighting with the real "beasts".

I know you and know you has the capabilities and the talent to make a SG, the real one.

Keep working
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Old Feb 27, 2013, 02:12 PM
gonzalo contreras
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An original..

HI Eric

I havenīt a full info about the SG, and only have an aprox of the bird. Itīs a effort to make me one but never have the original dimensions, airfoils or material of the SG. Of course, the only way to have one original is making one from the box. or with all the info about the airfoil, plans, user manual, etc.

If you want any info of the SG in RcGroups or other pages, donīt find nothing about it. Maybe itīs the first build log of the SG in the page, and itīs good for me. You can find enough info of the Gryphon of full wood, but nothing of the SG.

30 years afther the creation of the SG the thecnics of build, materials, and technology are very diferent, and in my build log i apply it in the construction. maybe itīs not an original SG but itīs an approach of it, and will be fly.

Today i apply the PVA and the first coat of fiberglass.

Cheers.
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Old Feb 27, 2013, 04:45 PM
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Gonzalo, I know is very difficult to obtain some extra info for the SG, not much planes were produced and at the end many people just throw it with all the base documents. Do you has the wing's turtle deck (wing fairing) ??? if yes you can cut by the top airfoil mark and put over the fuselage in that way you can has the original airfoil, the airfoil in the SG do not has transitions like in the SR7 and Coyote, is almost impossible to make airfoils transitions in a plank. I was looking and may be do you has this picture but there you can see how the components were located on the SG.

Maybe if you ask for the instruction manual in the flying wing section you can find the info material, basically in the SG the important think is how much is the elevons movements and which is the up position of the elevons to make the reflex.
A plank with +/- the same design as the SG is the Robbe Galaxy but is a more modern design and very large compared with the SG. At the end you can ask to Mr. Martin and be sure about all your doubts.

I don't know, just suggestions. Keep working

PS: LOOK HERE http://www.rcgroups.com/forums/showp...1&postcount=65 maybe NAVINOD can help you with the plans and construction manual before he sale the kit.
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Old Feb 27, 2013, 04:54 PM
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Gonzalo,
I have the SG manual. Do you need it?

Eric
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Old Feb 27, 2013, 05:19 PM
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I don't know how true this is so please double check but IIRC, I was once told the section that was used on the Cygnus (this also used the same Duralene fuselage) was quite similar to E374 (but with the elevons reflexed). Maybe this snippet of info [if true] is of some help..? Hope so.
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Old Feb 27, 2013, 06:03 PM
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YES, many years ago I heard the same info but I don't have any more to contrast ..... in the evening was looking the pictures from Eric and compare with the E374 and looks very similar ....... I don't know, is possible to print out a template for the original E374 and compare it, at least with the medium low part of the airfoil on the fuselage.

Gonzalo, if is the E374 maybe you are very happy.
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Old Feb 27, 2013, 07:13 PM
gonzalo contreras
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little info

Hi all

All the comments and apreciations about the SG confirm the little info on web pages about the SG, and itīs good for me, because itīs a challenge, and need a lot of investigation, deduction and comments of others, and my personal apreciation and experience to make one soar. Itīs not a easy work, ,and i like it.

I havenīt the turtle deck of the fuse, only can draw the lower side of the airfoil, and the other side keep in the space... is pure imagination.

Of course, i considered the E374, itīs one of my favorite airfoils, and itīs used in my SR-7 ( with 2 inch aileron ),

Eric, Thanks a lot for your info, and apreciate the Instruction manual, maybe you can search the mode to send it to me.

thanks again for the interest and comments in the project. Today i apply the first coat of fiberglas, ( i apply a lot of cabosil because the upper side is very intrincated.

Maybe i use the E374 in root and other in the tip, with 0 washout and 0 dihedral

Thanks a lot.

Gonzalo
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Old Feb 27, 2013, 08:06 PM
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Quote:
Originally Posted by gonzalo contrera View Post
Eric, Thanks a lot for your info, and apreciate the Instruction manual, maybe you can search the mode to send it to me.
Gonzalo - check your PM folder.

Eric
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Old Mar 01, 2013, 12:02 PM
gonzalo contreras
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yhe fuse

finally the fuse was made and itīs time to wait 3 or 4 days to complete cure.
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Old Mar 01, 2013, 02:00 PM
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Looking GOOD and nice wet seam finish, there you has the first breeding

Did you test the E-374 on the wing saddle

Another question, why did you a negative mold for the canopy and now you need to do the positive the mold is was done with plaster

I ask you because when I have an original canopy just clean the inner canopy with clear water and soap and after dry put a thin layer of vaseline rubbing with cotton to avoid scratches and fill with the plaster mix, this with the idea to maintain the exact dimensions and a nice finish. Is very easy to unmold the canopy without any damage, then I have the positive mold almost ready for vacuum forming or glassing.

BTW, the wood Gryphon need to be completed, is a very nice plane to fly

Keep working

PS:
Quote:
Originally Posted by gonzalo contrera View Post
... Alfredo you flight this model and view the two diferent types of flight in comparision with the original.
Yeeeesss, I remember when I flew your modified SR-7 after more than 25 years without touch one, is really a good upgrade for the SR-7, GREAT PERFORMANCE !!!
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