HobbyKing.com New Products Flash Sale
Thread Tools
Old Aug 22, 2014, 04:11 PM
Registered User
Joined Dec 2004
162 Posts
MK retracts question


I'm building an Atlanta 60 and the instructions I've seen on the web say to use either MK S60 or SP types. Can anyone tell me what the difference is between the two (Sp vs S60) ?

I've looked around but I cannot find S60 retracts anywhere and the numbering system seems different for the MK retracts I can find at eg Singa Hobby where they have MK 0706 S types vs MK 0704S SP types.

Can anyone tell me which type I need for an Atlanta 60 ? Or is there a cheaper alternative that is a drop in replacement ? I've seen people recommend the Dave Brown retracts but AIUI the nose gear is bulkhead mounted so that's out...


Boo is offline Find More Posts by Boo
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 24, 2014, 05:15 PM
Kevin S. Gribben
Kevin2035's Avatar
Joined Mar 2011
437 Posts
I have done a couple with spring air.......
Kevin2035 is online now Find More Posts by Kevin2035
Reply With Quote
Old Sep 05, 2014, 02:07 AM
Registered User
United States, CA, SF
Joined Sep 2001
159 Posts

On the MK S vs SP retracts: you can use either the S or SP for the precut rails in the wings of the Atlanta. Both will drop straight in. Golden Gate's instructions recommend S for the mains and SP for the nose.

Here's the difference if you're interested: The SP is the original standard version, the S is the newer "lightweight" (and cheaper) version.

They are actually completely different designs: SP pull to extend, while S pushes to extend. The SPs use an aluminum rail with plastic trunion body, the S uses full plastic body. S is much lower profile, making them suitable for thin wings, SPs are quite a bit taller.

In actual use, the SPs give a more solid lock and allow for some play in the pushrods while still maintaining locking integrity. The aluminum rails design gives it more room to lock/unlock. It also pulls to extend, so the rods are at tension when locked gear down, giving it strongest strength. S on the other hand have very little tolerance for play; slight play in the pushrods and the retract will tend to collapse. It pushes to extend, so locking at gear down is maintained by compression of the rods which tends to be weaker.

The downside of SPs are that even though the rails are aluminum, the plastic trunions and square bushings will wear and break over time. IMO the later Hanno designed OK / EZ Supras (not MKs) give easiest locking/setup and durability. The cheap Hobbico mechanical retracts sold by Tower Hobbies are a direct copy of the EZ Supras, just with less precision and cheaper materials. But they are not a drop in fit for the Atlanta wings which which was cutout for the MKs.

Hope that helps!
Huang is offline Find More Posts by Huang
RCG Plus Member
Reply With Quote

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion ParkZone Mosquito Mk VI – Retract & Flap ready, 49” span Plane Chaos Electric Warbirds 3308 Today 01:47 PM
Found Durafly Supermarine Spitfire Mk 24 with Retracts/Flaps/Nav Lights abjets Aircraft - Electric - Airplanes (FS/W) 4 May 14, 2014 03:48 PM
Sold Bnf-pz spitfire mk ix-with retracts-lpu xlrDALLAS Aircraft - Electric - Airplanes (FS/W) 2 Nov 04, 2013 09:16 PM
Sold Bnf-pz spitfire mk ix-with retracts-lpu xlrDALLAS Aircraft - Electric - Airplanes (FS/W) 0 Nov 02, 2013 11:53 AM
Sold Parkzone Spitfire MK IX w/ Retracts - SoCal LPU Only smokeytbear Aircraft - Electric - Airplanes (FS/W) 0 Sep 19, 2013 04:42 PM