Mlg 238-246
08-30-2002, 02:58 AM
Tom Saccio | Mlg 238-246
After I don't know how many hours I think I've finally completed the main landing gear. The nose gear is also completed but not installed. I'm waiting to paint the compartments before reinstalling it. As usual some of the mesurements were wrong and after speaking to other builders, I gather they,ve been wrong for some time. I don't know why, when these mistakes are realized, The manual can't be updated so that the next builder doesn't have to waste so much time trying to dear with errors that most of us have had to deal with. I'm real happy that this faze of the build process is mostly completed. Although I won't be completely sure until everything is pumped up and functioning. Tom Saccio
239 - Posted by John Ricciotti on August 31, 2002 at 09:03:34:
In Reply to: MLG posted by Tom Saccio on August 30, 2002 at 21:36:21:
Tom, Thanks for sharing the difficulties you had in the MLG area. I am presently finishing the reinforcements in that area and I will be fitting everything next. Could you possibly tell me which measurements were wrong for you. That might save me a lot of head scratching. Thanks, John
240 - Posted by Brent Carlson on September 03, 2002 at 13:03:21:
In Reply to: Re: MLG posted by John Ricciotti on August 31, 2002 at 09:03:34:
Thanks for the post guys. Interesting, but I too spent my Labor Day holidays fitting the main gear legs. Lest I be crucified, let me first say that in my career, I have written dozens of manuals and work instructions, and I know how difficult it is to make them clear. I also know that no matter how good they are, they are subject to interpretation by several people, and we all see things in widely varying and different ways. I think that, for the kit plane industry, the Seawind manuals are pretty typical, and in places, pretty good. Having said all that, the section on the MLG and it’s associated reinforcements inside the hull are especially dismal and need complete revision. Here are my findings so far. Since I have only just now located the main gear legs and not yet installed the retract arms, I’m sure I have a lot more to learn. First, check the revisions in the MLG section. Mine are as follows: Page 1: April 1992 Page1A: June 1994 Page 2:August 1993 Page 3: April 1992 Page 4: October 1996 Page 5 & 6: August 1995 Page 10: December 1997 Page 15: December 1999 You get the idea here (also, much of this is repeated with a slightly different slant in section 8). Also, make sure to read the builder letter dated October 21, 1996. I used the dimensions shown on page 4 (which includes the suggestion from the above builder letter to lower the gear by ½ inch to better accommodate the upper connection point). I located the hole on the aft face of the gear pocket as shown, then, I varied the position of the hole in the forward face to get the gear leg aligned. I started with 1/8” holes, and then if slight repositioning was required, I went up one or two drill sizes and re-drilled the location, and the wooden dowel, to accommodate the new drill size. This all seemed to work pretty well. OK, the next things are the various reinforcements in the hull. First of all, the angle supports shown on page 18 should actually be dry fitted first, not last. They interfere with the MLG aft floor bulkhead shown on page 16. If the manual is followed for their length, they actually extend under the bulkhead two or three inches. After talking with Mike Bowes, I decided to leave them as long as possible because they are tying the hull together across the step. In addition to bonding them as shown in the manual, I also put a lay-up across the flange to the aft bottom, then, I cut the bulkhead to fit over the top of these flanges and lay-ups ensuring a good seal. Next, the under-floor transverse channel supports shown on page 13 and 15 are not properly described in the manual. In fact, the aft channel support is shown on page 15, but never even mentioned, let alone installed, in the text (at least that I can find). Also, the pictures and description are not very clear about the fact the these channels should be trimmed at the floor beam flange, so that they are flush with the top of the floor beams and fit tightly against the bottom of the aft floor. I also believe that the flanges of the aft channel support face aft, as do the flanges on the adjacent bulkhead sections. I also had to modify templates 5.1 and 5.2 some to fit my hull more precisely. This wasn’t a big deal. Just make sure you check them for a good fit before cutting up all that 7781. I hope this helps some. I would also like to hear which of the dimensions Tom found to be in error. I will be talking to Tom about this at the upcoming splash-in. Thanks guys. Best, Brent (SNA Kit#71)
241 - Posted by Brent Carlson on September 03, 2002 at 14:15:53:
In Reply to: Re: MLG posted by Brent Carlson on September 03, 2002 at 13:03:21:
Oh yes, while at Oshkosh I talked to Paul Marshall (and Dick) briefly about the builder manuals. Paul is in the process of doing some revising and updating. After returning from Oshkosh, I had Paul send me some instructions he has prepared for installing the vents in the forward ridge of the tail. They are excellent. I’m sure Paul will be receptive to some constructive feedback from the builder community. Revising the manuals is a huge task and will take considerable time and dedication. We’re pulling for you Paul. Great Job! Best, Brent (SNA Kit#71)
242 - Posted by scott devlin on September 04, 2002 at 14:57:55:
In Reply to: Re: MLG posted by Brent Carlson on September 03, 2002 at 14:15:53:
Hey guys Mike did a nice post some time back on mlg geometry. You bring up an important though. First read the manual till you have it memorized and cross referenced. Then think like an engineer. visualze the loads that the layups transfer from one place to another. It will become obvious where everything goes. (At least it will after you have done it!) What the manual means to convey is not complicated. The loads dictate where the layups go. In my personal experience the gear pockets were previously installed tilted. this put the main tire thru the aft spar on retraction (potentialy). If you intend to use larger tires the spacing of the tire between the aft and front spar is critical. This, not the dimensions given in the manual provide your pivot point location. The same applies to all other points. The given dimensions are a starting point only. I would gladly post all my dimensions to the centimeter but Seawinds are like trees, no two are the same under .5 an inch. I installed my gear pockets using two 4 foot straight edges for jigs and cut to fit inside the hull. this helped keep everything in line. this is necesary to transfer the opposing loads on plane and prevent collapse. gotta go to work scott
243 - Posted by Fred Lohr on September 04, 2002 at 16:16:45:
In Reply to: Re: MLG posted by scott devlin on September 04, 2002 at 14:57:55:
I has been some time since I fitted my main gear but I will now put in my two cents. The trial and error method of aligning things worked the best. To do this most easily, It helps to have a temporary main gear axle. I used 5/8 (or was it 1/2") threaded rod available at the hardware store. A female threaded coupling with about 3 inches of rod sticking out each side works as your temporary axle. You have to grind one end to a point or better, just drill the center of the rod and insert a piece of smooth 1/4 or 1/8 rod ground to a point. The main gear legs are assembled and the temporary axle located in about the right place. With a wrench/pliers, you can turn the rods outward until they impact the sides of the gear pockets. Friction is enough for the first trial swings of the main gear legs only. Then drill a small 1/4 in hole on the aft side pocket, expand your temporary axle. Check it a few times, drill 1/4 in hole front pocket, check it. The straight edge inside is a good idea. Put the wheels on, cut the wings skin, Check it, assemble rest of gear.etc. If you need to move the 1/4 hole, no problem. The axle slightly lower than reccomended sounds right so the pivot point above clears the interior skin. Now's the time to consider whether larger tires will clear that aft spar. The thing is, you really don't have to commit to that 3/4 (or was it 5/8) hole in the gear pockets for main axle bushing until you have everything fitting OK. Ream that up to size last. When done, give your "temporary axles" to another builder. Hope this helps
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245 - Posted by Tom Saccio on September 04, 2002 at 16:42:43:
In Reply to: MLG posted by Tom Saccio on August 30, 2002 at 21:36:21:
All this information helps now but it's too late. I've already installed the gear. I took the manual literally and did it step by step until I found out the measurements were not exact. I had to refill the holes I drilled incorectly twice. After drilling them I found that the retract arms were not aligned in the up position. This made the actuators misaligned and they did not line up with the support bracket that they attach too. I will not take the manual as fact ever again. Thanks for all your imput guys. Hope to see you all at the Splash-in.
246 - Posted by JMB on September 04, 2002 at 22:14:42:
In Reply to: MLG posted by Tom Saccio on August 30, 2002 at 21:36:21:
See posting number 91. Tricks to make your main gear work properly developed in the course of rigging 14 Seawinds. Some, or all of these, may be required on yours. Also, elsewhere on this site, are the ISPA Newsletters that I had a hand in writing over a 2 year period. Those letters are full of useful stuff. Do you ever look at them anymore? One of the articles in those letters gives credit to builder Bob Darrah and is about a full page on the subject of rigging main gear. The procedure and the oleo jig described in that article has been used by us to rig every Seawind without reference to the building manual. Required reading for any builder about to do this very difficult and important step. I think that says it all. Thanks again, Bob. Anyone who wants it and can't find it, advise, and I will bring copies to Manteo to hand out. Mike N369JB
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