| Author |
Message |
Chris Gudgel (Yodelbus) (65.200.143.73)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 24, 2004 - 4:21 pm: | |
We are looking at a product put out by farmtek that we were thinking of using on the sides of our MC8. It's called poly tech. I am not entirely sure what it is made of, but we can get it in 50' rolls that are 60" wide, and 1/8th" thick which will be a nearly perfect fit from the bottom trim piece to the drip rail over the windows. Has anyone else ever used that, or what are our alternatives. The sides have a lot of rust, and the skin is starting to corode in spots that are 2-3" in diameter. Thanks for the help |
TWO DOGS (63.185.72.208)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 24, 2004 - 5:42 pm: | |
the skin on a bus is a structural part of the bus...sounds like you are attempting to make the worlds largest acordian |
FishbowlBrian (Fishbowlbrian) (67.165.212.171)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 24, 2004 - 7:23 pm: | |
Yup. Your bus, like most MCIs and GMs, is constructed largely without a frame, much like an airplane. This is called monocoque constuction, French for "single shell". In your case, the MC8 is semi-monocoque, because there are some framing members, but they can't do their job w/o the skin, which is a structural component, like TD says.
Here's a page showing some nice illustrations of monocoque... http://www.centennialofflight.gov/essay/Dictionary/monocoque/DI89.htm
You'll have to re-skin those rusted areas with stainless and appropriate rivets. The window areas you choose to remove can be skinned with whatever you like.
HT,
FBB |
Ray D (64.160.117.164)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 24, 2004 - 11:56 pm: | |
My buddy has an MCI and it is fiberglass from the bay doors up and it was profesionally converted. I have seen several others like this, not saying it's right, but they are out there. My friend has put lots of miles on it.
Ray D |
Marc Bourget (209.142.38.81)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 25, 2004 - 6:18 am: | |
The shear plates that comprise the "monocoque" of the MCI's semi-monocoque structure are on the inside wall of the passenger area below the window almost to the floor. The exterior skin obviously contributes to the chassis structural strength but it doesnt have the rivet style or spacing of the shear plates.
On my MCI-9 both the shear plates and the exterior skin below the drip rail and above the trim where the aluminium abuts the lower stainless are aluminum. Aluminim Oxide is not Ferric Oxide (rust) was this a "mis-spoke" or has the external skin been replaced with steel?
Onward and Upward
Marc Bourget |
Chris Gudgel (Yodelbus) (65.200.143.190)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 25, 2004 - 8:43 am: | |
Marc, I took all the interior shear plates out. I assume those are the green covered aluminum sheets on the interior of the bus. behind that you get to the steel framing in the walls of the bus. This framing in spots is badly rusted, and some of it rusted away. we thought that with that out we could weld in new frame pieces. Then we would attach our interior wall board right to that framing. The skin itself is still aluminum, and where the rust is the worst in the frame work, is where the corrosion is taking place in the exterior aluminum skin. What I am being told though is that the skin of the bus in structural as well as the shear plates. I still have the shear plates, and I could put them back in. is that what I am going to have to do? Chris |
madbrit (67.136.81.54)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 25, 2004 - 8:58 am: | |
Chris,
The structure of the bus is both the inner and outer skins. Some have gotten away with replacing the inner skins with 1/2" ply but whether that is a structural alternative or not, and how many screws would be required and in what pattern, who knows. I am not an engineer to say yes or no, and I haven't seen any evidence that there are any actual structural engineers on any of these groups or boards, willing to state what is what either.
My advice to you is to put it back exactly as you found it, using the correct rivets too and then cover with ply or whatever interior surface you want.
Peter. |
Marc Bourget (209.142.38.81)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 25, 2004 - 9:43 am: | |
Madbrit has it right!
Typically, AFAIK, a diligent MCI -7,8,9 converter removes the shear plates, rather than the external skin, to replace the fiberglass insulation with a material of higher "R" value, inspect and correct for intrawall corrosion and some needed conversion related efforts (depending on needs and interests). Once the inside is exposed you can decide whether the outside skin has to come off. I have a section of exterior skin that will have to be replaced.
The shear plates, if carefully removed, by that I mean holes not enlarged in either the plates or the walls, can, more than likely be re-installed in place (especially if bus is carefully blocked-up BEFORE the shear plates are removed). I plan on using adjustible screw jacks. The chassis can be checked for level and twist before removing by simple procedures - applying high school geometry.
Don't plan on relying upon "Clecos", alone, for the alignment of the shear plates on re-installation!
Be sure to use the correct rivets. No soft, non-structural, rivets for the shear plates.
For anybody contemplating raising the roof, don't ignore the benefit of raising the window sill height, (better clearance for furniture, and increased privacy, etc.) and if you do so, raise the shear plate and top shear-plate chord member heigths to match. As a rule of thumb, the contribution of the shear plate increases the square of the increase in vertical dimension. Increasing height 10% gives a 21%, increase height 50% gives a 225% increase.
Since my shear plates are painted (an orange brown color not the green of zinc chromate) I don't see any alloy markings for reference. If anybody knows whether the shear plates are 2024, 6061 or 7075, I'd like to know. I'll be raising my shear plate height and want to obtain the proper alloy.
The question about whether plywood can replace the aluminum shear plate is so basically negligent that it's hard to get an engineer to do the simple calc's necessary to give you hard figures. I know Galey talks about the relative strength and stiffness of aluminum vs. steel in his Bible. He also gives equivalent data for wood in other areas of the chapter (I believe) but he never goes near replacing aluminum with wood, only discussing why a converter shouldn't be replacing an (non-monocoque) Eagle skin with FRP.
Loads on a moving structure like a vehicle are both varied and dynamic, meaning they change from moment to moment, come from different sources and can "gang up". Common Sense from a lay person's point of view usually addresses a single mode of loading, not realizing vibration and (impact) accelleration loads can OCCASIONALLY group together suddenly reaching a total several times that of a single method. So, stories of guys who have "SAFELY" (bs!!!!) driven their busses with a back yard slide-out with the shear plates removed are true! However, We havent seen the situation where all these load factors and other points merge in a single instant in time. For instance, with a swerve due to backed up traffic and a pothole on a poorly maintained highway all after 10 years of rust from a poorly sealed and MARGINALLY WELDED slide-out installation.
I really don't care if that particular converter ends up sliding on his butt down the road holding the steering wheel below a shocked expression, but I DO CARE about the other passengers or travellers on the road. IT COULD BE YOUR DAUGHTER WITH THREE GRANDKIDS IN THE ONCOMING CAR
Such conduct, albeit, from an unlikely cause, is INEXCUSABLE in any responsible society!
Onward and Upward
Marc Bourget |
Gordon (64.12.116.135)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 28, 2004 - 10:19 pm: | |
Marc
Regarding your comment from the Bible "converter shouldn't be replacing an (non-monocoque) Eagle skin with FRP". I couldn't find anything to that extent on the chapter regarding siding. I Am in the process of buying FRP that attaches directly to the frame work for my Eagle. I would appreciate any input as to why this is not a recommended process
Gordon |
Gary McFarland (Gearheadgary) (68.252.126.82)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 28, 2004 - 11:16 pm: | |
Gordon,
What is the source and type of your FRP?
I can think of numerous reasons why a composite is inadvisable in a monocoque, not just for reasons of flex and strength, but the inability to hold a fastener would be a big convern.
Gary |
Marc Bourget (209.142.38.81)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 29, 2004 - 1:06 am: | |
Gordon,
Absorbed in my task, I got that backwards and thanks for catching me on it.
FRP in typical thicknesses has about 1/8th the stiffness of Aluminum and 1/24th of steel.
I should not be used as a replacement for semi- and monocoque structures. For greater reason, 1/2" plywood shouldn't replace the shear plates on the inside of MCI's and other semi-monocoques.
The Eagle relies on the tubing for full structural loads, the fluting in its skin is just a skin stiffener. All else being equal, the support structure is heavier as a result.
Onward and Upward
Marc Bourget |
Gordon (205.188.116.135)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 29, 2004 - 7:28 pm: | |
Mark & Gary
Thanks for the input. I'll be using Kemlite's new product, Reflections, .120, which is designed to go directly on the frame, no wood backing. This is going on my Eagle, so it is not a structial member.
I plan on using a single 72" tall piece,8" roof raise, for the full lenght. Originallly planned on using sikaflex, but I am now considering 3M tape as it allows for some flex.
Would appreciate any input on this concept.
Thanks
Gordon |
Gary McFarland (Gearheadgary) (68.252.126.82)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 29, 2004 - 8:37 pm: | |
I went to the Kemlite site, but can't find anything about the "Reflections" product.
Can you post a link to the actual product?
How long are the 72" tall pieces?
I would stick with the sikaflex. (haha no pun intended)
Gary |
Bob (Bobb) (142.179.61.236)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, September 29, 2004 - 9:39 pm: | |
http://www.kemlite.com/filon_frp/filon_reflections.cfm
I wish they had this when I did my bus... |
Richard Jones (63.80.251.75)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 30, 2004 - 6:28 am: | |
"Reflections" can be made in lengths up to 400'. |
Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 30, 2004 - 1:52 pm: | |
VERY Cool.
I searched long and hard for material to build my deckhouse (On my boat). the closest thing that I found was "Pultruded" fiberglass, which is super-strong, but did not have a perfectly smooth finish. I would have had to lay several "filler" coats before I could get a good finish.
I'm glad I didn't buy the stuff, I'll go with Kemlite when I'm ready.
FYI--in my case, the shipping costs were about 60% of the material cost.
someone else will have to comment about how suitable this is for you, structurally, for an eagle. It will sure look good though...
Gary |
Gordon Hummel (Gordon) (152.163.100.132)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 30, 2004 - 10:01 pm: | |
Gary
I have samples & the finish is excellent. My cost is about $3.00 per sq ft delivered in Tulsa, OK
If u have trouble getting samples as I did, I can send u a piece
Gordon |
Gary McFarland (Gearheadgary) (209.128.79.46)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 30, 2004 - 10:07 pm: | |
No thanks, I only have one more trip to my boat this year, and that's to "Bag it up" for the winter. I won't be doing anything with the deckhouse for at least 6 - 8 months.
thanks though.
I wish someone that was an Eagle Expert, at least on structural issues would comment, I don't feel like we have a definitive answer on whether or not an Eagle is Monocoque.
I'll say this, My bird has a full frame under it, and I wouldn't use FRP in place of the 18ga skin....
But it'll look great on my Deckhouse!
gary |
Gordon Hummel (Gordon) (205.188.116.135)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 01, 2004 - 9:04 pm: | |
Gary
I'm no Eagle expert, but it's NOT a Monocoque chassis
Gordon |
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