Questions about replacing ski bottoms

I spend the last hour reading everything I could find on SC.org about ski's

I have a set of Fed 2000A's I am going to clean up and use on my cub here in Central/Eastern Wa this winter. The bottoms have 1/4" plastic with an alum skeg on them now. I would like to put new UHMW on and would like to extend them out past the edge a bit.


I was wondering how thick and wide I should make the new skeg using UHMW.

Is there a certain amount you can extend the width with out needing approval?

What is the consensus on 3/16" vs' 1/4" thick.



Jason

jgerard said:

I spend the last hour reading everything I could find on SC.org about ski's

I have a set of Fed 2000A's I am going to clean up and use on my cub here in Central/Eastern Wa this winter. The bottoms have 1/4" plastic with an alum skeg on them now. I would like to put new UHMW on and would like to extend them out past the edge a bit.


I was wondering how thick and wide I should make the new skeg using UHMW.

Is there a certain amount you can extend the width with out needing approval?

What is the consensus on 3/16" vs' 1/4" thick.



Jason

Click to expand...

I'm replacing mine also. Plan on going with 3/16 and extending them 1.5". I plan on taking them to a shop I know with a press brake and having them put a 45on the edges 1" in before I mount them.

Tim

1/4 is toooo thick.. 3/16's will last a life time and 1/8" is easier to work with, brake up the edges for your overhang and heat/form if needed.

As for approvals... don't think a set of Federals ever came out of the factory with UHMW on them.. so don't think I'd be askin!

Jason,, i read all the old posts too, I just replaced my AERO 2000's with 1/4" UMHW based on the recommendation of a few on this site, plus the fact we dont get a lot of snow and have a lot of rocks. I called AERO and they offer that size replacement too, but I just bought the stuff at a plastic supply in Tulsa. Anyway, I went a full 2" wider all around and turned them into AERO 3000's, well, the same size anyway. The curvature of the bottoms helped the UMHW curve up anyway, so I didnt need to bend it..... it was 5 lbs per ski heavier than what I had.. Flip the coin if I would go 3/16 or 1/4 again.. The 1/4 will be stiffer on the outer edges that stick out past the ski, good thing. These will probably last me forever. I am no ski expert by any means,, but thats what I did. I left my metal skeg on, its 1" wide by about 3'long. If it gets stuck, I'll just kick it good.

Just an FYI... when you store the skis in the summer, put them in the dark somewhere or at least out of any direct sunlight/shop light. Not sure on the newer UHMW.. but the older stuff in white isn't/wasn't UV stable and it will deteriate and crack/dry out when left in the sun. Might as well get as many years as you can out of the stuff.

3/16" does the job, and is 25 percent lighter than 1/4"!! Store them out of the sun, as Wayne/Irish said.

I use 3/8"UHMW for replacing metal skegs. Works great!

UHMW springs back quite a way when bent, but forms nicely if the springback is taken into account. Edges that are kicked up give the skis some resistance to side-slide on off-camber LZ's or when turning fast. This resistance is a very good thing. Skiplanes are damaged due to side slip/sliding turns every season!

Aero3000's with the UHMW 2.5 inches wider per side is common here in SouthCentral Ak for Cubs, and works well, even on Cesnna 180's at gross weight.

Check your 43.13 for what percentage wider you can go.

PS, some of the "V" bottom skis (Federals) cannot be helped for deep snow performance. I was told that in the ultimate deep, cold, light fluff powder snow, a "V" bottom ski seems to just plow itself a trough and bury, never stopping until bottom is found or the wings are resting on the snow. The indivivdual who mentioned this has the credentials and experience to corroborate this statement, and says he's seen a stock flat bottom ski sit on top of the fluff, right next to a buried airplane with a V bottom ski. FYI

PPS, make sure the pedestal/tunnel rivets and tunnel/deck rivets are all tight. They get loose!!

you can also heat form the stuff, for your angles..... and around fun shapes like round tail skis...

practice on scraps first of course....

I don't remember if we did 3/16 or 1/4 mostly, see bunch of both in scrap pile here...
think I once used 1/8" and it was wimpy and wavy pain..... would not try again, and not for extending edges...

Federal skis all look the same but there are left and right skis, It's hard to tell and a lot of ski guys don't know the difference. If you put them on a level table and view from the front you will notice that the pedestal is not perpendicular to the ski bottom. The pedestal should lean away from the airplane so that when installed the outside edge is higher then the inside edge. Had an old timer here that had flown skis all his life and we had a ski flyin and another old timer walks up and is admiring his plane and say's " nice Pa11 but your skis are on backwards " and showed us why. I even saw one with 2 lefts or 2 rights but forget which way it was. My point is just because the guy you bought them from had the cable/bungee tabs pointing to one side doesn't mean they are on correct. The early Fed SC1 and SC2 skis has a rectangular pedestal that is perpendicular to the bottom but the axel bushing welded into the pedestal is at an angle to get the outside edge higher.

Glenn

How do you experts attach the 3/16, or 1/4 inch to the bottom of aero skis, rivets or counter sunk screws with nuts on top.
Another question, on one of my skis the bottom is bent up under the tunnel, so now the skeg is even with the bottom of the ski, I know driver abuse.
Is it time for a new aluminum bottom?

Tim, either way. I used stainless #10 machine screws w stainless lock nuts. 100 degree countersunk heads so they will work w the micro countersink drill tool. Took some time to drill out the old rivets. But for your skis, I would use gorilla glue.

I thought my bottoms were bad till I took off the old plastic, they looked good as new. You might find out the same thing.

Tim said:

How do you experts attach the 3/16, or 1/4 inch to the bottom of aero skis, rivets or counter sunk screws with nuts on top.
Another question, on one of my skis the bottom is bent up under the tunnel, so now the skeg is even with the bottom of the ski, I know driver abuse.
Is it time for a new aluminum bottom?

Click to expand...

ski still strong? taller skeg....

I use regular AN countersunk screws & countersunk washers and nuts, not stainless.... and the usually painting the ski after new bottoms installed....

riveted one set (the 1/8" bottoms), to save weight, not worth it....

Jason,

Does that mean that you do not want me to send this set????

Ok... So I drilled off the plastic bottom and skeg to see how much repair work was needed. This ski has a patch on the front and a few cracks in the bottom where the pedestal rivets on. One of the cracks has opened back up. Someone had tried to fill in the concave bottom surface with bondo and fiberglass to make a smooth surface for the 1/8" plastic that was riveted on.

What do you ski experts say? I can grind out the cracked weld and re-weld that area. What about the welded on patch on the nose of the ski? The flange just below the pedestal where the center tunnel rivets to the bottom skin is bent more than I think it should be. Both skis show the flange area under the pedestal to be bent much more than the rest of the rivet seam.

I need to take the bottom off the other ski to see what it looks like but from the out side that ski is in better condition.

Should I try to take the kinks out the bottom skin along the sides?

Should I try to fill in the concave areas on the bottom of the ski before putting UHMW on?

Or should I just have George send me his serviceable set of Fed 2000's from Juneau?



Jason

Does you want to ski fly this month, or in April??????


Bet you though you got a good deal, didn't you

Next time, take Eatons Good set!

I can truck freight them to Seattle for about $35.... but will be gone until next week, so puts them there in about 12 days.

Jason, we have just replaced the bottoms of my Federal 2200 skis with 1/4" UHMW, and it did add 10 lbs per ski, if I recall correctly. As Steve mentioned, we, too, used stainless steel screws that were countersunk, with locknuts. I know that rivets would be less in weight, but I want to be able to replace the bottoms easily, should they crack.

The UHMW is really easy to work with. We extended the bottoms about an inch all the way around, but did not bend up the edges. Jason Erickson at Wipaire suggested that it really doesn't need to be bent up for this small increase in size, but that if you are doing much more than 2" you should bend the outboard edge of the ski.

Darrel Starr will be posting more photos of the skis...see the other thread on "Rerigging Federal Skis". We are going to put the finishing touches on the skis tomorrow, mount and rig them Saturday morning. They look terrific.

Regarding the increase in weight, I am not too concerned about this when I compare the relatively mild increase in the weight of the skis as compared to amphib floats!

Randy

Jason,
I like 3/16 with 2" extra, bent 30-45'. Would not use 1/4. I riveted on the last couple sets of aero 3000s with 6 softs. I think I like them better than screws. You will do a hell of alot of flying b4 u replace a bottom unless u r doin it wrong.
Skeg of uhmw for sure. If u are on much glare ice have a bolt head sticking down for drag. (inside row of screws on landes or atlee. 2nd to last skeg bolt on aero)
All that is opinions and probably wrong. But working on several planes here. Like Dave said, the aero 3000 with big bottoms is first rate for deep pow.

Those skis look about ready for the scrap pile btw.

Sorry about those skis Jason. Bummer!

these ones were riveted on with #6's. Super Clean set of skis. They were new from Aero...went straight to BigLake powdercoaters (AeroSKi's aren't known for their stock paint lasting a full season), then got 3/16 plastic.

These are on Ron T.'s very nice exp. SmithCub ("Skydozer")

I didn't buy them, they were sitting in the back one of the hangars on the field here. I was told I could use them but will probably just return them to their hiding spot

Jason

George,

I sent you a PM with shipping info - Thanks!!!!

Jason

Here are a couple pics of Aero 2000's that are now 2" wider.

Steve,

all you need is snow!!!

(and all I need is a plane)

suks for both!

Jason, check pms

Not predicting much snow this year,,

Jason;
I have done both 1/8" and 3/16" when replacing the bottoms on 4 sets of Federals now. I would not use 1/8"again as it is wavy and not holding up well where the rock have gouged back when I had a long tow to the lake on dolly wheels. Replacing the aluminum bottoms I used 1/8" 2024 T3 and have broke the edges up 1 1/2" on the sides on the first couple but have found it easier to keep the metal bottoms flat and extend the 3/16" plastic as much as 2"which is easier to form upwards depending how big of a foot print U want. Somewhere around 18" wide has been the best on my Cubs and Glastar. Riveting with soft counter sunk rivets is light, clean and quick with the pnumatic squeeze to hold on the bottoms and side skegs. 3/16" bolts with the heads on the bottom, 6" back of the axle on each side skeg will give enough drag on ice to help stop. I have pictures posted on the site that show the skis, dolly wheels and tow bar. Enough for now my two fingers are worn out -I go fly to check the traps. B

Imagine moving stuff from two hangers 100 miles... packing into a trailer, pulling it out and putting it into storage as you organize...

And as we unpacked this load, (second to last), I finally got to the box I thought I had seen my 1.25-1.5 axle adapters in...

And you know what, found them in 30 seconds...

All will be well Jason, just tell me how many parts you want... skis, landing gear, cabane vee, extenders for cabane vee to fit 3" gear (did you order those?), bushwheels...

Will send out when I get to Juneau, just get a picture of your bird is some cool spots!

Any reason to not use black uhmw on ski bottoms?

Jerry

cubflier said:

Any reason to not use black uhmw on ski bottoms?

Jerry

Click to expand...

No, I have black UHMW on the bottom of my skis and see no problem. Reason I went with black, it was free

cubflier said:

Any reason to not use black uhmw on ski bottoms?

Jerry

Click to expand...

Everything dark colored near my airplane parking melts out a lot faster this time of year. I have to pile extra snow underneath it while it's parked, to extend my ski-flying season a couple weeks. I figured the white UHMW would keep the snow around just that much longer, but I suppose it's the difference of a week or two at the end of the season. And, free is free!!!

cubflier said:

Any reason to not use black uhmw on ski bottoms?

Jerry

Click to expand...

wouldn't you be thawing and refreezing more??? from sun when still bellow freezing?

Do you think "Cub Yellow" is in the "too dark" category for skis vs. white? The majority of my ski tops are "Cub Yellow", bottoms are white.

Colors accelerate endothermic heating. To what extent?

I have run the Aeroski R2800s for several years and thought I'd show the recent recover job.
Had a flat tire when landing resulting in a need to redo my bottoms. Wish I would have looked at the forum before I started. I used 1/8th inch UHMW material on the bottoms and1/4" for the skegs, because that was what was on there before. I think the 3/16th would have been better and maybe 3/8" skegs. Talking to Aeroski, they use the 6-7AD rivets, so that's what I purchased and finished both skis using a hand squeezer around the edges. Didn't burst any aneurysms or hernias, but probably came close. Those are big AD(hard) rivets. Got hold of some 6-7A (soft) rivets as I was finishing - SO much better/easier for non structural stuff like the ski bottoms. Live and learn. At least I got some good practice and a workout.
Extended the outside edges an inch, but could easily have done 2" with the 3/16. Left the back decks closed in and it has worked well on flights since. Haven't done any deep snow since, but did notice that when manually turning the plane, I didn't have to pull the skis around much as they were sliding around better. Have now thought of getting rid of the big U bar in the back, but nice to have a place to grab when turning the plane and skis manually. I have always had the rear cross-bar hoop/axle mounted on the tops. Just had to machine out some room for the tunnels so they would lay against the ski top. You lose some clearance on the pavement, but if you're not operating on gravel, it won't matter. They aren't good for gravel ops anyway.
For many years having the kids around the hangar has reduced my ability to get much of anything done, unless they are otherwise occupied destroying something that I have to clean up later. At 6, Miles now was kicking my butt to keep up with the work flow and we got the second ski done in an afternoon. He wasn't around when I did the first ski and it ended up taking several evenings and quite a few adult beverages.
The sheets for the bottoms were $100 a piece and the 1"wide strips for the skegs were $5 each

Getting the plane back to the hangar

Starting point

Bottoms look good

Skegs first. The 1/8th was a benefit here as I could see through it when drilling the holes in the bottom sheets to line up with the pre existing holes in the skis

The 1/8th molded nicely to the curve of the ski after left lying on the ski bottom overnight. I didn't do that with the first one and was struggling with it a bit more to avoid bulges or waves in the UHMW.

Speedy countersinker and rivet bucker!





Marking the wheel cut outs which can be quite a bit smaller than original.