Sign in to follow this  
Followers 0

Just joined the Fat Avid Club

233 posts in this topic

Posted (edited)

Randy,  I thought you bought the Just Aircraft spar inserts?  Then why are you making homemade ones that are shorter?  The Kitfox and Just inserts are more than a vertical beam, they are an I-beam combined with a partial tube within the spar tube.  It shouldn't be too hard to take .018 off of top and bottom to make it fit .083 wall spars - TJay did that. 

I agree with Doug Holly - Unless you have the ribs made already, I would use the Kitfox Riblett ribs and the wider chord symmetrical flaperons, and if you have undercamber ribs, you can modify them like I did mine.

BTW Doug,  I think you misprinted Avid spar root to strut fitting - It is standard 90" and not 80".  Kitfox started at 86", but went to 96" starting with model 3.  Their current aluminum spar insert is 60" long same as Just Aircraft with .065 spar walls and 1550 GW, but Just sells cheaper.  I have one Kitfox insert and four Just inserts.  EDMO

Edited by EDMO

Share this post


Link to post
Share on other sites

Posted

Hi Ed - Double check your build manual or the wing data thread in the Files and Forms section here for the diagram with measures, I believe you will find 80" is correct for Avid. KF3, KF4-1050 and KF4-1200 is 96-3/4". KF Speedster is 97-3/4". That is a significant difference in lift strut location. Along with the updated airfoil, just another reason why I would use the KF wing and lift struts. The KF .065" wall spar doesn't bother me, provided the KF struts and stiffeners are used as designed. Well proven with no wing failures on 1550lb gross KF 5-7 planes to date.

Share this post


Link to post
Share on other sites

Posted (edited)

Hi Ed - Double check your build manual or the wing data thread in the Files and Forms section here for the diagram with measures, I believe you will find 80" is correct for Avid. KF3, KF4-1050 and KF4-1200 is 96-3/4". KF Speedster is 97-3/4". That is a significant difference in lift strut location. Along with the updated airfoil, just another reason why I would use the KF wing and lift struts. The KF .065" wall spar doesn't bother me, provided the KF struts and stiffeners are used as designed. Well proven with no wing failures on 1550lb gross KF 5-7 planes to date.

Doug,  I don't remember where I got the 90" for Avid strut attachments - thought it was correct, as it was about where Kitfox located theirs.  80" seems awfully short except for the Speedwing.  I talked to Randy Hollman who was one of the engineers for Dan Denny when he owned Kitfox, and I guess the engineers decided that 96 3/4" strut attachment was better for the 32' wingspan than the original 86"?  Denny was a salesman and not a designer.  I think that moving the strut attachment farther out and lengthening the insert must have produced better figures for wing support and should be done if you lengthen Avid wings to Kitfox length.  EDMO

Edited by EDMO

Share this post


Link to post
Share on other sites

Posted

I haven't installed the lift strut brackets so still could position them out farther and lengthen the lift struts.  Does anyone have the exact specifications for the KF lift struts and position of the lift strut bracket?  Also, does anyone know if the vertical height of the fuselage from the lift strut mounting point to the carry through/spar mount is the same between the KF and the Avid so I could know that the dihedral would be correct?

I bought a set of the aluminum spar inserts from Just but they are $400 a set not $40.  Anyway, the main problem is they are made for the .065 spars and after much thought about it I didn't have a good accurate way to machine them down to fit the .083 spars that I have so I decided to build the inserts you see in the picture.  About the only way I could see to accurately thin them to fit in the .083 spar would be to turn them on a lathe and then polish them really well to get tool marks out.   If someone wants the Just insert I would be happy to sell them at a good price.

I agree with Dog that the KF wing kit would be the way to go if I didn't already have a complete new Avid MKIV kit with everything to build the wings. I would probably look at doing the KF wings but don't really want to spend $10K (for the KF high lift wing kit).  The undercamber wing is definitely not as fast as the ribblet but from what I read, it is as good or possibly slightly better on the slow end which is what I am most interested in.

So, does anyone have a set of KF wing drawings and build instructions along with the lift strut dimensions?

Share this post


Link to post
Share on other sites

Posted

First I want to say that I was out of line with my comment about Airdale. I've met Steve a few times driving down to Airdale when friends were doing their planes. He is safety conscious. I am just disappointed. 

i borrowed a camera to go into the spars and see what is in there exactly for stiffeners. I can  only see in from the end and do not know how long they are. I will peer in there with the camera this evening and see what is in there. This plane does not have extensions. The spars are one piece of tubing but they are longer than the MKiv wings. They are about the same length as my magnum wings but use the mkiv struts. The magnum struts are longer and attach further out the wing. With the tips removed the fat avid wings are virtually the same length as the standard mkiv wing with tips on.

 

Share this post


Link to post
Share on other sites

Posted

My spar tubes are 08 thick and 162 inches long, not the regular 144 inch spars. Before I cut off the wingtips the wings were 180 inches long. The stiffener is 1/4 thick and 18 inches long. Does anyone else have these wings?

Share this post


Link to post
Share on other sites

Posted

Thanks for checking that Chris.

Jim, just to double check my understanding; the KF-4 lift struts are 108" from the bottom mounting hole to the front spar bracket cross bolt hole.  Can you get me a measurement from the bottom mounting hole to the rear spar bracket cross bolt hole?  Also, is this the lift strut used on the spars with the brackets mounted at 96 3/4" from the root end of the spar to the bracket cross bolt hole?

Thanks for the help and advice All.

Randy

Share this post


Link to post
Share on other sites

Posted

I used the router table to get mine down close, Worked really well but I did spend probably 10 to 15 hrs sanding and polishing with the hand held disk sander to get them smooth. There is so much material on them things, I don't think taking .008 off top and bottom lost much strength at all and if it did the thickness of the spar made up for it.

Share this post


Link to post
Share on other sites

Posted

Thanks for checking that Chris.

Jim, just to double check my understanding; the KF-4 lift struts are 108" from the bottom mounting hole to the front spar bracket cross bolt hole.  Can you get me a measurement from the bottom mounting hole to the rear spar bracket cross bolt hole?  Also, is this the lift strut used on the spars with the brackets mounted at 96 3/4" from the root end of the spar to the bracket cross bolt hole?

Thanks for the help and advice All.

Randy

Randy,  You are correct in your understanding of the 108" length of the lift struts.  I will try to get the other measurements today and post them.  Another thing that affects this is the Kitfox 4 has 2"  more headroom than the Avid MK IV  Not sure how that changes the distance from the wing attachment at the top of the fuselage, to the lift strut attachment at the bottom of the fuselage, but the greater that distance is, the less the angel is of the liftstrut to the wing.  (for instance, I'm guessing that a 10 degree angel would support less weight than a 15 degree angel and create more of a load on the strut) Hope that didn't confuse the issue.  JImChuk

PS  just looked in my Kitfox 4 manual, and it does call out that 96 3/4" dimention for the lift strut bracket location on the wing.  For the speedster, they call out 97 3/4" length.  Just ran out to the garage where I have the Kitfox 4 fuselage, and see that it measures 38 1/2" from center or rear wing carry though tube to the top of the lift strut bracket at the bottom of the fuselage.  Remember, the Kitfox bracket is only 1/4" thick verses the Avid MK IV which is 1"

Share this post


Link to post
Share on other sites

Posted

Lift struts on fat avid are out 79-80 inches depending on if you measure length of tubing or to the pin, same as all avids except magnum.

i think it would have been better to move the strut out for these longer wings like they did on the magnum.  Or to use a longer stiffener????

If i carefully drill out the rivets on the strut mount that secure the brace I should be able to push it out and install a new longer stiffener right?

Share this post


Link to post
Share on other sites

Posted

I would guess that if you are able to get the old stiffener out without scratching the inside of the spar, then use the old rivet holes in the spar for new rivets into the new stiffener, no harm would be caused.  I'm going out to the hangar in a bit, I'll do some more measuring.  JImChuk

Share this post


Link to post
Share on other sites

Posted (edited)

Lift struts on fat avid are out 79-80 inches depending on if you measure length of tubing or to the pin, same as all avids except magnum.

i think it would have been better to move the strut out for these longer wings like they did on the magnum.  Or to use a longer stiffener????

If i carefully drill out the rivets on the strut mount that secure the brace I should be able to push it out and install a new longer stiffener right?

Chris,  I have a new set of the 60" Just inserts still in the box - If you want them, give me the $200 I paid plus shipping.  I think you could use the old rivet holes in your spars to put new rivets in to attach the inserts there, and you could move your strut attachments farther out and drill thru the spar and inserts for more rivets and your wing would be far stronger.   The Just inserts don't have the V cut in the web ends like Kitfox does, and the outside ends are not rounded, but you could do that easily.  You would still have to sand down the outsides of them to fit them into the .083 spars like TJay did.   Let me know if you want them.  EDMO

Edited by EDMO

Share this post


Link to post
Share on other sites

Posted

That's what I'm thinking. Going to think about changing out stiffener for a while and keep adjusting and tinkering with rigging and see what I can do improve things. I've already discovered too much reflex and tuning that out of the no flaps position and it also helped.

Share this post


Link to post
Share on other sites

Posted (edited)

That's what I'm thinking. Going to think about changing out stiffener for a while and keep adjusting and tinkering with rigging and see what I can do improve things. I've already discovered too much reflex and tuning that out of the no flaps position and it also helped.

I thought about trying to find a 60" long aluminum tube that would fit snugly inside of the spars, and put a beam inside of that and slide the whole thing into place and rivet it.  Maybe a coat of 9460 to glue them together?  Might be possible?  EDMO

Edited by EDMO

Share this post


Link to post
Share on other sites

Posted

I was in the hangar a bit ago, and measured the Avid From the center of the rear wing carry through tube to the top of the fuselage strut attachment bracket was 36".  On the Kitfox 4, that was 38".   Strut attachment was about 80" from the end of inboard end of the front spar to the bolt that holds the strut to the wing.  JImChuk

Share this post


Link to post
Share on other sites

Posted

Chris,  I have a new set of the 60" Just inserts still in the box - If you want them, give me the $200 I paid plus shipping. 

Hey ED if Chris doesn't need them Ill buy them from you wouldn't mind having another set around I will put them to good use in the future,

Share this post


Link to post
Share on other sites

Posted (edited)

Chris,  I have a new set of the 60" Just inserts still in the box - If you want them, give me the $200 I paid plus shipping. 

Hey ED if Chris doesn't need them Ill buy them from you wouldn't mind having another set around I will put them to good use in the future,

TJay, Ask Chris directly, and one of you let me know who gets them.  I have never unpacked them - donno what shipping would be.  PM address.  EDMO

Edited by EDMO

Share this post


Link to post
Share on other sites

Posted

Thanks Ed, since I am not sure what I am doing yet TJay you can take the stiffeners. I have access to plywood to make some stiffeners.

Share this post


Link to post
Share on other sites

Posted

Thanks so much Jim for getting all those measurements for me!

I think I will plan to mount my brackets at the KF distance of 96 3/4" but will have to calculate the length of the lift strut since the fuselage height is different and I want to keep the dihedral the same as the Avid..  Should be a lot stiffer wing with the longer lift struts and the 3' stiffeners.  I noticed that the Magnum only uses 2' stiffeners.  The 5' stiffeners Just and KF use are probably required with the .065 spars.

I hadn't planned to modify my lift struts but looks like I will have to build a jig for them since I will have to tweak the angles some and will go to 1" tubes to slip over the 7/8" tubes stubs.  Will likely have to cut and reweld the jury struts as well I am thinking.  A lot more work than I intended but need to be sure the wings are plenty stiff if I am going to extend them.  It all just dominoes and adds more weight, ARRRGH!

Share this post


Link to post
Share on other sites

Posted (edited)

Chris - your A+ wing configuration of 162"L x .083" 1-pc spars w/ Mk-IV lift struts sound like a one-off to me.

Again, I would be very surprised if [old] Airdale sanctioned their use on an A+. I was told more than once that the Avid Plus fuselage and kits were originally designed to use the same 144"L wing and lift strut configuration as the Mk-IV Heavy Hauler, with a single exception of the longer 18" 5mm ply wing stiffener. Officially, [old] Airdale set MTOW of the A+ with this wing/strut/stiffener at 1250lb.

It should be noted that [old] Airdale also sold the A+ fuselage as the Fat Avid upgrade kit and approved the reuse of Avid Model B, C, Mk-IV, Bandit wings/struts on the Fat Avid upgrade. Even the short Speed and Aerobat wing/struts. However, in every case, Fat Avid MTOW is limited to the original wing/strut configuration (950-1200lb). This even though the larger, heavier A+ fuselage resulted in slightly higher empty weight.

That is why I am very careful to distinguish between an Airdale Avid Plus (or, as I like to call it, the A+) and a Fat Avid.

As far as I know, Vince was the original owner/builder of your plane. I seem to recall Steve Winder saying it was one of the very few complete A+ kits, maybe even the first complete kit, and that they (Airdale) had to split a Mk-IV cowl to supply him with. I suppose that might happen whether it was a complete A+ kit or Fat Avid upgrade kit, so do you know definitively whether it started as a complete A+ kit or a Fat Avid upgrade kit? Ie., when you bought the plane from him, did you get the A+ kit inventory pull sheets showing which spars and stiffeners were supplied from Airdale? Or perhaps simply a receipt showing Fat oAvid upgrade kit parts only?

FWIW, my A+ pull sheets (copy posted here on site) show "HW-21: Pre-drilled Spar" with no measures. However, my Mk-IV pull sheets (also posted here on site) show "HW-21: Spars, 2-1/2" x .083" x 12' 6061 T6". And, of course, I know I do have 144"L 1-pc .083" spar tubes on my A+ build. I do find it interesting that you have 18" vs 12" stiffeners in your spars. Again, what do your pull sheets show? My Mk-IV pull sheets show "W-24: Spar Stiffener, Plywood, 5mm", my A+ pull sheets show "W-24: 1/4" Plywood Spar Stiffener". Neither reference a stiffener length.

Does your and the other Magnums use 162"L x .083" 1-pc spars as standard equipment? Do your 162"L x .083" 1-pc A+ wings use the Magnum drag tube configuration (i.e. steel vs. aluminum tubes and specific Magnum attachment points and brackets)? Do they use the standard Avid Flyer wingtips or the Finch tips used on the Magnums? I know Vince also built a Magnum, I just wonder if he mixed and matched parts for whatever reason?

I think if I were in your shoes, assuming the drag tube location allowed, I would simply trim the spars to 144", reattach the wing tips and go fly (actually, I would source and install a set of KF 4 Hoerner wingtips to facilitate quick access and easy inspection). We know the Mk-IV HH wing/strut static load test by Dean Wilson showed that combo failed well over the 'official' Mk-IV 1200lb gross with NO spar stiffener installed. If your existing 18" stiffener is a concern, no reason you couldn't simply limit your MTOW to 1200lb. regardless what MTOW Vince used.

Good luck, this plane needs to fly!

Edited by dholly
1 person likes this

Share this post


Link to post
Share on other sites

Posted

any chance he may have built catalina wings but didn't move the struts outboard?  What washout did he use on the wings?  I dont like using reflex in my flaperons as it really makes the roll feel heavy and not right.  I still need to mark mine and put a stop on it.  After take off I normally bleed the flaps off and wiggle the stick to get the lightest roll force as I play with the flap handle a little.  You will see a noticeable difference in airspeed and ground speed as well as you play with the flap handle to get the sweet spot.

:BC:

 

Share this post


Link to post
Share on other sites

Posted

As far as I know this was a complete kit wings and all. Strut attach points and struts are MKiv all the way. Cutting the wingtips off made a huge difference and it is easier to fit in the hangar. I've got it flying pretty darn good now by messing with rigging. I think smartest thing for me to do is see if I can remove and replace the stiffeners with longer ones. But that is a big risk if it doesn't work and I end up ruining the wings. Right now I'll just fly and continue to play with rigging. The bend is not very bad right now with total wingspan being that of a MKIV. But there is more than I remember from either of my other Avids.

Share this post


Link to post
Share on other sites

Posted

From looking in my wings when I first got my airplane, I believe I must have the 5 foot Just/KitFox style inserts in my .083" spars.

Share this post


Link to post
Share on other sites

Posted

As far as I know this was a complete kit wings and all. Strut attach points and struts are MKiv all the way. Cutting the wingtips off made a huge difference and it is easier to fit in the hangar. I've got it flying pretty darn good now by messing with rigging. I think smartest thing for me to do is see if I can remove and replace the stiffeners with longer ones. But that is a big risk if it doesn't work and I end up ruining the wings. Right now I'll just fly and continue to play with rigging. The bend is not very bad right now with total wingspan being that of a MKIV. But there is more than I remember from either of my other Avids.

As far as you know?? You're only the second owner, didn't you receive any detailed info when you purchased the plane? Ie., order and delivery records, inventory pull sheets, build manual and documentation, photos etc.?

I would agree that attempting to replace the existing 18" stiffeners is risky business. If by chance you don't damage the spars in the process, you still cannot perform the recommended spar clamping procedure for installation of the long aluminum I-beam stiffeners on a constructed and pre-covered wing. Is having those new stiffeners worth cutting access into or recovering and repainting your wings? A new sleeve style stiffener might be possible (that's what my Aerotrek uses) if you can find the proper material, but that sounds like a real beotch to install too. Plus many more holes in your spars and you would likely having to cut access thru your fabric to rivet them properly as well. It all sounds rather impractical to me.

If you feel the existing wing flex with your current 162"L straight spars is unacceptable, I think trimming the spars to the A+ designed 144"L spar spec and replacing the wingtips makes the most sense. Same LOA to fit your hangar, but shorter spars flex less and we all know there are plenty of 144" Avid wings safely flying with shorter 12" stiffeners. Of course, the existing drag tube location might make that impractical which is why I asked but, unfortunately, you have a knack for dodging my direct questions so I'm done here and can only wish you well.

Just be aware if you want to replace stiffeners to increase MTOW, Steve Winder counseled there are several other potential failure points in addition to stiffeners that also need to be addressed. I posted his comments in the A+ forum if you care to search.

Share this post


Link to post
Share on other sites

Posted

Doug,

NOT dodging your direct questions! You have knowledge I don't about Airdale history and to some degree Vince's plane. I do NOT want you to drop out of the discussion. I basically bought the complete plane unflown from Vince. I went down a couple of times to look it over. He wanted to part it out and tear up the AW cert. I convinced him not to and to sell it to me. It was purchased by me a "parts" (with a valid AW  cert)  and the only reason he did that was because of my extensive time and experience with Avids.  He had a concern about the wings although he was never completely clear with me about what the concerns were. Another friend told me the wings flexed which he heard from Vince and it wasn't till I flew it that I saw it for myself. I am grateful he sold it to me and do not and would not hold him accountable for anything. i still feel good about the transaction and do not blame Vince for anything. As I took the plane apart I found all kinds of things installed to compensate for it not flying right. I figured it was just not rigged right and I would easily be able to correct whatever I found. And for the most part I have. it flies pretty much hands off, performs beyond my expectations WRT takeoff and landing performance. Now that I have cut off the wing tips it has become very flyable and I have no concern whatsoever that the wings are going to fail or anything like that. i will dig thru documentation and see if he gave me build sheets. i suspect he did not or I think I would remember having seen them. 

He DID tell me that it was a complete kit. I do not remember a conversation about the wings exactly. He gave me quite a bit of stuff with the plane and to be honest I have not sifted thru everything to see if the spars came with the kit. I will do that and report back.

I know I came off as blaming Airdale for shipping an untested configuration. I wish I could take that back because I really don't know. I was asking if anyone else on this board received these wings trying to find out if this was a one off or something they sold.

Anyway please stick with me here. I value your opinion and questions. Sometimes I don't know the answer to your questions and it takes time to get the answers if I even can,  so I reply with short answers that are what I have discovered or what I am currently thinking even though I may not have the answer to a specific question. It's not that I am not reading your replies and processing the info! I am reading everything and processing it.

I SINCERELY APPRECIATE YOUR TIME SPENT HELPING ME TRY TO SORT THIS OUT.

 

2 people like this

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0