Author Topic: Spar phenolic inserts  (Read 5704 times)

Offline Richfroh

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Spar phenolic inserts
« on: December 19, 2014, 06:14:29 PM »
I'm in the process of drilling my DE spars and ran into a possible issue. Pages 42, 42A and 42C reference the locations of the phenolic inserts. All is good for front and rear strut fittings and the front spar fuselage fitting. The problem is with the rear spar fuselage fitting. Of the four phenolic inserts shown, the one closest to the upper spar cap would protrude about 1/8" into the upper spar cap if I drill the 3/4" hole for the insert. I assume I do not want to do that. Should I leave this insert out, drill partially into the spar cap, or perhaps use a smaller insert? A 1/2" insert will just touch the glue line of the spar cap but will not touch the wood.

The fitting is made per the plans. The fuselage attach hole on the fitting is located per the plans and the fitting is at a 30 degree angle to the spar as per the plans. Did I do something wrong or is it supposed to be this way?

Please help! I want to get the inserts installed and start assembling the wings this weekend.

Rich
Rich Frohmiller

Offline Sam Buchanan

Re: Spar phenolic inserts
« Reply #1 on: December 19, 2014, 06:30:09 PM »
Rich, you should get guidance from one of the DE builders, but as proper build practice I would not drill into the spar cap. Either use a smaller bushing or relocate the hole on the fitting.

Offline Richfroh

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Re: Spar phenolic inserts
« Reply #2 on: December 19, 2014, 07:03:04 PM »
Yes Sam, I agree it is best to not drill into the spar cap. But I don't know the best thing to do. My first choice would be to omit that insert but I would like to hear from those that have built Double Eagles already. Thanks.
Rich Frohmiller

Offline Steve

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Re: Spar phenolic inserts
« Reply #3 on: December 19, 2014, 10:06:42 PM »
I'm in the process of drilling my DE spars and ran into a possible issue. Pages 42, 42A and 42C reference the locations of the phenolic inserts. All is good for front and rear strut fittings and the front spar fuselage fitting. The problem is with the rear spar fuselage fitting. Of the four phenolic inserts shown, the one closest to the upper spar cap would protrude about 1/8" into the upper spar cap if I drill the 3/4" hole for the insert. I assume I do not want to do that. Should I leave this insert out, drill partially into the spar cap, or perhaps use a smaller insert? A 1/2" insert will just touch the glue line of the spar cap but will not touch the wood.

The fitting is made per the plans. The fuselage attach hole on the fitting is located per the plans and the fitting is at a 30 degree angle to the spar as per the plans. Did I do something wrong or is it supposed to be this way?

Please help! I want to get the inserts installed and start assembling the wings this weekend.

Rich

This alignment has perplexed other DE builders and your purposed solution to avoid cutting into the spar cap by using the smaller 1/2" bushing is correct...

The discussion started with Joao in Brazil (an early builder) and was responded to by Leonard and I think John Bolding too in the Yahoo Group - then it came up again a few times... There may be something in photos or attachments but the current search tools over in yahoo groups do not yield the goods... Again, don't cut into the spar cap - go with the 1/2" bushing if it clears the cap...

Offline MrG

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Re: Spar phenolic inserts
« Reply #4 on: December 19, 2014, 11:47:32 PM »
I did mine with no issues
i made a jig so the attache bolt ( that cant move and has to be spot on ) was correct 
and rotated the brackets to make sure that spar cap was missed
MrG
Temora Airport  Australia
1st Aussie DE built / flown
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1 Oct 2015 First Flight
11 July 2018 - 125 hrs Flown

Offline Richfroh

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Re: Spar phenolic inserts
« Reply #5 on: December 20, 2014, 12:10:00 AM »
Thanks for the quick responses. I'll plan on using a 1/2" insert in that location unless someone gives a good reason not to before I drill the holes.
Rich Frohmiller

Offline Sam Buchanan

Re: Spar phenolic inserts
« Reply #6 on: December 20, 2014, 11:55:44 AM »
Thanks for the quick responses. I'll plan on using a 1/2" insert in that location unless someone gives a good reason not to before I drill the holes.
Rich, definitely use your own judgment in this situation, but I would probably just omit the bushing for that hole. The LE and XL don't use bushings for any of the fittings. I would prefer no bushing if it preserves some edge distance for the bolt.

Offline Richfroh

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Re: Spar phenolic inserts
« Reply #7 on: December 23, 2014, 10:31:20 PM »
Thanks Sam,
Omitting the insert will leave some edge distance for the bolt hole. Using a 1/2" insert would leave no edge distance as the edge of the insert would be at the edge of the filler wood but not into the spar cap. I think I will be omitting the insert and preserving some edge distance on that hole.
Rich Frohmiller

Offline Steve

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Re: Spar phenolic inserts
« Reply #8 on: December 24, 2014, 12:09:14 PM »
Thanks Sam,
Omitting the insert will leave some edge distance for the bolt hole. Using a 1/2" insert would leave no edge distance as the edge of the insert would be at the edge of the filler wood but not into the spar cap. I think I will be omitting the insert and preserving some edge distance on that hole.
The  inserts are mostly for preventing the bolts from rust thru contact with the wood... Coat the hole and bolt liberally with epoxy and you'll be good up there on the Delta...

Offline Bob S.

Re: Spar phenolic inserts
« Reply #9 on: December 24, 2014, 01:50:11 PM »
I would have thought that the bushing is more to protect the wood from being crushed by the bolt...
But what do I know....
Bob Severance
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Offline Steve

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Re: Spar phenolic inserts
« Reply #10 on: December 24, 2014, 02:31:32 PM »
I would have thought that the bushing is more to protect the wood from being crushed by the bolt...
But what do I know....

I've attached a couple photos - the first is a Piet restoration with the bolt in the fore-ground showing rust for sure and the rear bolt probably too...

I've worked on building restorations that the bolt shanks had been reduced to the size of a match stick...

Offline docmatt

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Re: Spar phenolic inserts
« Reply #11 on: January 27, 2015, 06:33:17 PM »
Just adding some thoughts from my recent experience on the inserts. 
You can save some time by drilling the 3/4'" holes first, then glue in the inserts and finally, use the metal fittings as a guide to drill the 1/4" holes on the drill press prior to threading on the ribs.  Then, only the 1/4" holes need to be placed with precision.  BE CAREFUL THOUGH:  the inserts on the fuselage end of the rear spar MUST be glued AFTER threading the ribs onto the spar.  You could drill them and carefully mark the positions with witness marks to get them back in for gluing.

On the holes that were too close to the spar caps to drill 3/4" holes, I drilled 1/4" holes, then used a 1 1/2" forsener bit to make a shallow pocket in the plywood to epoxy in a stainless steel fender washer to reinforce the hole.
doc matt
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Offline Richfroh

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Re: Spar phenolic inserts
« Reply #12 on: January 27, 2015, 08:44:01 PM »
Doc,
Your suggestion is exactly what I did minus the fender washer. Assembly and gluing has begun on my first wing. It's nice to see it looking like a wing!
Rich Frohmiller

Offline docmatt

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Re: Spar phenolic inserts
« Reply #13 on: January 27, 2015, 09:37:15 PM »
Rich,
yea, it's cool to see it take shape after so long as a big pile of tiny parts!
doc matt
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