Re: Resin volume placed on foam

Eugen Pilarski

Dear Q-community, 

wow, thank you very much for your notes, hints and the very valuable information. For anyone that build in his own walls is very important to get a different point of view! Thank Q-Groupe.

So the bag is open and the bulkhead FS89 part looks in my point of view, very good. Please find below some picture about the part, at the end of that email.  The ratio from resin to glas is around 50%, so the proposal from Rob looks good for that part, based on the fact that it goes 46g to the part and 35g in the Compoflex (Ply) and somewhere. The vacuum level was hold all time long around 850 hpa ( around 1500 kg/m2 or 3306 lbs/m2) served my pump station. Please find below the source I catch up all information about the pump station

The numbers FS89 top and down:

determine description weight   weight %
weighted Foam  82 g 0,185 lbs 48%
weighted Glass 44 g 0,099 lbs 20%
weighted Foam+1st layer + Resin 172 g 0,387 lbs 100% ratio Resin to glass
calculated Resin 46 g 0,104 lbs 27% 51%
I think that I will go further with vacuum bags so far not any big issue come up during that process. Especially for the fuselage and the other parts that will work with vacuum bag so far. It is a pity that there is no more detailed information on the individual component weights from other Q1 projects from the past

Well, the point of the whole weight issue is I need to go with the Q1 lower than 120kg (264,5lbs) all In, because the German ultralight rules don not allowed more. And for sure, I will get my ass in better condition if the bird will start at first time, not yet, but in due corse :-) 

Of course, the finishing is a very important step like Sam show up in his video at youtube (Micro - sand - micro  - sand - done). 

Best regards from Germany 


Am 24.03.2021 um 18:53 schrieb Robert Cringely <bob@...>:

Ideally you want 50 percent glass and 50 percent resin by weight, which is what you generally get with pre-preg. But, as another poster noted, there can be a dry lay-up problem if you push too hard in that direction, hence that original guidance about aiming for 60 percent resin, which is pretty okay and better than most. But there's another problem to be considered with Rutan construction, which is whatever weight you save in the lay-up you are likely to lose in the finishing. It amazes me to see builders who fight for that last ounce of resin then slather Bondo on the final surface for finishing. Yes, most of the Bondo is sanded off and yes, you can use micro instead of Bondo, but it still makes good sense to take a holistic approach to composite work. Your vacuum bagging sounds great, but keep the finish line in mind.

I'll always remember the wisdom of Dragonfly designer Bob Walters, writing in Sport Aviation. Bob maintained that humans can tolerate only so much sanding and paint prep, so if you spend too much time on the prep you can't help yourself but rush to finish the painting. He thought the psychological sanding limit was 250 hours. So if you obsess too much with the early stuff, you'll rush too much at the end and the plane will show it. Wise man.

On Wed, Mar 24, 2021 at 10:18 AM <smeshno1@...> wrote:
 Yes.. and with caul sheet and/or tooling surfaces this is especially true. Saves lots of TIME..but not a lot in weight. 

 Of course, in a production setting time reduction is a major part of the path to profits. Big difference in mission of the projects. Our project out in our shop is not demanding a profit margin for the stockholders.  I personally have no problems with anyone using all the up to date techniques if one wishes to do so..if the structure is problem. God knows we have (and STILL have) plenty of failures in mass production in parts...even with the most fancy dancy methods and toys money can buy!.   Not me.. I'm not looking to save 10 pounds over all and spend oodles of time and greenbacks to get them. I had to do that as a job over 30 years..chasing time and methods all over the place for a few pounds or minutes saving.  

 I'm interested in adding safety and access using the existing methods and structure as much as possible.


From: <> on behalf of Bruce Crain <jcrain2@...>
Sent: Tuesday, March 23, 2021 7:56 PM
To: <>
Subject: Re: [Q-List] Resin volume placed on foam
From memory the Cozy girls said “you won’t save any weight with their vacuum bagging.  It just made smooth uniform pieces that didn’t need much filler”.  That’s from about 10+ years ago so I can’t “etch that in stone”.

On Mar 23, 2021, at 7:01 PM, smeshno1@... wrote:

 Vern at one time owned Cozy plans set #43... and my plan back then was to build a 13B rotary which was pretty innovative in 1982..I had the engine all ready.. lots of Racing Beat ideas and parts. 

 My fellow Starship R&D techs used to razz me about which fuel I was going to use.. maybe Saki? Dave Blanton jr was also on the Starship Department 45 team and his Dad had a company building reduction drives for V6 Fords. He had a 172 with one under cowling in Augusta Kansas. That was the drive I intended to mate to the Rotary. The drive never did pan out well..lots of bad noises as I learned.    
 I never met the Cozy girls but did read some of the blog in the past. It warms my heart that the aircraft did get built and that engine does indeed perform well. 

I also searched today as Jay did.. didn't find the vacuum lite either, but it is interesting to learn process differences.

 Me wonders if they can send a link to our list group if it still exists?    

From: <> on behalf of Jay Scheevel <jay@...>
Sent: Tuesday, March 23, 2021 3:21 PM
To: <>
Subject: Re: [Q-List] Resin volume placed on foam
I looked there too, Bruce, but I could not find their videos on vacuum bagging. Maybe they took them down.  I remember them using a fish tank pump for vacuum.


-----Original Message-----
From: <> On Behalf Of Bruce Crain
Sent: Tuesday, March 23, 2021 1:25 PM
Subject: Re: [Q-List] Resin volume placed on foam

Hey Sammy Hoskins had the Cozy Girls show us some light vacuum bagging at one of our Field Of Dreams events in Illinois.  It was very interesting and may be what you’re looking for.
Bruce Crain
> On Mar 23, 2021, at 12:10 PM, Rob de Bie <robdebie@...> wrote:
> Eugen, I would be careful with vacuum bagging your parts. You're making quite a big change from the original building methods. The foam is not meant for full vacuum. And possibly it will absorb more resin due to the vacuum. I've done lots of vacuum injection, and the resin that goes into the foam cancels out all weight gains.
> I fully understand your desire to build quality parts, but this might not work out so well. Maybe a light vacuum (if that exists :-) is a better way, say -0.1 or -0.2 bar.
> Rob
>> On 23 Mar 2021 13:30, Eugen Pilarski wrote:
>> Dear Q-community,
>> the bulkheads of the Q1 are already cut and the worktable for vacuum-wrap is ready to go. After I study again the Quickie wokshop manual on page 3-11 in Step 7: Squeegeeing .......... If you’ve done an excellent job, the weight of resin will be about 2/3 of the weight of cloth used. ........
>> So we use glass with a weight of 296g/m2 and based on the number of Step 7 in Quickie built manual show up, that the requested resin will be 200g/m2 ( 2/3 of 300g/m is 200g). Is that correct?
>> But the laminate calculator of R&G get me out 243 g/m2 and is 20%
>> more that Rutan numbers indicate, please find the link below: R&G
>> laminate calculator <>
>> Framework:
>> Fibre type: glass fibre - 2.6 g/cm3
>> Areal weight: 296g/m2
>> Fibre volume fraction: Hand-lay-up 35% Number of layers: 1 Laminate
>> thickness: 1mm
>> Width: 1000 mm
>> Lenkt: 1000 mm
>> Resin type: Epoxy Resin  - 1.15 g/cm3 print
>>      Result:
>> Number of layers    1 Layers
>> Laminate thickness    0.33 mm
>> Fibre reinforcement surface area    1.00 m²
>> Fibre reinforcement gross weight    296 g
>> Resin quantity    243 g
>> Laminate weight    539 g
>> Fibre content (weight)    54.9 %
>> Fibre content (volume)    35.0 %
>> Did you guys fixed a resin volume per square meter during your building process as maximum or just the wet as should and dry as possible rule?
>> I ask to understood how may resin should be placed on the foam to reach the material strength and stay in low weight at all parts that need to produce. So sounds like the old story......
>> Best regards
>> Eugen

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