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  1. dcarr

    Interesting composites problem

    Here is an interesting composites problem for the brain trust... I have a rectangular "shop made" large overhead console/air duct about 10-12" wide and ~3" deep running down the length of the ceiling of my plane (~6' long). The duct walls are 2-3 plies of 8oz E-glass with spanwise balsa/glass...
  2. dcarr

    How to make liquid tight fiberglass?

    Hi all, I'd like to make a custom shape ice cooler to really fit well in the baggage area. I was thinking I'd use 1" expanded styrofoam insulation with fiberglass on the inside/outside. Only catch is that I've never had to make a thin yet watertight glass layup before. I'd like to keep the...
  3. dcarr

    If you were in charge of Raptor...

    If you were in charge of Raptor and had to fly it 6 months from now, what would you change/test/do? Starter ideas: - Install 300hp IO-540 and new cowl - Flip aircraft and do sandbag load tests - Carefully review pushrods, bellcranks, and control system attach points - Remove any non-critical...
  4. dcarr

    Engine control forces?

    Does anyone have guidance from FAR 23 on how much force engine controls must be designed to handle? I can find numbers for stick/rudder forces but nothing on secondary controls like throttle, mixture, etc. Thanks, David
  5. dcarr

    Anyone tried a soft solid rivet in fiberglass?

    Hi HBA, I'm working on my RV-10 fuselage and have reached a point where the plans call for the use of blind rivets to attach a composite piece to a aluminum skin. I'd like to substitute soft (A, 1100) solid rivets because I'll get a much nicer cosmetic result. The strength is good, but I'm...
  6. dcarr

    Field rivet spacing

    This is a diagram from Niu showing shear reinforcement around a fuselage cutout. In the shaded areas, a doubler is attached to the existing skin with a set of "field rivets". Does anyone have insight on the proper spacing for these rivets? I believe their main purpose is not to carry...
  7. dcarr

    How to "capture" shape for a custom rib?

    I need to fabricate a vertical "rib"/mini-bulkhead that fits at an intermediate point between two fuselage stations on my metal airplane. Forming the rib should be pretty straightforward, but I'm not sure how best to capture the skin curvature at that location and transfer it to my forming...
  8. dcarr

    What are you using for sanding blocks?

    Very simple question: I often read things on composite builders' websites like "sand with 100 grit on a medium foam block". What is a medium foam block and how do I make and/or get one? Thanks for the help, David
  9. dcarr

    DIY Aircraft Air Conditioning

    I've been working for a while on an electric air conditioning system for my RV-10 and thought it might be interesting for some folks. The basic system consists of a 28V electric compressor (purple), a ~14x20" parallel flow condenser (right), and a ~10x10" evaporator controlled by a TXV (left...
  10. dcarr

    Metal guy building a big composite part, would love your thoughts.

    Hey HBA, I need a little advice from some of the composite gurus on the forum. Building an RV-10 has greatly improved my sheet metal skills, but I’m still pretty low level when it comes to fiberglass. My next project is to build a composite overhead console/air duct that will ultimately be...
  11. dcarr

    Software to estimate aircraft pressure distribution

    Is there any software available at an amateur price point that can calculate a wing/fuselage pressure distribution? I think a simple panel analysis would be fine. I tried this with XFLR5, but the big pressure discontinuity between the wing and the fuselage makes me believe the results are...
  12. dcarr

    Electric glider tug

    I was thinking today about applications where electric power could be a practical today, and I hit upon the idea of an electric glider tow plane. I must confess that I don't know a whole lot about glider towing operations but it seems like there are several factors that could make a good fit...
  13. dcarr

    Structural quandry

    I'm looking at a set of CH 701 plans for educational purposes and I found something that really confuses me. The attached image shows a diagram of the forward wing strut attach fitting. It consists of a primary .125" plate and a .063" doubler. A 5/16" bolt attaches the forward strut to this...
  14. dcarr

    Designing inlets/outlets for A/C on aft fuselage of RV-10

    Hi guys, I've got an RV-10 underway in my garage right now, and one of the things I'd like to do is give it a real air-conditioning system. My specific challenge at the moment is coming up with a good way to ingest and then expel the air for the condenser. The airflow is about 500 cfm and is...
  15. dcarr

    Allowable loads for hinges?

    Hi all, Can anyone point me to information on the allowable loads for MS20257 and MS20001 piano hinges? I'm coming up dry with my searches. Any information much appreciated. David
  16. dcarr

    Help identify historical alloy designation?

    If anyone could help me out with an identification of alloy "SO", I would be much obliged. See drawing below:
  17. dcarr

    Lift strut with fixed as opposed to pinned ends

    Hi all, For longer lift struts it seems that a moderate savings in strut size and weight could be had by adopting struts with end fixity greater than 1. Bruhn says that end fixity up to 1.5 is permissible in trusses with riveted joints (C4.11). Using C=1.5 reduces the effective length of the...
  18. dcarr

    Airfoil suggestion?

    Hi all, I'm looking to query the group wisdom about an airfoil selection, here are the parameters: Re range: 1.4e6 climb to 2.4e6 cruise Climb Cl is approximately .83 Cruise Cl is approximately .32 Metal wing limits laminar flow on both surfaces to about .25 c Target thickness 15% High Clmax...